The development of an organism depends on the regulated expression of individual genes and the integration of the products of these genes into units of function. The overall goal of the research in this lab is to use the imaginal discs of Drosophila as a model system to discover principles according to which the products of specific genes are integrated into such units of function. This is a proposal to continue work on two genes, each of which is required for a different aspect of imaginal disc development. The abnormal wing discs (awd) gene is required for the normal development of wing, leg and eye-antenna discs. The entire amino acid sequence of the awd product is 78% identical to the product of the mammalian metastatic tumor suppressor gene, nm23. In human breast carcinomas and murine melanomas reduced expression of nm23 is highly correlated with increased metastatic potential; elevated expression of nm23 following transfection into metastatic cells of nm23 driven by an SV40 promoter is highly correlated with decreased metastatic potential. The extreme degree of conservation between awd and nm23 amino acid sequences implies that they are functionally homologous. One objective of the research in this lab has been to understand the normal role of awd in Drosophila development in order to understand how the loss of nm23 function in mammalian tumors might lead to metastases. Recent evidence has led to the hypothesis that awd codes for the subunit of a hexameric enzyme, nucleoside diphosphate kinase (NDP kinase). The enzymatic activity of NDP kinases has been well characterized. Four forms of the enzyme have been purified from mammals, one associated with microtubules, one associated with membranes, one associated with erythrocytes, and one associated with mitochondria.
One aim of this proposal is to test the hypothesis that the Drosophila awd gene codes for the microtubule-associated NDP kinase. awd mutants provide the first animal system in which the biological consequences of lack of this critical activity can be studied. The mammalian nm23 gene codes for an NDP kinase that may not be microtubule-associated.
A second aim i s to identify the gene that codes for the Drosophila cognate of nm23 using molecular genetic techniques and to recover mutations in that gene using Drosophila genetic techniques. The hyperplastic discs (hyd) gene is required for the termination of wing and haltere disc proliferation. Loss of function of this gene leads to hyperplastic growth of wing and haltere discs. The DNA sequence corresponding to the hyd gene has been isolated by transposon tagging and a putative transcript of the gene has been identified.
The third aim i s to discover the role of the hyd product in the termination of imaginal disc proliferation. To do so, hyd cDNAs will be isolated for nucleotide sequencing, antibodies that recognize the hyd product will be raised for determining its intra-cellular localization and the interaction of hyd mutations with mutations in three other genes which cause similar phenotypes will be analyzed.
