Spectrins are common components of cytoskeletons, binding to cytoskeletal elements and the plasma membrane, allowing proper localization of essential membrane proteins, signal transduction, and cellular scaffolding. Spectrins are assembled from α and β subunits, encoded by SPTA1 and SPTAN1 (α) and SPTB, SPTBN1, SPTBN2, SPTBN4, and SPTBN5 (β). Pathogenic variants in various spectrin genes are associated with erythroid cell disorders (SPTA1, SPTB) and neurologic disorders (SPTAN1, SPTBN2, and SPTBN4), but no phenotypes have been definitively associated with variants in SPTBN1 or SPTBN5. Through exome sequencing and case matching, we identified seven unrelated individuals with heterozygous SPTBN1 variants: two with de novo missense variants and five with predicted loss‐of‐function variants (found to be de novo in two, while one was inherited from a mother with a history of learning disabilities). Common features include global developmental delays, intellectual disability, and behavioral disturbances. Autistic features (4/6) and epilepsy (2/7) or abnormal electroencephalogram without overt seizures (1/7) were present in a subset. Identification of loss‐of‐function variants suggests a haploinsufficiency mechanism, but additional functional studies are required to fully elucidate disease pathogenesis. Our findings support the essential roles of SPTBN1 in human neurodevelopment and expand the knowledge of human spectrinopathy disorders.
Focal dermal hypoplasia (FDH, Goltz syndrome), is an X-linked dominant mesoectodermal developmental disorder, involving skin, skeleton, eyes, teeth, and other organs. Mutations in PORCN, which stimulates the secretion of wingless family signal proteins, are found in FDH patients. A female fetus presented at 34 weeks gestation with interuterine growth restriction (IUGR), asymmetry, limb anomalies, microphthalmia, and lung anomaly. Focal dermal hypoplasia was confirmed at birth, with hypoplastic areas of skin, malformation of the limbs, diaphragmatic hernia, and ocular anomalies. Mutation analysis of PORCN revealed a nonsense mutation-Y359X. She presented natal teeth, an unexpected feature considering the role of the Wnt pathway in tooth development.
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