Epab KO mice lack exon 2 of the poly(A) binding protein, cytoplasmic 1-like Pabpc1l gene, abolishing gene function. Exon 2 encodes a portion of the first RNA-recognition motif (RRM)1 domain and removal of it results in a premature stop codon and the production of a EPAB protein with truncated RRM1, and lacking the remaining three RRMs and poly(A)-binding (PAB) C-terminal domain.
EPAB is required for the regulation of maternal gene expression during oocyte development and maturation, fertilization, and early embryo development until zygotic genome activation. Homozygous Epab-/- males and heterozygous Epab+/- mice are viable and fertile, while homozygous Epab-/- females are viable but infertile. Homozygous Epab-/- females cannot generate embryos or mature oocytes in vivo or in vitro. Oocytes from these females failed to achieve translational activation of maternally-stored mRNAs upon stimulation of oocyte maturation. Spindle formation and chromosome alignment during meiotic divisions are impaired in Epab-/- oocytes. Microinjection of Epab mRNA into germinal vesicle stage Epab-/- oocytes did not rescue maturation, while microinjection of Epab mRNA into preantral follicle enclosed oocytes does.
