FOXJ2, Forkhead box protein J2, is a 574 amino acid protein encoded by the human gene FOXJ2. FOXJ2 is a novel forkhead factor, belonging to the forkhead family, with a dual DNA binding specificity. The HNF3/forkhead family includes a large number of transcription factors that share a structurally related DNA binding domain. forkhead factors are known to play important roles both during development and in adults. 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 have been found to express FOXJ2. However, both the trophectoderm (TE) and the inner cell mass (ICM) cell layers of the blastocyst express FOXJ2.