The mapping of a cDNA from the human X-linked Duchenne muscular dystrophy gene to the mouse X chromosome

Abstract

The recent discovery of sequences at the site of the Duchenne muscular dystrophy (DMD) gene in humans has opened up the possibility of a detailed molecular analysis of the genes in humans and in related mammalian species. Until relatively recently, there was no obvious mouse model of this genetic disease for the development of therapeutic strategies. The identification of a mouse X-linked mutant showing muscular dystrophy, mdx, has provided a candidate mouse genetic homologue to the DMD locus; the relatively mild pathological features of mdx suggest it may have more in common with mutations of the Becker muscular dystrophy type at the same human locus, however. But the close genetic linkage of mdx to G6PD and Hprt on the mouse X chromosome, coupled with its comparatively mild pathology, have suggested that the mdx mutation may instead correspond to Emery Dreifuss muscular dystrophy which itself is closely linked to DNA markers at Xq28-qter in the region of G6PD on the human X chromosome. Using an interspecific mouse domesticus/spretus cross, segregating for a variety of markers on the mouse X chromosome, we have positioned on the mouse X chromosome sequences homologous to a DMD cDNA clone. These sequences map provocatively close to the mdx mutation and unexpectedly distant from sparse fur, spf, the mouse homologue of OTC (ornithine transcarbamylase) which is closely linked to DMD on the human X chromosome.

Unusual molecular characteristics of a repeat sequence island within a Giemsa-positive band on the mouse X chromosome.

“…An interspecific Mus domesticus/Mus spretus cross segregating for the coattexture mutations Hq, Ta, and Li (13) was used to generate backcross progeny for the genetic analysis of DXSmh141 and other microclones and has been described in detail (14,15). High molecular weight DNA was prepared from mouse tails (14).…”

“…Progeny DNAs from the backcross were restriction digested and Southern blotted onto Hybond-N membranes (Amersham) by standard methods. Filters were hybridized as described (15) and washed with 2x NaCl/Cit/0.1% NaDodSO4 at 650C and autoradiographed overnight at -70'C with intensification (lx NaCl/Cit = 0.15 M NaCI/0.015 M sodium citrate). Clone versus clone hybridizations were washed extensively in 0.1x NaCI/Cit/0.1% NaDodSO4 at 650C and autoradiographed at room temperature for <1 hr.…”

Genetic aspects of susceptibility to air pollution: Table 1

“…These strategies, alone or in combination, have been utilised in inbred mice to identify genetic mechanisms of a number of diseases. These include models of Huntingtons disease [6,7], Duchenne muscular dystrophy [8], amyotrophic lateral sclerosis [9], insulindependent diabetes mellitus [10], Alzheimer9s disease [11], von Willebrand disease [12], chronic granulomatous disease [13], and Niemann-Pick C1 disease [14]. The considerable resources and energy applied to mapping of the mouse genome as an integral component of the Human Genome Project underlie the importance of this animal model for human diseases [15].…”

Localization of the mdx mutation within the mouse dystrophin gene.

“…Some mapping studies have shown that the mdx mutation is in a region of the mouse X chromosome close to the mouse homologue of DMD (Brockdorff et al, 1987a;Heilig et al, 1987). However, it has also been mapped close to a cluster of genes which, on the human chromosome, includes the Emery -Dreifus muscular dystrophy (EDMD) locus Chamberlain et al, 1987), making it uncertain to which, if either, of these two loci on the human X chromosome mdx is equivalent.…”