Trish Berger

Trish Berger

Trish Berger, Ph.D.

Department of Animal Science
University of California, Davis
1 Shields Ave
Davis, CA 95616, USA

Phone: +1 530-752-1267
FAX: +1 530-752-0175


B.A., Biochemistry, University of Kansas, 1975.
(Year Abroad) Physiology and Biochemistry of Farm Animals, University of Reading, England, 1974-1975
M.S., Animal Science, Purdue University, 1977.
Ph.D., Animal Science, Purdue University, 1980.


The long-term focus in our laboratory is mammalian fertilization and the molecules involved in the fertilization process. Research is centered on interactions between sperm and oocyte plasma membrane molecules after sperm have undergone the acrosome reaction since our earlier work demonstrated that this was frequently the limiting step in vivo in subfertile animals. Details of these interactions including receptor/ligand pairings are still largely unknown. Environmental stresses such as elevated ambient temperature affect both the sperm’s ability and the oocyte’s ability to interact with each other at the plasma membrane level. We hypothesize that this is due to decreased/defective synthesis of interacting molecules. Our research typically involves in vitro fertilization or aspects of those procedures such as sperm penetration of zona-free oocytes as bioassays to support molecular studies evaluating individual molecules. Occasionally, research includes artificial or natural insemination to assess differences in in vivo fertility among males or females or to assess other parameters of reproduction in conjunction with sperm-oocyte interaction.

The pig is one of the primary species studied due in part to the availability of large numbers of gametes and hence molecules derived from gametes. Studies occasionally use other domestic species and gametes from exotic species as conservation of gamete receptors/ligands is of particular interest as well. Environmental toxicant-induced changes in the gamete receptors/ligands during rat gametogenesis and maturation was a previous model for our laboratory and also provided the opportunity to manipulate the system.

A second focus in our laboratory is the prepuberal regulation of Sertoli cell proliferation. Sertoli cell numbers are a major determinant of postpuberal testis size and sperm production. The number of Sertoli cells is generally believed to be determined prepuberally. In collaborative research, we have found that reducing endogenous estrogen in the boars postnatally leads to increased proliferation of Sertoli cells and larger postpuberal testes. In the pig, this can be accomplished independent of altered pituitary hormones. This strongly suggests a locally mediated mechanism. 

Opportunities for Graduate Studies

Graduate students in the Gamete Biology Laboratory work toward the M.S. or Ph.D. degree in Animal Biology. Details on these programs are available on their homepages or contact me for further information.

Animal Biology
Molecular, Cellular and Integrative Physiology