Intellectual merit: This is an Accomplishment-Based Renewal of a project supported by NSF since 1984. The research seeks to understand development at the cellular and molecular levels in leeches (phylum Annelida). Comparing development in various animals should contribute to understanding how body plans of modern animals evolved from those of ancestral species.
Recent years have seen the reorganization of most animal phyla into three main clades, Deuterostomia, Ecdysozoa and Lophotrochozoa. Most invertebrate phyla, including Annelida, belong the latter group, but most of our understanding of development has come from Deuterostomia [vertebrates, sea urchins] or Ecdysozoa [insects, nematodes]. Work on the leech Helobdella make it a useful point of departure for comparisons with other annelids (oligochaetes and polychaetes), other lophotrochozoans (e.g. flatworms and mollusks) and the "model" systems.
Helobdella is useful for studying development because its embryos are suited for cellular and molecular techniques. This proposal is to continue investigations of cell fate determination, combining reverse genetic approaches (injecting anti-sense morpholino oligonucleotides to knock down gene expression or mRNAs synthesized in vitro to ectopically express native genes, fluorescent proteins or dominant negative constructs) with embryological techniques already available for Helobdella. Specific topics include: 1. Significance of the maternally inherited Hro-nos, a nanos-class gene in Helobdella . We propose to test the hypothesis that gradually declining levels of HRO-NOS protein, translated from maternally inherited transcripts, control the duration of blast cell (segmental founder cell) production in individual embryonic stem cells (teloblasts). 2. The dynamics of early WNT and NOTCH signaling in Helobdella. Immunostaining for HRO-WNTA protein reveals a dynamic pattern during the 2-cell stage; HRO-WNTA signaling seems to regulate cell-cell adhesion following the first cell division. In situ staining for Hro-notch transcripts shows a similar pattern, but time shifted about 30 minutes ahead of the HRO-WNTA pattern. We propose to test the hypothesis that Notch and Wnt signaling pathways interact in the 2-cell stage, to investigate the mechanisms by which this interaction is achieved. Broader impacts: 1) The PI remains committed to expanding the national pool of scientific talent by recruiting and training women and members of underrepresented groups. Currently, the lab group consists of 1 assistant researcher (woman), 5 graduate students (3 women, including 1 of Mexican/native American origins) and 2 undergraduates (both of Filipino origin). One of the current undergrads, joined the lab via the "Junior Transfer Consortium", a program to identify, recruit and mentor science students who transfer to Berkeley with junior status from community colleges. A previous undergrad and postbac researcher (African-American male) from the PI's lab matriculated at UCSF medical school in the summer of 2002. 2) The PI also works to enhance the undergraduate experience at this large, research university by evaluating applicants for various research programs, and by participating in various faculty-undergrad forums. 3) The PI is active in promoting scientific goodwill and collaborations between the USA and developing nations. To this end, he has helped to organize and teach intensive and interactive lab and lecture courses in development and neurodevelopment, for students at the graduate level and beyond in Mexico, India and Brazil.
