We have constructed a series of strains to facilitate the generation and analysis of clones of genetically distinct cells in developing and adult tissues of Drosophila. Each of these strains carries an FRT element, the target for the yeast FLP recombinase, near the base of a major chromosome arm, as well as a gratuitous cellautonomous marker. Novel markers that carry epitope tags and that are localized to either the cell nucleus or cell membrane have been generated. As a demonstration of how these strains can be used to study a partic ular gene, we have analyzed the developmental role of the Drosophila EGF receptor homolog. Moreover, we have shown that these strains can be utilized to identify new mutations in mosaic animals in an efficient and unbiased way, thereby providing an unprecedented opportunity to perform systematic genetic screens for mutations affecting many biological processes. SUMMARY

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Analysis of genetic mosaics in developing and adult Drosophila tissues

Antibodies specific for horseradish peroxidase (HRPeroxase) bind to neuronal membranes in Drosophila and serve as a specific neuronal marker. Immunocytochemical staining with these antibodies marks sensory neurons, peripheral nerves, and fiber tracks in the central nervous system of embryos, larvae, and adult flies. Similar patterns of staining also were seen in embryos of the grasshopper. It appears that an antigen associated with the nervous system and appearing early in differentiation is recognized by antibodies to HRPeroxase. Using this staining method, we followed embryogenesis of the central nervous system in Drosophila and found that the organization of central fiber tracks resembled that in the previously well-characterized grasshopper. We have used the anti-HRPeroxase antibodies to show that mutations affecting segmentation in Drosophila affect the organization of the embryonic nervous system.

https://www.pnas.org/content/pnas/79/8/2700.full.pdf

Antibodies to horseradish peroxidase as specific neuronal markers in Drosophila and in grasshopper embryos

In order to elucidate the behavioral significance of the central complex (CC), we have examined walking in 15 Drosophila mutant strains belonging to eight independent X-linked genes that affect the structure of the CC. Compared to four different wild-type strains, all are impaired either in a general or in a paradigm-dependent manner. Behavioral deficits concern walking activity, walking speed, or "straightness of walking" as measured in an object fixation task, in fast phototaxis, and in negative geotaxis. Behavioral deficits of three strains with mutations in different genes were studied in detail using mosaic analysis and high-speed cinematography. In all cases the focus for declining walking activity is located in the brain and is fully correlated with the respective defect of the CC. A high correlation between the degree of the behavioral impairment and the severity of the structural defect in two strains further adds to the evidence. Declining walking activity is not an unspecific side effect of structural brain defects, as steady walking is observed in structural mutants of the visual system and mushroom bodies. In mutant flies no-bridgeKS49 (nob), step size as a function of the stepping period is reduced. The focus of the resulting reduced average and maximum walking speeds resides in the brain and, again, the behavioral impairment fully correlates with the structural defects of the CC. While no indication is found for a role of the CC in setting up the basic stepping rhythm in straight walking (a respective phenotype in mutant central-complexKS181 flies resides in the ventral ganglion), a role in turning and start/stop maneuvers is suggested by aberrations in the stepping pattern of nob flies during such episodes.

https://www.jneurosci.org/content/jneuro/13/5/1852.full.pdf

A higher control center of locomotor behavior in the Drosophila brain

https://www.cell.com/neuron/pdf/0896-6273(94)90437-5.pdf

Genetic dissection of mechanosensory transduction : mechanoreception-defective mutations of drosophila

The product of the period (per) gene of Drosophila melanogaster is continuously required for the functioning of the circadian pacemaker of locomotor activity. We have used internally marked mosaics to determine the anatomical locations at which per expression is required for adult rhythmicity, and thus where the fly's circadian pacemaker is likely located in this holometabolous insect. We first provide a detailed description of the distribution and nature of per-expressing cells in the fly's CNS. Using an antibody to the per gene product, or to that of a reporter of per expression, in conjunction with an antibody to the embryonic lethal-abnormal visual system (elav) gene product--which is used as a marker of neuronal identity--we have experimentally confirmed previously proposed assignments of per-expressing cells to the neuronal and glial classes. Thus, we found that per expression and elav immunoreactivity colocalized in large cells located in the lateral cortex of the central brain, as well as in more dorsally located cells in the posterior central brain. In contrast, we found that cells located at the margins of the cortex and the neuropil, and within the neuropil, as well as smaller cortical cells found throughout the brain's cortex, were elav negative, supporting the notion that they are glial in nature. Using internally marked mosaics, we find that the pacemaker is located in brain but is not exclusive to the eyes, the ocelli, or the optic lobes, which is consistent with previous reports obtained in this and other insects of this class. Although the pacemaker may be a paired structure, we show that the functioning of one of them is sufficient for rhythmicity. Finally, we report that glial expression is sufficient for some behavioral rhythmicity to be manifest. However, the rhythmicities of animals for which per expression was confined to glia were weak, suggesting that neuronal per expression as well may be required for normal pacemaker function.

/pdf/expression-of-the-period-clock-gene-within-different-cell-1uf0wvq88j.pdf

Expression of the period clock gene within different cell types in the brain of Drosophila adults and mosaic analysis of these cells' influence on circadian behavioral rhythms.

Jeffrey C. Hall

Papers

Fate mapping of nervous system and other internal tissues in genetic mosaics of Drosophila melanogaster.