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Pediatric cardiomyopathy (CM) represents a group of rare, severe disorders that affect the myocardium. To date, the etiology and mechanisms underlying pediatric CM are incompletely understood, hampering accurate diagnosis and individualized therapy development. Here, we identified biallelic variants in the highly conserved flightless-I (FLII) gene in 3 families with idiopathic, early-onset dilated CM. We demonstrated that patient-specific FLII variants, when brought into the zebrafish genome using CRISPR/Cas9 genome editing, resulted in the manifestation of key aspects of morphological and functional abnormalities of the heart, as observed in our patients. Importantly, using these genetic animal models, complemented with in-depth loss-of-function studies, we provided insights into the function of Flii during ventricular chamber morphogenesis in vivo, including myofibril organization and cardiomyocyte cell adhesion, as well as trabeculation. In addition, we identified Flii function to be important for the regulation of Notch and Hippo signaling, crucial pathways associated with cardiac morphogenesis and function. Taken together, our data provide experimental evidence for a role for FLII in the pathogenesis of pediatric CM and report biallelic variants as a genetic cause of pediatric CM.

Background: Multiple acyl-CoA dehydrogenase deficiency (MADD), also known as glutaric aciduria II, is a rare autosomal recessively inherited disorder of inborn error of metabolism. It can mainly be presented in three phenotypes: severe neonatal onset with a dysmorphic feature, neonatal-onset without dysmorphic features, and less severe mild late-onset phenotype. Case presentation: A 34-year-old Saudi female previously healthy, Para 4, with severe metabolic acidosis, rhabdomyolysis intrapartum was presented to us. Her previous pregnancy history and deliveries were unremarkable; she has three healthy sons. Since the beginning of this pregnancy, she complained of fatigability and muscle weakness which was progressive with time. At 36 weeks of gestation, she was presented to the emergency room with labor pain. She deteriorated rapidly with significant drowsiness. Her arterial blood gas showed severe metabolic acidosis with a high anion gap and normal lactate. She was intubated and underwent emergency cesarean delivery under general anesthesia. After the operation, she was sent to the intensive care unit. She passed away after a few days. A molecular test confirmed the diagnosis of MADD. Conclusion: First, late-onset MADD is a rare, underdiagnosed disease in adults. Second, the biochemical diagnosis of late-onset MADD is challenging as it mimics medium chain acyl CoA dehydrogenase deficiency which makes the molecular diagnosis essential for diagnosis. Third, for any unexplained myopathy, cardiac dysfunction, encephalopathy, or metabolic acidosis, metabolic disorders must be considered as early consultation with metabolic service. [JBCGenetics 2022; 5(1.000): 20-24]

Abstract Succinyl‐CoA:3‐ketoacid CoA transferase (SCOT) deficiency is an inherited metabolic disease caused by mutated OXCT1 gene resulting in recurrent ketoacidosis. Analysis of longitudinal data in such an ultra‐rare disease is warranted to delineate genotype–phenotype correlations and management outcome. A retrospective analysis of 17 patients, from nine unrelated families, with SCOT deficiency who were followed up in the Medical Genetics Clinic at King Faisal Specialist Hospital and Research Centre was conducted. All the patients were homozygous for p.R468C in OXCT1 gene. Most of the patients (n = 15, 88.2%) were symptomatic presenting with recurrent ketoacidosis, the onset of which ranged from 6 months to 4 years (median 2 years). A striking inter‐ and intrafamilial variability that ranged from being entirely asymptomatic to death during the first episode. All patients were instructed to avoid fasting, restrict protein in diet, and receive carnitine supplementation. However, there was no correlation between following instructions of chronic management and outcome. Most of the patients had their crises resolved and all of them had normal neurodevelopmental outcome. Our data suggest that SCOT deficiency caused by homozygous p.R468C has variable clinical presentation and incomplete penetrance. The apparent lack of correlation between protein restriction +/− carnitine supplementation and outcome suggests that chronic dietary restriction may not be warranted. However, a longer follow‐up on larger and heterogenous cohort of cases is needed before a clear conclusion on the long‐term management can be reached.

