Mybl1 (myeloblastosis oncogene-like 1; also called A-Myb) is a transcription factor that has been identified as a male-specific master regulator of several crucial meiotic processes.
These Mybl1repro9 mice carry an ENU-generated point mutation (A213E) associated with homozygous male infertility. Testes exhibit a histopathological phenotype indistinguishable from that of Mybl1 knockout animals. Spermatocytes demonstrate subtle defects in autosome synapsis in pachynema, a high incidence of unsynapsed sex chromosomes, incomplete double-strand break repair on synapsed pachytene chromosomes, and a lack of crossing over. Homozygous females are fertile and viability is unaffected.
Homozygous Mybl1repro9 mice do not exhibit the runting or abnormal breast development observed in homozygous knockout mice. This indicates that the mutation is a hypomorphic or separation-of-function allele that specifically impairs the spermatogenesis function of MYBL1. Western blot indicates that MYBL1repro9 protein is reduced, but not absent in mutant testes.
