MAPPING OF THE SPINAL MUSCULAR-ATROPHY (SMA) GENE TO A 750-KB INTERVAL FLANKED BY 2 NEW MICROSATELLITES

The gene for autosomal recessive proximal spinal muscular atrophy (SMA ) has recently been mapped between D5S629 and D5S557. We report here a new single-locus microsatellite A31 (D5S823) and two multicopy micros atellites 97T-CA and 95/23-CA. The marker A31 maps to the region of ov erlap between YACs y116, y55 and y122, distal to D5S629; 97T-CA origin ates from a cosmid corresponding to the STS97T, localized distally to A31, while 95/23-CA derives from a cosmid corresponding to the STS 97U , localized proximally to D5S557. We tested all our key recombinant fa milies with these markers. In one type I/II SMA family, a recombinant was found that placed the SMA locus distal to D5S823. Homozygosity map ping in a consanguineous type I SMA family indicates that the SMA gene lies proximal to 95/23-CA. Thus, the two new markers, A31 and 95/23-C A further refine the SMA gene to an approximately 750-kb interval.