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Genetic factors play a significant role in the pathogenesis of mitral valve diseases, including mitral valve prolapse (MVP) and mitral valve regurgitation. Genes like Fibrillin-1 (FBN1), Filamin A (FLNA), matrix metalloproteinase 2 (MMP2), and SRY-box transcription factor 9 (SOX9) are known to influence mitral valve pathology but knowledge of the exact mechanism is far from clear. Data regarding serum parameters, transesophageal echocardiography, and genetic and histopathologic parameters were investigated in 54 patients who underwent cardiovascular surgery for mitral valve regurgitation. The possible association between Fibrillin-1, Filamin A, MMP2, and SOX9 gene expressions was checked in relationship with the parameters of systemic inflammatory response. The mRNA expression levels (RQ-relative quantification) were categorized into three distinct groups: low (RQ < 1), medium/normal (RQ = 1-2), and high (RQ > 2). Severe fibrosis of the mitral valve was reflected by high expression of FBN1 and low expression of MMP2 ( p < 0.05). The myxoid degeneration level was associated with the mRNA expression level for FBN1 and a low lymphocyte-monocyte ratio was associated with an increased mRNA expression of FBN1 ( p < 0.05). A high number of monocytes was associated with high values of FBN1 whereas the increase in the number of lymphocytes was associated with high levels of MMP2. In addition, we observed that the risk of severe hyalinization was enhanced by a low mRNA expression of FLNA and/or SOX9. In conclusion, a lower FLNA mRNA expression can reflect the aging process that is highlighted in mitral valve pathology as a higher risk for hyalinization, especially in males, that might be prevented by upregulation of the SOX9 gene. FBN1 and MMP2 influence the inflammation-related fibrotic degeneration of the mitral valve. Understanding the genetic base of mitral valve pathology can provide insights into disease mechanisms, risk stratification, and potential therapeutic targets.

Coordinated cell shape changes are a major driver of tissue morphogenesis, with apical constriction of epithelial cells leading to tissue bending. We previously identified that interplay between the apical-medial actomyosin, which drives apical constriction, and the underlying longitudinal microtubule array has a key role during tube budding of salivary glands in the Drosophila embryo. At this microtubule-actomyosin interface, a hub of proteins accumulates, and we have shown before that this hub includes the microtubule-actin crosslinker Shot and the microtubule minus-end-binding protein Patronin. Here, we identify two actin-crosslinkers, β-heavy (H)-Spectrin (also known as Karst) and Filamin (also known as Cheerio), and the multi-PDZ-domain protein Big bang as components of the protein hub. We show that tissue-specific degradation of β-H-Spectrin leads to reduction of apical-medial F-actin, Shot, Patronin and Big bang, as well as concomitant defects in apical constriction, but that residual Patronin is still sufficient to assist microtubule reorganisation. We find that, unlike Patronin and Shot, neither β-H-Spectrin nor Big bang require microtubules for their localisation. β-H-Spectrin is instead recruited via binding to apical-medial phosphoinositides, and overexpression of the C-terminal pleckstrin homology domain-containing region of β-H-Spectrin (β-H-33) displaces endogenous β-H-Spectrin and leads to strong morphogenetic defects. This protein hub therefore requires the synergy and coincidence of membrane- and microtubule-associated components for its assembly and function in sustaining apical constriction during tubulogenesis., Competing Interests: Competing interests The authors declare no competing or financial interests., (© 2024. Published by The Company of Biologists Ltd.)

Periventricular nodular heterotopia (PNH), the most common brain malformation diagnosed in adulthood, is characterized by the presence of neuronal nodules along the ventricular walls. PNH is mainly associated with mutations in the FLNA gene - encoding an actin-binding protein - and patients often develop epilepsy. However, the molecular mechanisms underlying the neuronal failure still remain elusive. It has been hypothesized that dysfunctional cortical circuitry, rather than ectopic neurons, may explain the clinical manifestations. To address this issue, we depleted FLNA from cortical pyramidal neurons of a conditional Flna flox/flox mice by timed in utero electroporation of Cre recombinase. We found that FLNA regulates dendritogenesis and spinogenesis thus promoting an appropriate excitatory/inhibitory inputs balance. We demonstrated that FLNA modulates RAC1 and cofilin activity through its interaction with the Rho-GTPase Activating Protein 24 (ARHGAP24). Collectively, we disclose an uncharacterized role of FLNA and provide strong support for neural circuit dysfunction being a consequence of FLNA mutations., Competing Interests: Declaration of competing interest None., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Thoracic aortic aneurysm (TAA) is associated with significant morbidity and mortality. Although individuals with family histories of TAA often undergo clinical molecular genetic testing, adults with nonsyndromic TAA are not typically evaluated for genetic causes. We sought to understand the genetic contribution of both germline and somatic mosaic variants in a cohort of adult individuals with nonsyndromic TAA at a single center., Methods and Results: One hundred eighty-one consecutive patients <60 years who presented with nonsyndromic TAA at the Massachusetts General Hospital underwent deep (>500×) targeted sequencing across 114 candidate genes associated with TAA and its related functional pathways. Samples from 354 age- and sex-matched individuals without TAA were also sequenced, with a 2:1 matching. We found significant enrichments for germline (odds ratio [OR], 2.44, P =4.6×10 -6 [95% CI, 1.67-3.58]) and also somatic mosaic variants (OR, 4.71, P =0.026 [95% CI, 1.20-18.43]) between individuals with and without TAA. Likely genetic causes were present in 24% with nonsyndromic TAA, of which 21% arose from germline variants and 3% from somatic mosaic alleles. The 3 most frequently mutated genes in our cohort were FLNA (encoding Filamin A), NOTCH3 (encoding Notch receptor 3), and FBN1 (encoding Fibrillin-1). There was increased frequency of both missense and loss of function variants in TAA individuals., Conclusions: Likely contributory dominant acting genetic variants were found in almost one quarter of nonsyndromic adults with TAA. Our findings suggest a more extensive genetic architecture to TAA than expected and that genetic testing may improve the care and clinical management of adults with nonsyndromic TAA.

Forensic pathologists are frequently asked to investigate cases of sudden death (SD), and identifying the cause of death can be of particular importance, especially where it may be necessary to perform family screening among the relatives of the victim. A multidisciplinary approach inclusive of genetic analysis is therefore strongly recommended. According to forensic practice, arrhythmogenic cardiomyopathy (ACM) is a well-known cause of SD. However, cases of SD caused by a left ventricular pattern of ACM diagnosed at autopsy are rarely reported in the literature. We present the case of an apparently healthy, 37-year-old male found dead at his home. At autopsy, multiple foci of epicardial and mid-wall fibrous and fibro-adipose tissue were observed within the left ventricle and, to a lesser extent, within the interventricular septum. Toxicology was negative, whereas a filamin C truncating mutation was detected through genetic analysis. To our knowledge, this is the first instance of arrhythmogenic left ventricular cardiomyopathy being diagnosed at autopsy., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The incidence of intrahepatic cholangiocarcinoma (ICC) is steadily rising, and it is associated with a high mortality rate. Clinical samples were collected to detect the expression of HSPB8 and BAG3 in ICC tissues. ICC cells were cultured and transfected with plasmids that overexpressed or silenced specific genes to investigate the impact of gene expression alterations on cell function. qPCR and Western blot techniques were utilized to measure gene and protein expression levels. A wound healing assay was conducted to assess cell migration ability. The Transwell assay was used to assess cell invasion ability. Co-IP was used to verify the binding relationship between HSPB8 and BAG3. The effects of HSPB8 and BAG3 on lung metastasis of tumors in vivo were verified by constructing a metastatic tumor model. Through the above experiments, we discovered that the expressions of HSPB8 and BAG3 were up-regulated in ICC tissues and cells, and their expressions were positively correlated. The metastatic ability of ICC cells could be promoted or inhibited by upregulating or downregulating the expression of BAG3. Furthermore, the HSPB8-BAG3 chaperone complex resulted in the abnormal degradation of Filamin A by activating autophagy. Increased expression of Filamin A inhibits the migration and invasion of ICC cells. Overexpression of HSPB8 and BAG3 in vivo promoted the lung metastasis ability of ICC cells. The HSPB8-BAG3 chaperone complex promotes ICC cell migration and invasion by regulating CASA-mediated degradation of Filamin A, offering insights for enhancing ICC therapeutic strategies.

