Targeted Disruption of Ing2 Results in Defective Spermatogenesis and Development of Soft-Tissue Sarcomas

Abstract

ING2 (inhibitor of growth family, member 2) is a member of the plant homeodomain (PHD)-containing ING family of putative tumor suppressors. As part of mSin3A-HDAC corepressor complexes, ING2 binds to tri-methylated lysine 4 of histone H3 (H3K4me3) to regulate chromatin modification and gene expression. ING2 also functionally interacts with the tumor suppressor protein p53 to regulate cellular senescence, apoptosis and DNA damage response in vitro, and is thus expected to modulate carcinogenesis and aging. Here we investigate the developmental and physiological functions of Ing2 through targeted germline disruption. Consistent with its abundant expression in mouse and human testes, male mice deficient for Ing2 showed abnormal spermatogenesis and were infertile. Numbers of mature sperm and sperm motility were significantly reduced in Ing2 −/− mice (∼2% of wild type, P<0.0001 and ∼10% of wild type, P<0.0001, respectively). Their testes showed degeneration of seminiferous tubules, meiotic arrest before pachytene stage with incomplete meiotic recombination, induction of p53, and enhanced apoptosis. This phenotype was only partially abrogated by concomitant loss of p53 in the germline. The arrested spermatocytes in Ing2 −/− testes were characterized by lack of specific HDAC1 accumulation and deregulated chromatin acetylation. The role of Ing2 in germ cell maturation may extend to human ING2 as well. Using publicly available gene expression datasets, low expression of ING2 was found in teratozoospermic sperm (>3-fold reduction) and in testes from patients with defective spermatogenesis (>7-fold reduction in Sertoli-cell only Syndrome). This study establishes ING2 as a novel regulator of spermatogenesis functioning through both p53- and chromatin-mediated mechanisms, suggests that an HDAC1/ING2/H3K4me3-regulated, stage-specific coordination of chromatin modifications is essential to normal spermatogenesis, and provides an animal model to study idiopathic and iatrogenic infertility in men. In addition, a bona fide tumor suppressive role of Ing2 is demonstrated by increased incidence of soft-tissue sarcomas in Ing2− /− mice.

Decreased expression of ING2 gene and its clinicopathological significance in Chinese NSCLC patients

“…This study revealed the knockdown of ING2 may accelerate cell cycle progression, which provides evidence for the potential link between loss of ING2 and cancer development. Another report by Saito M provides an animal model to study idiopathic and iatrogenic infertility in men found the function of ING2 in spermatogenesis and also demonstrated an evidence of ING2 as a tumor suppressor by increased incidence of soft-tissue sarcomas in Ing2-/-mice [33]. Interestingly, a research on colon cancer suggest ING2 also play roles as a tumor oncogene, which demonstrated ING2 was upregulated and increased invasion by enhanced MMP-13 [22].…”

A novel crosstalk between the tumor suppressors ING1 and ING2 regulates androgen receptor signaling

“…Apart from reduced size and higher incidence of lymphomas, Ing1 KO mice exhibit no other obvious morphological, physiological, or behavioral abnormalities, indicating that Ing1 function is dispensable for the viability under normal physiological conditions [14] and Ing2 might play a compensatory role in Ing1-depleted condition. In spite of high homology between ING1 and ING2, a different phenotype has been observed in their corresponding KO mice models [13][14][15]. Ing2 KO mice are characterized by defective spermatogenesis in males and higher incidence of soft tissue sarcomas [15].…”

“…In spite of high homology between ING1 and ING2, a different phenotype has been observed in their corresponding KO mice models [13][14][15]. Ing2 KO mice are characterized by defective spermatogenesis in males and higher incidence of soft tissue sarcomas [15]. Interestingly, the major tumor type observed in Ing2 KO mice was histiocytic sarcoma which showed increased incidence preferentially in males.…”

“…Their role as tumor suppressors is supported by the fact that their expression is decreased or lost in many human tumors [12]. Moreover, both Ing1 and Ing2 knockout (KO) mice were reported to promote tumor development [13][14][15]. However, analyzing the available microarray gene expression data from Oncomine database [16] has revealed that ING1 or ING2 messenger RNA (mRNA) is controversially either upregulated or downregulated in PCa compared to normal prostate gland [17][18][19][20][21].…”

Sertoli Cell-specific Expression of Metastasis-associated Protein 2 (MTA2) Is Required for Transcriptional Regulation of the Follicle-stimulating Hormone Receptor (FSHR) Gene during Spermatogenesis

“…6G). Thus, the homologous down- (27). We therefore investigated the localization of MTA2 immunoexpression in testicular tissues of patients with impairment of spermatogenesis and in controls.…”