Dmel/Gfat2 is an essential gene in D. melanogaster embryonic development.

Glutamine:fructose-6-phosphate aminotransferase (Gfat) functions as the rate-limiting enzyme in the hexosamine biosynthesis pathway. There are two Gfat-encoding genes and, thus, two discrete enzymes, Gfat1 and Gfat2, in humans and other metazoans, including Drosophila melanogaster. Thus, the functional characterization of fly orthologues should help to elucidate the roles of the human enzymes in developmental processes and metabolic diseases. Particularly, since increased flow of glucose through the hexosamine pathway has been associated with the development of insulin resistance, the Gfat enzyme may serve as a key therapeutic target in the treatment of type 2 diabetes in humans. In Drosophila, mutations in Gfat1 are lethal, and the mutants are defective in formation of the embryonic cuticle. However, there are no known mutant alleles of Gfat2 and, thus, the requirements for this form of the enzyme are essentially undefined. Therefore, the objective of the current study was to identify and characterize putative P-element-induced lethal excisions that affect the Gfat2 gene. From 81 such excisions, we have identified 16 that are lethal in combination with known deficiencies for the Gfat2 genomic region (i.e. these deletions remove Gfat2 and varying numbers of adjacent loci). Through a combination of genetic crosses and molecular methods, we have confirmed that 14 of these mutant chromosomes contain intact larp and moca-cyp genes (the two genes that immediately flank Gfat2 on the Drosophila genomic map). Further studies on four of these excision chromosomes have confirmed at least partial deletion of the Gfat2 gene and the absence of second-site mutations. These four Gfat2- lesions were shown to have an embryonic lethal phase, thereby indicating that the Dmel/Gfat2 gene is essential for embryonic development. [ABSTRACT FROM AUTHOR]