Abstract
The identification of mutants through forward genetic screens is the backbone of Drosophila genetics research, yet many mutants identified through these screens have yet to be mapped to the Drosophila genome. This is especially true of mutants that have been identified as mutagen-sensitive (mus), but have not yet been mapped to their associated molecular locus. Our study addressed the need for additional mus gene identification by determining the locus and exploring the function of the X-linked mutagen-sensitive gene mus109 using three available mutant alleles: mus109D1, mus109D2, and mus109lS. After first confirming that all three mus109 alleles were sensitive to methyl methanesulfonate (MMS) using complementation analysis, we used deletion mapping to narrow the candidate genes for mus109. Through DNA sequencing, we were able to determine that mus109 is the uncharacterized gene CG2990, which encodes the Drosophila ortholog of the highly conserved DNA2 protein that is important for DNA replication and repair. We further used the sequence and structure of DNA2 to predict the impact of the mus109 allele mutations on the final gene product. Together, these results provide a tool for researchers to further investigate the role of DNA2 in DNA repair processes in Drosophila.
Highlights
The development of gene mapping techniques has a long and storied history in the Drosophila melanogaster model system, beginning with Alfred Sturtevant’s fundamental publication of the first genetic map in 1913 [2]
Sturtevant showed that genes are arranged in a linear order along chromosomes and that the recombination frequency between two genes could be used as a measure of the distance between them. This discovery created the foundation for other key advances in Drosophila gene mapping, including the generation of detailed polytene chromosome cytogenetic maps [3,4], the development of deletion kits covering the genome [5,6,7], and the sequencing of the D. melanogaster genome [8]. Despite these advances, the current D. melanogaster genome annotation includes 14,184 genes that have not yet been mapped to the molecular genome (FlyBase R6.43; [9]), including many genes that were discovered in forward genetic screens
Each mapped mus gene has encoded an ortholog of a human DNA repair protein [17], including proteins implicated in disorders such as Bloom syndrome [18], Fanconi anemia [16], and xeroderma pigmentosum [19]
Summary
The development of gene mapping techniques has a long and storied history in the Drosophila melanogaster model system (reviewed in [1]), beginning with Alfred Sturtevant’s fundamental publication of the first genetic map in 1913 [2]. Sturtevant showed that genes are arranged in a linear order along chromosomes and that the recombination frequency between two genes could be used as a measure of the distance between them This discovery created the foundation for other key advances in Drosophila gene mapping, including the generation of detailed polytene chromosome cytogenetic maps [3,4], the development of deletion kits covering the genome [5,6,7], and the sequencing of the D. melanogaster genome [8]. We further discuss the potential functionality of the mus109 mutant alleles by comparing the mutations to conserved catalytic regions in DNA2
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