CIP2A is co-expressed with PLZF in proliferatively active primordial germ cells and spermatogonia.

<p>(A) Most primitive male germ cells, spermatogonia (indicated by arrows), locate most basally in the seminiferous tubules and contain highest CIP2A, PLZF and ki-67 expression levels in the mouse testis. (B) Immunohistochemical staining of CIP2A, PLZF and ki-67 in adult mouse testis show that CIP2A is expressed in both PLZF and ki-67 positive spermatogonia (white arrow heads). (C) CIP2A gene promoter is exclusively active in basal spermatogonia. Enzymatic LacZ staining was used to detect expression of ß-galactosidase protein from the gene-trap cassette under CIP2A promoter. ß-galactosidase activity was observed only in the CIP2A^HOZ spermatogonia (arrowheads in larger magnification). (D) Human testicular gonocytes (Fetal) and pubertal spermatogonia (Pubertal) express CIP2A, PLZF and ki-67 (arrowheads) whereas juvenile testis samples (Juvenile) were devoid of expression of any of these markers. White bar represents 25 µm, black bar – 50 µm.