Studies Within the T-Complex of the Mouse Utilizing a New Embryonic Lethal (Tcl(0)), and the Genetical Markers Rb7 and Tcp-1.

The Robertsonian translocation chromosome, Rb(16:17)7, has been widely used in studies of the t-complex. It is reported here that Rb(16:17)7 has strong and divergent effects on t-complex determined transmission ratio distortion and crossing-over suppression. The results are interpreted according to the model of Lyon and Mason (1977). It is suggested that the Rb(16:17)7 chromosome contains a gene(s) near Brachyury (T) that interacts with t-haplotypes to cause distortion of transmission ratios. In addition, it was found that Ttf/Rb7 males exhibit normal recombination frequencies (7%) in the T to tufted (tf) interval, yet t('0)/Rb7 animals showed a high rate (12.5%) of recombination between the centromere and the t('0) lethal gene. It is proposed that the de-suppression of crossing-over noted for t('0)/Rb7 animals is due to a matching of t and Rb7 chromatin types similar to that reported by Silver and Artzt (1981). The fact that the Rb(16:17)7 chromosome was derived from the sub-species Mus musculus poschiavinus is discussed in light of the idea of Silver (1982) that t chromosomes originated from one or a few introgressions of a genetically distinct population of mouse into the Mus musculus genome. A spontaneous t embryonic lethal mutation (tcl('0)) has been discovered and characterized. This point mutation arose in the T('hp) chromosome, is allelic to t('0), and has no effects on transmission ratio distortion and crossing-over suppression. It now provides the opportunity to study t aberrations of development in the complete absence of other genes and effects typically associated with t-haplotypes. tcl('0) is the first example of a t recessive lethal not derived from wild mice. The implications of this finding are discussed in terms of the complementation test used to discover this mutation and with regards to the functional and evolutionary relationship of embryonic lethal mutations to t-haplotypes. The Tcp-1 locus is the only t-complex gene whose product has been identified (Silver et al., 1979). It is reported here that this product, p63/6.9, is synthesized by spermatides and by peri-implantation stage embryos as detected by two-dimensional gel fluorography. Synthesis of p63/6.9 begins at the morula stage and increases in blastocysts. Two cell embryos did not demonstrate detectable amounts of p63/6.9. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMIPhDGeneticsUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/160028/1/8412239.pd