ISOLATION OF TRANSPOSON MEDIATED TRANSGLUTAMINASE MUTANTS OF DROSOPHILA MELANOGASTER
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Transglutaminase, Tg, catalyzes the formation of isopeptide bonds crosslinking and stabilizing protein complexes. The best-known factor XIII crosslinks fibrin in clots. Paradoxically, there is an unexpected and counterintuitive correlation between factor XIII levels and heart attack mortality. Since factor XIII strengthens fibrin and resists fibrinolysis, higher XIII activity would be expected to lead to more stable fibrin clots and so more fatal atherosclerotic plaques; but it actually results in reduced mortality. One hypothesis to explain this is that Tg activity may also stabilize cardiac muscle tissue. Studies have shown that Tg is expressed in human embryonic myoblasts. Therefore, we suggest that muscular attachments may be strengthened by Tg, and play a vital unrecognized role in the muscular attachment. Humans have 9 Tg genes, complicating studies. However Drosophila melanogaster, D.m., has only one Tg gene, and is an attractive model system. We isolated 39 mutant D.m. lines gene produced by transposon mobilization in locus in a "dirty" fashion expected to create random deletions within the Tg locus. We then characterized them by PCR and sequencing, as well as functional assays, in an attempt to develop a Tg null line to test this hypothesis. The aim is to identify a line with all of Tg removed, but with neighboring genes unperturbed. Once the approximate break points were identified by PCR, we did DNA sequencing to fully characterize the genomic breakpoint. According to the DNA sequencing results, one line is specific for Tg exon1, and eliminates one of the two known Tg transcripts. Another line eliminated almost the entire catalytic domain. We also did RT-qPCR for two lines that were sequenced to determine their genomic characteristics. Both of these lines are viable but with subtle developmental defects, showing that Tg deficiency is not lethal in D.m.