Background: Clear cell renal cell carcinoma (ccRCC) remains a deadly disease with a poor prognosis. Here, we identified the ETS homologous factor (EHF) and its target Filamin-B (FLNB) as molecules related to immune evasion in ccRCC. We also explored the upstream modifier that manipulates EHF in ccRCC., Design: Cell proliferation and apoptosis assay, wound healing assay, and Transwell assay were designed to analyze the effects of EHF or FLNB knockdown on the biological activity of ccRCC cells. The growth of differently treated ccRCC cells was assessed by orthotopic tumors. ccRCC cells with different treatments were co-cultured with macrophages, and the role of the lysine-specific demethylase 5B (KDM5B)/EHF/FLNB axis on macrophage polarization or ccRCC progression was characterized by detecting the expression of M2 macrophage markers in the co-culture system or tumor tissues of tumor-bearing mice., Results: The expression of EHF and FLNB was higher, while KDM5B was lower in HK2 cells than in ccRCC cells. EHF overexpression inhibited the biological behavior of ccRCC cells and tumor growth in mice. EHF activated FLNB transcription. Knockdown of FLNB supported the biological activity of ccRCC cells and tumor growth and reversed M2 macrophage polarization in tumor tissues of mice in the presence of EHF. KDM5B inhibited EHF expression by H3K4me3 demethylation, and EHF knockdown potentiated M2 macrophage polarization and tumor growth in vivo repressed by KDM5B knockdown., Conclusions: KDM5B inhibited the expression of EHF by repressing H3K4me3 modification and the transcription of FLNB by EHF to promote immune evasion and progression of ccRCC., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Filamins are mechanosensitive actin crosslinking proteins that organize the actin cytoskeleton in a variety of shapes and tissues. In muscles, filamin crosslinks actin filaments from opposing sarcomeres, the smallest contractile units of muscles. This happens at the Z-disc, the actin-organizing center of sarcomeres. In flies and vertebrates, filamin mutations lead to fragile muscles that appear ruptured, suggesting filamin helps counteract muscle rupturing during muscle contractions by providing elastic support and/or through signaling. An elastic region at the C-terminus of filamin is called the mechanosensitive region and has been proposed to sense and counteract contractile damage. Here we use molecularly defined mutants and microscopy analysis of the Drosophila indirect flight muscles to investigate the molecular details by which filamin provides cohesion to the Z-disc. We made novel filamin mutations affecting the C-terminal region to interrogate the mechanosensitive region and detected three Z-disc phenotypes: dissociation of actin filaments, Z-disc rupture, and Z-disc enlargement. We tested a constitutively closed filamin mutant, which prevents the elastic changes in the mechanosensitive region and results in ruptured Z-discs, and a constitutively open mutant which has the opposite elastic effect on the mechanosensitive region and gives rise to enlarged Z-discs. Finally, we show that muscle contraction is required for Z-disc rupture. We propose that filamin senses myofibril damage by elastic changes in its mechanosensory region, stabilizes the Z-disc, and counteracts contractile damage at the Z-disc., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Fisher et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Arrhythmogenic cardiomyopathy (ACM) is an inherited myocardial disease at risk of sudden death. Genetic testing impacts greatly in ACM diagnosis, but gene-disease associations have yet to be determined for the increasing number of genes included in clinical panels. Genetic variants evaluation was undertaken for the most relevant non-desmosomal disease genes. We retrospectively studied 320 unrelated Italian ACM patients, including 243 cases with predominant right-ventricular (ARVC) and 77 cases with predominant left-ventricular (ALVC) involvement, who did not carry pathogenic/likely pathogenic (P/LP) variants in desmosome-coding genes. The aim was to assess rare genetic variants in transmembrane protein 43 ( TMEM43 ), desmin ( DES ), phospholamban ( PLN ), filamin c ( FLNC ), cadherin 2 ( CDH2 ), and tight junction protein 1 ( TJP1 ), based on current adjudication guidelines and reappraisal on reported literature data. Thirty-five rare genetic variants, including 23 (64%) P/LP, were identified in 39 patients (16/243 ARVC; 23/77 ALVC): 22 FLNC , 9 DES , 2 TMEM43 , and 2 CDH2 . No P/LP variants were found in PLN and TJP1 genes. Gene-based burden analysis, including P/LP variants reported in literature, showed significant enrichment for TMEM43 (3.79-fold), DES (10.31-fold), PLN (117.8-fold) and FLNC (107-fold). A non-desmosomal rare genetic variant is found in a minority of ARVC patients but in about one third of ALVC patients; as such, clinical decision-making should be driven by genes with robust evidence. More than two thirds of non-desmosomal P/LP variants occur in FLNC.

Filamin C (FLNC) is a highly important actin crosslinker and multi-adaptor protein in striated skeletal and cardiac muscle. Mutations have been linked to a range of cardiomyopathy types. Here, we generated induced pluripotent stem cells (iPSC) from a patient with dilated cardiomyopathy (DCM) harboring a new, unique heterozygous FLNC mutation p.R2187P. From this patient-specific iPSC line, a corresponding isogenic control line was created by CRISPR/Cas9 genome editing. Both, the patient-specific and isogenic-control iPSC maintained full pluripotency, genomic integrity, and in vitro differentiation capacity. All iPSC lines differentiate into iPSC-cardiomyocytes, hence providing the possibility to study the pathogenesis of FLNC-mediated DCM further., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Wiebke Maurer reports financial support was provided by Deutsche Forschungsgemeinschaft. Katrin Streckfuss-Boemeke reports financial support was provided by Deutsche Forschungsgemeinschaft. Katrin Streckfuss-Boemeke reports a relationship with Novartis AG that includes: funding grants and speaking and lecture fees. Katrin Streckfuss-Boemeke reports a relationship with BioNTech Research & Development, Inc. that includes: funding grants. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Background: Many cardiomyopathy-associated FLNC pathogenic variants are heterozygous truncations, and FLNC pathogenic variants are associated with arrhythmias. Arrhythmia triggers in filaminopathy are incompletely understood., Methods and Results: We describe an individual with biallelic FLNC pathogenic variants, p.Arg650X and c.970-4A>G, with peripartum cardiomyopathy and ventricular arrhythmias. We also describe clinical findings in probands with FLNC variants including Val2715fs87X, Glu2458Serfs71X, Phe106Leu, and c.970-4A>G with hypertrophic and dilated cardiomyopathy, atrial fibrillation, and ventricular tachycardia. Induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) were generated. The FLNC truncation, Arg650X/c.970-4A>G, showed a marked reduction in filamin C protein consistent with biallelic loss of function mutations. To assess loss of filamin C, gene editing of a healthy control iPSC line was used to generate a homozygous FLNC disruption in the actin binding domain. Because filamin C has been linked to protein quality control, we assessed the necessity of filamin C in iPSC-CMs for response to the proteasome inhibitor bortezomib. After exposure to low-dose bortezomib, FLNC- null iPSC-CMs showed an increase in the chaperone proteins BAG3, HSP70 (heat shock protein 70), and HSPB8 (small heat shock protein B8) and in the autophagy marker LC3I/II. FLNC null iPSC-CMs had prolonged electric field potential, which was further prolonged in the presence of low-dose bortezomib. FLNC null engineered heart tissues had impaired function after low-dose bortezomib., Conclusions: FLNC pathogenic variants associate with a predisposition to arrhythmias, which can be modeled in iPSC-CMs. Reduction of filamin C prolonged field potential, a surrogate for action potential, and with bortezomib-induced proteasome inhibition, reduced filamin C led to greater arrhythmia potential and impaired function.

