FAM126A

FAM126A, or family with sequence similarity 126 member A, is a protein-coding gene in humans. The gene encodes a protein commonly referred to as hyccin. The biological function of FAM126A is not fully understood, but it is implicated in the development and maintenance of myelin in the central nervous system.

Clinical significance: Pathogenic variants in FAM126A cause Hypomyelination with Congenital Cataracts (HCC), an autosomal recessive neurodevelopmental disorder. Affected individuals typically show early-onset hypomyelination on brain imaging, intellectual disability or developmental delay, motor dysfunction, and congenital or early cataracts. The condition reflects impaired formation or maintenance of myelin rather than a primary neuronal defect.

Genetics and structure: The syndrome results from loss-of-function variants in FAM126A. The protein's precise cellular role remains to be clarified, but evidence points to an essential function in central nervous system myelin formation. Expression studies indicate that FAM126A is expressed in the brain and detectable in other tissues as well.

Research status: Because the function of Hyccin is not fully defined, research continues to elucidate its molecular interactions, localization, and how its disruption leads to hypomyelination. Studies in model systems are used to investigate the pathways involved and to explore potential therapeutic approaches.