Dowling-Degos disease (DDD), or reticular pigmented anomaly of the flexures, is a type of rare autosomal-dominant genodermatosis characterized by reticular hyperpigmentation and hypopigmentation of the flexures, such as the neck, axilla, and areas below the breasts and groin, and shows considerable heterogeneity. Loss-of-function mutations of keratin 5 (KRT5) have been identified in DDD individuals. In this study, we collected DNA samples from a large Chinese family affected by generalized DDD and found no mutation of KRT5. We performed a genome-wide linkage analysis of this family and mapped generalized DDD to a region between rs1293713 and rs244123 on chromosome 20 [corrected]. By exome sequencing, we identified nonsense mutation c.430G>T (p.Glu144(∗)) in POFUT1, which encodes protein O-fucosyltransferase 1, in the family. Study of an additional generalized DDD individual revealed the heterozygous deletion mutation c.482delA (p.Lys161Serfs(∗)42) in POFUT1. Knockdown of POFUT1 reduces the expression of NOTCH1, NOTCH2, HES1, and KRT5 in HaCaT cells. Using zebrafish, we showed that pofut1 is expressed in the skin and other organs. Morpholino knockdown of pofut1 in zebrafish produced a phenotype characteristic of hypopigmentation at 48 hr postfertilization (hpf) and abnormal melanin distribution at 72 hpf, replicating the clinical phenotype observed in our DDD individuals. At 48 and 72 hpf, tyrosinase activities decreased by 33% and 45%, respectively, and melanin protein contents decreased by 20% and 25%, respectively. Our findings demonstrate that POFUT1 mutations cause generalized DDD. These results strongly suggest that the protein product of POFUT1 plays a significant and conserved role in melanin synthesis and transport.
The JmjC domain histone H3K36me2/me1 demethylase NDY1/KDM2B is overexpressed in various types of cancer. Here we show that knocking down NDY1 in a set of ten cell lines derived from a broad range of human tumors inhibited their anchorage-dependent and anchorage-independent growth by inducing senescence and/or apoptosis in some and by inhibiting G1 progression in all. We further show that the knockdown of NDY1 in mammary adenocarcinoma cell lines decreased the number, size and replating efficiency of mammospheres and downregulated the stem cell markers ALDH and CD44, while upregulating CD24. These findings combined, suggest that NDY1 is required for the self-renewal of cancer stem cells and are in agreement with additional findings showing that, tumor cells in which NDY1 was knocked down undergo differentiation and a higher number of them is required to induce mammary adenocarcinomas, upon orthotopic injection in animals. Mechanistically, NDY1 functions as a master regulator of a set of microRNAs that target several members of the polycomb complexes PRC1 and PRC2 and its knockdown results in the de-repression of these microRNAs and the downregulation of their polycomb targets. Consistent with these observations, NDY1/KDM2B is expressed at higher levels in basal-like triple negative breast cancers and its overexpression is associated with higher rates of relapse after treatment. In addition, NDY1-regulated microRNAs are downregulated in both normal and cancer mammary stem cells. Finally, in primary human breast cancer, NDY1/KDM2B expression correlates negatively with the expression of the NDY1-regulated microRNAs, and positively with the expression of their PRC targets.
The skin is the largest organ of the body. The establishment of immunological memory in the skin is a crucial component of the adaptive immune response. Once naive T cells are activated by antigen-presenting cells, a small fraction of them differentiate into precursor memory T cells. These precursor cells ultimately develop into several subsets of memory T cells, including central memory T (T CM ) cells, effector memory T (T EM ) cells, and tissue resident memory T (T RM ) cells. T RM cells have a unique transcriptional profile, and their most striking characteristics are their long-term survival (longevity) and low migration in peripheral tissues, including the skin. Under physiological conditions, T RM cells that reside in the skin can respond rapidly to pathogenic challenges. However, there is emerging evidence to support the vital role of T RM cells in the recurrence of chronic inflammatory skin disorders, including psoriasis, vitiligo, and fixed drug eruption, under pathological or uncontrolled conditions. Clarifying and characterizing the mechanisms that are involved in skin T RM cells will help provide promising strategies for reducing the frequency and magnitude of skin inflammation recurrence. Here, we discuss recent insights into the generation, homing, retention, and survival of T RM cells and share our perspectives on the biological characteristics of T RM cells in the recurrence of inflammatory skin disorders.
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