Objectives: Genetic disorders involved in skeleton system arise due to the disturbance in skeletal development, growth and homeostasis. Filamin B is an actin binding protein which is large dimeric protein which cross link actin cytoskeleton filaments into dynamic structure. A single nucleotide changes in the FLNB gene causes spondylocarpotarsal synostosis syndrome, a rare bone disorder due to which the fusion of carpels and tarsals synostosis occurred along with fused vertebrae. In the current study we investigated a family residing in north-western areas of Pakistan., Methods: The whole exome sequencing of proband was performed followed by Sanger sequencing of all family members of the subject to validate the variant segregation within the family. Bioinformatics tools were utilized to assess the pathogenicity of the variant., Results: Whole Exome Sequencing revealed a novel variant (NM&#95;001457: c.209C>T and p.Pro70Leu) in the FLNB gene which was homozygous missense mutation in the FLNB gene. The variant was further validated and visualized by Sanger sequencing and protein structure studies respectively as mentioned before., Conclusions: The findings have highlighted the importance of the molecular diagnosis in SCT (spondylocarpotarsal synostosis syndrome) for genetic risk counselling in consanguineous families., (© 2024 Walter de Gruyter GmbH, Berlin/Boston.)

Objective: To analyze the clinical phenotype and genetic basis of a Chinese pedigree affected with Otopalatodigital syndrome type 1 (OPD1)., Methods: A pedigree which was evaluated at the Department of Endocrinology, General Hospital of the Central Theater Command on December 3, 2020 was selected as the study subject. Clinical phenotype and genetic features of the proband were analyzed. Whole exome sequencing was employed to screen for genetic variants in the proband, and Sanger sequencing was used to verify the candidate variants in the proband's mother, uncle, maternal aunt, and paternal aunt. Pathogenicity analysis was also conducted for the candidate variants., Results: The proband, a 16-year-old male, had shown distinctive facial features including mildly prominent eyebrows, down-slanting palpebral fissures, hypertelorism, and depressed nasal bridge. Additionally, he had clubbing of bilateral thumbs and big toes, and central type diabetes insipidus. Genetic sequencing revealed that he has harbored a heterozygous c.586C>T (p.R196W) missense variant of the FLNA gene (NM&#95;001110556.2), which was also carried by his mother and uncle. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), this variant was classified as likely pathogenic (PM1+PM2&#95;Supporting+PP2+PP3+PS4 Supporting)., Conclusion: The heterozygous c.586C>T (p.R196W) variant of the FLNA gene probably underlay the pathogenesis in this OPD1 family. The central type diabetes insipidus in the proband may represent a newly discovered phenotype of OPD1. Above finding has contributed crucial information for the comprehensive understanding of the clinical manifestations and pathogenic mechanisms of OPD1.

Disulfidptosis, a newly recognized cell death triggered by disulfide stress, has garnered attention for its potential role in osteoporosis (OP) pathogenesis. Although sulfide-related proteins are reported to regulate the balance of bone metabolism in OP, the precise involvement of disulfidptosis regulators remains elusive. Herein, leveraging the GSE56815 dataset, we conducted an analysis to delineate disulfidptosis-associated diagnostic clusters and immune landscapes in OP. Subsequently, vertebral bone tissues obtained from OP patients and controls were subjected to RNA sequencing (RNA-seq) for the validation of key disulfidptosis gene expression. Our analysis unveiled seven significant disulfidptosis regulators, including FLNA, ACTB, PRDX1, SLC7A11, NUBPL, OXSM, and RAC1, distinguishing OP samples from controls. Furthermore, employing a random forest model, we identified four diagnostic disulfidptosis regulators including FLNA, SLC7A11, NUBPL, and RAC1 potentially predictive of OP risk. A nomogram model integrating these four regulators was constructed and validated using the GSE35956 dataset, demonstrating promising utility in clinical decision-making, as affirmed by decision curve analysis. Subsequent consensus clustering analysis stratified OP samples into two different disulfidptosis subgroups (clusters A and B) using significant disulfidptosis regulators, with cluster B exhibiting higher disulfidptosis scores and implicating monocyte immunity, closely linked to osteoclastogenesis. Notably, RNA-seq analysis corroborated the expression patterns of two disulfidptosis modulators, PRDX1 and OXSM, consistent with bioinformatics predictions. Collectively, our study sheds light on disulfidptosis patterns, offering potential markers and immunotherapeutic avenues for future OP management.

Triple-negative breast cancer is a rare but highly heterogeneous breast cancer subtype with a limited choice of specific treatments. Chemotherapy remains the only efficient treatment, but its side effects and the development of resistance consolidate the urgent need to discover new targets. In TNBC, filamin A expression correlates to grade and TNM stage. Accordingly, this protein could constitute a new target for this BC subtype. Even if most of the data indicates its direct involvement in cancer progression, some contrasting results underline the need to deepen the studies. To elucidate a possible function of this protein as a TNBC marker, we summarized the main characteristic of filamin A and its involvement in physiological and pathological processes such as cancer. Lastly, we scrutinized its actions in triple-negative breast cancer and highlighted the need to increase the number of studies useful to better clarify the role of this versatile protein as a marker and target in TNBC, alone or in "collaboration" with other proteins with a relevant role in this BC subgroup., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

Objective: The contribution of somatic variants to epilepsy has recently been demonstrated, particularly in the etiology of malformations of cortical development. The aim of this study was to determine the diagnostic yield of somatic variants in genes that have been previously associated with a somatic or germline epilepsy model, ascertained from resected brain tissue from patients with multidrug-resistant focal epilepsy., Methods: Forty-two patients were recruited across three categories: (1) malformations of cortical development, (2) mesial temporal lobe epilepsy with hippocampal sclerosis, and (3) nonlesional focal epilepsy. Participants were subdivided based on histopathology of the resected brain. Paired blood- and brain-derived DNA samples were sequenced using high-coverage targeted next generation sequencing to high depth (585× and 1360×, respectively). Variants were identified using Genome Analysis ToolKit (GATK4) MuTect-2 and confirmed using high-coverage Amplicon-EZ sequencing., Results: Sequence data on 41 patients passed quality control. Four somatic variants were validated following amplicon sequencing: within CBL, ALG13, MTOR, and FLNA. The diagnostic yield across 41 patients was 10%, 9% in mesial temporal lobe epilepsy with hippocampal sclerosis and 20% in malformations of cortical development., Significance: This study provides novel insights into the etiology of mesial temporal lobe epilepsy with hippocampal sclerosis, highlighting a potential pathogenic role of somatic variants in CBL and ALG13. We also report candidate diagnostic somatic variants in FLNA in focal cortical dysplasia, while providing further insight into the importance of MTOR and related genes in focal cortical dysplasia. This work demonstrates the potential molecular diagnostic value of variants in both germline and somatic epilepsy genes., (© 2024 The Authors. Epilepsia published by Wiley Periodicals LLC on behalf of International League Against Epilepsy.)

