טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentNirit Assaf-Reizel
SubjectStudies on eff-1 and lin-15 Mutants Affecting Cell Fusion
in C. elegans
DepartmentDepartment of Biology
Supervisor Full Professor Podbilewicz Benjamin


Abstract

             Cell fusion is a ubiquitous developmental process, involving the union of two separate membranes into one. Despite intense research on fusion, we are still far from understanding the cell fusion process.

The current study deals with structure-function analysis of eff-1, a fusion gene recently isolated in the nematode C. elegans (Mohler et al., 2002). Two strategies to eliminate eff-1 activity showed correlation between eff-1 levels, cell fusion, and the severity of various phenotypes. Isolation of new eff-1 alleles by noncomplementation screens yielded one new allele that was characterized and compared with other eff-1 alleles. Phenotypic characterization of the various eff-1 alleles showed their variable effects on C. elegans development, morphogenesis, behavior, viability, and fertility, suggesting that in addition to its role in hypodermal fusion, the eff-1 gene has a role in the nervous and reproductive systems.

The eff-1 gene is predicted to encode two membrane and two secreted isoforms. Studying the developmental expression of these isoforms, at the mRNA level, showed that temporal and spatial differential expression of eff-1 isoforms may explain some of the control mechanisms that mediate the fusion process, as well as some fusion independent eff-1 functions.

The current study describes the cellular events of fusion during vulva development in the vulva-signaling mutant lin-15lf. Lack of lin-15 has been shown to affect the cellular events during real and pseudo vulvae formation, suggesting that LIN-15 may play a role in the regulation of cell fusion and cell migration during normal vulva morphogenesis. Phenotypic characterization of the eff-1; lin-15 double mutants suggests that these genes may interact.

A model for EFF-1 proteins function during development is proposed in light of the results of the current study.