Gluckman Thanh-Lan, Mundy Nicholas I
Department of Zoology, University of Cambridge, Downing Street, Cambridge, United Kingdom.
Center for Interdisciplinary Research in Biology, Collège de France, Paris, France.
PLoS One. 2017 Mar 29;12(3):e0174714. doi: 10.1371/journal.pone.0174714. eCollection 2017.
Melanin pigmentation patterns are ubiquitous in animals and function in crypsis, physical protection, thermoregulation and signalling. In vertebrates, pigmentation patterns formed over large body regions as well as within appendages (hair/feathers) may be due to the differential distribution of pigment producing cells (melanocytes) and/or regulation of the melanin synthesis pathway. We took advantage of the pigmentation patterns of Japanese quail embryos (pale ventrum and patterned feathers dorsally) to explore the role of genes and their transcripts in regulating the function of the melanocortin-1-receptor (MC1R) via 1. activation: pro-opiomelanocortin (POMC), endoproteases prohormone convertase 1 (PC1) and 2 (PC2), and 2. inhibition-agouti signaling and agouti-related protein (ASIP and AGRP, respectively). Melanocytes are present in all feather follicles at both 8 and 12 days post-fertilisation (E8/E12), so differential deposition of melanocytes is not responsible for pigmentation patterns in embryonic quail. POMC transcripts expressed were a subset of those found in chicken and POMC expression within feather follicles was strong. PC1 was not expressed in feather follicles. PC2 was strongly expressed in all feather follicles at E12. ASIP transcript expression was variable and we report four novel ASIP transcripts. ASIP is strongly expressed in ventral feather follicles, but not dorsally. AGRP expression within feather follicles was weak. These results demonstrate that the pale-bellied quail phenotype probably involves inhibition of MC1R, as found previously. However, quail may require MC1R activation for eumelanogenesis in dorsal feathers which may have important implications for an understanding of colour pattern formation in vertebrates.
黑色素沉着模式在动物中普遍存在，具有伪装、物理保护、体温调节和信号传导等功能。在脊椎动物中，在大的身体区域以及附属器官（毛发/羽毛）内形成的色素沉着模式可能是由于产生色素的细胞（黑素细胞）的差异分布和/或黑色素合成途径的调节。我们利用日本鹌鹑胚胎的色素沉着模式（腹部浅色，背部羽毛有图案）来探索基因及其转录本通过以下方式调节黑素皮质素-1-受体（MC1R）功能的作用：1. 激活：阿黑皮素原（POMC）、激素原转化酶1（PC1）和2（PC2）；2. 抑制：刺鼠信号蛋白和刺鼠相关蛋白（分别为ASIP和AGRP）。在受精后8天和12天（E8/E12）时，所有毛囊中均存在黑素细胞，因此黑素细胞的差异沉积不是胚胎鹌鹑色素沉着模式的原因。所表达的POMC转录本是在鸡中发现的转录本的一个子集，并且毛囊内POMC的表达很强。PC1在毛囊中不表达。PC2在E12时在所有毛囊中均强烈表达。ASIP转录本的表达是可变的，我们报告了四种新的ASIP转录本。ASIP在腹部毛囊中强烈表达，但在背部则不表达。毛囊内AGRP的表达较弱。这些结果表明，如先前发现的那样，腹部浅色的鹌鹑表型可能涉及对MC1R的抑制。然而，鹌鹑背部羽毛的真黑素生成可能需要MC1R的激活，这可能对理解脊椎动物的颜色模式形成具有重要意义。
