Structural Characterisation of the Drosophila Mushroom Bodies

[摘要] The brain of the fruit fly Drosophila melanogaster, although only comprising some 200 thousand neurons, displays a remarkable repertoire of behavioural responses to it's environment. The relative simplicity of it's brain structure in comparison with vertebrate models or even higher invertebrates, wealth of genetic data and availability of both quantitative and qualitative behavioural assays, make it an ideal model organism for studying brain structure/function relationships. The recent development of P-element based enhancer-trap technology has provided a new tool both for visualisation and for manipulation of neurons. This technology has been used here to investigate the structure of the mushroom bodies. One of the major regions of higher function in the insect brain, the mushroom bodies have been compared to the mammalian hippocampus. Confocal microscopy of enhancer-trap expression pattems reveals neuronal structure to a higher degree of resolution than is possible usin most traditional neuroanatomical techniques. A total of 31 P{GAL4} enhancer-trap lines isolated from a screen of 1800 were chosen for detailed analysis. Structural subdivisions in terms of gene expression invisible to classical neuroanatomy are evident, suggesting a possible degree of functional subdivision. The expression pattems in the larval mushroom bodies also show subdivisions. The nature of the subdivisions are different at the two developmental stages. Analysis of the developing brain during the pupal stages illustrates the structural re-organisation of the mushroom bodies during this period. Hydroxyurea ablation of the mushroom body neuroblasts in the early larvae results in a small renuiant that survives from the embryo to the adult Extrinsic output from the mb lobes and input to the calyx appears unaffected by the ablation of the mushroom bodies. Partial ablation of the neuroblasts provides evidence that the four fold symmetry of the mb structure is a reflection of the clonal nature of each of the four clusters and tracts and that the mushroom bodies are closely related to the lower order olfactory centre, the antennal lobes.

[发布机构] University:University of Glasgow

[关键词] Neurosciences, Developmental biology