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A screen for modifiers of Deformed function in Drosophila
K W Harding1, G Gellon, N McGinnis
1Department of Molecular Biophysics and Biochemistry, Yale University, New Haven Connecticut 06520-8114, USA.
Abstract:
Proteins produced by the homeotic genes of the Hox family assign different identifies to cells on the anterior/posterior axis. Relatively little is known about the signalling pathways that modulate their activities or the factors with which they interact to assign specific segmental identifies. To identify genes that might encode such functions, we performed a screen for second site mutations that reduce the viability of animals carrying hypomorphic mutant alleles of the Drosophila homeotic locus, Deformed. Genes mapping to six complementation groups on the third chromosome were isolated as modifiers of Deformed function. Products of two of these genes, sallimus and moira, have been previously proposed as homeotic activators since they suppress the dominant adult phenotype of Polycomb mutants. Mutations in hedgehog, which encodes secreted signalling proteins, were also isolated as Deformed loss-of-function enhancers. Hedgehog mutant alleles also suppress the Polycomb phenotype. Mutations were also isolated in a few genes that interact with Deformed but not with Polycomb, indicating that the screen identified genes that are not general homeotic activators. Two of these genes, cap 'n' collar and defaced, have defects in embryonic head development that are similar to defects seen in loss of function Deformed mutants.
Insights
Researchers screened for mutations affecting Drosophila homeotic gene Deformed. They identified new genes, including hedgehog, sallimus, and moira, that interact with Deformed and influence segment identity.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- Homeotic genes, particularly the Hox family, are crucial for establishing anterior-posterior identity in developing organisms.
- The signaling pathways and interacting factors that modulate homeotic gene activity remain incompletely understood.
Purpose of the Study:
- To identify novel genes involved in modulating the function of the Drosophila homeotic gene Deformed.
- To uncover factors that interact with Deformed to specify segmental identities.
Main Methods:
- A genetic screen was conducted for second-site mutations that reduce the viability of Drosophila carrying hypomorphic Deformed alleles.
- Complementation analysis was used to map identified mutations to specific genes.
- Interactions with the Polycomb gene were also assessed.
Main Results:
- Six complementation groups of modifier genes on the third chromosome were identified.
- Mutations in hedgehog, sallimus, and moira were found to interact with Deformed.
- Some identified genes, like cap 'n' collar and defaced, specifically interact with Deformed and not Polycomb, showing distinct roles.
Conclusions:
- The screen successfully identified novel genes that modify Deformed function, providing insights into the regulation of homeotic gene activity.
- The findings highlight the complex genetic interactions underlying the precise specification of segmental identity in Drosophila development.
- The identification of genes with specific interactions with Deformed suggests a nuanced regulatory network for Hox gene function.