Dowling–Degos disease (DDD) is an autosomal dominant hereditary skin disease characterized by acquired reticular hyperpigmentation in flexural sites, and one of its causative genes is KRT5 gene. But the effect of KRT5, expressed only in keratinocytes, on melanocytes is unclear. Other pathogenic genes of DDD include POFUT1, POGLUT1 and PSENEN genes, which is involved in posttranslational modification of Notch receptor. In this study, we aim to determine the ablation of keratinocyte KRT5 affect melanogenesis in melanocyte through Notch signalling pathway. Here we found that KRT5 downregulation decreased the expression of the Notch ligand in keratinocytes and Notch1 intracellular domain in melanocytes, by establishing two cell models of ablation of KRT5 in keratinocytes based on CRISPR/Cas9 site-directed mutation and lentivirus-mediated shRNA. Treatment of melanocytes with Notch inhibitors had same effects with ablation of KRT5 on increase of TYR and decrease of Fascin1. Activation of Notch signalling reverses the effect of ablation of KRT5 on melanogenesis. Immunohistochemistry of DDD lesions with KRT5 gene mutation confirmed changes in the expression of relevant molecules in Notch signalling. Our research elucidates molecular mechanism of KRT5-Notch signalling pathway in the regulation of melanocytes by keratinocytes, and preliminary reveal the mechanism of DDD pigment abnormality caused by KRT5 mutation. These findings identify potential therapeutic targets of the Notch signalling pathway for the treatment of skin pigment disorders.

中文翻译：

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KRT5突变通过角质形成细胞和黑色素细胞之间的notch信号通路调控黑色素代谢

Dowling-Degos病（DDD）是一种常染色体显性遗传性皮肤病，其特征是弯曲部位获得性网状色素沉着过度，其致病基因之一是KRT5基因。但仅在角质形成细胞中表达的 KRT5 对黑素细胞的影响尚不清楚。DDD的其他致病基因包括POFUT1、POGLUT1和PSENEN基因，参与 Notch 受体的翻译后修饰。在这项研究中，我们旨在确定角质形成细胞 KRT5 的消融通过 Notch 信号通路影响黑色素细胞中的黑色素生成。在这里，我们发现 KRT5 下调降低了角质形成细胞中 Notch 配体和黑素细胞中 Notch1 胞内结构域的表达，通过建立两种基于 CRISPR/Cas9 定点突变和慢病毒介导的 shRNA 消融角质形成细胞中 KRT5 的细胞模型。用 Notch 抑制剂处理黑素细胞与 KRT5 消融对 TYR 增加和 Fascin1 减少具有相同的效果。Notch 信号的激活逆转了 KRT5 消融对黑色素生成的影响。具有 KRT5 基因突变的 DDD 病变的免疫组织化学证实了 Notch 信号传导中相关分子表达的变化。本研究阐明了KRT5-Notch信号通路在角质形成细胞调控黑素细胞中的分子机制，初步揭示了DDD色素异常引起的角质形成机制。KRT5突变。这些发现确定了用于治疗皮肤色素紊乱的 Notch 信号通路的潜在治疗靶点。