Doctoral Dissertation Improvement: Primate Cranial Morphology in a Comparative Context

该项目由圣路易斯华盛顿大学的博士研究生杰西卡·乔加尼克在詹姆斯·切弗鲁德博士的指导下进行，将遗传学、解剖学和进化生物学领域结合在一起，对灵长类动物的颅骨形态进行了比较研究。这项研究考察了导致灵长类头骨正常变异的遗传变异，以及在人类和灵长类进化中导致头骨大小和形状戏剧性变化的基因的分子进化和人类种群变异。人类头骨的组织结构与典型的哺乳动物模式截然不同。它有一个扩大的神经穹顶，一个短小的直立的脸，和一个弯曲的颅底。导致这些特征变异的基因可能已经在人类谱系中被修改，这些基因将使用灵长类动物模型--狒狒--来识别。这将通过以下方式完成：1)测量纯种狒狒种群的头面部大小和形状变异，2)识别导致这种变异的遗传变异，以及3)表征这些遗传变异的分子进化，包括在灵长类动物的广泛样本中，以及在人类群体中。为了实现这些目标，将使用3D数字化仪和CT扫描从大量纯种狒狒的头骨表面和内部获得三维地标坐标。这些特征将与狒狒基因组的变异进行对比测试，以确定分子变异导致头面部变异的区域。将对这些区域进行调查，以确定灵长类动物之间以及人类种群内的选择和进化率异质性的特征。由于遗传变异是进化变化的基础，识别性状变异的遗传位点是研究像人类头盖骨这样的复杂形态进化的必要步骤。了解一种性状的遗传基础和进化史也有助于我们管理、治疗和研究颅骨异常和具有临床和生物医学相关性的疾病的起源。

This project by doctoral student Jessica Joganic, under the supervision of Dr. James Cheverud at Washington University, St. Louis, brings together the fields of genetics, anatomy, and evolutionary biology in a comparative examination of primate cranial morphology. The research examines the genetic variants contributing to normal variation in primate skulls, as well as the molecular evolution and human population variation of genes responsible for the dramatic changes in the size and shape of the skull in human and primate evolution. The organization of the human skull represents a unique departure from the typical mammalian pattern. It has an enlarged neural vault, a short upright face, and a flexed cranial base. Genes contributing to variation in these traits that may have been modified in the human lineage will be identified using a primate model, the baboon. This will be accomplished by: 1) measuring craniofacial size and shape variation in a population of pedigreed baboons, 2) identifying genetic variants contributing to this variation, and 3) characterizing the molecular evolution of these genetic variants, both across a broad sample of primates, as well as within human populations. To achieve these goals, three-dimensional landmark coordinates will be obtained from the surface and interior of skulls from a large population of pedigreed baboons using a 3D digitizer and CT scans. These traits will be tested against variation in the baboon's genomes to identify regions where molecular variation contributes to craniofacial variation. These regions will be investigated for signatures of selection and evolutionary rate heterogeneity across primates as well as within human populations. As genetic variation is the basis for evolutionary change, identifying the genetic loci underlying trait variation is a necessary step in studying the evolution of complex morphologies like the human cranium. Knowledge of a trait's genetic basis and evolutionary history also informs our ability to manage, treat, and study the origin of skull abnormalities and diseases that have clinical and biomedical relevance.