Background: Variants in Filamin-C (FLNC) have been associated with various hereditary cardiomyopathies. Recent literature reports a prevalence of sudden cardiac death (SCD) of 13-25% among carriers of truncating-variants, with mean age of 42±15 years for first SCD event. This study reports two familial cases of SCD and the results of cascade screening of their large family., Methods: Molecular-autopsy of the SCD victims revealed a novel truncating-variant in the FLNC gene (chr 7:128496880 [hg19]; NM&#95;001458.5; c.7467&#95;7474del; p.(Ser2490fs)). We screened thirty-two family members following genetic counseling, and variant carriers underwent a comprehensive workup followed by consultation with a cardiologist with expertise in the genetics of cardiac diseases., Results: Seventeen variant carriers were identified: ages between 9 and 85 (mean 47±26). Fifteen underwent clinical evaluation. To date, none of the identified carriers has had major adverse events. In evaluated patients, ECG showed right-axis deviation in 60% (n = 9). Holter recorded frequent premature ventricular contractions (PVCs) (991±2030 per 24 h) in 33% (n = 5) with 4 patients having polymorphic PVC morphology. Three carriers had echocardiographic evidence of mild left-ventricular (LV) systolic dysfunction and another with mild LV dilatation. Cardiac magnetic-resonance (CMR) exhibited late‑gadolinium-enhancement in 10 out of 11 exams, mainly in the mid-myocardium and sub-epicardium, frequently involving the septum and the inferior-lateral wall., Conclusion: This large FLNC truncating variant carrier family exhibits high cardiomyopathy penetrance, best diagnosed by CMR, with variable clinical expressions. These findings present a challenge in SCD prevention management and underscoring the imperative for better risk stratification measures., Competing Interests: Declaration of competing interest The authors have no conflicts to disclose., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Objective: Variants in the FLNA gene have been associated with mitral valve dystrophy (MVD), and even polyvalvular disease has been reported. This study aimed to analyse the aortic valve and root involvement in FLNA -MVD families and its impact on outcomes., Methods: 262 subjects (37 (18-53) years, 140 male, 79 carriers: FLNA +) from 4 FLNA -MVD families were included. Echocardiography was performed in 185 patients and histological analysis in 3 explanted aortic valves. The outcomes were defined as aortic valve surgery or all-cause mortality., Results: Aortic valve alterations were found in 58% of FLNA + compared with 6% of FLNA - (p<0.001). 9 (13.4%) FLNA + had bicuspid aortic valve compared with 4 (3.4%) FLNA - (p=0.03). Overall, the transvalvular mean gradient was slightly increased in FLNA + (4.8 (4.1-6.1) vs 4.0 (2.9-4.9) mm Hg, p=0.02). The sinuses of Valsalva and sinotubular junction diameters were enlarged in FLNA + subjects (all p<0.05). 8 FLNA + patients underwent aortic valve surgery (0 in relatives; p<0.001). Myxomatous remodelling with an infiltration of immune cells was observed. Overall survival was similar between FLNA+ versus FLNA - subjects (86±5% vs 85±6%, p=0.36). There was no statistical evidence for an interaction between genetic status and sex (p=0.15), but the survival tended to be impaired in FLNA + men (p=0.06) whereas not in women (p=0.71)., Conclusion: The patients with FLNA variants present frequent aortic valve disease and worse outcomes. Bicuspid aortic valve is more frequent in patients carrying the FLNA -MVD variants. These unique features should be factored into the management of patients with dystrophic and/or bicuspid aortic valve., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Here we introduce the human induced pluripotent stem cell lines (hiPSCs), HIMRi004-A and HIMRi005-A from dermal fibroblasts of a 48-year-old female (HIMRi004-A) carrying missense mutation that translate to the first described filamin C isoform p.W2710X and from a 56-year-old female (HIMRi005-A) carrying a recently described mutation in the same domain p.Y2704X. Both lines are generated via lentiviral expression of OCT4, SOX2, KLF4 and c-MYC. The lines display a typical embryonic stem cell-like morphology, express pluripotency markers, retain a normal karyotype (46, XX) and have the differentiation capacity in all three germ layers. The two lines can be used to elucidate the pathomechanisms of FLNC myofibrillar myopathies and to develop novel therapeutic options., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Vaccinia virus (VACV) is a large DNA virus that encodes scores of proteins that modulate the host immune response. VACV protein C4 is one such immunomodulator known to inhibit the activation of both the NF-κB signaling cascade and the DNA-PK-mediated DNA sensing pathway. Here, we show that the N-terminal region of C4, which neither inhibits NF-κB nor mediates interaction with DNA-PK, still contributes to virus virulence. Furthermore, this domain interacts directly and with high affinity to the C-terminal domain of filamin B (FLNB). FLNB is a large actin-binding protein that stabilizes the F-actin network and is implicated in other cellular processes. Deletion of FLNB from cells results in larger VACV plaques and increased infectious viral yield, indicating that FLNB restricts VACV spread. These data demonstrate that C4 has a new function that contributes to virulence and engages the cytoskeleton. Furthermore, we show that the cytoskeleton performs further previously uncharacterized functions during VACV infection., Importance: Vaccinia virus (VACV), the vaccine against smallpox and monkeypox, encodes many proteins to counteract the host immune response. Investigating these proteins provides insights into viral immune evasion mechanisms and thereby indicates how to engineer safer and more immunogenic VACV-based vaccines. Here, we report that the N-terminal domain of VACV protein C4 interacts directly with the cytoskeletal protein filamin B (FLNB), and this domain of C4 contributes to virus virulence. Furthermore, VACV replicates and spreads better in cells lacking FLNB, thus demonstrating that FLNB has antiviral activity. VACV utilizes the cytoskeleton for movement within and between cells; however, previous studies show no involvement of C4 in VACV replication or spread. Thus, C4 associates with FLNB for a different reason, suggesting that the cytoskeleton has further uncharacterized roles during virus infection., Competing Interests: The authors declare no conflict of interest.

