Analysis of polymorphic markers segregating in both intra- and intersp
ecific crosses has allowed us to map the autosomal recessive mutation
progressive motor neuronopathy (pmn) to mouse Chr 13. Although this mu
tation, based on its histological description, was reported as a model
for infantile spinal muscular atrophy of the Werdnig-Hoffmann type, i
ts localization to a region that is not homologous with human 5q makes
it unlikely to be a homologue to SMA. The presence of the Extra-toe (
Xt) locus in proximity to pmn will help in the detection of affected p
rogenies before the onset of the degenerative process. (C) 1995 Academ
ic Press, Inc.