THE MOSQUITO DIHYDROFOLATE-REDUCTASE GENE FUNCTIONS AS A DOMINANT SELECTABLE MARKER IN TRANSFECTED CELLS

An Aedes albopictus dihydrofolate reductase gene was used to construct two chimeric DNA vectors that functioned as dominant selectable marke rs in transfected, wild type mosquito cells. Stably transformed clones were recovered after 10-15 days in the presence of selective medium c ontaining 1 muM methotrexate. The transformed clones contained an esti mated 100-500 copies of transfected DNA per nucleus. Combined data fro m Southern blots and in situ hybridization to metaphase chromosomes in dicated that transfected DNA was likely integrated into chromosomes bo th as repeated structures and as randomly integrated single copy molec ules, with minimal rearrangement of coding sequences. Transfected DNA was stably maintained under selective conditions, but in some cases wa s lost when cells were maintained for prolonged periods in the absence of methotrexate. These observations provide a general framework for f urther development of stable gene transfer systems for mosquito cells in culture.