Cassandra G. Extavour

Cassandra G. Extavour

Timken Professor of Organismic and Evolutionary Biology and of Molecular and Cellular Biology
Harvard College Professor
Howard Hughes Medical Institute Investigator
Cassandra G. Extavour

Faculty Support: Esther Jules
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


Church, S.H., de Medeiros, B.A.S., Donoughe, S.D., Marquez Reyes, N.L. and Extavour, C.G. Repeated loss of variation in insect ovary morphology highlights the role of developmental constraint in life-history evolution. Proceedings of the Royal Society - Part B, (in press) (2021).

Whittle, C.A., Kulkarni, A., Chung, N. and Extavour, C.G. Adaptation of codon and amino acid use for translational functions in highly expressed cricket genes. BMC Genomics, (2021).

Kumar, T., Blondel, L. and Extavour, C.G. Topology-driven analysis of protein-protein interaction networks detects functional genetic modules regulating reproductive capacity. eLife, 10.7554/eLife.54082 (2020).

Kulkarni, A., Lopez, D., and Extavour, C.G. Shared cell biological functions may underlie pleiotropy of gene regulatory modules in the germ lines and nervous systems of animals. Frontiers in Ecology and Evolution, doi: 10.3389/fevo.2020.00215 (2020).

Whittle, C.A., Kulkarni, A. and Extavour, C.G. Sex-biased genes expressed in the cricket brain evolve rapidly. bioRxiv (2020).

Ylla G., Nakamura T., Itoh T., Kajitani R., Atsuhi T., Sayuri T., Tetsuya B., Yoshiyasu I., Watanabe T., Fuketa M., Matsuoka Y., Barnett, A.,Noji S., Mito T. and Extavour C.G. Insights into the genomic evolution of insects from cricket genomes. bioRxiv

Church, S.H. and Extavour, C.G. Null hypotheses for developmental evolution. Development, 147, dev178004 (2020).

Whittle, C.A., Kulkarni, A. and Extavour, C.G. Absence of a faster-X effect in beetles (Tribolium, Coleoptera). G3: Genes, Genomes, Genetics, doi:10.1534/g3.120.401074 (2020).

Blondel, L., Jones, T.E.M. and Extavour, C.G. Bacterial contribution to genesis of the novel germ line determinant oskar. eLife, 9:e45539 (2020).

Whittle, C.A., Kulkarni, A. and Extavour, C.G. Evidence of multifaceted functions of codon usage in translation within the model beetle Tribolium castaneum. DNA Research, 26(6): 473-484 (2019).


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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