Department of Cell Biology and Anatomy, Hotchkiss Brain Institute, Alberta Children's Hospital Research Institute, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada.
Pigment Cell Melanoma Res. 2019 Jul;32(4):510-527. doi: 10.1111/pcmr.12776. Epub 2019 Mar 10.
Different camouflages work best with some background matching colour. Our understanding of the evolution of skin colour is based mainly on the genetics of pigmentation ("background matching"), with little known about the evolution of the neuroendocrine systems that facilitate "background adaptation" through colour phenotypic plasticity. To address the latter, we studied the evolution in vertebrates of three genes, pomc, pmch and pmchl, that code for α-MSH and two melanin-concentrating hormones (MCH and MCHL). These hormones induce either dispersion/aggregation or the synthesis of pigments. We find that α-MSH is highly conserved during evolution, as is its role in dispersing/synthesizing pigments. Also conserved is the three-exon pmch gene that encodes MCH, which participates in feeding behaviours. In contrast, pmchl (known previously as pmch), is a teleost-specific intron-less gene. Our data indicate that in zebrafish, pmchl-expressing neurons extend axons to the pituitary, supportive of an MCHL hormonal role, whereas zebrafish and Xenopus pmch+ neurons send axons dorsally in the brain. The evolution of these genes and acquisition of hormonal status for MCHL explain different mechanisms used by vertebrates to background-adapt.
不同的伪装在与某些背景匹配的颜色下效果最佳。我们对皮肤颜色进化的理解主要基于色素沉着的遗传学（“背景匹配”），而对于促进通过颜色表型可塑性进行“背景适应”的神经内分泌系统的进化知之甚少。为了解决后者，我们研究了三个基因在脊椎动物中的进化，即编码α-MSH 和两种黑色素浓缩激素（MCH 和 MCHL）的 pomc、pmch 和 pmchl。这些激素诱导色素的分散/聚集或合成。我们发现，α-MSH 在进化过程中高度保守，其分散/合成色素的作用也是如此。同样保守的是编码 MCH 的三外显子 pmch 基因，它参与摄食行为。相比之下，pmchl（以前称为 pmch）是一种硬骨鱼特有的无内含子基因。我们的数据表明，在斑马鱼中，pmchl 表达的神经元向垂体延伸轴突，支持 MCHL 激素的作用，而斑马鱼和非洲爪蟾的 pmch+神经元在大脑中背向发送轴突。这些基因的进化和 MCHL 的激素状态的获得解释了脊椎动物用于背景适应的不同机制。
