Fhx (Foxj2) expression is activated during spermatogenesis and very early in embryonic development.

FHX (FOXJ2) is a recently characterized human fork head transcriptional activator that binds DNA with a dual sequence specificity. We have cloned the cDNA for the mouse orthologue Foxj2 and characterized its expression in the gonads and along the early pre-implantation development of the mouse. In the testis, Foxj2 is expressed from pachytene spermatocytes to round spermatids, but not in spermatogonia. In addition to the germ lineage, only Sertoli cells of the testis showed expression of Foxj2. In the ovary, only granulosa cells of the follicles express the factor. Neither mature spermatozoa nor oocytes showed expression of Foxj2. Foxj2 expression is early activated in zygotic development, being detected since as early as 8-cell stage embryos. Both cell layers of the blastocyst: the trophectoderm (TE) and the inner cell mass (ICM), express Foxj2.