p19^Ink4d and p18^Ink4c cyclin‐dependent kinase inhibitors in the male reproductive axis

Abstract

The loss of the cyclin-dependent kinase inhibitors (CKIs) p18(Ink4c) and p19(Ink4d) leads to male reproductive defects (Franklin et al., 1998. Genes Dev 12: 2899-2911; Zindy et al., 2000. Mol Cell Biol 20: 372-378; Zindy et al., 2001. Mol Cell Biol 21: 3244-3255). In order to assess whether these inhibitors directly or indirectly affect male germ cell differentiation, we examined the expression of p18(Ink4c) and p19(Ink4d) in spermatogenic and supporting cells in the testis and in pituitary gonadotropes. Both p18(Ink4c) and p19(Ink4d) are most abundant in the testis after 18 days of age and are expressed in purified populations of spermatogenic and testicular somatic cells. Different p18(Ink4c) mRNAs are expressed in isolated spermatogenic and Leydig cells. Spermatogenic cells also express a novel p19(Ink4d) transcript that is distinct from the smaller transcript expressed in Sertoli cells, Leydig cells and in other tissues. Immunohistochemistry detected significant levels of p19(Ink4d) in preleptotene spermatocytes, pachytene spermatocytes, condensing spermatids, and Sertoli cells. Immunoprecipitation-Western analysis detected both CKI proteins in isolated pachytene spermatocytes and round spermatids. CDK4/6-CKI complexes were detected in germ cells by co-immunoprecipitation, although the composition differed by cell type. p19(Ink4d) was also identified in FSH+ gonadotrophs, suggesting that this CKI may be independently required in the pituitary. Possible cell autonomous and paracrine mechanisms for the spermatogenic defects in mice lacking p18(Ink4c) or p19(Ink4d) are supported by expression of these CKIs in spermatogenic cells and in somatic cells of the testis and pituitary.

p19Ink4d Is a Tumor Suppressor and Controls Pituitary Anterior Lobe Cell Proliferation

“…4A). Though the testes of p19 Ϫ/Ϫ male mice were slightly smaller than those of WT mice, p19-deficient males were fertile, which is in agreement with previous findings (27,28,40). After monitoring a cohort of 24 p19 Ϫ/Ϫ , 9 p19 ϩ/Ϫ , and 15 wild-type mice for 27 months, we found that 14 (58.3%) p19 Ϫ/Ϫ and 3 (30%) p19 ϩ/Ϫ mice spontaneously developed tumors, whereas only 2 (13.3%) WT mice displayed tumors at a similar age ( Fig.…”

“…2C), supporting the activation of Cdk4 and/or Cdk6. These data are also consistent with the previous finding that p19 is predominantly expressed in the AL of pituitary (40). We then determined the kinase activity of Cdk4 and Cdk6 using GST-Rb as the substrate.…”

GASZ Is Essential for Male Meiosis and Suppression of Retrotransposon Expression in the Male Germline

“…One mg of testicular lysates from WT mice were prepared with 0.5% NP-40 lysis buffer as described previously [62]. Pre-cleared lysates were incubated overnight at 4°C with anti-GASZ, anti-MIWI, or no primary antibody, followed by incubation with protein G beads in 5% BSA to precipitate immune complexes.…”

Genetic disruption of the Nrf2 compromises cell-cycle progression by impairing GSH-induced redox signaling

“…An Nrf2 deficiency is associated with enhanced expression levels of genes involved in cell-cycle checkpoints' regulation, including the cyclin-dependent kinase inhibitor 2D (Cdkn2d, p19) and promyelocytic leukemia (PML). Cdkn2d inhibits Cdk4 leading to cell-cycle arrest at the G 1 /S transition (Buchold et al, 2007;Laine et al, 2007), whereas PML recruits Chk family kinases and p53 into the PML nuclear bodies, enhances the p53/Chk2 interaction (Louria-Hayon et al, 2003) and also orchestrates a nuclear tumor suppressor network that inactivate nuclear pAkt (Trotman et al, 2006). Cenp-F and Cenp-E have been implicated in spindle checkpoint regulation, kinetochore-microtubule capture and chromosome alignment and stability (Parra et al, 2002;Putkey et al, 2002).…”