Cassandra G. Extavour

Cassandra G. Extavour

Professor of Organismic and Evolutionary Biology and of Molecular and Cellular Biology
Harvard College Professor
Cassandra G. Extavour

Faculty Support: Rosa Capellan
Extavour Lab Website

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.

Recent Publications

Barry, S., Nakamura, T., Matsuoka, Y., Straub, C., Horch, H.W. and Extavour, C.G. Injecting Gryllus bimaculatus Eggs. JoVE. (in Press)

Deas, J.B., Blondel, L., and Extavour, C.G. Ancestral and offspring nutrition interact to affect life history traits in Drosophila melanogasterProceesings of the Royal Society B, 336665:38:00 (2019)

Panfilio, K.A., et. al. Molecular evolutionary trends and feeding ecology diversification in the Hemiptera, anchored by the milkweed bug genome. Genome Biology (in press) (2019) 

Wittle, C.A.. and Extavour, C.G. Contrasting patterns of molecular evolution in metazoan germ line genes. BMC Evolutionary Biology 19(1):53 (2019)

Whittle, C.A. and Extavour, C.G. Selection shapes turnover and magnitude of sex-biased expression in Drosophila gonads. BMC Evolutionary Biology 19(1):60 (2019)

Blondel, L., Jones, T.E.M. and Extavour, C.G. Bacterial contribution to genesis of the novel germ line determinant oskar. bioRxiv, 453514 (2018)

Donoughe, S.D., Kim, C. and Extavour, C.G. High-throughout live-imaging of embryos in microwell arrays using a module, inexpensive specimen mounting system. Biology Open, 7(7) pii: bio.031260, (2018)

Courses Taught

OEB 51 Biology and Evolution of Invertebrate Animals
OEB 371 Comparative and Evolutionary Invertebrate Developmental Biology
LIFESCI50A Integrated Science
LIFESCI50B Integrated Science

Contact Information

Biological Laboratories 2087
16 Divinity Avenue
Cambridge, MA 02138
p: 617-496-1935



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