The role of RNP biogenesis in spinal muscular atrophy.

Mutations that affect pre-mRNA processing are the cause for many genetic diseases. Most such mutations target cis-acting regulatory sequences in a given transcript, thus preventing its proper maturation. Only recently however, mutations in trans-acting factors involved in pre-mRNA processing have likewise been linked to disease. One prominent example is spinal muscular atrophy (SMA), a monogenic, neuromuscular disorder caused by reduced levels of functional survival motor neuron (SMN) protein. This ubiquitous factor is part of a complex that mediates the formation of spliceosomal snRNPs. The detailed biochemical investigation of SMN under normal conditions and in SMA has provided clues how mutations in factors with general functions elicit tissue-specific phenotypes.