A late adolescent primigravida was found to have a fetus with a cystic hygroma and significant shortening of the limbs on first-trimester ultrasound. She underwent chorionic villus sampling with normal microarray result. In the early second trimester, the fetus was found to have the absence of all four limbs and a thorough skeletal dysplasia workup was pursued, identifying a variant in the FLNB gene (c.62C>G). The patient underwent termination of pregnancy. The care of this patient was expedited by first-trimester sonographic evidence of limb abnormalities enabling timely clinical management., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Truncating mutations in filamin C ( FLNC ) are associated with dilated cardiomyopathy and arrhythmogenic cardiomyopathy. FLNC is an actin-binding protein and is known to interact with transmembrane and structural proteins; hence, the ablation of FLNC in cardiomyocytes is expected to dysregulate cell adhesion, cytoskeletal organization, sarcomere structural integrity, and likely nuclear function. Our previous study showed that the transcriptional profiles of FLNC homozygous deletions in human pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are highly comparable to the transcriptome profiles of hiPSC-CMs from patients with FLNC truncating mutations. Therefore, in this study, we used CRISPR-Cas-engineered hiPSC-derived FLNC knockout cardiac myocytes as a model of FLNC cardiomyopathy to determine pathogenic mechanisms and to examine structural changes caused by FLNC deficiency. RNA sequencing data indicated the significant upregulation of focal adhesion signaling and the dysregulation of thin filament genes in FLNC -knockout (FLNC KO ) hiPSC-CMs compared to isogenic hiPSC-CMs. Furthermore, our findings suggest that the complete loss of FLNC in cardiomyocytes led to cytoskeletal defects and the activation of focal adhesion kinase. Pharmacological inhibition of PDGFRA signaling using crenolanib (an FDA-approved drug) reduced focal adhesion kinase activation and partially normalized the focal adhesion signaling pathway. The findings from this study suggest the opportunity in repurposing FDA-approved drug as a therapeutic strategy to treat FLNC cardiomyopathy.

Background & Aims: Intrahepatic cholangiocarcinoma (iCCA) is a primary liver tumour, characterized by poor prognosis and lack of effective therapy. The cytoskeleton protein Filamin A (FLNA) is involved in cancer progression and metastasis, including primary liver cancer. FLNA is cleaved by calpain, producing a 90 kDa fragment (FLNA CT ) that can translocate to the nucleus and inhibit gene transcription. We herein aim to define the role of FLNA and its cleavage in iCCA carcinogenesis., Methods & Results: We evaluated the expression and localization of FLNA and FLNA CT in liver samples from iCCA patients (n = 82) revealing that FLNA expression was independently correlated with disease-free survival. Primary tumour cells isolated from resected iCCA patients expressed both FLNA and FLNA CT , and bulk RNA sequencing revealed a significant enrichment of cell proliferation and cell motility pathways in iCCAs with high FLNA expression. Further, we defined the impact of FLNA and FLNA CT on the proliferation and migration of primary iCCA cells (n = 3) and HuCCT1 cell line using silencing and Calpeptin, a calpain inhibitor. We observed that FLNA silencing decreased cell proliferation and migration and Calpeptin was able to reduce FLNA CT expression in both the HuCCT1 and iCCA cells (p < .05 vs. control). Moreover, Calpeptin 100 μM decreased HuCCT1 and primary iCCA cell proliferation (p <.00001 vs. control) and migration (p < .05 vs. control)., Conclusions: These findings demonstrate that FLNA is involved in human iCCA progression and calpeptin strongly decreased FLNA CT expression, reducing cell proliferation and migration., (© 2023 The Authors. Liver International published by John Wiley & Sons Ltd.)

Orofacial clefts (OFCs) are the most common congenital craniofacial disorders, of which the etiology is closely related to rare coding variants. Filamin B (FLNB) is an actin-binding protein implicated in bone formation. FLNB mutations have been identified in several types of syndromic OFCs and previous studies suggest a role of FLNB in the onset of non-syndromic OFCs (NSOFCs). Here, we report two rare heterozygous variants (p.P441T and p.G565R) in FLNB in two unrelated hereditary families with NSOFCs. Bioinformatics analysis suggests that both variants may disrupt the function of FLNB. In mammalian cells, p.P441T and p.G565R variants are less potent to induce cell stretches than wild type FLNB, suggesting that they are loss-of-function mutations. Immunohistochemistry analysis demonstrates that FLNB is abundantly expressed during palatal development. Importantly, Flnb -/- embryos display cleft palates and previously defined skeletal defects. Taken together, our findings reveal that FLNB is required for development of palates in mice and FLNB is a bona fide causal gene for NSOFCs in humans., Competing Interests: Conflict of interest The authors declare that they have no conflict of interests., (Copyright © 2023 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Abstract: Glycoprotein Ibα (GPIbα) is expressed on the surface of platelets and megakaryocytes (MKs) and anchored to the membrane skeleton by filamin A (flnA). Although GPIb and flnA have fundamental roles in platelet biogenesis, the nature of this interaction in megakaryocyte biology remains ill-defined. We generated a mouse model expressing either human wild-type (WT) GPIbα (hGPIbαWT) or a flnA-binding mutant (hGPIbαFW) and lacking endogenous mouse GPIbα. Mice expressing the mutant GPIbα transgene exhibited macrothrombocytopenia with preserved GPIb surface expression. Platelet clearance was normal and differentiation of MKs to proplatelets was unimpaired in hGPIbαFW mice. The most striking abnormalities in hGPIbαFW MKs were the defective formation of the demarcation membrane system (DMS) and the redistribution of flnA from the cytoplasm to the peripheral margin of MKs. These abnormalities led to disorganized internal MK membranes and the generation of enlarged megakaryocyte membrane buds. The defective flnA-GPIbα interaction also resulted in misdirected release of buds away from the vasculature into bone marrow interstitium. Restoring the linkage between flnA and GPIbα corrected the flnA redistribution within MKs and DMS ultrastructural defects as well as restored normal bud size and release into sinusoids. These studies define a new mechanism of macrothrombocytopenia resulting from dysregulated MK budding. The link between flnA and GPIbα is not essential for the MK budding process, however, it plays a major role in regulating the structure of the DMS, bud morphogenesis, and the localized release of buds into the circulation., (© 2024 American Society of Hematology. Published by Elsevier Inc. All rights are reserved, including those for text and data mining, AI training, and similar technologies.)

Competing Interests: Competing interests: None declared.

