Pilgrim, David

Currently Professor, Department of Biological Sciences, University of Alberta

B.Sc. Biochemistry, Simon Fraser (Vancouver), 1982
Ph.D. Biochemistry, U. Washington (Seattle), 1987
PDF, MRC Laboratory of Molecular Biology, Cambridge, UK

A Précis of Current Research Projects in the Pilgrim Lab

1). Role of the UNC-119 protein in neurogenesis
A major part of our research effort concerns development of the nervous system. C. elegans has an invariant cell lineage, with similar locations and patterns of connectivity of neurons in every animal. Genes required in the nervous system of C. elegans often have subtle mutant phenotypes, affecting behaviours such as response to gentle touch, sensitivity to volatile attractants, contraction of muscles and feeding. One of our projects concerns the unc-119 gene. The behavioural defect in unc-119 mutants lies in at least two aspects; chemosensation and movement. At the cell biological level, it appears that all neuronal growth cones in unc-119 mutants are aberrant, resulting in neurite branching and axonal fasciculation defects. We have identified and isolated UNC-119 homologues from other metazoans (Drosophila, zebrafish, and mammals), these homologues are also neuronally expressed, and, when expressed in C. elegans, these homologues can rescue all aspects of the unc-119 mutant phenotype. Vertebrates we have examined all have two UNC-119 related genes, UNC-119a and UNC-119b. Therefore, we have identified a new family of evolutionarily conserved neuronal proteins. Since most of the other identified components of the C. elegans nervous system have direct human homologues, this work may also shed light on the processes and products involved in the development of the human nervous system. Over the next year we will be using genetic and molecular approaches to identify proteins with which UNC-119 interacts, in C. elegans, Drosophila and humans.
2). UNC-45, a novel myosin interacting protein with distinct roles in muscle and cytokinesis
The Caenorhabditis elegans unc-45 gene is essential for normal thick filament development in body wall muscles. The protein product (UNC-45) contains TPR repeats and has similarity to the yeast She4p protein which is involved in asymmetric segregation of specific mRNAs, but its biochemical function is unknown. UNC-45 differentially co-localizes in body wall muscle thick filaments with myosin heavy chain B (MHC B) but not MHC A. Surprisingly for a gene with muscle phenotype, unc-45 is also maternally contributed and the protein and mRNA are present in all cells of the early embryo. However, zygotic unc-45 expression is only detected in the developing muscle cells. Yeast two-hybrid screens show that UNC-45 interacts with at least two non-muscle myosins, including NMY-2, a type II myosin necessary for asymmetric cell division in C. elegans embryos. UNC-45 and NMY-2 also co-localize in vivo, at the cortex of the cell in early embryos, and localization of UNC-45 is dependent on the presence of NMY-2. Rather than being a muscle-specific protein, this would argue that the UNC-45 protein may have a more general role as a myosin chaperone, stabilizer, or assemblase. We have recently found UNC-45 sequence homologues in Drosophila and humans, and a lethal mutation in the Drosophila gene, leading us to propose that this family of proteins may be an evolutionarily conserved class of myosin interacting proteins.
3). Evolution and functional role of a signal transduction pathway controlling sex determination
C. elegans is proven as a genetic system to study oncogene mediated signal transduction, and we are developing a molecular picture of a signal transduction system involved in sex determination. Although sex is determined in C. elegans by the number of sex (X) chromosomes, mutations have been isolated which cause the animal to completely ignore the chromosomal signal. One such gene is fem-2, which acts at an important branch point in the pathway for the regulation of sex determination in both the soma and germ line. C. elegans are normally hermaphrodites or males, but fem-2 mutants develop as females, regardless of the number of X chromosomes. We have cloned and characterized the fem-2 gene and characterized its product. FEM-2 is a protein phosphatase and is thought to signal between a cell surface receptor (TRA-2) and a nuclear transcription factor (TRA-1). FEM-2 is most similar in its structure to a protein involved in abscisic acid signaling in plants (ABI1), and to a human protein which is a potential regulator of cell death (apoptosis). We have shown that FEM-2 can functionally complement a yeast deficient in PP2C activity, and that the amino terminus of FEM-2 is not necessary for activity in vitro or in vivo . FEM-2 is typical of sex determining genes in many systems in that it is evolving very rapidly. We are presently undertaking a molecular, genetic and cell biological characterization of the fem-2 gene and the interaction of its product with other genes in the pathway. Very recently, we found that FEM-2 expression is controlled at the post-transcriptional level, by a sequence in the 3' UTR, and we are looking for the trans-acting factors which bind there.