Genetic and molecular analysis of synthetic multivulva genes in Caenorhabditis elegans

A synthetic multivulva phenotype results from mutations in interacting genes that negatively regulate the ras-mediated intercellular signaling system of Caenorhabditis elegans vulval induction. The interaction of two synthetic multivulva mutations in two different classes of genes, class A and class B, is required to produce the multivulva phenotype in which all six vulval precursor cells adopt vulval fates thereby forming ectopic vulval tissue in addition to a normal vulva. Mutations in either class alone do not cause a vulval phenotype. To further characterize these pathways, mutations in both classes of synthetic multivulva genes were isolated. A total of 49 mutations were isolated and characterized. The analysis of some of these mutations and some previously isolated mutations allowed the identification of five new class B genes and one new class A gene. The class B gene lin-36 was characterized in greater detail. lin-36 mutations alone did not cause vulval lineage fate transformations, but in conjunction with a class A mutation, caused all vulval precursor cells to adopt vulval fates. lin-36 was cloned and shown to encode a novel protein. Genetic mosaic analysis suggests that lin-36 is required cell autonomously, and a lin-36 reporter is expressed in the nuclei of vulval precursor cells. The interaction between synthetic multivulva genes and genes that positively regulate the ras-mediated signaling system was studied. Thesis Supervisor: H. Robert Horvitz Title: Professor of Biology Acknowledgments It is a daunting task to thank all of the myriad people who have influenced the writing of this thesis. It is impossible to thank them all. However, several stand out as having had a particular impact on this work. Bob Horvitz has been invaluable as my advisor for this thesis. His rigorous standards for experimental interpretation and presentation will always remain with me. The members of my thesis committee have provided useful guidance and perspective. In particular, Ruth Lehmann has been the source of excellent scientific and career advice. My fellow lab members have contributed immensely to the experience this thesis represents, especially my former baymates, Kerry Kornfeld and Michel Labouesse. Other members of the lab, notably Michael Stern, Scott Clark, Erik Jorgensen, Cori Bargmann, and Sander van den Heuvel were influential. Shai Shaham deserves special mention. A great friend and a powerful intellect, the Horvitz lab has never been the same without him. The friendship of Greg Beitel, Brad Hersh, Gordon Campbell, Tory Herman, and Zheng Zhou has been a source of great happiness over the years. Xiaowei Lu and Craig Ceol have made the past two years in the lab intellectually exciting. Robert Grainger is in large part responsible for my interest in developmental biology and for my interest in the problem this thesis addresses. Mary Franklin Fulghum showed me how exciting biology was and bears some responsibility for my study of this field. Frances Dameron knew I would write this long before anyone else. My parents, Melvin and Rebecca, have encouraged me in this as they have in all things. Their limitless love and support has always been the foundation in my life. I cannot imagine better parents. My sister Lesley has always been a source of encouragement and sound advice. I thank all of these people.