Cardiac sarcoidosis is an unpredictable, rare and potentially lethal condition whereby patients are exposed to sudden cardiac death. However, despite sophisticated imaging techniques and the need for careful multidisciplinary team assessment and management, the contribution from genetic mutations is uncertain. Hence, the case describes a novel observation of a patient who possessed both a filamin C mutation and cardiac sarcoidosis. The case highlights the need for detailed dedicated investigation and highlights the need for the consideration of genetic screening within patients with cardiac sarcoidosis., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2024. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Long-chain noncoding RNA (lncRNA), LINC01569, is important for regulating the extracellular matrix, which affects cell migration. However, its involvement in the occurrence and development of triple-negative breast cancer (TNBC) remains unclear., Objective: This study is aimed to investigate the role of LINC01569 on TNBC., Methods: Online database was used for clinical data analysis. Cell viability and migration capability were monitored using cell counting kit-8 and transwell assays, respectively. Luciferase reporter assay and RNA pull-down were used to confirm the binding capability between noncoding RNAs and filamin A-interacting protein 1-like (FILIP1L). Western blotting was used to determine the protein content., Results: Compared with normal breast tissue, LINC01569 was significantly reduced in patients with TNBC subtype, and LINC01569 expression gradually decreased with the progression of tumor stage. Patients with TNBC with high lncRNA LINC01569 levels had a better prognosis than did patients with low LINC01569 levels. LINC01569 overexpression inhibited the migration capability, whereas siRNA-mediated LINC01569 downregulation promoted the migration capability in TNBC cells. Using ENCORI and lncRNA SNP online databases, miR-300 was screened as the potential sponge of LINC01569. The binding of LINC01569 to miR-300 was confirmed using the dual-luciferase reporter and RNA pull-down assays. miR-300 was negatively correlated with LINC01569, and miR-300 mimics eliminated the anti-proliferation and anti-migration effects of LINC01569 on TNBC cells. Additionally, FILIP1L was further verified as the downstream target of miR-300. miR-300 mimics blocked LINC01569 upregulation-mediated elevation of FILIP1L. Importantly, the anti-tumor effects mediated by LINC01569 overexpression were abolished by miR-300 mimics and further restored by FILIP1L upregulation., Conclusions: LINC01569 was expressed at a low level in TNBC and could sponge miR-300 to promote FILIP1L expression, reducing the proliferation and metastasis capability of TNBC. Thus, LINC01569 might be a useful biomarker in the diagnosis and prognosis of metastatic TNBC.

Due to the current limited knowledge about the role of filamin A (FLNA) in pituitary tumour progression, we aimed to analyse FLNA expression levels and its impact on aggressive markers of pituitary neuroendocrine tumours (PitNETs), using an integrative approach of in vivo and in vitro models and human samples. An increase in the expression levels of FLNA was observed in the advanced tumoural stages of the hyperplastic adenomatous pituitary model, concomitant with a decrease in cell proliferation and with a modification in the subcellular localisation of this protein. Similarly, overexpression of FLNA in the somatolactotropic GH3 cell line induced a decrease in the cell proliferation, promoted a migratory phenotype, increased invasion activity, and decreased the prolactin secretion. Cyclin D1 (CCND1) and cyclin-dependent kinase 4 (CDK4) expression increased in both models in correlation with the increase observed in FLNA levels. When human tissues were analysed a significant increase of FLNA was observed in PitNETs compared to normal pituitary gland, with heterogeneous intracellular localisation. Higher levels of FLNA expression were observed in tumours with invasive characteristics. These results underline the crucial roles of FLNA as a modulator of pathological markers and as a potential prognostic marker in pituitary tumours.

The insulin-like growth factor 2 (IGF2) promotes cell growth by overactivating the IGF system in an autocrine loop in adrenocortical carcinomas (ACCs). The cytoskeleton protein filamin A (FLNA) acts as a repressor of IGF2 mitogenic signalling in ACC cells. The aims of this study were to test FLNA expression by immunohistochemistry in 119 ACCs and 26 adrenocortical adenomas (ACAs) and to evaluate its relationship with clinicopathological features and outcome in ACCs. We found that 71.4% of ACCs did not express FLNA, whereas FLNA absence was a rare event in ACAs (15.4%, p < 0.001 vs. ACCs). In addition, the expression of FLNA was associated with a less aggressive tumour behaviour in ACCs. Indeed, the subgroup of ACCs with high FLNA showed a lower ENSAT stage, Weiss score, and S-GRAS score compared to ACCs with low FLNA expression ( p < 0.05). Moreover, patients with high FLNA had a longer overall survival than those with low FLNA ( p < 0.05). In conclusion, our data suggest that FLNA may represent a "protective" factor in ACCs, and the integration of FLNA immunohistochemical expression in ACC tissues along with other clinical and molecular markers could be helpful to improve diagnostic accuracy and prognosis prediction in ACCs.

Whereas truncating variants of the giant protein Titin (TTNtv) are the main cause of familial dilated cardiomyopathy (DCM), recently Filamin C truncating variants (FLNCtv) were identified as a cause of arrhythmogenic cardiomyopathy (ACM). Our aim was to characterize and compare clinical and MRI features of TTNtv and FLNCtv in the Belgian population. In index patients referred for genetic testing of ACM/DCM, FLNCtv and TTNtv were found in 17 (3.6%) and 33 (12.3%) subjects, respectively. Further family cascade screening yielded 24 and 19 additional truncating variant carriers in FLNC and TTN, respectively. The main phenotype was ACM in FLNCtv carriers whereas TTNtv carriers showed either an ACM or DCM phenotype. Non-sustained Ventricular Tachycardia was frequent in both populations. MRI data, available in 28/40 FLNCtv and 32/52 TTNtv patients, showed lower Left Ventricular (LV) ejection fraction and lower LV strain in TTNtv patients (p < 0.01). Conversely, both the frequency (68% vs 22%) and extent of non-ischemic myocardial late gadolinium enhancement (LGE) was significantly higher in FLNCtv patients (p < 0.01). Hereby, ring-like LGE was found in 16/19 (84%) FLNCtv versus 1/7 (14%) of TTNtv patients (p < 0.01). In conclusion, a large number of FLNCtv and TTNtv patients present with an ACM phenotype but can be separated by cardiac MRI. Whereas FLNCtv patients often have extensive myocardial fibrosis, typically following a ring-like pattern, LV dysfunction without or limited replacement fibrosis is the common TTNtv phenotype., (© 2023. The Author(s), under exclusive licence to European Society of Human Genetics.)

Background: Dilated cardiomyopathy (DCM) can be caused by truncating variants in the filamin C gene (FLNC). A new pathogenic FLNC variant, c.6864&#95;6867dup, p.(Val2290Argfs∗23), was recently identified in Dutch patients with DCM., Objectives: The report aimed to evaluate the phenotype of FLNC variant carriers and to determine whether this variant is a founder variant., Methods: Clinical and genetic data were retrospectively collected from variant carriers. Cardiovascular magnetic resonance studies were reassessed. Haplotypes were reconstructed to determine a founder effect. The geographical distribution and age of the variant were determined., Results: Thirty-three individuals (of whom 23 [70%] were female) from 9 families were identified. Sudden cardiac death was the first presentation in a carrier at the age of 28 years. The median age at diagnosis was 41 years (range 19-67 years). The phenotype was heterogeneous. DCM with left ventricular dilation and reduced ejection fraction (<45%) was present in 11 (33%) individuals, 3 (9%) of whom underwent heart transplantation. Cardiovascular magnetic resonance showed late gadolinium enhancement in 13 (65%) of the assessed individuals, primarily in a ringlike distribution. Nonsustained ventricular arrhythmias were detected in 6 (18%), and 5 (15%) individuals received an implantable cardioverter-defibrillator. A shared haplotype spanning 2.1 Mb was found in all haplotyped individuals. The variant originated between 275 and 650 years ago., Conclusion: The pathogenic FLNC variant c.6864&#95;6867dup, p.(Val2290Argfs∗23) is a founder variant originating from the south of the Netherlands. Carriers are susceptible to developing heart failure and ventricular arrhythmias. The cardiac phenotype is characterized by ringlike late gadolinium enhancement, even in individuals without significantly reduced left ventricular function., (Copyright © 2023. Published by Elsevier Inc.)

