The long-term objective is to increase the usefulness and """"""""connectivity"""""""" of easily cultured Haliotis (molluscan) larvae as a model system for biomedical research. Development in these larvae is synchronously induced by chemosensory recognition of an exogenous morphogen; the receptors, signal transducers and pathways involved in this control have been found to be closely homologous to counterparts in mammalian systems. We propose to increase the connectivity of this model system by characterizing the link between the chemosensory signal recognition/transduction mechanisms already characterized at the molecular level, and the developmental and genetic mechanisms that regulate specific target gene expression, cellular differentiation and proliferation.
The specific aims of this proposal are: (1) to identify the """"""""primary response"""""""" genes and transcription regulators they may encode, that control larval metamorphosis and early post-larval growth in Haliotis in response to chemosensory recognition of exogenous morphogens; (2) to identify the molecular mechanisms by which these genes and transcription activators interact with gene- and tissue-specific cis-acting DNA (and mRNA) regulatory sequences to control the expression of essential """"""""secondary response"""""""" target genes, leading to metamorphosis; (3) to identify, through the analysis of G protein and phosphoprotein cDNAs, the centrally important mechanisms by which receptor-regulated G proteins and protein phosphorylations transduce the inductive signals generated by larval recognition of exogenous chemical morphogens; and (4) to establish the relatedness of the mechanisms of chemosensory signal-dependent gene expression found in this research to corresponding mechanisms in mammals. Morphogen-induced primary response gene transcripts and their cDNAs will be purified by (a) PCR-amplification and hybridization using highly conserved oligonucleotides, corresponding to mammalian transcription factors (c-myc, c-fos, c-jun, and homeoprotein gene families), and by (b) direct isolation by subtractive hybridization. These will be cloned and sequenced, and the mechanisms and locations of action of their protein products determined by in situ hybridization, and blockade of target gene induction with anti- sense RNA. The mechanisms of these morphogen-induced transcription factors will be further characterized by footprinting analyses of the regulatory sites with which they interact on the genomic DNA sequences of their target (secondary response) genes. Results of the proposed studies should be significant in providing the most detailed understanding yet available of the molecular mechanisms by which chemosensory recognition of exogenous morphogens and regulatory chemical signals controls gene expression, differentiation and cellular proliferation in multicellular organisms. This link is of fundamental biomedical importance in the processes of normal development, hormonal regulation, wound healing, antibody synthesis, long-term memory, and cancer. The proposed research thus should increase the usefulness of the Haliotis larvae as a model system with high connectivity to research in these areas.

Agency
National Institute of Health (NIH)
Institute
National Center for Research Resources (NCRR)
Type
Research Project (R01)
Project #
5R01RR006640-04
Application #
3421663
Study Section
Special Emphasis Panel (SRC (BM))
Project Start
1990-09-30
Project End
1995-09-29
Budget Start
1993-09-30
Budget End
1994-09-29
Support Year
4
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of California Santa Barbara
Department
Type
Organized Research Units
DUNS #
City
Santa Barbara
State
CA
Country
United States
Zip Code
93106
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Groppe, J C; Morse, D E (1995) Sequence-independent detection of gene family homologs: identification of a transcript encoding a molluscan serine protease homologous to the pancreatic enzymes of vertebrates. Comp Biochem Physiol B Biochem Mol Biol 110:75-82
Degnan, B M; Degnan, S M; Giusti, A et al. (1995) A hox/hom homeobox gene in sponges. Gene 155:175-7
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Degnan, B M; Morse, D E (1993) Identification of eight homeobox-containing transcripts expressed during larval development and at metamorphosis in the gastropod mollusc Haliotis rufescens. Mol Mar Biol Biotechnol 2:1-9
Groppe, J C; Morse, D E (1993) Molluscan chymotrypsin-like protease: structure, localization, and substrate specificity. Arch Biochem Biophys 305:159-69
Groppe, J C; Morse, D E (1993) Isolation of full-length RNA templates for reverse transcription from tissues rich in RNase and proteoglycans. Anal Biochem 210:337-43
Degnan, B M; Degnan, S M; Naganuma, T et al. (1993) The ets multigene family is conserved throughout the Metazoa. Nucleic Acids Res 21:3479-84
Ilan, M; Jensen, R A; Morse, D E (1993) Calcium control of metamorphosis in polychaete larvae. J Exp Zool 267:423-30
Spaulding, D C; Morse, D E (1991) Purification and characterization of sulfatases from Haliotis rufescens: evidence for changes in synthesis and heterogeneity during development. J Comp Physiol B 161:498-515