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Kinesins are canonical molecular motors but can also function as modulators of intracellular signaling. KIF26A, an unconventional kinesin that lacks motor activity, inhibits growth-factor-receptor-bound protein 2 (GRB2)- and focal adhesion kinase (FAK)-dependent signal transduction, but its functions in the brain have not been characterized. We report a patient cohort with biallelic loss-of-function variants in KIF26A, exhibiting a spectrum of congenital brain malformations. In the developing brain, KIF26A is preferentially expressed during early- and mid-gestation in excitatory neurons. Combining mice and human iPSC-derived organoid models, we discovered that loss of KIF26A causes excitatory neuron-specific defects in radial migration, localization, dendritic and axonal growth, and apoptosis, offering a convincing explanation of the disease etiology in patients. Single-cell RNA sequencing in KIF26A knockout organoids revealed transcriptional changes in MAPK, MYC, and E2F pathways. Our findings illustrate the pathogenesis of KIF26A loss-of-function variants and identify the surprising versatility of this non-motor kinesin.

The apical Par complex, which contains atypical protein kinase C (aPKC), Bazooka (Par-3), and Par-6, is required for establishing polarity during asymmetric division of neuroblasts in Drosophila, and its activity depends on L(2)gl. We show that loss of Ankle2, a protein associated with microcephaly in humans and known to interact with Zika protein NS4A, reduces brain volume in flies and impacts the function of the Par complex. Reducing Ankle2 levels disrupts endoplasmic reticulum (ER) and nuclear envelope morphology, releasing the kinase Ballchen-VRK1 into the cytosol. These defects are associated with reduced phosphorylation of aPKC, disruption of Par-complex localization, and spindle alignment defects. Importantly, removal of one copy of ballchen or l(2)gl suppresses Ankle2 mutant phenotypes and restores viability and brain size. Human mutational studies implicate the above-mentioned genes in microcephaly and motor neuron disease. We suggest that NS4A, ANKLE2, VRK1, and LLGL1 define a pathway impinging on asymmetric determinants of neural stem cell division.

BACKGROUND. Arthrogryposis, defined as congenital joint contractures in 2 or more body areas, is a clinical sign rather than a specific disease diagnosis. To date, more than 400 different disorders have been described that present with arthrogryposis, and variants of more than 220 genes have been associated with these disorders; however, the underlying molecular etiology remains unknown in the considerable majority of these cases. METHODS. We performed whole exome sequencing (WES) of 52 patients with clinical presentation of arthrogryposis from 48 different families. RESULTS. Affected individuals from 17 families (35.4%) had variants in known arthrogryposis-associated genes, including homozygous variants of cholinergic y nicotinic receptor (CHRNG, 6 subjects) and endothelin converting enzyme-like 1 (ECEL1, 4 subjects). Deleterious variants in candidate arthrogryposis-causing genes (fibrillin 3 [FBNS], myosin IXA [MYO9A], and pleckstrin and Sec7 domain containing 3 [PSDS]) were identified in 3 families (6.2%). Moreover, in 8 families with a homozygous mutation in an arthrogryposis-associated gene, we identified a second locus with either a homozygous or compound heterozygous variant in a candidate gene (myosin binding protein C, fast type [MYBPC2] and vacuolar protein sorting 8 [UPSS], 2 families, 4.2%) or in another disease-associated genes (6 families, 12.5%), indicating a potential mutational burden contributing to disease expression. CONCLUSION. In 58.3% of families, the arthrogryposis manifestation could be explained by a molecular diagnosis; however, the molecular etiology in subjects from 20 families remained unsolved by WES. Only 5 of these 20 unrelated subjects had a clinical presentation consistent with amyoplasia; a phenotype not thought to be of genetic origin. Our results indicate that increased use of genome-wide technologies will provide opportunities to better understand genetic models for diseases and molecular mechanisms of genetically heterogeneous disorders, such as arthrogryposis. FUNDING. This work was supported in part by US National Human Genome Research Institute (NHGRI)/National Heart, Lung, and Blood Institute (NHLBI) grant U54HG006542 to the Baylor-Hopkins Center for Mendelian Genomics, and US National Institute of Neurological Disorders and Stroke (NINDS) grant R01NS058529 to J.R. Lupski., Introduction Arthrogryposis, also known as arthrogryposis multiplex congenita, is clinically defined as congenital joint contractures or movement restriction in multiple body areas. It should be distinguished from isolated congenital contractures [...]

