New SMA Gene Mapped To Chromosome 1

Researchers in France have identified a new genetic form of spinal muscular atrophy (SMA), a disease in which motor neurons (nerve cells) in the spinal cord and sometimes the brainstem degenerate.

Most cases of SMA are due to the inheritance of mutations in each of a child’s two (one from each parent) chromosome 5 genes that instruct for the SMN protein. Another recessive (requiring genetic flaws from both parents) form of SMA, with respiratory failure occurring in the first weeks of life, results from mutations in a gene on chromosome 11. But some patients with SMA remain without a genetic diagnosis.

Now, Isabelle Maystadt at Hospital Necker Enfants Malades in Paris and colleagues, by studying a large family originating from Mali (near Algeria), have localized a region on chromosome 1 as containing the gene that, when mutated, can also cause another recessive form of SMA. This form looks similar to the type 3 form of SMN-linked SMA, but it’s more severe and involves the breathing muscles and muscles of the hands and feet.

The investigators, who published their findings in the July 11 issue of Neurology, are working on identifying the specific gene involved, which should allow more patients to obtain a specific diagnosis. In addition, they say, “Identification of a new gene will, it is hoped, contribute to a better understanding of the molecular mechanisms involved in motor neuron degeneration.”