Bullard D C, Ticknor C, Schimenti J C
Baylor College of Medicine, Institute for Molecular Genetics, Houston, Texas 77030.
Mamm Genome. 1992;3(10):579-87. doi: 10.1007/BF00350625.
Transmission ratio distortion (TRD) of mouse t haplotypes occurs through the interaction of multiple distorter loci with the t complex responder (Tcr) locus. Males heterozygous for a t haplotype will transmit the t-bearing chromosome to nearly all of their offspring. This process is mediated by the production of functionally inequivalent gametes: wild-type meiotic partners of t spermatozoa are rendered functionally inactive. The Tcr locus, which is required for TRD to occur, is thought to somehow protect its host spermatid from the sperm-inactivating effects of linked distorter genes (Lyon 1984). In previous work, Tcr was mapped to a small genetic interval in t haplotypes, and a candidate gene from this region was isolated (Tcp-10bt). In this work, we further localize Tcr to a 40-kb region that contains the 21-kb Tcp-10bt gene. A cloned genomic copy of Tcp-10bt was used to generate transgenic mice. The transgene was bred into a variety of genetic backgrounds to test for non-Mendelian segregation. Abberrant segregation was observed in some mice carrying either a complete t haplotype or a combination of certain partial t haplotypes. These observations, coupled with those of Snyder and colleagues (in this issue), provide genetic and functional evidence that the Tcp-10bt gene is Tcr. However, other genotypes that were predicted to produce distortion did not. The unexpected data from a variety of crosses in this work and those of our colleagues suggest that elements to the TRD system and the Tcr locus remain to be identified.
小鼠t单倍型的传递比率畸变（TRD）通过多个畸变基因座与t复合体反应基因（Tcr）座的相互作用而发生。携带t单倍型的雄性杂合子会将携带t的染色体传递给几乎所有后代。这个过程是由功能不等价配子的产生介导的：t精子的野生型减数分裂伴侣在功能上变得无活性。TRD发生所需的Tcr座被认为以某种方式保护其宿主精子细胞免受连锁畸变基因的精子失活效应（Lyon，1984）。在之前的工作中，Tcr被定位到t单倍型的一个小遗传区间，并从该区域分离出一个候选基因（Tcp-10bt）。在这项工作中，我们进一步将Tcr定位到一个包含21 kb Tcp-10bt基因的40 kb区域。使用克隆的Tcp-10bt基因组拷贝来生成转基因小鼠。将转基因培育到多种遗传背景中以测试非孟德尔分离。在一些携带完整t单倍型或某些部分t单倍型组合的小鼠中观察到异常分离。这些观察结果，再加上Snyder及其同事（在本期）的观察结果，提供了遗传和功能证据，表明Tcp-10bt基因就是Tcr。然而，其他预计会产生畸变的基因型却没有。这项工作以及我们同事的各种杂交实验中出现的意外数据表明，TRD系统和Tcr座的元件仍有待确定。
