Functional Aspects of the Structure of the Sea Urchin Bindin Gene and the Molecular Basis of Its Regulation

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In this application Dr. Davidson proposes to capitalize on recent discoveries made in our lab in respect to the molecular basis of bindin-receptor interaction. The species specificity of fertilization in certain sympatic sea urchin species depends on molecular recognition of the acrosomal bindin protein by egg receptor. Previously he has cloned bindin mRNAs and compared the bindin protein sequences from several species of sea urchin, and we have recently identified specific short regions of the protein that are apparently engaged in contact with the receptor, and that are at least in part responsible for the species specificity of the interaction. Here he proposes a series of new experiments: i, we will generate transgenic S. purpuratus expressing S. franciscanus bindin to determine whether presentation of the bindin sequence per se will promote interspecific fertilization; ii, he will also test in vivo the functional significance of alterations in specific regions of bindin sequence; iii, he will determine the polymorphism of the bindin/receptor interaction in S.franciscanus in order to understand how speciation might have come about; iv, he will carry out studies on the interaction of recombinant mutant bindin fragments with the receptor fragment recently described by Foltz and Lennarz; v, he will investigate incorporation of exogenous bindin (and other) genes in growing spermatocytes in culture, and determine whether transgenic spermatocytes can mature into functional sperm in culture.