Shiroishi T, Sagai T, Moriwaki K
Department of Cell Genetics, National Institute of Genetics, Shizuoka-ken, Japan.
Genetica. 1993;88(2-3):187-96. doi: 10.1007/BF02424475.
Meiotic recombination is not random in the proximal region of the mouse major histocompatibility complex (MHC). It is clustered at four restricted positions, so-called hotspots. Some of the MHC haplotypes derived from Asian wild mice enhance recombination at the hotspots in genetic crosses with standard MHC haplotypes of laboratory mouse strains. In particular, the wm7 haplotype derived from Japanese wild mouse indicated an approximately 2% recombination frequency within a 1.2 kb fragment of DNA in the interval between the Pb and Ob genes. Interestingly, this enhancement of recombination was observed only in female meiosis but not in male meiosis. Mating experiments demonstrated that the wm7 haplotype carries a genetic factor in the region proximal to the hotspot, which instigates recombination. In addition, the wm7 haplotype has a genetic factor located in the region distal to the hotspot, which suppresses recombination. From the molecular characterization of the two hotspots located in the Eb gene and the Pb-Ob interval, it appeared that there are several common molecular elements, the consensus of the middle repetitive MT-family, TCTG or CCTG tetramer repeats, and the solitary long terminal repeat (LTR) of mouse retrovirus.
减数分裂重组在小鼠主要组织相容性复合体（MHC）的近端区域并非随机发生。它聚集在四个受限位置，即所谓的热点。一些源自亚洲野生小鼠的MHC单倍型在与实验室小鼠品系的标准MHC单倍型进行遗传杂交时，会增强热点处的重组。特别是，源自日本野生小鼠的wm7单倍型在Pb和Ob基因之间的间隔内，1.2 kb的DNA片段中显示出约2%的重组频率。有趣的是，这种重组增强仅在雌性减数分裂中观察到，而在雄性减数分裂中未观察到。交配实验表明，wm7单倍型在热点近端区域携带一个遗传因子，该因子会引发重组。此外，wm7单倍型在热点远端区域有一个遗传因子，该因子会抑制重组。从位于Eb基因和Pb-Ob间隔内的两个热点的分子特征来看，似乎存在几个共同的分子元件，即中间重复MT家族的共有序列、TCTG或CCTG四聚体重复序列以及小鼠逆转录病毒的孤立长末端重复序列（LTR）。