Cornelia de Lange syndrome (CdLS) is a genetically heterogeneous disorder that presents with extensive phenotypic variability, including facial dysmorphism, developmental delay/intellectual disability (DD/ID), abnormal extremities, and hirsutism. About 65% of patients harbor mutations in genes that encode subunits or regulators of the cohesin complex, including NIPBL, SMC1A, SMC3, RAD21, and HDAC8. Wiedemann-Steiner syndrome (WDSTS), which shares CdLS phenotypic features, is caused by mutations in lysine-specific methyltransferase 2A (KMT2A). Here, we performed whole-exome sequencing (WES) of 2 male siblings clinically diagnosed with WDSTS; this revealed a hemizygous, missense mutation in SMC1A that was predicted to be deleterious. Extensive clinical evaluation and WES of 32 Turkish patients clinically diagnosed with CdLS revealed the presence of a de novo heterozygous nonsense KMT2A mutation in 1 patient without characteristic WDSTS features. We also identified de novo heterozygous mutations in SMC3 or SMC1A that affected RNA splicing in 2 independent patients with combined CdLS and WDSTS features. Furthermore, in families from 2 separate world populations segregating an autosomal-recessive disorder with CdLS-like features, we identified homozygous mutations in TAF6, which encodes a core transcriptional regulatory pathway component. Together, our data, along with recent transcriptome studies, suggest that CdLS and related phenotypes may be 'transcriptomopathies' rather than cohesinopathies., Introduction Cornelia de Lange syndrome (CdLS, MIM # 122470, MIM # 300590, MIM # 610759, MIM # 614701, and MIM # 300882) was initially described by Brachmann in 1916 and [...]

Dubowitz syndrome (DubS) is considered a recognizable syndrome characterized by a distinctive facial appearance and deficits in growth and development. There have been over 200 individuals reported with Dubowitz or a "Dubowitz‐like" condition, although no single gene has been implicated as responsible for its cause. We have performed exome (ES) or genome sequencing (GS) for 31 individuals clinically diagnosed with DubS. After genome‐wide sequencing, rare variant filtering and computational and Mendelian genomic analyses, a presumptive molecular diagnosis was made in 13/27 (48%) families. The molecular diagnoses included biallelic variants in SKIV2L, SLC35C1, BRCA1, NSUN2; de novo variants in ARID1B, ARID1A, CREBBP, POGZ, TAF1, HDAC8, and copy‐number variation at1p36.11(ARID1A), 8q22.2(VPS13B), Xp22, and Xq13(HDAC8). Variants of unknown significance in known disease genes, and also in genes of uncertain significance, were observed in 7/27 (26%) additional families. Only one gene, HDAC8, could explain the phenotype in more than one family (N = 2). All but two of the genomic diagnoses were for genes discovered, or for conditions recognized, since the introduction of next‐generation sequencing. Overall, the DubS‐like clinical phenotype is associated with extensive locus heterogeneity and the molecular diagnoses made are for emerging clinical conditions sharing characteristic features that overlap the DubS phenotype. [ABSTRACT FROM AUTHOR]

Background: To assessFactor V Leiden (FVL)(rs6025),Prothrombin G20210A(rs1799963),MTHFR C677T(rs1801133), andMTHFR A1298C(rs1801131) gene mutations as risk factors in the development of retinopathy of prematurity (ROP). Materials and methods: A total of 105 children were included in this cross-sectional study. Patients were divided into two groups. The study group consisted of 55 infants with a history of ROP and the control group comprised 50 healthy infants with term birth. All subjects were screened for the presence of certain mutations (FVL, Prothrombin G20210A, MTHFR C677TandMTHFR A1298C) by Real-Time PCR at 1 year of age. Results: The mean gestational age (GA) and birth weight (BW) of the study group were, 28.65 ± 2.85 weeks and 1171 ± 385.74 g, respectively. There were no significant differences of genotype and allele frequency ofProthrombin G20210A, MTHFR A1298CandMTHFR C677Tbetween the study and control groups (p> 0.05). Eight children (14.5 %) had heterozygous and one child (1.8%) had homozygousFVLmutation in the study group. One child (2%) in the control group had heterozygousFVLmutation. There was statistically significant differences ofFVLallele and genotype frequencies between the groups (p< 0.05). Conclusions: The prevalence ofFVLpolymorphism (16.3 %) was higher in ROP patients than control subjects in this Turkish cohort. We suggest a possible association ofFVLmutation with ROP at the end of the study. [ABSTRACT FROM AUTHOR]

