Genedeletions inspinal muscular atrophy

Two candidate genes(NAIPandSMN) haverecently beenreported forchildhood onsetspinal muscular atrophy (SMA).Althoughaffected subjects showdeletions of thesegenes,thesedeletions canleadto either averymildorasevere phenotype. We haveanalysed alarge numberofclinically welldefined patients, carriers, and normalcontrols toassessthefrequency andextent ofdeletions encompassing both ofthesegenes.A genotype analysis indicates thatmoreextensive deletions are seeninthesevereformofSMA thanin themilderforms.Inaddition, 19% of phenotypically normalcarriers aredeleted fortheNAIPgene; nocarriers weredeleted fortheSMN gene.Ourdatasuggest that deletions inbothofthesegenes, using the currently available assays, areassociated withbothasevereandverymildphenotype.