Molecular analysis of the genetic relationship of trans interacting factors at the T/t complex

The T/t complex is an extensive genetic region proximal to the H-2 complex on mouse chromosome 17, with multiple effects on embryonic development, spermatogenesis and recombination. Recently, two-dimensional gel analysis of testicular cell proteins identified a gene within the T/t complex that codes for a major cell surface-associated protein, p63/6.9 (ref. 4). The wild-type gene, Tcp-1b, codes for a 63,000-molecular weight protein (p63/6.9b), whereas a mutant allele, Tcp-1a, which occurs in all intact t haplotypes, codes for a more acidic form of the protein (p63/6.9a). Analysis of partial t haplotypes obtained from rare recombination events showed that Tcp-1a correlated completely with the tail interaction factor tT, which is thought to be a genetic allele of T, thus raising the possibility that the locus of T codes for the p63/6.9 protein. We report here that the p63/6.9 proteins produced by seven chromosomes carrying independently derived dominant mutations at the locus of T are all indistinguishable from the wild-type form; thus, the cumulative data indicate that the Tcp-1 gene is most probably not at the locus of T.