12.2018 | THE SCIENTIST 55MARIANNE BRONNER
Albert Billings Ruddock Chair of Biology, California Institute
of Technology, Pasadena, CA
Visiting and Honorary Professor, University College London,
United Kingdom
National Academy of Sciences member (2015)
ASCIT Award for Excellence in Teaching (2015–16, 1997–1998)
Conklin Medal, Society for Developmental Biology (2013)
Women in Cell Biology Senior Award (2012)
American Academy of Arts and Sciences fellow (2009)
Greatest Hits
- Using Nicole Le Douarin’s quail-chick embryo chimera work
as a basis, demonstrated that cloned and primary quail
neural crest cells injected into early chick embryos followed
the normal neural crest cell migration route of the early
embryo, populating the appropriate organs. - Using single-cell lineage analysis, demonstrated the
multipotency of a neural crest precursor cell in vivo by
tracking a single neural crest cell in the chicken embryo
and showing it could give rise to multiple cell lineages. - Demonstrated that neural crest cells of the early embryo
are an induced cell type. - Identified Wnt as a signaling inducer of neural crest cell fate
in the early chick embryo. - Found that induction of neural crest cells occurs early in
embryogenesis, during gastrulation.
She completed her thesis in 1977 and received her PhD in- Her project focused on testing the developmental poten-
tial of a single neural crest cell in the chicken embryo. Cohen
had developed a method for cloning neural crest cells from quail
embryos in vitro, and Bronner’s task was to put those cells into
the chicken embryo and watch what they could become. Bron-
ner used a technique based on Le Douarin’s work, showing that
staining the DNA of the cells could distinguish quail and chick
embryo cells in vivo because the heterochromatin in the nucleoli
of quail cells is more condensed than in chick cells. When Bron-
ner injected the cloned quail neural crest–derived cells into two-
day-old chicken embryos, she saw that the quail cells migrated
along the neural crest pathway and populated different struc-
tures in the body, including the gut and gonads.
Bronner followed up this work with another paper showing
that not just cloned quail cells but also clonally derived pigment
cells from quail embryos could travel the typical neural crest cell
path. “The surprising thing was that my experiments showed
that many cells could migrate along neural crest pathways,
including neural crest–derived pigment cells that had already
differentiated,” she says. This “suggested there was a passive
component to the migration and that perhaps some cells were
carried to the right places while undergoing a random walk.”
Although successful in her graduate studies, Bronner recalls
a terrible environment for women in biophysics in the late 1970s
and early 1980s. “There were no female professors and very few
women in the program. There was a lot of sexism,” she says.
“Women were told that we were not good enough to do this job.
Some of the faculty members would call up the women graduate
student candidates and discourage them, saying ‘You shouldn’t
come here because this is not a good place for a woman.’”
Despite the challenges, Bronner stuck with her program.
After completing her PhD, Bronner and Scott Fraser, a bio-
physicist who was then her husband, moved to the University
of California, Irvine, in 1980. “Scott got the tenure track posi-I always tell my undergraduate students to
take English courses because, as a scientist,
you spend the majority of your time writing.