IDENTIFICATION OF KEY RECOMBINANTS IN MULTIPLEX SMA FAMILIES

Recent reports have provided evidence that a major gene for autosomal recessive proximal spinal muscular atrophy (SMA) resides in a small ge netic interval in bands q12-q13 of chromosome 5, a 4-cM region proxima lly flanked by D5S125 (EF(TG/AG)n) and distally by MAP1B/D5S112 or a 0 .7-cM interval (range 0.1-2.1 cM) flanked by D5S435 proximally and MAP 1B/D5S112 distally. We present the identification of key recombinants between SMA and the closest flanking DNA-markers in an analysis of Dut ch and Italian SMA families. These crossovers may serve as reference p oints for new markers in this region and may thus be instrumental in a further refined mapping of the SMA gene. Two markers, D5S351 (I105) a nd D5S357 (Mfd151), could be mapped distally to SMA in the interval SM A-D5S112. (C) 1994 Academic Press, Inc.