Explanation of sterility in txty male mice

Abstract

The lethal t alleles of the T complex on mouse chromosome 7 have been assigned to 6 complementation groups (the definitive classes being t0, t9, t12, tw1, tw5 and tw73), each causing embryonic death at a particular stage. Intercomplementation heterozygotes (txty) show partial complementation, so that only some txty offspring survive. These survivors appear morphologically normal; indeed the females, being fertile, seem entirely normal. The txty males are sterile. Among the reasons given for this sterility in some txty males are low motility of the txty spermatozoa and an inability to effect fertilization either in vitro or in vivo even when already present at the site of fertilization. Spermatozoa from sterile txty males were reported to be apparently present in normal numbers in the uterus, although actual ejaculate numbers have not been quoted for these, or indeed for normal fertile males. The comparison of numbers of spermatozoa ejaculated into the female tract by sterile t6tw5, t6tw32 and tw5tw32 (all strong mutations) and control mice clearly shows oligozoospermia (about 100 times less than controls) occurring in the txty males.