MITF: master regulator of melanocyte development, pigmentation, and UV-related skin disease risk

项目摘要 这是我们对MITF项目的竞争性更新，MITF是一种bHLHzip转录因子，我们已经证明， 在黑色素细胞中起主要的调节作用。我们的成就包括发现MITF 转录调节几乎所有已知的黑色素细胞特异性黑色素生物合成介质。我们联系了 MITF表达对黑素细胞刺激激素/MC 1 R信号传导和对翻译后调节的影响 c-Kit/MAPK，并利用这些见解来分子定义UV晒黑途径。我们生成了 分析了红头发/浅色皮肤致癌模型，发现内啡肽介导的行为 紫外线照射对皮肤的影响。我们的研究确定了MITF的靶基因和生物学行为， 皮肤癌预防（通过有效的色素作用）和肿瘤发生（如果基因组突变）。在 在最近的资助期内，我们产生了丰富的数据，包括为 当前应用。在分析MITF靶基因时，我们意外地观察到MITF占据和调控， PDL 1基因。MITF和一个关键的普遍存在的免疫耐受因子之间的这种奇怪的联系也被 值得注意的是，因为已知白癜风患者表现出显著低于预期的非黑色素瘤皮肤 癌症发病率这使我们认为PDL 1可能对紫外线诱导的高浓度积累具有耐受性。 新抗原负荷，特别是在非再生细胞中。除了广泛的分子分析，我们观察到， 白癜风样黑素细胞耗竭与免疫浸润在紫外线照射的PDL 1缺陷小鼠。这表明 利用PD 1抑制免疫清除新抗原积累性皮肤癌的机会 我们将在临床前模型中进行测试（目标1）。我们深入分析了 红头发/浅色皮肤表型，以及紫外线依赖性和独立的黑色素瘤风险。在小鼠模型中， 我们观察到几种cAMP诱导剂可以挽救深色/真黑素色素沉着并防止紫外线 致癌作用然而，这些试剂不能局部渗透人体皮肤，足以影响 色素沉着我们现在研究另一个靶点，即SIK，它的激酶抑制诱导CREB和MITF， 以及色素沉着。全身性的SIK抑制剂正在研究各种疾病，我们发现局部 给药在人和小鼠皮肤中都诱导强烈的真黑素变暗。鉴于潜在的翻译 对于人类，我们将使用临床前模型（目标2）评估其预防皮肤癌的作用，并测试其效果 对于BRAF或NRAS诱导的小鼠痣的安全性。最后，我们发现MITF是一种转录抑制因子， 神经元或许旺细胞发育中的许多基因。其中一些是已知的， 自身，拮抗MITF表达。这表明了一种相互压抑的发展“双重开关” 以确定神经嵴衍生物的谱系命运。我们将（目标3）仔细研究 MITF的抑制活性，使用模型来生物学测试这种谱系转换，并测试被抑制的靶点， 低MITF黑色素瘤亚型（促结缔组织增生）中的表达，需要诊断标志物。

PROJECT SUMMARY This is the competitive renewal of our program on MITF, a bHLHzip transcription factor that we have shown to play a master regulatory role in melanocytes. Our accomplishments include the discovery that MITF transcriptionally regulates nearly all known melanocyte-specific mediators of melanin biosynthesis. We linked MITF expression to Melanocyte Stimulating Hormone/MC1R signaling and to post-translational modulation by c-Kit/MAPK, and utilized these insights to molecularly define the UV-tanning pathway. We generated and analyzed red hair/light skin models of carcinogenesis, and discovered an endorphin-mediated behavioral impact of UV irradiation to skin. Our studies identified MITF target genes and biological behaviors that impact skin cancer prevention (through potent pigmentation effects) and oncogenesis (if genomically mutated). In the most recent grant period, we generated abundant data, including discoveries that set the background for the current application. In profiling MITF target genes, we unexpectedly observed MITF occupancy and regulation of the PDL1 gene. This odd connection between MITF and a key ubiquitous immune-tolerance factor was also notable because vitiligo patients are known to exhibit significantly lower-than-expected non-melanoma skin cancer incidence. This led us to consider that PDL1 may exert tolerance for accumulation of UV-induced high- neoantigen burdens, particularly in non-regenerating cells. Beyond extensive molecular analyses, we observed vitiligo-like melanocyte depletion with immune infiltration in UV-irradiated PDL1-deficient mice. This suggests an opportunity to use PD1 suppression for immune clearance of neoantigen-accumulating skin cancer precursors in high-risk individuals—which we will test in preclinical models (Aim 1). We have deeply analyzed red hair/light skin phenotypes, as well as UV-dependent and independent melanoma risk. In mouse models, we observed several cAMP-inducing agents to rescue dark/eumelanin pigmentation and protect against UV carcinogenesis. However, these agents could not topically penetrate human skin sufficiently to affect pigmentation. We now study an alternative target, SIK, whose kinase suppression induces CREB and MITF, as well as pigmentation. Systemic SIK inhibitors are being studied in a variety of diseases, and we found topical administration induces strong eumelanin-darkening in both human and mouse skin. Given potential translation to humans, we will evaluate this for skin cancer prevention using preclinical models (Aim 2), and test its effects for safety on BRAF- or NRAS-induced nevi in mice. Finally, we discovered MITF as a transcriptional repressor of numerous genes involved in neuron or Schwann cell development. Some of these are known to, themselves, antagonize MITF expression. This suggests a mutually repressive developmental “double-switch” to determine lineage destiny for neural crest derivatives. We will (Aim 3) scrutinize mechanisms underlying MITF's repressive activity, use models to biologically test such lineage switching, and test repressed targets for expression in a low-MITF melanoma subtype (desmoplastic) that is in need of diagnostic markers.