The Evolution of Cranial Neural Crest in Mammals: The Genetic Origins of Heterochronic Change

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0316353SmithMarsupial and placental mammals are distinguished by their reproductive and life history strategies. All marsupials are highly altricial at birth, but must possess sufficient functional independence to function at this altricial state. Previous work has shown that when compared to other mammals, the cranial neural crest differentiates early relative to the neural or mesodermal tissues in marsupials. This is of interest as proper craniofacial patterning depends on a series of intricate relations between these tissues. The current proposal will examine the relation between genetic differentiation of the neural plate differentiation and neural crest differentiation and migration. Specific aims: The specific aims of the current proposal are: 1) To test hypotheses that subpopulations of first arch crest, must be segregated in order to establish proper muscular-skeletal patterning in the first arch. 2) To examine the possible role of the isthmus as an organizing center in at the midbrain/hindbrain boundary, by establishing the relation between FGF8 expression, and Hoxa2 expression in the neural plate and migrating neural crest cells into aches 1 and 2. 3) To test the hypothesis that genetic differentiation of R3 and R5 as exhibited by Krox 20 expression is a necessary component of the suppression of neural crest migration from these zones. Intellectual merit: This study will contribute to the understanding of a number of specific mechanisms of craniofacial patterning in vertebrates and in particular the role of neural crest in that patterning. Further, this project is part of a long-term study of the ways that developmental changes produce evolutionary changes. Finally, the study speaks to the constraints and possibilities of change in development, and helps reveal the ways in which developmental mechanisms may evolve.Broader impacts: The most important is educational. The previous grant supported the work of 14 undergraduates. Two were supported on REU supplements, including a woman of African American descent and a woman of Latin-American descent. Thirteen of these students were women. Educating undergraduates (and in particular under-represented groups) by providing research experience has been a life long pattern, and support by NSF will allow the Smith lab to continue to contribute to science education. In addition, during the past 10- years of NSF funding one of the larger collections of marsupial embryos in the world has accumulated. In the past two years this collection has been used by individuals from Finland, Germany, Brazil and the US. Further funding will support this collection. .