Epigenetic and transcriptional mechanisms driving human pigmentation diversity

黑色素是人类色素沉着的关键决定因素，它在自然选择下进化， 人类肤色的多样化。重要的是，产生黑色素的黑色素细胞的数量及其 解剖位置在人类之间没有变化，只有不同的黑素生成决定了人类的 色素多样性我们的长期目标是建立一个全面的了解表观遗传和 转录机制决定了精确的人类黑素生成基因表达程序， 正常范围的人类色素变化和疾病易感性。关于人类的关键见解 黑色素生成来自于绘制与色素沉着不足和色素沉着过度疾病有关的基因，基因组， 在人群中正常范围的皮肤和头发颜色变化的广泛关联研究（GWAS）和遗传 小鼠毛色的研究尽管如此，目前的遗传知识只能解释一小部分的肤色 在人类中的变异表明许多控制色素沉着的位点仍然未知。通过进行 在全基因组CRISPR筛选中，PI发现了驱动人类色素沉着的新候选基因。之间 新的色素沉着基因的鉴定，我们发现KLF转录因子的差异表达， 浅色和深色的人黑素细胞，并在基因剂量下对黑素生成起拮抗作用 依赖的方式。我们将研究这些密切相关的因子的细胞和分子机制 了解它们在人类色素变化中的作用。与其他人类表型一致，我们 假设大多数DNA变异驱动正常范围的人类色素沉着和皮肤病易感性 可能位于基因组的非蛋白质编码区。我们将绘制黑素细胞的顺式调节景观， 通过进行无偏见的表观基因组分析来揭示具有不同肤色的人的推定增强子， 基因调控活性。我们将优先考虑候选趋异增强子的功能分析， 在先前与肤色GWAS研究相关或与新的 黑素生成基因通过我们的全基因组遗传筛选鉴定。通过遗传扰动研究， 将证实顺式调节变化是否定量地影响基因表达。在PI的博士后基础上 在接下来的五年里，该实验室将联合收割机多种方法来理解基因型到表型的关系。 人类皮肤色素变化的联系。这些方法包括多能干细胞分化 体外重现人类黑素生成的模型，基因组工程，大规模平行报告分析， 单细胞分析方法、定量黑色素测量和转基因动物中的验证实验 小鼠模型。通过我们对黑色素等高度可量化性状的研究，我们将提供以下见解： 基因组中编码的基因型变异如何引起基因表达的差异并导致表型 人类物种内部的差异，这对人类发展、健康和疾病都有影响。

Melanin is the key determinant of human pigmentation that has evolved under natural selection and has led to diversification of human skin color. Importantly, the number of melanin-producing-melanocytes and their anatomical location do not vary among humans, only varying melanogenesis determines the human pigmentation diversity. Our long-term goal is to build a comprehensive understanding of the epigenetic and transcriptional machinery that dictate precise human melanogenesis gene expression programs that governs normal-range human pigmentation variation and disease susceptibility. The key insights about human melanogenesis have come from mapping genes involved in hypo- and hyper pigmentation diseases, Genome- wide Association Studies (GWAS) of normal-range skin and hair color variation in human populations and genetic studies on mouse coat color. Nonetheless, current genetic knowledge can explain only a fraction of skin color variation in humans suggesting that many loci controlling pigmentation remain unknown. By conducting a genome-wide CRISPR screen, PI has uncovered novel candidate genes driving human pigmentation. Among the novel pigmentation genes identified, we found that KLF transcription factors are differentially expressed in light and dark colored human melanocytes and play an antagonistic role in melanogenesis in a gene dosage dependent manner. We will investigate the cellular and molecular mechanisms of these closely related factors to understand their roles in human pigmentation variation. Consistent with other human phenotypes, we hypothesize that most DNA variants driving normal-range human pigmentation and skin disease susceptibility may lie in non-protein-coding regions of genome. We will map the cis-regulatory landscape of melanocytes from diverse color humans by performing unbiased epigenomic profiling to uncover putative enhancers with divergent gene regulatory activity. We will prioritize the candidate divergent enhancers for functional analysis by focusing on loci that have either previously been associated with skin color GWAS studies or overlap with novel melanogenesis genes identified by our genome-wide genetic screen. Through genetic perturbation studies we will confirm whether cis-regulatory changes affect gene expression quantitatively. Building on PI’s postdoctoral work, over the next five years, the lab will combine diverse approaches to understand the genotype-to-phenotype connection in human skin pigmentation variation. These approaches include pluripotent stem cell differentiation models that recapitulate human melanogenesis in vitro, genome-engineering, massively parallel reporter assays, single-cell profiling methods, quantitative melanin measurements, and validation experiments in transgenic mouse models. Through our studies on a highly quantifiable trait such as melanin, we will provide insights into how genotypic variation encoded in genome give rise to differences in gene expression and leads to phenotypic divergence within human species, which has implication for human development, health and disease.