Related Experiment Videos
Novel behavioral and developmental defects associated with Drosophila single-minded
Jan Pielage1, Georg Steffes, Dan C Lau
1Institut für Neurobiologie, Universität Münster, Badestrasse 9, D-48149 Münster, Germany.
Abstract:
In Drosophila, the development of the midline cells of the embryonic ventral nerve cord depends on the function of the bHLH-PAS transcription factor Single-minded (Sim). The expression domain of sim, however, is also found anterior and posterior to the developing ventral cord throughout the germ band. Indeed, mutations in sim were identified based on their characteristic cuticle phenotype. Eight abdominal segments (A1-A8) can be easily seen in the larval cuticle, while three more can be identified during embryogenesis. Cells located in A8-A10 give rise to the formation of the genital imaginal discs, and a highly modified A11 segment gives rise to the anal pads that flank the anus. sim is expressed in all these segments and is required for the formation of both the anal pads and the genital imaginal discs. A new temperature-sensitive sim allele allowed an assessment of possible postembryonic function(s) of sim. Reduction of sim function below a 50% threshold leads to sterile flies with marked behavioral deficits. Most mutant sim flies were only able to walk in circles. Further analyses indicated that this phenotype is likely due to defects in the brain central complex. This brain region, which has previously been implicated in the control of walking behavior, expresses high levels of nuclear Sim protein in three clusters of neurons in each central brain hemisphere. Additional Sim localization in the medullary and laminar neurons of the optic lobes may correlate with the presence of ectopic axon bundles observed in the optic lobes of sim mutant flies.
Insights
The transcription factor Single-minded (Sim) is crucial for Drosophila development, including the nervous system and reproductive structures. New findings reveal Sim
Area of Science:
- Developmental Biology
- Neuroscience
- Genetics
Background:
- The bHLH-PAS transcription factor Single-minded (Sim) is essential for Drosophila embryonic ventral nerve cord midline development.
- Sim expression extends beyond the ventral cord, implicating it in other developmental processes.
Purpose of the Study:
- To investigate the postembryonic functions of Sim using a new temperature-sensitive allele.
- To understand the role of Sim in adult behavior and brain development.
Main Methods:
- Utilized a temperature-sensitive sim allele to modulate Sim function post-development.
- Observed and analyzed behavioral deficits, focusing on locomotion.
- Examined Sim protein localization in adult brain structures, including the central complex and optic lobes.
- Investigated potential correlations between Sim expression and axonal organization in the optic lobes.
Main Results:
- Reduced Sim function (<50%) resulted in sterile adult flies with significant behavioral deficits, primarily circular walking.
- The observed behavioral defects are linked to abnormalities in the central complex, a key brain region for motor control.
- Sim protein is highly expressed in specific neuronal clusters within the central brain hemispheres.
- Sim is also localized in optic lobe neurons, and sim mutants exhibit ectopic axon bundles in these regions.
Conclusions:
- Sim plays a critical role in postembryonic development, influencing adult behavior and brain function.
- Sim's function in the central complex is essential for normal locomotion.
- Sim's presence in optic lobe neurons suggests a role in visual system development or function.