Juriloff D M, Porter S D, Harris M J
Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Genome. 1994 Apr;37(2):190-7. doi: 10.1139/g94-026.
The SELH/Bc inbred mouse stock has produced an unusually high number of spontaneous mutations, including sph2Bc, nuBc, a recessive lens opacity, and three mutations at the c locus. Classical genetic and molecular genetic studies were done to investigate the origin of the albino locus mutations. Southern blots probed with the mouse tyrosinase cDNA showed that two of the mutations, cBc and c2Bc, are deletions of exons 1, 2 and 3. The third mutation, c3Bc, showed a disruption, either a rearrangement or an insertion, in the region of exon 1. The deletion of the cBc mutation is anticipated to be large as the mutation has inactivated the Mod-2 locus 2 cM away, and an essential locus for post-implantation survival outside the c-Mod-2 interval, whereas the c2Bc mutation is viable and fertile in homozygotes. Homozygotes for c3Bc are also viable and fertile. We conclude that at least some of the molecular events leading to the three albino mutations were independent. The mutations differ from each other and from the classical albino point mutation. All three new mutations originated from parents who were germline mosaics, and the mutational events were therefore all postmeiotic. All three mosaics shared one common ancestor six generations previously, raising the possibility that an instability of the albino locus might have been inherited. SELH/Bc mice may provide an animal model for the study of mechanisms underlying genetic instability.
SELH/Bc近交系小鼠产生了异常高数量的自发突变,包括sph2Bc、nuBc、一种隐性晶状体混浊以及c位点的三个突变。开展了经典遗传学和分子遗传学研究以探究白化病位点突变的起源。用小鼠酪氨酸酶cDNA进行探针杂交的Southern印迹分析表明,其中两个突变,即cBc和c2Bc,是外显子1、2和3的缺失。第三个突变c3Bc在外显子1区域显示出一种破坏,要么是重排要么是插入。预计cBc突变的缺失很大,因为该突变使距离2 cM的Mod-2位点失活,且该位点是c-Mod-2区间外植入后存活的必需位点,而c2Bc突变的纯合子是可存活且可育的。c3Bc的纯合子也是可存活且可育的。我们得出结论,导致这三种白化病突变的至少一些分子事件是独立的。这些突变彼此不同,也与经典的白化病点突变不同。所有这三个新突变均源自种系嵌合体的亲本,因此突变事件均发生在减数分裂后。所有这三个嵌合体在六代之前有一个共同祖先,这增加了白化病位点不稳定性可能是可遗传的可能性。SELH/Bc小鼠可能为研究遗传不稳定性潜在机制提供一种动物模型。