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，它是在自然选择下进化出来的，并导致了 人类肤色的多样化。重要的是，产生黑色素的黑素细胞的数量及其 人体的解剖位置没有差异，只有不同的黑色素生成决定了人类的 色素沉着多样性。我们的长期目标是建立对表观遗传学和 转录机制，规定精确的人类黑素生成基因表达程序，管理 人类正常范围的色素变化和疾病易感性。关于人类的关键洞察 黑素生成来自于对涉及色素沉着过少和过度疾病的基因进行定位，基因组- 人群中正常肤色和毛发颜色变异与遗传的广谱关联研究 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肤色 人类的变异表明，许多控制色素沉着的基因座仍然未知。通过进行一次 在全基因组CRISPR屏幕上，PI发现了驱动人类色素沉着的新候选基因。其中 在新发现的色素沉着基因中，我们发现KLF转录因子在 浅色和深色人黑素细胞并在基因剂量上对黑素合成起拮抗作用 依赖的态度。我们将研究这些密切相关因素的细胞和分子机制。 以了解它们在人类色素沉着变异中的作用。与其他人类表型一致，我们 假设大多数DNA变异导致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控图景 通过执行无偏见的表观基因组图谱来发现具有差异的假定增强子，从而实现不同肤色的人类 基因调控活动。我们将通过聚焦功能分析来确定候选发散增强因子的优先顺序 关于以前与肤色研究相关或与新发现重叠的基因座 由我们的全基因组遗传筛查确定的黑色素生成基因。通过基因扰动研究，我们 将从数量上证实顺式调控变化是否会影响基因表达。在少年派博士后的基础上 在接下来的五年里，该实验室将结合不同的方法来了解基因型到表型 人类皮肤色素沉着变异中的关联。这些方法包括多能干细胞分化。 概括了人类体外黑素合成的模型，基因组工程，大规模平行的报告分析， 转基因的单细胞图谱方法、黑色素定量测量和验证实验 老鼠模型。通过我们对黑色素等高度可量化特征的研究，我们将提供对 基因组中的基因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，这对人类的发展、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.