Somatic mutations distinguish melanocyte subpopulations in human skin
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PROVIDER: PRJNA1210612 | ENA |
REPOSITORIES: ENA
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Project description:To better understand the homeostatic mechanisms governing melanocytes, we performed deep phenotyping of single-cell expansions of melanocytes from human skin. In total, we interrogated the mutational landscapes, gene expression profiles, and morphological features of 297 melanocytes from 31 donors. To our surprise, a population of melanocytes with low mutation burden was maintained in sun damaged skin. These melanocytes were more stem-like, smaller, and less dendritic than their counterparts with high mutation burdens. We used single-cell spatial transcriptomics (10X Xenium) to reveal the spatial distribution of melanocytes inferred to have low and high mutation burdens (LowMut and HighMut cells), based on their gene expression profiles. LowMut melanocytes were found in hair follicles as well as in the interfollicular epidermis, whereas HighMut melanocytes resided almost exclusively in the interfollicular epidermis. We propose that melanocytes in the hair follicle occupy a privileged niche, protected from UV radiation, but periodically migrate out of the hair follicle to replenish the interfollicular epidermis after waves of photodamage. More broadly, our study illustrates the advantages of a cell atlas that includes mutational information, as cells can change their cellular states and positional coordinates over time, but mutations are like scars, providing a historical record of the homeostatic processes that were operative on each cell.
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Project description:Somatic mutations in individual skin cells
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Project description:Somatic mutations in individual skin cells
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Project description:Melanocyte stem cells (McSCs) of the hair follicle are a rare cell population within the skin and are notably underrepresented in whole-skin, single-cell RNA sequencing (scRNA-seq) datasets. Using a cell enrichment strategy to isolate KIT+/CD45- cells from the telogen skin of adult female C57BL/6J mice, we evaluated the transcriptional landscape of quiescent McSCs (qMcSCs) at high resolution. Through this evaluation, we confirmed existing molecular signatures for qMcCS subpopulations (e.g., Kit+, Cd34+/-, Plp1+, Cd274+/-, Thy1+, Cdh3+/-) and identified novel qMcSC subpopulations, including two that differentially regulate their immune privilege status. Within qMcSC subpopulations, we also predicted melanocyte differentiation potential, neural crest potential, and quiescence depth. Taken together, the results demonstrate that the qMcSC population is heterogenous and future studies focused on investigating changes in qMcSCs should consider changes in subpopulation composition.
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Project description:A better understanding of human melanocyte and melanocyte stem cell (McSC) biology is essential for treating melanocyte-related diseases. This study employed an inherited pigmentation disorder carrying the SASH1S519N variant in a Hispanic family to investigate the SASH1 function in melanocyte lineage and the underlying mechanism for this disorder. We used a multidisciplinary approach, including clinical exams, human cell assays, yeast two-hybrid screening, and biochemical techniques. Results linked early hair graying to the SASH1S519N variant, a previously unrecognized clinical phenotype in hyperpigmentation disorders. We identified SASH1 as a novel regulator in McSC maintenance and discovered that TNKS2 is crucial for SASH1’s role in vitro. Additionally, the S519N variant is located in one of multiple tankyrase binding motifs and alters the binding kinetics and affinity of the interaction. In summary, this disorder showcases accelerated aging in human McSC, linking both gain and loss of pigmentation to McSC dysfunction in the same individuals. The findings offer new insights into the roles of SASH1 and TNKS2 in McSC maintenance and the molecular mechanisms of pigmentation disorders. We propose that a comprehensive clinical evaluation of patients with skin disorders should include an assessment and history of hair pigmentation loss.
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Project description:To elucidate mechanisms governing McSC self-renewal and differentiation we analyzed individual transcriptomes from thousands of melanocyte lineage cells during the regeneration process. We identified transcriptional signatures for McSCs, deciphered transcriptional changes and intermediate cell states during regeneration, and analyzed cell-cell signaling changes to discover mechanisms governing melanocyte regeneration.
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Project description:MIcrophthalmia-associated Transcription Factor (MITF) regulates melanocyte and melanoma physiology. ShRNA-mediated silencing of the NURF subunit BPTF revealed its essential role in several melanoma cell lines and in untransformed melanocytes in vitro. Comparative RNA-seq shows that MITF and BPTF co-regulate overlapping gene expression programs in cell lines in vitro. Somatic and specific inactivation of Bptf in developing murine melanoblasts in vivo shows that Bptf regulates their proliferation, migration and morphology. Once born, Bptf-mutant mice display premature greying where the second post-natal coat is white. This second coat is normally pigmented by differentiated melanocytes derived from the adult melanocyte stem cell (MSC) population that is stimulated to proliferate and differentiate at anagen. An MSC population is established and maintained throughout the life of the Bptf- mutant mice, but these MSCs are abnormal and at anagen, give rise to reduced numbers of transient amplifying cells (TACs) that do not express melanocyte markers and fail to differentiate into mature melanin producing melanocytes. MSCs display a transcriptionally repressed chromatin state and Bptf is essential for reactivation of the melanocyte gene expression program at anagen, the subsequent normal proliferation of TACs and their differentiation into mature melanocytes.
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Project description:Recent genome sequencing efforts have identified millions of somatic mutations in cancer. However, the functional impact of most variants is poorly understood. Here we characterize 194 somatic mutations identified in primary lung adenocarcinomas using L1000 high-throughput gene-expression assays followed by expression-based variant impact phenotyping (eVIP), a method that uses gene expression changes to distinguish impactful from netural somatic mutations. This series represents the main experiment of the study where 8 replicates of wild-type and mutant ORFs are introduced into A549 cell lines. An ORF library containing wild-type and mutated versions of genes found to be mutated in lung cancer are introduced in A549 cell lines and measurements are made using the L1000 high-throughput gene-expression assay. These are done with 8 replicate experiemnts. The data are processed through a computational system, that converts raw fluorescence intensities into differential gene expression signatures. The data at each stage of the pre-processing are available: (LXB) - raw, unprocessed flow cytometry data from Luminex scanners. One LXB file is generated for each well of a 384-well plate, and each file contains a fluorescence intensity value for every observed analyte in the well. (Q2NORM) - gene expression profiles of directly measured landmark transcripts. Normalized using invariant set scaling followed by quantile normalization. (Z-SCORES) - signatures with differentially expressed genes computed by robust z-scores for each profile relative to control (relative to plate population as control)
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Project description:Melanocyte are melanin-producing cells located in the bottom layer of the skin's epidermis and in the hair follicle. Melanin is the pigment primarily responsible notably for skin and hair color. Our team had previously shown a role for B-raf and C-raf genes in the maintenance of melanocyte stem cells located in mice hair follicle (Valluet et al, 2012). The aim of the present project was to understand the role of B-RAF and C-RAF kinases in melanocyte stem cell self-renewal. To reach this goal, we have generated a new mouse model in which cells of the melanocyte lineage can be followed by GFP expression. We performed gene array on melanocyte stem cell B-raf+/+; C-raf+/+ and B-raf-/-; C-raf-/-in order to identify the RAF kinases target genes which are involved in melanocyte stem cell self-renewal. Moreover, to better characterize the melanocyte stem cell population, we compared its gene expression profile to the melanoblast one (melanocyte stem cell's progenitors).
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