Human Sensory Neurons Modulate Melanocytes Through Secretion of RGMB

Melanocytes are surrounded by diverse cells including sensory neurons in our skin, but their interaction and functional importance has been poorly investigated. In this study, we found that melanocytes and nociceptive neurons contact more in human skin color patch tissue than control. Co-culture with human iPS cell-derived sensory neurons significantly induced morphogenesis and pigmentation of human melanocytes. To reveal melanocytes-stimulating factors secreted from neurons, we performed proteomic analyses and identified RGMB in the sensory neuron-conditioned media. RGMB protein induced morphogenesis and melanin production of melanocytes, demonstrating that RGMB is a melanocyte-stimulating factor released from sensory neurons. Transcriptome analysis suggested that the melanosome transport machinery could be controlled by RGMB, which led us to identify vesicle production response of melanocytes upon RGMB treatment. This study discovered a role of sensory neurons to modulate multiple aspects of human melanocytes through secretion of a key factor RGMB. RNA-seq of melanocytes upon recombinant RGMB treatment and RGMB depleted IPSC-derived sensory neuron conditioned media.

皮肤中的黑素细胞（melanocytes）周围存在包括感觉神经元（sensory neurons）在内的多种细胞，但二者间的相互作用及其功能重要性迄今尚未得到充分研究。本研究发现，相较于对照组，人类皮肤色素斑组织中黑素细胞与伤害感受性神经元（nociceptive neurons）的接触更为频繁。将人类诱导多能干细胞（induced pluripotent stem cells, iPS）分化得到的感觉神经元与人类黑素细胞共培养，可显著诱导黑素细胞发生形态改变并促进其色素沉着。为筛选神经元分泌的黑素细胞刺激因子，本研究开展了蛋白组学分析（proteomic analyses），并在感觉神经元条件培养基（conditioned media）中鉴定出RGMB蛋白。RGMB蛋白可诱导黑素细胞发生形态改变并促进黑色素生成，由此证实RGMB是感觉神经元释放的黑素细胞刺激因子。转录组分析（transcriptome analysis）结果显示，黑素小体转运机制（melanosome transport machinery）可受RGMB调控，这一发现指引我们进一步探究了黑素细胞在RGMB处理后的囊泡生成应答。本研究揭示了感觉神经元通过分泌关键因子RGMB，调控人类黑素细胞多项生命活动的全新功能。本研究还针对两组样本开展了RNA测序（RNA sequencing, RNA-seq）：一组为经重组RGMB处理的黑素细胞，另一组为经RGMB敲低的iPS细胞来源感觉神经元条件培养基处理的黑素细胞。