Lm. Brzustowicz et al., LINKAGE DISEQUILIBRIUM AND HAPLOTYPE ANALYSIS AMONG POLISH FAMILIES WITH SPINAL MUSCULAR-ATROPHY, American journal of human genetics, 56(1), 1995, pp. 210-215
Spinal Muscular Atrophy (SMA) is an inherited degenerative disorder of
anterior horn cells that results in progressive muscle weakness and a
trophy. The autosomal recessive forms of childhood-onset SMA have been
mapped to chromosome 5q11.2-13.3, in a number of studies examining di
fferent populations. A total of 9 simple sequence repeat markers were
genotyped against 32 Polish families with SMA. The markers span an sim
ilar to 0.7 cM region defined by the SMA flanking markers D5S435 and M
AP1B. Significant linkage disequilibrium (corrected P < .05) was detec
ted at four of these markers, with D/D-max values of less than or equa
l to.83. Extended haplotype analysis revealed a predominant haplotype
associated with SMA. The apparently high mutation rate of some of the
markers has resulted in a number of haplotypes that vary slightly from
this predominant haplotype. The predominant haplotype and these close
ly related patterns represent 25% of the disease chromosomes and none
of the nontransmitted parental chromosomes. This predominant haplotype
is present both in patients with acute (type I) and in chronic (types
II and III) forms of SMA and occurs twice in a homozygous state, both
times in children with chronic SMA.