Survival motor neuron protein 1 (SMN1) (SMN1)

Survival motor neuron protein 1 (SMN1) is a protein essential for the biogenesis of small nuclear ribonucleoproteins (snRNPs), which are core components of the spliceosome (UniProt P63162). It plays a pivotal role in pre-mRNA splicing and is also involved in the transport of mRNA within the axons of motor neurons (PubMed: 23459575). Deficiency of the SMN1 gene, typically due to homozygous deletion or mutation, results in Spinal Muscular Atrophy (SMA), a severe neuromuscular disorder characterized by the loss of alpha motor neurons (NIH: MedlinePlus). While the nearly identical SMN2 gene exists, it cannot fully compensate for the loss of SMN1 because a single nucleotide difference causes the exclusion of exon 7 in most of its transcripts, leading to a truncated, unstable protein (PubMed: 10369862). Modern therapeutics target this deficiency by either replacing the SMN1 gene via viral vector-mediated gene therapy or by using antisense oligonucleotides and small molecules to correct SMN2 splicing (FDA: Zolgensma, Spinraza, Evrysdi). These interventions aim to increase the cellular pool of functional SMN protein to prevent neuronal death and preserve muscle function. Monitoring treatment efficacy often involves measuring SMN protein levels or neurofilament light chain concentrations in biofluids (PubMed: 33164315). Safety considerations for these therapies include monitoring for hepatotoxicity, thrombocytopenia, and potential renal effects depending on the modality used.

Other names

SMNGemin-1Survival of motor neuron 1, telomericSMA1SMA2SMA3SMA4BCDDF1T-BCD

Gene replacement therapy restores the SMN1 gene, while antisense oligonucleotides and small molecules modulate SMN2 pre-mRNA splicing to include exon 7, thereby increasing functional SMN protein levels.