The eukaryotic CDC45/MCM2-7/GINS (CMG) helicase unwinds the DNA double helix during DNA replication. The GINS subcomplex is required for helicase activity and is, therefore, essential for DNA replication and cell viability. Here, we report the identification of 7 individuals from 5 unrelated families presenting with a Meier-Gorlin syndrome–like (MGS-like) phenotype associated with hypomorphic variants of GINS3, a gene not previously associated with this syndrome. We found that MGS-associated GINS3 variants affecting aspartic acid 24 (D24) compromised cell proliferation and caused accumulation of cells in S phase. These variants shortened the protein half-life, altered key protein interactions at the replisome, and negatively influenced DNA replication fork progression. Yeast expressing MGS-associated variants of PSF3 (the yeast GINS3 ortholog) also displayed impaired growth, S phase progression defects, and decreased Psf3 protein stability. We further showed that mouse embryos homozygous for a D24 variant presented intrauterine growth retardation and did not survive to birth, and that fibroblasts derived from these embryos displayed accelerated cellular senescence. Taken together, our findings implicate GINS3 in the pathogenesis of MGS and support the notion that hypomorphic variants identified in this gene impaired cell and organismal growth by compromising DNA replication.

Hypertrophic cardiomyopathy (HCM) is a group of heterogeneous disorders that are most commonly passed on in a heritable manner. It is a relatively rare disease around the globe, but due to increased rates of consanguinity within the Kingdom of Saudi Arabia, we speculate a high incidence of undiagnosed cases. The aim of this paper is to elucidate a systematic approach in dealing with HCM patients and since HCM has variable presentation, we have summarized differentials for diagnosis and how different subtypes and genes can have an impact on the clinical picture, management and prognosis. Moreover, we propose a referral multi-disciplinary team HCM-Family Unit in Saudi Arabia and an integrated role in a network between King Faisal Hospital and Inherited and Rare Cardiovascular Disease Unit-Monaldi Hospital, Italy (among the 24 excellence centers of the European Reference Network (ERN) GUARD-Heart). Graphical Abstract

Internal ribosome entry site (IRES) sequences have become a valuable tool in the construction of gene transfer and therapeutic vectors for multi-cistronic gene expression from a single mRNA transcript. The optimal conditions for effective use of this sequence to construct a functional expression vector are not precisely defined but it is generally assumed that the internal ribosome entry site dependent expression of the second gene in such as cassette is less efficient than the cap-dependent expression of the first gene. Mainly tailoring inter-cistronic sequence significantly enhances IRES dependent second gene expression in bicistronic vector further in construction of optimised cassette for gene therapy of familial hypercholesterolemia. We tailored the size of the inter-cistronic spacer sequence at the 5′ region of the internal ribosome entry site sequence using sequential deletions and demonstrated that the expression of the 3′ gene can be significantly increased to similar levels as the cap-dependent expression of the 5’ gene. Maximum expression efficiency of the downstream gene was obtained when the spacer is composed of 18–141 base pairs. In this case a single mRNA transcriptional unit containing both the first and the second Cistron was detected. Whilst constructs with spacer sequences of 216 bp or longer generate a single transcriptional unit containing only the first Cistron. This suggests that long spacers may affect transcription termination. When the spacer is 188 bp, both transcripts were produced simultaneously in most transfected cells, while a fraction of them expressed only the first but not the second gene. Expression analyses of vectors containing optimised cassettes clearly confirm that efficiency of gene transfer and biological activity of the expressed transgenic proteins in the transduced cells can be achieved. Furthermore, Computational analysis was carried out by molecular dynamics (MD) simulation to determine the most emerges as viable containing specific binding site and bridging of 5′ and 3′ ends involving direct RNA-RNA contacts and RNA-protein interactions. These results provide a mechanistic basis for translation stimulation and RNA resembling for the synergistic stimulation of cap-dependent translation. Keywords: Internal ribosome entry site, IRES, Gene therapy, Inter-cistronic sequences, MD simulation, Protein structure modeling, Familial hypercholesterolemia

