Functional and molecular characterization of the transcriptional regulatory region of Tcp-10bt, a testes-expressed gene from the t complex responder locus.

Mouse t haplotypes contain several mutant alleles that disrupt spermatogenesis. Their phenotypes include sterility, reduced fertility and transmission ratio distortion (TRD). The substantial genetic analyses of these mutant alleles, coupled with intensive physical characterization of the t complex, provides a fertile ground for identifying and understanding genes essential to male gametogenesis. The t complex responder (Tcr) locus plays a central role in this process, interacting with other t haplotype-encoded genes to mediate TRD. A candidate responder gene, Tcp-10bt, has been cloned and subjected to molecular characterization. Here, we define the transcriptional regulatory regions of this gene in transgenic mice. A 1.6 kb (but not 0.6 kb) DNA fragment upstream of the transcription start site contains all the regulatory signals for appropriate temporal and germ cell-specific expression of this gene. Two smaller fragments within this region bound specifically to nuclear factor(s) from germ cell protein extracts in gel shift assays. This work is a step towards understanding the mechanism of Tcp-10bt regulated expression and may ultimately help reveal a common regulatory pathway shared by other similarly expressed spermatogenic genes.