Objectives: Our aim was to evaluate ultrasound findings and perinatal outcome after prenatal diagnosis of lymphangioma.Methods: This was a retrospective case series study. We searched the archives of our ultrasound database at our center for cases with the prenatal diagnosis of the lymphangioma in the period between January 2008 and November 2014. We described maternal, fetal and perinatal variables for all cases.Results: Nine fetuses with lymphangioma were identified. All cases were diagnosed during the second and third trimesters with the average gestational age of 22.6 ± 3.9 weeks. The average diameter of lymphangioma was 55.4 ± 20.1 mm at the time of diagnosis. Five fetuses (55.6%) had lymphangioma on the neck, and four fetuses (44.4%) had lymphangioma on other localizations. Normal fetal karyotype was detected in all cases. There were a total of six live births, one intrauterine death and two medical terminations of pregnancy following the diagnosis of lymphangioma. No abnormal Doppler finding or hydrops were detected in the antenatal follow-up of remaining six cases.Conclusion: The risk of chromosomal abnormalities is very low in pregnancies with isolated lymphangioma. The outcome of pregnancies with lymphangioma is generally favorable and prognosis depends on their locations and size. [ABSTRACT FROM AUTHOR]

Neural tube defects arise from failure of embryonic development in 4th-6th weeks. Defects of the cranial region (anencephaly) and lower spine (open spina bifida, myelomeningocele) are the most common neural tube defects. The cases of two male patients aged 9 and 12 years with spina bifida and renal anomaly are described. The first patient presented with unilateral renal agenesis, spina bifida, hydrocephalus, and plegia. The second presented with spina bifida, hydrocephalus, plegia, polydactyly, anal atresia, and unilateral renal hypoplasia. Though both patients had the same neural tube defect, findings differed. [ABSTRACT FROM AUTHOR]

Whole-exome sequencing (WES) is a type of disruptive technology that has tremendous influence on human and clinical genetics research. An efficient and cost-effective method, WES is now widely used as a diagnostic tool for identifying the molecular basis of genetic syndromes that are often challenging to diagnose. Here we report a patient with a clinical diagnosis of cerebro-facio-thoracic dysplasia (CFTD; MIM#213980) in whom we identified a homozygous splice-site mutation in the transmembrane and coiled-coil domains 1 (TMCO1) gene using WES. TMCO1 mutations cause craniofacial dysmorphism, skeletal anomalies characterized by multiple malformations of the vertebrae and ribs, and intellectual disability (MIM#614132). A retrospective review revealed that clinical manifestations of both syndromes are very similar and overlap remarkably. We propose that mutations of TMCO1 are not only responsible for craniofacial dysmorphism, skeletal anomalies and mental retardation syndrome but also for CFTD. [ABSTRACT FROM AUTHOR]

Caudal regression syndrome (CRS) is part of a spectrum of conditions that include imperforate anus, sacral agenesis and syringomyelia. Most cases of caudal regression are sporadic or associated with gestational diabetes. We describe a case of characteristic CRS in a patient who with hydrocephalus, esophageal atresia, anal atresia, hypoplastic kidneys, pes equinovarus, and the absence of a sacrum and coccyx. [ABSTRACT FROM AUTHOR]

Objective: Our aim was to evaluate ultrasound findings and perinatal outcome after prenatal diagnosis of lymphangiomas Methods: We searched the archives of our ultrasound database at our center for cases with a prenatal diagnosis of the lymphangioma in the period from 2008 to 2013. We described maternal, fetal and perinatal variables for all cases. Results: Seven fetuses were diagnosed in our center as having the lymphangioma between 2008 and 2013. All cases were diagnosed during the second and third trimesters with the average gestational age of 24±4 weeks. The average diameter of lymphangioma were 58.4±22.5 mm at time of diagnosis. Four of the seven fetuses (57.1%) had lymphangioma in the neck. Three of the seven fetuses (42.9%) had lymphangioma in locations other than fetal neck. Fetal karyotyping was normal in all cases. Two of these fetuses was terminated. No abnormal doppler finding or hydrops were detected in the antenatal follow-up of remaining five cases. Cesarean section was performed due to dystocia for all cases. Conclusion: The risk of chromosomal abnormalities is very low in pregnancies with isolated lymphangioma. The outcome of pregnancies with lymphangioma is generally favorable and prognosis depends on their locations and size. [ABSTRACT FROM AUTHOR]