Epostatic connections between microphthalmia-associated trancecription factor and endothelin signaling in Waardenburg syndrome and other pigmentary disorders

Division of Stem Cell Medicin

Key role for transforming growth factor-β in melanocyte stem cell immaturity and quiescence

Division of Stem Cell Medicin

A stem cell-derived gene (Sddr) negatively regulates differentiation of embryonic stem cells

金沢大学医薬保健研究域医学系Embryonic stem (ES) cells, derived from the inner cell mass of blastocysts, are pluripotent and continue to self-renew. To better understand the molecular mechanisms under-lying self-renewal, we have been searching for a gene(s) which is specifically expressed in self-renewing ES cells. Here we report the isolation and characterization of a novel gene, Sddr (stem cell-derived differentiation regulator). Sddr was highly expressed in undifferentiated ES cells, and its expression was downregulated upon differentiation. In addition to ES cells, Sddr expression was observed strongly in ovary, and weakly in lung. Immunostaining and cellular fractionation analyses suggested that Sddr is a cytoplasmic protein associated with the cytoskeleton. Sddr-null ES cells showed no remarkable abnormalities in their undifferentiated state. In contrast, in differentiating Sddr-null cells, induction of several differentiation-associated markers was enhanced, and downregulation of self-renewal marker genes was accelerated, as compared with wild-type cells. These results suggest that although it is dispensable for ES cell self-renewal, Sddr is a negative regulator of ES cell differentiation. © 2009 UBC Press

Genotoxic Stress Abrogates Renewal of Melanocyte Stem Cells by Triggering Their Differentiation

SummarySomatic stem cell depletion due to the accumulation of DNA damage has been implicated in the appearance of aging-related phenotypes. Hair graying, a typical sign of aging in mammals, is caused by the incomplete maintenance of melanocyte stem cells (MSCs) with age. Here, we report that irreparable DNA damage, as caused by ionizing radiation, abrogates renewal of MSCs in mice. Surprisingly, the DNA-damage response triggers MSC differentiation into mature melanocytes in the niche, rather than inducing their apoptosis or senescence. The resulting MSC depletion leads to irreversible hair graying. Furthermore, deficiency of Ataxia-telangiectasia mutated (ATM), a central transducer kinase of the DNA-damage response, sensitizes MSCs to ectopic differentiation, demonstrating that the kinase protects MSCs from their premature differentiation by functioning as a “stemness checkpoint” to maintain the stem cell quality and quantity

Genotoxic stress abrogates renewal of melanocyte stem cells by triggering their differentiation.

金沢大学医薬保健研究域　医学系Somatic stem cell depletion due to the accumulation of DNA damage has been implicated in the appearance of aging-related phenotypes. Hair graying, a typical sign of aging in mammals, is caused by the incomplete maintenance of melanocyte stem cells (MSCs) with age. Here, we report that irreparable DNA damage, as caused by ionizing radiation, abrogates renewal of MSCs in mice. Surprisingly, the DNA-damage response triggers MSC differentiation into mature melanocytes in the niche, rather than inducing their apoptosis or senescence. The resulting MSC depletion leads to irreversible hair graying. Furthermore, deficiency of Ataxia-telangiectasia mutated (ATM), a central transducer kinase of the DNA-damage response, sensitizes MSCs to ectopic differentiation, demonstrating that the kinase protects MSCs from their premature differentiation by functioning as a "stemness checkpoint" to maintain the stem cell quality and quantity. © 2009 Elsevier Inc. All rights reserved

Intracrine activity involving NAD-dependent circadian steroidogenic activity governs age-associated meibomian gland dysfunction

新たなイントラクライン機構を用いた加齢性眼疾患治療へ --眼局所のホルモンの加齢変化とサーカディアンリズムが鍵--. 京都大学プレスリリース. 2022-02-14.Canonically, hormones are produced in the endocrine organs and delivered to target tissues. However, for steroids, the concept of tissue intracrinology, whereby hormones are produced in the tissues where they exert their effect without release into circulation, has been proposed, but its role in physiology/disease remains unclear. The meibomian glands in the eyelids produce oil to prevent tear evaporation, which reduces with aging. Here, we demonstrate that (re)activation of local intracrine activity through nicotinamide adenine dinucleotide (NAD+)-dependent circadian 3β-hydroxyl-steroid dehydrogenase (3β-HSD) activity ameliorates age-associated meibomian gland dysfunction and accompanying evaporative dry eye disease. Genetic ablation of 3β-HSD nullified local steroidogenesis and led to atrophy of the meibomian gland. Conversely, reactivation of 3β-HSD activity by boosting its coenzyme NAD+ availability improved glandular cell proliferation and alleviated the dry eye disease phenotype. Both women and men express 3β-HSD in the meibomian gland. Enhancing local steroidogenesis may help combat age-associated meibomian gland dysfunction

Review: Melanocyte Migration and Survival Controlled by SCF/c-kit Expression

Melanocytes are derived from neural crest and migrate along the dorsolateral pathway to colonize the final destination in the skin. Stem cell factor and its receptor c-kit were identified as gene products of Sl and W mutant loci; both of them were known to have defects in melanocytes survival. In this review, we focus on the function of stem cell factor and c-kit in melanocyte migration and survival, which has become clearer in the last decade. By analysis of both molecules in wild-type and white spotting mutant mice, ligand and receptor set were shown to play multiple roles in the development of melanocytes in mouse ontogeny. Functional blockade of c-kit by specific monoclonal antibody illustrated distinct c-kit dependent and independent stages in melanocyte development. Finally, SCF transgene expression demonstrated that part of the c-kit dependent step is regulated by spatiotemporally specific ligand expression and also indicated the presence of c-kit independent melanocyte stem cells in postnatal skin