We investigated the effect of stem cell marker dopamine receptor D2 (DRD2) on the proliferation of hormone-receptor-negative breast cancer cells. High-throughput DNA methylation sequencing on an 850 K chip was used to pre-screen breast cancer tissues with significant methylation differences. The expression of DRD2 in breast cancer and normal breast tissues, and clinical risk factors, were detected by pyrophosphoric acid validation and immunohistochemistry. In vitro and in vivo experiments verified the possible molecular signaling pathways. DRD2 promoter region was hypomethylated in hormone-receptor-negative breast cancer or with high-risk factors compared to the normal tissues. The proliferation of breast cancer cells was enhanced after DRD2 was upregulated and decreased after DRD2 was downregulated. In vivo experiments found that tumor growth and the expression of antigen KI-67 (Ki67) and the cluster of differentiation 31 (CD31) were improved by the overexpression of DRD2 and inhibited by the down expression of DRD2. In vivo and in vitro experiments demonstrated the phosphorylation of filamin A and extracellular signal-regulated kinase (FLNA-ERK) was influenced by the expression of DRD2, suggesting DRD2 plays a role in the FLNA-ERK signaling pathway. Methylation inhibitors (5-aza-2-deoxycytidine, 5-azadc) partially reversed the inhibitory effect of DRD2 down expression on cell proliferation, migration, and tumor growth in animal models, indicating that inhibition of DRD2 methylation promotes cancer development. This study demonstrated the DRD2 promoter region is hypomethylated in hormone-receptor-negative breast cancer or with high-risk factors. The methylation status of the DRD2 promoter and FLNA-ERK signaling pathway and the DRD2 expression in breast cancer treatment need to be considered., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Filamin-A-interacting protein 1 (FILIP1) is a structural protein that is involved in neuronal and muscle function and integrity and interacts with FLNa and FLNc. Pathogenic variants in filamin-encoding genes have been linked to neurological disorders (FLNA) and muscle diseases characterized by myofibrillar perturbations (FLNC), but human diseases associated with FILIP1 variants have not yet been described. Here, we report on five patients from four unrelated consanguineous families with homozygous FILIP1 variants (two nonsense and two missense). Functional studies indicated altered stability of the FILIP1 protein carrying the p.[Pro1133Leu] variant. Patients exhibit a broad spectrum of neurological symptoms including brain malformations, neurodevelopmental delay, muscle weakness and pathology and dysmorphic features. Electron and immunofluorescence microscopy on the muscle biopsy derived from the patient harbouring the homozygous p.[Pro1133Leu] missense variant revealed core-like zones of myofibrillar disintegration, autophagic vacuoles and accumulation of FLNc. Proteomic studies on the fibroblasts derived from the same patient showed dysregulation of a variety of proteins including FLNc and alpha-B-crystallin, a finding (confirmed by immunofluorescence) which is in line with the manifestation of symptoms associated with the syndromic phenotype of FILIP1opathy. The combined findings of this study show that the loss of functional FILIP1 leads to a recessive disorder characterized by neurological and muscular manifestations as well as dysmorphic features accompanied by perturbed proteostasis and myopathology., (© The Author(s) 2023. Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Developmental dysplasia of the hip (DDH), characterized by acetabular deformity that manifests from loose ligaments to complete dislocation of the hip, can cause notable pain and dysfunction and lead to hip dislocation, secondary fractures, scoliosis, and osteoarthritis of hip. Variants in FLNA may produce a spectrum of malformations in multiple organs, especially the skeleton. This study aimed to identify the genetic etiologies of DDH patients and provide genetic testing information for further diagnosis and treatment of DDH. We recruited a Chinese woman with DDH and her family members. Whole-exome sequencing was used to identify the patient's genetic etiologies. Protein models were used to analyze the pathogenic mechanism of the identified variants. A novel variant (c.3493T>G, p.C1165G) of FLNA was detected. The structural models of the mutant FLNA protein indicated that the variant would lose its sulfhydryl side chain and destroy the attraction between benzene rings and sulfhydryl. We reported a novel variant (c.3493T>G, p.C1165G) of FLNA in a Chinese woman with DDH. Our research outcome enriches the gene pool for hip dysplasia and emphasizes the pathogenicity of sulfhydryl side chain disruption in FLNA .

Spondylocarpotarsal synostosis (SCT) syndrome is a very rare and severe form of skeletal dysplasia. The hallmark features of SCT are disproportionate short stature, scoliosis, fusion of carpal and tarsal bones, and clubfoot. Other common manifestations are cleft palate, conductive and sensorineural hearing loss, joint stiffness, and dental enamel hypoplasia. Homozygous variants in FLNB are known to cause SCT. This study was aimed to investigate the phenotypic and genetic basis of unique presentation of SCT syndrome segregating in a consanguineous Pakistani family. Three of the four affected siblings evaluated had severe short stature, short trunk, short neck, kyphoscoliosis, pectus carinatum, and winged scapula. The subjects had difficulty in walking and gait problems and complained of knee pain and backache. Roentgenographic examination of the eldest patient revealed gross anomalies in the axial skeleton including thoracolumbar and cervical fusion of ribs, severe kyphoscoliosis, thoracic and lumbar lordosis, coxa valga, fusion of certain carpals and tarsals, and clinodactyly. The patients had normal faces and lacked other typical features of SCT like cleft palate, conductive and sensorineural hearing loss, joint stiffness, and dental enamel hypoplasia. Whole exome sequencing (WES) of two affected siblings led to the discovery of a rare stop-gain variant c.220C>T (p.(Gln74*)) in exon 1 of the FLNB gene. The variant was homozygous and segregated with the malformation in this family. This study reports extensive phenotypic variability in SCT and expands the mutation spectrum of FLNB ., (Copyright ©2023, Yale Journal of Biology and Medicine.)

The ZAK gene encodes two functionally distinct kinases, ZAKα and ZAKβ. Homozygous loss of function mutations affecting both isoforms causes a congenital muscle disease. ZAKβ is the only isoform expressed in skeletal muscle and is activated by muscle contraction and cellular compression. The ZAKβ substrates in skeletal muscle or the mechanism whereby ZAKβ senses mechanical stress remains to be determined. To gain insights into the pathogenic mechanism, we exploited ZAK-deficient cell lines, zebrafish, mice and a human biopsy. ZAK-deficient mice and zebrafish show a mild phenotype. In mice, comparative histopathology data from regeneration, overloading, ageing and sex conditions indicate that while age and activity are drivers of the pathology, ZAKβ appears to have a marginal role in myoblast fusion in vitro or muscle regeneration in vivo. The presence of SYNPO2, BAG3 and Filamin C (FLNC) in a phosphoproteomics assay and extended analyses suggested a role for ZAKβ in the turnover of FLNC. Immunofluorescence analysis of muscle sections from mice and a human biopsy showed evidence of FLNC and BAG3 accumulations as well as other myofibrillar myopathy markers. Moreover, endogenous overloading of skeletal muscle exacerbated the presence of fibres with FLNC accumulations in mice, indicating that ZAKβ signalling is necessary for an adaptive turnover of FLNC that allows for the normal physiological response to sustained mechanical stress. We suggest that accumulation of mislocalized FLNC and BAG3 in highly immunoreactive fibres contributes to the pathogenic mechanism of ZAK deficiency., (© The Author(s) 2023. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

