Dihydrofolate reductase activity and resistance to aminopterin in various species of Drosophila

Abstract

The aim of our work was to compare the mechanisms of resistance to aminopterin, inhibitor of the dihydrofolate reductase enzyme, between different Drosophila species and those described for cultured cells. Moreover we compared the systematic species divisions based on morphological traits and those based on a molecular approach. For this purpose, the effect of aminopterin on viability and wing phenotype was studied in different Drosophila species. Dihydrofolate reductase was measured in adult flies. We found an important dihydrofolate reductase activity in the melanogaster sub-group compared to the other species studies. Wing effect was observed only in this sub-group. The effects of aminopterin on the wing phenotype were very similar to the phenotype of rudimentary mutants. Both deplete the pyrimidine pool and it has been shown by the studies of the structural genes of the nucleotide pyrimidine pathway that the wing tissue is very sensitive to every pertubation of this metabolism. The D. ananassae species was found to be fully resistant at the concentrations of the inhibitor tested. No or very little dihydrofolate reductase activity was detected. The binding of the enzyme to the inhibitor was comparable to that found in the Oregon strain of D. melanogaster. The purine and pyrimidine salvage pathways were investigated and the D. ananassae species displayed an important thymidine kinase activity. The D. ananassae flies were sensitive on Sang medium compared to the Oregon flies but were able to use exogenous bases or nucleosides more efficiently.(ABSTRACT TRUNCATED AT 250 WORDS)

A Drosophila model to study the functions of TWIST orthologs in apoptosis and proliferation

“…Aminopterin, an analog of methotrexate, induces massive cell death and a well characterized wing phenotype when cell death occurs in the part of the wing disc that will give the future wing margin. 28 This drug is an inhibitor of dihydrofolate reductase activity, and therefore inhibits DNA replication and the G1/S transition.…”

Selection for methotrexate resistance in mammalian cells bearing a Drosophila dihydrofolate reductase transgene

“…Re-replication attempts and subsequent chromosome breaks in the vicinity of replication origins then ultimately result in DNA amplification (Singer et al 2000). Thus, it is curious that, in Drosophila, acquired resistance has only been reported to occur by substitution mutations resulting in a DHFR with an altered affinity to MTX (Silber et al 1985;Neumann et al 2003;Affleck et al 2006). To determine if the observed disparity between Drosophila and murine cells could be attributed to differences in cell growth characteristics, the effect of MTX on cell proliferation was investigated.…”

vestigial suppressor genes and resistance to aminopterin in Drosophila melanogaster

“…The existence of a closed inter-relation between the eight parameters tested made the interpretation of our results rather difficult. We had previously studied the nucleotide metabolism variability in different species (Silber et a!., 1985) and in different wild-type strains of D. melanogaster (Le Menn et at., 1987a and b). These results indicated that with the exception of the vg mutant, aminopterin resistance is not correlated with DHRF activity but mainly with the use of salvage pathways and particularly TdR.…”