A Molecular Analysis of Mutations at the Complex dumpy Locus in Drosophila melanogaster

Amber Carmon,Ross Macintyre,Brad Marshall,Olga Grushko,Michael J Guertin,Bassem A Hassan

doi:10.1371/journal.pone.0012319

Amber Carmon, Ross Macintyre + Show 4 more

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https://doi.org/10.1371/journal.pone.0012319

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Abstract

The Drosophila dumpy gene consists of seventy eight coding exons and encodes a huge extracellular matrix protein containing large numbers of epidermal growth factor-like (EGF) modules and a novel module called dumpy (DPY). A molecular analysis of forty five mutations in the dumpy gene of Drosophila melanogaster was carried out. Mutations in this gene affect three phenotypes: wing shape, thoracic cuticular defects, and lethality. Most of the mutations were chemically induced in a single dumpy allele and were analyzed using a nuclease that cleaves single base pair mismatches in reannealed duplexes followed by dHPLC. Additionally, several spontaneous mutations were analyzed. Virtually all of the chemically induced mutations, except for several in a single exon, either generate nonsense codons or lesions that result in downstream stop codons in the reading frame. The remaining chemically induced mutations remove splice sites in the nascent dumpy message. We propose that the vast majority of nonsense mutations that affect all three basic dumpy phenotypes are in constitutive exons, whereas nonsense mutants that remove only one or two of the basic functions are in alternatively spliced exons. Evolutionary comparisons of the dumpy gene from seven Drosophila species show strong conservation of the 5′ ends of exons where mutants with partial dumpy function are found. In addition, reverse transcription PCR analyses reveal transcripts in which exons marked by nonsense mutations with partial dumpy function are absent.

Highlights

The history of the dumpy gene in Drosophila melanogaster encompasses virtually the entire history of Drosophila genetics itself
In the 1950s, Elof Carlson, at UCLA, and his students generated a large number of dumpy mutant alleles, primarily with chemical mutagens [9,10,11,12,13]
From the screens depicted in crosses 2A and 2B in Table 2, we recovered 90 transmitted dumpy mutants, 46 from cross 2A in the net chromosome and 44 from cross 2B in the clot chromosome

Summary

Introduction

The history of the dumpy gene in Drosophila melanogaster encompasses virtually the entire history of Drosophila genetics itself. In 1918 [5] a fly was discovered with both shortened wings and with whorls of bristles and hairs on the thorax. This mutant was called dumpy, the first time this term was used. These mutants, along with a second vortex mutant and another mutant named thoraxate showing thoracic vortices and homozygous lethality, were eventually combined by Bridges and Muller as a series of recessive allelomorphs possibly occurring in different parts of a single gene [6,7,8]. A genetic fine structure map with discrete subloci was developed culminating in the map published by Dale Grace in 1980 [14,15,16,17]

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