question: What is the molecular pathogenesis of Spinal Muscular Atrophy?
answer: Spinal muscular atrophy is an autosomal recessive neurodegenerative disease characterised by degeneration of spinal cord motor neurons, atrophy of skeletal muscles, and generalised weakness. It is caused by homozygous disruption of the survival motor neuron 1 (SMN1) gene by deletion, conversion, or mutation, resulting in downregulated biogenesis of uridine-rich small nuclear RNAs (U snRNAs), which are major components of the splicing machinery.