Dr. Extavour is a developmental biologist interested in using genetic approaches to study how, during embryonic development, specific cells become germ line cells — the cells that will go on to form eggs or sperm.

Dr. Extavour grew up in Toronto and earned her undergraduate degree from the University of Toronto, before continuing her education in Europe: first, completing her Ph.D. at the University of Madrid, and then in two post-doctoral fellowships, one in Crete (Greece) and one at the University of Cambridge. She was recruited to start her own lab at Harvard in 2007. She’s also a classically-trained soprano, and continues to perform professionally.

All multi-cellular organisms develop from a single-cell stage, with that one first cell dividing and the “daughter” cells gradually gaining more and more specific roles (often called “fates” by developmental biologists.) One crucially important cell fate is to be a germ line cell — the cells that will divide to form either egg or sperm (depending on sex). It’s important to keep in mind that even though babies aren’t born with mature egg/sperm, “setting aside” the germ line cells is one of the first things that happens during embryonic development. They make the next generation, so they’re kept particularly insulated from potential damage.

Dr. Extavour is interested in understanding what it is that causes specific cells to have that germ line fate. In many species (including humans), germ line fate is largely determined by the egg’s contribution to the new embryo — proteins and messenger RNA made by the mother are put into one side of the egg and whichever newly divided cells end up with those maternal contributions will go on to make the germ line. However, in many insects, this does not happen and germ cells are “set aside” later on during embryonic development. Dr. Extavour looks at crickets, milkweed bugs, and spiders to see what these species are doing instead, in order to better understand how and when different parts of these systems have evolved. She proposed a controversial theory in 2003, which is gaining acceptance, that the signal-based system in these insects is the more “ancestral” way to specify germ line cells.

Another big project in Dr. Extavour’s lab involves a gene called oskar, which is strange for two reasons. First, although it is crucial for germ line development in fruit flies, oskar does not exist in any non-insect species — even though early germ line development is similar for flies and humans. Second, oskar serves other, important non-germ line functions in other insects — for example, it is critical for neural development in crickets. This gives Dr. Extavour the opportunity to look in depth at the emergence of a new gene and to try to track down what ancestral species gained oskar and what its original purpose was.