6533b82efe1ef96bd12939e6

RESEARCH PRODUCT

Développement postnatal et évolution du complexe craniofacial chezles rongeurs

subject

description

Understanding developmental mechanisms in evolution is crucial to apprehend the diversification of organismal forms. In mammals, changes occur during all development phases (prenatal and postnatal). Postnatal growth plays an essential role in the acquisition of the adult shape. During this period, the craniofacial complex undergoes many changes in functional constraint forcing the different tissue to accommodate while adjusting, along the growth and at the adult stage, to a certain level of functional performance. These different developmental interactions respond to several influencing factors such as molecular, genetic and cellular processes but also the environment. The latter will play on these interactions, but in different ways between the prenatal and postnatal phases, as gestational environment and environment at birth are different. For testing the interactions between the developing organism and its environment and the potential evolutionary consequences, Rodentia is a good example of broad diversity in all aspects (wide variety of forms, in diets, behavior and ecology) and thus a study group of choice. It is a very diverse and disparate mammal order, in which changes can be observed on a large scale. In addition, it includes model organisms that can be easily reared in laboratory following a precise experimental configuration to test the effects of diverse sources of variation. The craniofacial complex is a highly integrated structure, architecturally complex, as it is composed of many skeletal elements, and functionally, as it is involved in various tasks essential to the organism. At the same time, and somewhat paradoxically, this unit is highly scalable and presents a great diversity of forms. The basis of craniofacial shape variation and its control are as much, related to the additive effects of genes as to their epigenetic and context-specific interactions during development. These epigenetic interactions during growth will respond to mechanical and other stimuli between the ossification centers, the tissues and organs making up the head. In particular, these interactions control the spatialization and intensity of bone remodeling in response to other tissue strain. They will thus compensate and coordinate the growth of the different tissues and organs in order to acquire and/or maintain certain functions, such as the occlusion between the upper and lower jaws. These epigenetic interactions are thus essential to the normal development of the skeleton in general and the skull in particular. By responding to changes in forces and movements, they will be a potential driver of microevolutionary changes (and thus macroevolutionary changes) at the morphological level favoring adaptive directions of variation and generating new functional covariations between traits. Despite this central role, the importance of these interactions in the expression of inter-specific differences and in the longer term in the dynamics of clades remains poorly understood. Analysis of the tempo of adult disparity acquisition during ontogeny is a key element in understanding the differential filling of the shape space by clades. This project aimed I) at studying the establishment of craniofacial disparity in rodents during development on a macroevolutionary scale and then on a finer taxonomic scale; and II) at estimating the importance of the epigenetic processes during this postnatal growth.