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Abstract：
Extensive morphological variation found in mammals reflects the wide spectrum of their ecological adaptations. The highest morphological diversity is present in the craniofacial region, where geometry is mainly dictated by the bony skull. Mammalian craniofacial development represents complex multistep processes governed by numerous conserved genes that require precise spatio-temporal control. A central question in contemporary evolutionary biology is how a defined set of conserved genes can orchestrate formation of fundamentally different structures, and therefore how morphological variability arises. In principle, differential gene expression patterns during development are the source of morphological variation. With the emergence of multicellular organisms, precise regulation of gene expression in time and space is attributed to cis-regulatory elements. These elements contribute to higher-order chromatin structure and together with trans-acting factors control transcriptional landscapes that underlie intricate morphogenetic processes. Consequently, divergence in cis-regulation is believed to rewire existing gene regulatory networks and form the core of morphological evolution. This review outlines the fundamental principles of the genetic code and genomic regulation interplay during development. Recent work that deepened our comprehension of cis-regulatory element origin, divergence and function is presented here to illustrate the state-of-the-art research that uncovered the principles of morphological novelty. This article is part of the theme issue \'The mammalian skull: development, structure and function\'.
摘要：
在哺乳动物中发现的广泛形态变异反映了其生态适应的广泛范围。最高的形态多样性存在于颅面区域，几何形状主要由骨头骨决定。哺乳动物颅面发育代表了复杂的多步骤过程，受许多保守基因控制，需要精确的时空控制。当代进化生物学中的一个核心问题是一组确定的保守基因如何协调根本不同结构的形成，因此形态变异是如何产生的。原则上,发育过程中的差异基因表达模式是形态变异的来源。随着多细胞生物的出现,基因表达在时间和空间上的精确调控归因于顺式调控元件。这些元素有助于高级染色质结构，并与反式作用因子一起控制着复杂形态发生过程的转录景观。因此,顺式调控的分歧被认为是重新连接现有的基因调控网络，并形成形态进化的核心。这篇综述概述了发育过程中遗传密码和基因组调控相互作用的基本原理。最近的工作加深了我们对顺式调控元素起源的理解，这里介绍了发散和功能，以说明揭示形态学新颖性原理的最新研究。这篇文章是主题问题的一部分\'哺乳动物的头骨:发展,结构和功能。