Abstract Background Rubinstein-Taybi syndrome (RSTS) Type 1 (OMIM 180849) is characterized by three main features: intellectual disability; broad and frequently angulated thumbs and halluces; and characteristic facial dysmorphism. Case presentation We report on a Saudi boy with RSTS Type 1 and the following distinct features: a midline notch of the upper lip, a bifid tip of the tongue, a midline groove of the lower lip, plump fingers with broad / flat fingertips, and brachydactyly. The child was found to be heterozygous in the CREBBP gene for a sequence variant designated c.4963del, which is predicted to result in premature protein termination p.Leu1655Cysfs*89. The child and his father were also found to be heterozygous in the EP300 gene for a sequence variant designated c.586A > G, which is predicted to result in the amino-acid substitution p.Ile196Val. Conclusion Our report expands the clinical spectrum of RSTS to include several distinct facial and limb features. The variant of the CREBBP gene is known to be causative of RSTS Type 1. The variant in the EP300 gene is benign since the father carried the same variant and exhibited no abnormalities. However, functional studies are required to investigate if this benign EP300 variant influences the phenotype in the presence of disease-causing CREBBP gene mutations.

The classic Rubinstein–Taybi syndrome Type 1 (RSTS1, OMIM 180849) is caused by heterozygous mutations or deletions of the CREBBP gene. Herein, we describe the case of a Saudi boy with chromosome 16p13.3 contiguous gene deletion syndrome (OMIM 610543) including the SLX4, DNASE1, TRAP1, and CREBBP genes, but presenting with a relatively mild RSTS1 syndrome phenotype. Compared with previously reported cases with severe phenotypes associated with 16p13.3 contiguous gene deletions, our patient had partial deletion of the CREBBP gene (with a preserved 5′ region), which might explain his relatively mild phenotype.

Infantile-Onset Pompe Disease (IOPD) is an autosomal recessive disorder of glycogen metabolism resulting from deficiency of the lysosomal hydrolase acid α-glucosidase encoded by GAA gene. Affected infants present before the age of 12 months with hypotonia, muscle weakness, and hypertrophic cardiomyopathy. Enzyme replacement therapy (ERT) has been shown to improve survival, cardiac mass, and motor skills. In this work, we aim to illustrate the genotypes of IOPD and the outcome of ERT in our population. The medical records of infants with confirmed diagnosis of IOPD who received ERT were reviewed. Eighteen infants (7 males, 11 females) were included in the study. The median age at presentation was 2 months and the median age at the start of ERT was 4.5 months. Fifteen (83.3%) infants died with a median age at death of 12 months. The 3 alive infants (whose current ages are 6½ years, 6 years, and 10 years), who were initiated on ERT at the age of 3 weeks, 5 months, and 8 months respectively, has had variable response with requirement of assisted ventilation in one child and tracheostomy in another child. All infants were homozygous for GAA mutations except one infant who was compound heterozygous. All infants (n = 8) with truncating mutations died. Our work provides insight into the correlation of genotypes and outcome of ERT in IOPD in Saudi Arabia. Our data suggest that early detection of cases, through newborn screening, and immunomodulation before the initiation of ERT may improve the outcome of ERT in Saudi infants with IOPD. Keywords: Pompe disease, Glycogen storage disease type II, Enzyme replacement therapy, GAA

