Sirt6 regulates postnatal growth plate differentiation and proliferation via Ihh signaling

Abstract

Sirtuin 6 (Sirt6) is a mammalian homologue of NAD 1 -dependent histone deacetylase Sir2. Although Sirt62/2 mice exhibit growth retardation, the role of Sirt6 in cartilage metabolism is unclear. The aim of this study was to investigate the Sirt6 signaling pathway in cartilage metabolism. Immunohistological evaluation of the tibial growth plate in Sirt62/2 mice exhibited impaired proliferation and differentiation of chondrocytes, reduced expression of Indian hedgehog (Ihh), and a senescent phenotype. When Sirt6 was knocked down in chondrocytes in vitro, expression of Ihh and its downstream genes were reduced. Impaired differentiation by Sirt6 silencing was completely rescued by administration of a Hh signal agonist. When sirtuins were activated, chondrocyte differentiation was enhanced together with activation of Ihh signal, and these effects were abrogated by Sirt6 silencing. ChIP assay revealed the affinity of ATF4 to the Ihh promoter was markedly decreased by Sirt6 knockdown. These data indicate Sirt6 directly controls proliferation and differentiation of chondrocytes.T he stress-response and chromatin-silencing factor Sir2, a yeast sirtuin, is a NAD 1 -dependent histone deacetylase and is involved in various nuclear actions 1 . Among the seven mammalian sirtuin family members, sirtuin 6 (Sirt6) is localized to the nucleus and is involved in transcriptional silencing, genome stability, and longevity 2,3 . Sirt6 was originally identified as an ADP-ribosyltransferase 4 . Recent studies have demonstrated that the Sirt6 protein is a NAD1-dependent histone 3 deacetylase that targets acetyl-H3K9 and acetyl-H3K56 5,6 . Sirt6 deacetylates histone H3 lysine 9 (H3K9) on telomeres and plays a role in their stability 5 . Human Sirt6 also deacetylates C-terminal binding protein interacting protein (CtIP) and promotes DNA end resection 7 . Recent studies have revealed multiple functions of Sirt6 in the regulation of inflammation and metabolism. Sirt6 inhibits inflammation by suppressing NF-kB target molecules via interaction with the RelA subunit of NF-kB and by deacetylating H3K9 at target promoters 8 . In glycometabolism, Sirt6 functions as a corepressor of the transcription factor Hif1a and inhibits glycolysis through suppression of Hif1a activity 9 . As a result, Sirt6 null mice die before 4 weeks of age due to lethal hypoglycemia 4 .Sirt62/2 mice develop normally for the first two weeks except for reduced body size, which is apparent early after birth 4 . Sirt62/2 mice also exhibit features of premature aging, such as osteopenia and lordokyphosis 4 . Serum insulin-like growth factor 1 (IGF-1) and glucose levels are both markedly reduced in Sirt6 2/2 mice by the age of 24 days 4 . A recent study demonstrated that neural-specific deletion of Sirt6 in mice leads to postnatal growth retardation due to somatotropic attenuation through low growth hormone (GH) and IGF-1 levels 10 . Thus, Sirt6 contributes to skeletal growth in part through the regulation of IGF-1 secretion. However, the local functions of Sirt6 in postnatal gr...

Developmental Regulation of the Growth Plate and Cranial Synchondrosis

“…On the contrary, activating transcription factor 4 (ATF4) can activate the transcription of Ihh by binding to its promoter ). Sirtuin 6 may regulate Ihh expression by increasing the affinity of ATF4 for the Ihh promoter (Piao et al 2013).…”

Effect of Nutrition on Statural Growth

“…Thus, in SIRT6 null mice, the heights of each of the different zones of the GP and of the primary spongiosa are reduced. Studies by Piao et al [170] pointed to the role of Ihh activation in SIRT6 action on cell proliferation. SIRT6 binds to the Ihh promoter in primary chondrocytes, and Ihh is a downstream target of SIRT6 in chondrogenesis.…”

Docosahexaenoic Acid Induces Cell Death through Downregulation of Hedgehog Signaling via Surt6 Activation in Human EGFR Mutant Non-Small Cell Lung Cancer

“…Because recent reports have suggested that SIRT6 regulates Hh signaling [5], and because DHA can also modulate Hh signaling [28], we examined the potential involvement of Hh signaling in SIRT6-mediated apoptosis induced by DHA. Firstly, to confirm that DHA modulates Hh signaling in NSCLC cells, the mRNA and protein expression levels of Hh signaling molecules were assessed by reverse transcription-PCR (RT-PCR) and western blot analysis.…”

“…SIRT6 is localized in the nucleus [1] and has two types of enzymatic activities: mono-adenosine diphosphate ribosyltransferase [3] and deacetylase [4] activities, both of which are dependent on nicotinamide adenine dinucleotide [5]. SIRT6 regulates various cellular processes, including telomere maintenance, repair of damaged DNA, aging, immunity, and glucose homeostasis, and is important in cancer [3,[6][7][8][9].…”

“…SIRT6 regulates the Hedgehog (Hh) signaling pathway [5], which plays a crucial role in controlling stem cell maintenance [12], cell differentiation, cell proliferation [13], and tissue polarity [14] in vertebrate embryonic development. Alteration of Hh signaling promotes tumorigenesis in advanced basal cell carcinoma and medulloblastoma [15,16].…”