Background: FLNC (filamin C), a member of the filamin family predominantly expressed in striated muscles, plays a crucial role in bridging the cytoskeleton and ECM (extracellular matrix) in cardiomyocytes, thereby maintaining heart integrity and function. Although genetic variants within the N-terminal ABD (actin-binding domain) of FLNC have been identified in patients with cardiomyopathy, the precise contribution of the actin-binding capability to FLNC's function in mammalian hearts remains poorly understood., Methods: We conducted in silico analysis of the 3-dimensional structure of mouse FLNC to identify key amino acid residues within the ABD that are essential for FLNC's actin-binding capacity. Subsequently, we performed coimmunoprecipitation and immunofluorescent assays to validate the in silico findings and assess the impact of these mutations on the interactions with other binding partners and the subcellular localization of FLNC. Additionally, we generated and analyzed knock-in mouse models in which the FLNC-actin interaction was completely disrupted by these mutations., Results: Our findings revealed that F93A/L98E mutations completely disrupted FLNC-actin interaction while preserving FLNC's ability to interact with other binding partners ITGB1 (β1 integrin) and γ-SAG (γ-sarcoglycan), as well as maintaining FLNC subcellular localization. Loss of FLNC-actin interaction in embryonic cardiomyocytes resulted in embryonic lethality and cardiac developmental defects, including ventricular wall malformation and reduced cardiomyocyte proliferation. Moreover, disruption of FLNC-actin interaction in adult cardiomyocytes led to severe dilated cardiomyopathy, enhanced lethality and dysregulation of key cytoskeleton components., Conclusions: Our data strongly support the crucial role of FLNC as a bridge between actin filaments and ECM through its interactions with actin, ITGB1, γ-SAG, and other associated proteins in cardiomyocytes. Disruption of FLN-actin interaction may result in detachment of actin filaments from the extracellular matrix, ultimately impairing normal cardiac development and function. These findings also provide insights into mechanisms underlying cardiomyopathy associated with genetic variants in FLNC ABD and other regions., Competing Interests: Disclosures J. Chen consults for LEXEO Therapeutics and Morphic Therapeutic. The other authors report no conflicts.

Ebola (EBOV) and Marburg viruses (MARV) cause severe hemorrhagic fever associated with high mortality rates in humans. A better understanding of filovirus-host interactions that regulate the EBOV and MARV lifecycles can provide biological and mechanistic insight critical for therapeutic development. EBOV glycoprotein (eGP) and MARV glycoprotein (mGP) mediate entry into host cells primarily by actin-dependent macropinocytosis. Here, we identified actin-binding cytoskeletal crosslinking proteins filamin A (FLNa) and B (FLNb) as important regulators of both EBOV and MARV entry. We found that entry of pseudotype psVSV-RFP-eGP, infectious recombinant rVSV-eGP-mCherry, and live authentic EBOV and MARV was inhibited in filamin A knockdown (FLNaKD) cells, but was surprisingly enhanced in filamin B knockdown (FLNbKD) cells. Mechanistically, our findings suggest that differential regulation of macropinocytosis by FLNa and FLNb likely contributes to their specific effects on EBOV and MARV entry. This study is the first to identify the filamin family of proteins as regulators of EBOV and MARV entry. These findings may provide insight into the development of new countermeasures to prevent EBOV and MARV infections., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Shepley-McTaggart et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Background: Truncating variants in filamin C (FLNC) can cause arrhythmogenic cardiomyopathy (ACM) through haploinsufficiency. Noncanonical splice-altering variants may contribute to this phenotype., Objective: The purpose of this study was to investigate the clinical and functional consequences of a recurrent FLNC intronic variant of uncertain significance (VUS), c.970-4A>G., Methods: Clinical data in 9 variant heterozygotes from 4 kindreds were obtained from 5 tertiary health care centers. We used in silico predictors and functional studies with peripheral blood and patient-specific induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). Isolated RNA was studied by reverse transcription polymerase chain reaction. iPSC-CMs were further characterized at baseline and after nonsense-mediated decay (NMD) inhibition, using quantitative polymerase chain reaction (qPCR), RNA-sequencing, and cellular electrophysiology. American College of Medical Genetics and Genomics (ACMG) criteria were used to adjudicate variant pathogenicity., Results: Variant heterozygotes displayed a spectrum of disease phenotypes, spanning from mild ventricular dysfunction with palpitations to severe ventricular arrhythmias requiring device shocks or progressive cardiomyopathy requiring heart transplantation. Consistent with in silico predictors, the c.970-4A>G FLNC variant activated a cryptic splice acceptor site, introducing a 3-bp insertion containing a premature termination codon. NMD inhibition upregulated aberrantly spliced transcripts by qPCR and RNA-sequencing. Patch clamp studies revealed irregular spontaneous action potentials, increased action potential duration, and increased sodium late current in proband-derived iPSC-CMs. These findings fulfilled multiple ACMG criteria for pathogenicity., Conclusion: Clinical, in silico, and functional evidence support the prediction that the intronic c.970-4A>G VUS disrupts splicing and drives ACM, enabling reclassification from VUS to pathogenic., (Copyright © 2023. Published by Elsevier Inc.)

Background: Periventricular nodular heterotopia (PNH), associated with FLNA mutations, is a rare clinical condition potentially associated with multiple systemic conditions, including cardiac, pulmonary, skeletal, and cutaneous diseases. However, due to a paucity of information in the literature, accurate prognostic advice cannot be provided to patients with the disease., Case Presentation: We report a 2-year-old female whose PNH was associated with a nonsense mutation in the q28 region of the X chromosome, in exon 31 of FLNA (c.5159dupA). The patient is currently seizure-free and has no congenital heart disease, lung disease or skeletal or joint issues, and her development is normal., Conclusions: FLNA-associated PNH is a genetically-heterogeneous disease, and the FLNA mutation, c.5159dupA (p.Tyr1720*) is a newly identified pathogenic variant. FLNA characterization will help the clinical diagnosis and treatment of PNH and provide individualized genetic counseling for patients., (© 2023. The Author(s).)

Variations in the gene encoding filamin-A-interacting protein 1 (FILIP1) were identified to be associated with a combination of neurological and muscular symptoms. While FILIP1 was shown to regulate motility of brain ventricular zone cells, a process important for corticogenesis, the function of the protein in muscle cells has been less well characterized. The expression of FILIP1 in regenerating muscle fibres predicted a role in early muscle differentiation. Here we analysed expression and localization of FILIP1 and its binding partners filamin-C (FLNc) and microtubule plus-end-binding protein EB3 in differentiating cultured myotubes and adult skeletal muscle. Prior to the development of cross-striated myofibrils, FILIP1 is associated with microtubules and colocalizes with EB3. During further myofibril maturation its localization changes, and FILIP1 localizes to myofibrillar Z-discs together with the actin-binding protein FLNc. Forced contractions of myotubes by electrical pulse stimulation (EPS) induce focal disruptions in myofibrils and translocation of both proteins from Z-discs to these lesions, suggesting a role in induction and/or repair of these structures. The immediate proximity of tyrosylated, dynamic microtubules and EB3 to lesions implies that also these play a role in these processes. This implication is supported by the fact that in nocodazole-treated myotubes that lack functional microtubules, the number of lesions induced by EPS is significantly reduced. In summary, we here show that FILIP1 is a cytolinker protein that is associated with both microtubules and actin filaments, and might play a role in the assembly of myofibrils and their stabilization upon mechanical stress to protect them from damage., (© 2023. The Author(s).)