The stem cell niche

How do distal tip cells migrate? The distal tip cell (DTC) leads gonad migration during larval development. We have identified new genetic regulators of DTC directional migration, integrated these genes in pathways with known regulators of migration, and are linking these directional regulatory pathways with effectors of DTC migration.

Cell integrity and cell-cell interactions

What maintains cellular integrity during a long migration? While investigating pathways that are required for robust DTC migration, we discovered that the Rac GTPase CED-10 and its tripartite GEF complex, CED-2/5/12, are required to maintain cellular integrity during DTC migration. A concurrently published study by another group found that cellular integrity is compromised by the dual loss of actomyosin contractility and nuclear positioning, pointing to potential targets of the Rac pathway in this role.

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Neighboring the DTC is a pair of somatic gonadal sheath (Sh1) cells that take up variable and asymmetric positions over the distal germ line. We found that Sh1 cells promote germ cell proliferation in the adult gonad and facilitate exit from the stem cell niche by germ cell division. A recent study by others reports that SDN-1 expressed by sheath cells promotes germ cell proliferation. We are currently examining what regulates the growth of these cells during larval development and at their distal boundary in adulthood.

How do cell-cell interactions shape the stem cell niche environment?

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The germ line

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Gonad growth is fueled by germ cell divisions. We study regulation of the germ line by somatic support cells at various stages of development, including the dauer larval stage. We have found that pre-dauer nutrition causes variation in dauer germ line size, which is correlated with differential post-dauer reproductive success.

Evolution of genes and gene expression

Dr. Gordon has a longstanding interest in evolution, especially the evolution of regulatory information in the genome. Approaching questions of evolutionary biology with the techniques of cell biology and developmental genetics will yield unique insights in the future.

Collaborations: genetically manipulated worms for toxicology studies

We collaborate with Dr. Jessica Hartman of MUSC on projects related to aging, exercise, metabolism, and toxicity by making transgenic worms that express human proteins or tagged worm proteins. We have also studied polyploid worms to model the effects of polyploidy on cell susceptibility to chemotherepeutics.