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Morrissey College of Arts and Sciences

William Petri

associate professor of biology, associate dean of arts & sciences


Ph.D., University of California at Berkeley

Phone: 617-552-2800

Fields of Interest

Developmental regulation of gene expression and molecular evolution of Drosophila eggshell genes.

Academic Profile

The interests of my laboratory center around the molecular and developmental biology of the fruit fly Drosophila melanogaster. We utilize the follicular epithelial cells of the ovary to investigate the mechanisms which allow genes to be turned on and off in a sex-, tissue- and developmental stage-specific manner. These cells produce proteins which form the protective eggshell surrounding the mature oocyte. Our laboratory and others have characterized many of the genes and proteins involved in making the two layers of the eggshell: the vitelline membrane (VM) and the chorion.

In the case of the genes encoding the proteins for the vitelline membrane, we have found that they are expressed only in the adult female, only in the follicular epithelium and only during stages 8, 9 and 10 of egg chamber development. Our long-term goal is to elucidate the details of how such a specific pattern of control of gene expression is regulated. To this end we have cloned the genes for two vitelline membrane proteins, VM26A1 and VM34C, and fused their modified upstream regulatory regions to b-galactosidase and chloramphenicol acetyl transferase reporter genes. These constructs have then been reintroduced into flies via P-element-mediated germline transformation. Using this approach, we have been able to define roughly 100 base pair long regions adjacent to both genes which contain the key, independently acting sex-, tissue- and stage-specific control functions. In addition, we have found a number of dependent control elements which require a functional independent element and which affect the spatial pattern of expression within the follicular epithelium and the quantitative levels of expression. We are now utilizing these defined cis-acting elements and gel retardation assays to search for the transacting molecules involved in switching on the VM genes. We have identified one factor which binds specifically to the key independent control region of the VM26A1 gene. Current work involves characterizing this factor and recovering a clone for its gene from an ovarian cDNA expression library.

A second area of research in the lab involves the field of molecular evolution. While sequencing the genes for VM proteins, we discovered that hidden within the coding sequence of each gene was a highly conserved 38-40 amino acid peptide we call the VM domain. We immediately wondered if the conservation of this VM domain extended beyond the melanogaster species, and hence might serve as a new model for the evolution of insect eggshells in general via the formation of a multi-gene family. We are currently using PCR and other techniques to search for VM domain-related sequence in other classes of insects.

Representative Publications

Rounds, E. and Petri, W.H. 2003. A Drosophila ovarian-specific splice variant of dTAFII25O associates with a developmental control region of the VM26A1 genes.

Scherer, L.F., Harris, D.H., White, M.K., Steel, L.F., Jin, J., and Petri, W.H. 1993. Comparative analysis of the sequence and structure of two Drosophila melanogaster genes encoding vitelline membrane proteins. Gene 136: 121–127 (link to PubMed abstract).

Jin, J. and Petri, W.H. 1993. Developmental control elements in the promoter of a Drosophila vitelline membrane gene. Developmental Biology 156: 557–565 (link to PubMed abstract).

Scherer, L.J., Harris, D.H., and Petri, W.H. 1988. Drosophila vitelline membrane contains a 114 base pair region of highly conserved coding sequence. Developmental Biology 130: 786–788 (link to PubMed abstract).

Mindrinos, M.N., Scherer, L.J., Garcini, F.J., Kwan, H., Jacobs, K.A., and Petri, W.H. 1985. Isolation and chromosomal location of putative vitelline membrane genes in Drosophila melanogaster. EMBO Journal 4: 147–153 (link to PubMed abstract).