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Professor of Organismic & Evolutionary Biology

Cassandra Extavour

Professor of Organismic & Evolutionary Biology

Professor of Molecular and Cellular Biology

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Research

Germ cells play a unique role in gamete production, heredity and evolution. Germ cells are likely also the closest wild type in vivo equivalent to laboratory-maintained stem cells. To understand the mechanisms that specify germ cells is therefore a central challenge in developmental and evolutionary biology.

Data from model organisms show that germ cells can be specified either by maternally inherited determinants or by inductive signals. Although the inheritance mode is seen in most model organisms, it is actually likely to be the less prevalent mode of germ cell specification, and inductive germ cell specification may be ancestral to the Metazoa.

Among the invertebrates, the only arthropod in which the germ line has been studied in detail is the dipteran Drosophila melanogaster. In this fruit fly, germ line precursors form as pole cells at the posterior end of the embryo very early in development. However, it is not clear whether this mechanism of germ cell specification is widespread among, or representative of, all arthropods. Moreover, there is great variation in the time and place of germ cell specification across all multicellular animals. My interests are the evolution and development of reproductive systems, and specifically, the mechanisms of initial specification of primordial germ cells. By using molecular markers, functional genetic analysis, and cellular analysis to study the embryonic development and reproductive systems of multiple emerging arthropod laboratory systems (spiders, crickets, milkweed bugs, amphipods and fruit flies), we hope to add to our understanding of which mechanisms may have been basal to arthropods, and ultimately to metazoans, in the specification of the germline.

 

Selected Publications