Spinal muscular atrophy (SMA) is an inherited disease that is one of the most common causes of death in infancy. It occurs in ~1 in 6,000 live births, second only to cystic fibrosis. Milder forms of SMA are also found in older children and adults.
In SMA, the certain cells in the spinal cord die, resulting in progressive muscle weakness and ultimately, in some cases, in the inability to breathe and swallow.
The gene that is mutated in SMA has been identified, but we still have little understanding of how the encoded protein functions to allow survival of the motor neurons. This protein is called the ‘survival of motor neuron’ (SMN) protein, and it has been implicated in the basic cellular process of RNA metabolism.
Now, Michael Sattler, of the European Molecular Biology Laboratory in Heidelberg, Germany, and colleagues present the three-dimensional structure of one part of the SMN protein (Nature Structural Biology, Vol. 8, Issue 1, 01 Jan 2001), determined using the technique of NMR spectroscopy. They also present the results of experiments with an SMN protein that harbors a mutation found in SMA patients. This mutation prevents SMN from interacting with key partner proteins, called Sm proteins. Sattler and colleagues show that this mutation has a very specific, local effect at the site of the mutation (instead of a global, deleterious structural effect on the protein).
The Sm proteins are fundamental components of the machinery in cells that performs the task of RNA splicing, one of the final steps in gene expression. The results of Sattler and colleagues are a step toward understanding how the loss of the interaction between SMN and the Sm proteins could lead to death of motor neurons in SMA patients.
The News and Views by Alex MacKenzie and Nathalie Gendron places this work into the context of the cellular machinery, and the Editorial discusses SMA more broadly.
Dr. Michael Sattler
European Molecular Biology Lab (EMBL)
Structural & Computational Biology
Meyerhofstrasse 1, Pf. 10.2209
Telephone: +49 6221 387 552
Fax: +49 6221 387 306
Dr. Alex E. MacKenzie
Children's Hospital of Eastern Ontario
Molecular Genetics Laboratory
401 Smyth Road
Ottawa, Ontario K1H 8L1
Telephone: +1 613 737 2772
Fax: +1 613 738 4833
(C) Nature Structural Biology press release.
Message posted by: Trevor M. D'Souza