Investigating brain and skull development using embryonic and early postnatal mice
Open Access
- Author:
- Lesciotto, Kate
- Graduate Program:
- Anthropology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 16, 2020
- Committee Members:
- Joan Therese Richtsmeier, Dissertation Advisor/Co-Advisor
Joan Therese Richtsmeier, Committee Chair/Co-Chair
Timothy Michael Ryan, Committee Member
George H Perry, Committee Member
Patrick James Drew, Outside Member
Mary Katherine Shenk, Program Head/Chair - Keywords:
- Encephalization
Human evolution
Contrast-enhanced microCT
Mouse models - Abstract:
- The research in this volume focuses on the relationship between encephalization and skull form during human evolution and methods for experimentally testing common encephalization hypotheses. Encephalization is the development of a larger brain relative to body size and is a hallmark characteristic of human evolution. Over a similar course of evolutionary time, the human skull developed a suite of cranial traits unique among extant primates: a domed cranial vault, highly flexed cranial base, and retracted facial skeleton. Anthropologists have commonly hypothesized that the increase in brain size was the primary driver of these changes in cranial morphology. Additional hypotheses posit that the energetic resources required for developing a larger brain during early growth may have diverted resources away from somatic tissues, including the skull, resulting in delays in growth. Traditionally, these hypotheses have been tested using data on brain size, skull morphology, and growth, primarily from fossils and comparative primate data sets. As a supplement to these commonly used data sets, I propose an experimental approach using laboratory mice, based on the deep genetic conservation of patterns of brain and craniofacial development. An experimental approach for testing encephalization hypotheses requires the development of new methods and creation of baseline data for laboratory mice. While microCT is commonly used to quantify and visualize mineralized tissues (e.g., bone and teeth), new methods are required to more fully investigate brain development and quantify brain size during embryonic and early postnatal growth in mice. I present new protocols for using phosphotungstic acid as a contrast agent to allow the visualization and quantification of soft tissue structures in embryonic and postnatal mice at high resolution with microCT scanning. Standard microCT scanning methods have been frequently used to study the craniofacial complex in embryonic and early postnatal mice, yet data for individual cranial bones in wild-type laboratory mice are lacking. I present bone volume and tissue mineral density data for twenty cranial bones for C57BL/6J mice at four ages that cover the initiation and early development of cranial mineralized tissue. These baseline data establish standards for the future investigations of the effect of encephalization on cranial bone development. I conclude by discussing the achievements and limitations of the research presented in this volume and suggest future directions for experimental approaches using laboratory mice to investigate the impact of an enlarging brain on prenatal growth on the skull.