Sirt1 Deficiency Attenuates Spermatogenesis and Germ Cell Function

Abstract

In mammals, Sirt1, a member of the sirtuin family of proteins, functions as a nicotinamide adenine dinucleotide-dependent protein deactylase, and has important physiological roles, including the regulation of glucose metabolism, cell survival, and mitochondrial respiration. The initial investigations of Sirt1 deficient mice have revealed a phenotype that includes a reduced lifespan, small size, and an increased frequency of abnormal sperm. We have now performed a detailed analysis of the molecular and functional effects of Sirt1 deficiency in the germ line of Sirt1 knock-out (−/−) mice. We find that Sirt1 deficiency markedly attenuates spermatogenesis, but not oogenesis. Numbers of mature sperm and spermatogenic precursors, as early as d15.5 of development, are significantly reduced (∼2-10-fold less; P≤0.004) in numbers in Sirt1−/− mice, whereas Sirt1 deficiency did not effect the efficiency oocyte production following superovulation of female mice. Furthermore, the proportion of mature sperm with elevated DNA damage (∼7.5% of total epididymal sperm; P = 0.02) was significantly increased in adult Sirt1−/− males. Analysis of global gene expression by microarray analysis in Sirt1 deficient testis revealed dysregulated expression of 85 genes, which were enriched (P<0.05) for genes involved in spermatogenesis and protein sumoylation. To assess the function of Sirt1 deficient germ cells, we compared the efficiency of generating embryos and viable offspring in in vitro fertilization (IVF) experiments using gametes from Sirt1−/− and sibling Sirt1+/− mice. While viable animals were derived in both Sirt1−/− X wild type and Sirt1−/− X Sirt1−/− crosses, the efficiency of producing both 2-cell zygotes and viable offspring was diminished when IVF was performed with Sirt1−/− sperm and/or oocytes. Together, these data support an important role for Sirt1 in spermatogenesis, including spermatogenic stem cells, as well as germ cell function.

SIRT1 stabilizes PML promoting its sumoylation

“…Interestingly, it has been described that in testis derived from SIRT1 À/À mice there is an overrepresentation of genes involved in sumoylation, a finding that has been proposed to represent a putative compensatory mechanism to promote sumoylation of specific proteins. 38 Regulation of PML by other HDACs has been reported. Thus, class I HDACs interact with PML and this interaction is required for the transcriptional repression function of PML.…”

NAMPT (visfatin) in the chicken testis: influence of sexual maturation on cellular localization, plasma levels and gene and protein expression

“…In mouse fibroblasts, NAMPT treatment lead to a dose-dependent increase in both cellular NAD levels as well as SIRT1 expression (Revollo et al 2004). SIRT1 itself appears to be an important enzyme for testicular function as SIRT1 deficiency has been found to attenuate spermatogenesis and germ cell function in mice (Coussens et al 2008). Moreover, male Sirt1 K/K knockout mice had increased proportion of mature sperm with elevated DNA damage, while a microarray analysis of SIRT1-deficient testis revealed dysregulated expression of 85 genes that are involved in spermatogenesis and protein sumoylation (Coussens et al 2008).…”

“…SIRT1 itself appears to be an important enzyme for testicular function as SIRT1 deficiency has been found to attenuate spermatogenesis and germ cell function in mice (Coussens et al 2008). Moreover, male Sirt1 K/K knockout mice had increased proportion of mature sperm with elevated DNA damage, while a microarray analysis of SIRT1-deficient testis revealed dysregulated expression of 85 genes that are involved in spermatogenesis and protein sumoylation (Coussens et al 2008). In addition to increasing NAD production, NAMPT has been found to increase expression of vascular endothelial growth factor (VEGFA) and VEGFA receptor-2 in vascular endothelial cells through activation of the MAP kinase (MAPK1) and phosphatidylinositol-3-kinase/ AKT1 pathways (Adya et al 2008).…”

Sirtuin 1 regulation of developmental genes during differentiation of stem cells

“…Sirt1 influences the neural and glial specification of neural precursors (5), regulates differentiation of skeletal myoblast (6), and inhibits spermatogenesis (7). Independently generated Sirt1-deficient mice are reported to exhibit severe neural defects, including exencephaly and disturbed neuroretinal morphogenesis (8,9).…”