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ID 16929

Genes Involved with SMA

Dr. Charlotte Sumner explains how SMA is related to changes in the SMN1 and SMN2 genes.
In the general population, individuals who have a normal SMN1 gene, do not require the SMN2 gene. So there are many of us in fact who have no SMN2 gene when we retain a normal SMN1 gene. But in the case of an individual who has SMA when both copies of the SMN1 gene are mutated, they rely completely on the presence of an SMN2 gene an in fact every patient with SMA retains at least one copy of the SMN2 gene. That gene is very similar to SMN1 almost identical, but it has a few changes in its spelling, in its sequence and one of those changes in particular, in fact a single change results in a difference in the way the RNAs that result from that gene are processes. And as a result, those RNAs most of the time that come from this SMN2 gene are too short. They lack an exon we call exon7 and that protein that's made from those RNAs that lack exon 7 is also too short and very, very unstable and becomes degraded very quickly. Some of the time, the RNA that comes from the SMN2 gene does retain exon 7. It's spliced so that it includes exon 7. It makes a normal length RNA molecule, a normal SMN protein and that little bit of SMN protein that comes from SMN2 is adequate to allow a child with SMA to be born. But unfortunately that reduced level of SMN protein makes motor neurons sick and motor neurons degenerate that's causing the disease SMA.
Spinal muscular atrophy, SMA, RNA, mRNA, splicing, gene, genetic, DNA, antisense, motor neuron, splice, SMN1, SMN2, SMN, sequence, code, exon, intron, motor neuron, alternative splicing, exon 7
Creative Commons License This work by Cold Spring Harbor Laboratory is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License.

Related content:

16941. 2D Animation of Alternative RNA Splicing
An animation shows alternate splicing of the SMN2 gene.
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16911. A simple description of the cause of SMA
Frank, an SMA parent, describes the genetics of SMA.
16948. Alternative RNA Splicing Therapy for Spinal Muscular Atrophy
Drs. Sharp and Sumner describe how RNA splicing can be used as a therapy for SMA.
16935. The Connection Between SMA and RNA Splicing
Dr. Krainer explains the connection between SMA and RNA splicing.
16910. Cause of SMA
Dr. Sumner explains what causes SMA.
16938. 3D Animation of RNA Splicing
An animation of the crucial RNA editing step called splicing.
16949. Antisense Oligonucletotide Therapy for SMA
Dr. Krainer explains the science behind antisense therapy for SMA.
16909. Introduction to SMA
Dr. De Vivo provides an overview of SMA, and describes the four SMA types.
16940. Alternative RNA Splicing
Drs. Sharp and Krainer explain how genes can be alternatively spliced.
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