SMN1

Spinal muscular atrophy (SMA) is a generic, lethal condition characterized by an inability to will voluntary muscles as desired. The motor neurons responsible for exciting muscular contractions are deficient and loss of usage in voluntary muscles results in their atrophy. Characterized early in life, children with SMA exhibit difficulty in early voluntary muscular activities such as crawling, sucking, imitation of facial expressions, and breathing. Three stage of SMA exist: SMA I for children younger than six months, SMA II for children between 6-18 months of age, and SMA III for all remaining children.

For many affected individuals, life expectancy depends upon the time in which symptoms began. The longer it takes for SMA symptoms to manifest in children, the higher the probability that the individual will live longer. Children with the earliest symptoms of SMA (SMA I) live an average of two years before passing away. Patients with SMA II tend to live until early adulthood. SMA II and SMA III patients may potentially have the average lifespan of healthy individuals with treatments.

Diagnosing the disease begins with visual diagnosis. Most SMA affected individuals exhibit symptoms shortly after birth or early toddlerhood. Babies may exhibit difficulty in sucking, responding to external stimuli, mirroring facial expressions, breathing, and crawling within the first six months of life. Worried parents visit their local physician who recommends them to various specialists. A visit to the neurologist will prompt DNA testing for common neuro-genetic disorders.

As with many neurological diseases, SMA has no known cure. However, treatments do exist to prevent the progression of SMA. Patients with SMA are subject of vari...

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... SMN1 is located region 1, band 3, sub-band 2 in the long arm of chromosome 13. SMN1 is flanked by two genes throughout the chromosome: NAIP and and SERF1A. Originally cloned in 1995 by Lefebvre et al., the identified SMA locus was cloned into a yeast artificial clone (YAC). The YAC was then probed for any sequences repeats. The SMN1 & 2 500 kb repeats were located within YAC of chromosome 5.

Several single-nucleotide polymorphisms (snp’s) are contained within SMN1, many of the snp’s are SMN family related snps: snps ID’s VAR_005617, VAR_034803, VAR_034809 are just a few of the 83 snps located within the SMN1 gene.

A SMN1 ortholog exists in Drosophila similarly named SMN and is located in 73A9-73A9 of the Drosophila genome. A Drosophila stasimon ortholog exists in humans termed TMEM41B, located region 1, band 5, sub-band 4 in the short band of chromosome 11.