Male Hypogonadism and Germ Cell Loss Caused by a Mutation in Polo-Like Kinase 4

Abstract

The genetic etiologies of male infertility remain largely unknown. To identify genes potentially involved in spermatogenesis and male infertility, we performed genome-wide mutagenesis in mice with N-ethyl-N-nitrosourea and identified a line with dominant hypogonadism and patchy germ cell loss. Genomic mapping and DNA sequence analysis identified a novel heterozygous missense mutation in the kinase domain of Polo-like kinase 4 (Plk4), altering an isoleucine to asparagine at residue 242 (I242N). Genetic complementation studies using a gene trap line with disruption in the Plk4 locus confirmed that the putative Plk4 missense mutation was causative. Plk4 is known to be involved in centriole formation and cell cycle progression. However, a specific role in mammalian spermatogenesis has not been examined. PLK4 was highly expressed in the testes both pre- and postnatally. In the adult, PLK4 expression was first detected in stage VIII pachytene spermatocytes and was present through step 16 elongated spermatids. Because the homozygous Plk4(I242N/I242N) mutation was embryonic lethal, all analyses were performed using the heterozygous Plk4(+/I242N) mice. Testis size was reduced by 17%, and histology revealed discrete regions of germ cell loss, leaving only Sertoli cells in these defective tubules. Testis cord formation (embryonic day 13.5) was normal. Testis histology was also normal at postnatal day (P)1, but germ cell loss was detected at P10 and subsequent ages. We conclude that the I242N heterozygous mutation in PLK4 is causative for patchy germ cell loss beginning at P10, suggesting a role for PLK4 during the initiation of spermatogenesis.

Identification and characterization of reproductive KRAB-ZF genes in mice

“…Thirteen genes were known to be required for the development of male germ cells (Vps54, Mdm2, Agfg1, Plk4, Ppp1cc, Bcl2l2, Cep55, Ccny, Hnrnpl, Etv5, Cdc7, Dicer1 and Ezh2) ( Table 1) (Kang-Decker et al, 2001;Kim et al, 2003;Yan et al, 2003;Schmitt-John et al, 2005;Liu et al, 2007;Tyagi et al, 2009;Chang et al, 2010;Harris et al, 2011;Korhonen et al, 2011;Lambrot et al, 2012;Li et al, 2012;Mikolcevic et al, 2012;Sinha et al, 2013) In addition, a number of the downregulated genes had been previously shown to induce apoptosis when deleted (Hnrnpl, Klf4, Ebf3, Map4k4, Zbtb18, Fbxo45, Setd8, Bcl2l2, Rrm2b, Cfdp1, Ugcg, Fut8, Ptpn11 Rpl23, Etv5, Atf2, Cul1, Tomm70a, Cdc7, and Dicer1) ( Table 2) (Diekwisch and Luan, 2002;Kim et al, 2003;Yan et al, 2003;Zhao et al, 2006;Devlin et al, 2008;Peschiaroli et al, 2009;Tyagi et al, 2009;Wang et al, 2009;Cai et al, 2011;Korhonen et al, 2011;Liu et al, 2011;Takano et al, 2011;Baubet et al, 2012;Driskell et al, 2012;Haynes et al, 2012;Li et al, 2012;Wu et al, 2012;Chen et al, 2013;El-Karim et al, 2013;Peng et al, 2013;Walluscheck et al, 2013). Further, we compared the genes having functions spermatogenesis or apoptosis with the 117 genes showing the expression pattern decreasing from spermatocyte to spermatid (Fig.…”

Polo-like kinase is required for synaptonemal complex disassembly and phosphorylation in mouse spermatocytes

“…Moreover homozygous deletions of Plk2 or Plk3 do not result in fertility defects in mice (Ma et al, 2003;Myer et al, 2011). Like Plk1, Plk4 is essential for cell viability and its meiotic role has not been definitively tested, although when heterozygous, an ENU-induced Plk4 mutation within the kinase domain (Plk4 m1Lja ) causes a testicular phenotype of focal regions of germ-cell loss (Harris et al, 2011), but not meiotic arrest or infertility. Our finding that PLK4 is sequestered to the X-Y body during pachynema and diplonema could implicate a role in meiotic sex chromosome inactivation (Royo et al, 2010).…”

Novel compound heterozygous variants in PLK4 identified in a patient with autosomal recessive microcephaly and chorioretinopathy

“…[19][20][21] Hence, our current study patient likely survived due to the residual marginal activity of PLK4. We speculate that the reduced activity of the p.(M148V) variant rather than a loss-of-function prevented embryonic lethality.…”