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

FHX (FOXJ2) is a recently characterized human fork head transcriptional act ivator 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 t he testis, Foxj2 is expressed from pachytene spermatocytes to round spermat ids, but not in spermatogonia. In addition to the germ lineage, only Sertol i cells of the testis showed expression of Foxj2. In the ovary, only granul osa cells of the follicles express the factor. Neither mature spermatozoa n or oocytes showed expression of Foxj2. Foxj2 expression is early activated in zygotic development, being detected since as early as 8-cell stage embry os. Both cell layers of the blastocyst: the trophectoderm (TE) and the inne r cell mass (ICM), express Foxj2. (C) 2000 Elsevier Science Ireland Ltd. Al l rights reserved.