Abstract Background Quick genetic diagnosis of a patient with congenital heart disease (CHD) is quite important for proper health care and management. Copy number variations (CNV), chromosomal imbalances and rearrangements have been frequently associated with CHD. Previously, due to limitations of microscope based standard karyotyping techniques copious CNVs and submicroscopic imbalances could not be detected in numerous CHD patients. The aim of our study is to identify cytogenetic abnormalities among the selected CHD cases (n = 17) of the cohort using high density oligo arrays. Results Our screening study indicated that six patients (~35%) have various cytogenetic abnormalities. Among the patients, only patient 2 had a duplication whereas the rest carried various deletions. The patients 1, 4 and 6 have only single large deletions throughout their genome; a 3.2 Mb deletion on chromosome 7, a 3.35 Mb deletion on chromosome 3, and a 2.78 Mb a deletion on chromosome 2, respectively. Patients 3 and 5 have two deletions on different chromosomes. Patient 3 has deletions on chromosome 2 (2q24.1; 249 kb) and 16 (16q22.2; 1.8 Mb). Patient 4 has a 3.35 Mb an interstitial deletion on chromosome 3 (3q13.2q13.31). Based on our search on the latest available literature, our study is the first inclusive array CGH evaluation on Saudi cohort of CHD patients. Conclusions This study emphasizes the importance of the arrays in genetic diagnosis of CHD. Based on our results the high resolution arrays should be utilized as first-tier diagnostic tool in clinical care as suggested before by others. Moreover, previously evaluated negative CHD cases (based on standard karyotyping methods) should be re-examined by microarray based cytogenetic methods.

Our knowledge of disease genes in neurological disorders is incomplete. With the aim of closing this gap, we performed whole-exome sequencing on 143 multiplex consanguineous families in whom known disease genes had been excluded by autozygosity mapping and candidate gene analysis. This prescreening step led to the identification of 69 recessive genes not previously associated with disease, of which 33 are here described (SPDL1, TUBA3E, INO80, NID1, TSEN15, DMBX1, CLHC1, C12orf4, WDR93, ST7, MATN4, SEC24D, PCDHB4, PTPN23, TAF6, TBCK, FAM177A1, KIAA1109, MTSS1L, XIRP1, KCTD3, CHAF1B, ARV1, ISCA2, PTRH2, GEMIN4, MYOCD, PDPR, DPH1, NUP107, TMEM92, EPB41L4A, and FAM120AOS). We also encountered instances in which the phenotype departed significantly from the established clinical presentation of a known disease gene. Overall, a likely causal mutation was identified in >73% of our cases. This study contributes to the global effort toward a full compendium of disease genes affecting brain function.

Familial hypercholesterolemia (FH) is an autosomal dominant disease most often caused by mutations in the low-density lipoprotein receptor (LDLR) gene, which consists of 18 exons spanning 45 kb and codes for a precursor protein of 860 amino acids. Mutations in the LDLR gene lead to a reduced hepatic clearance of LDL as well as a high risk of coronary artery disease (CAD) and sudden cardiac death (SCD). Recently, LDLR transgenes have generated interest as potential therapeutic agents. However, LDLR packaging using a lentiviral vector (LVV) system pseudotyped with a vesicular stomatitis virus (VSV)-G envelope is not efficient. In this study, we modified the LVV system to improve transduction efficiency and investigated the LDLR regions responsible for transduction inhibition. Transduction efficiency of 293T cells with a 5′-LDLReGFP-3′ fusion construct was only 1.55% compared to 42.32% for the eGFP construct. Moreover, co-expression of LDLR affected eGFP packaging. To determine the specific region of the LDLR protein responsible for packaging inhibition, we designed constructs with mutations or sequential deletions at the 3′ and 5′ ends of LDLR cDNA. All constructs except one without the ligand-binding domain (LBD) (pWoLBD−eGFP) resulted in low transduction efficiency, despite successful packaging of viral RNA in the VSV envelope, as confirmed through RT-PCR. When we evaluated a direct interaction between LDLR and the VSV envelope glycoprotein using MD simulation and protein−protein interactions, we uncovered Val119, Thr120, Thr67, and Thr118 as exposed residues in the LDLR receptor that interact with the VSV protein. Together, our results suggest that the LBD of LDLR interacts with the VSV-G protein during viral packaging, which significantly reduces transduction efficiency.