Publisher Summary The genetics of Drosophila provides a number of different approaches toward initiating the investigation of the areas of biogenic-amine metabolism that have previously not been studied or are completely novel to any organism. Biogenic amines are particularly important compounds in insects, for they not only serve as neurotransmitters and modulaters of adenylate cyclase activity in their neurophysiology but also are essential for cross-linking proteins and chitin during sclerotization in the insect cuticle throughout development and especially at times of eclosion (hatching) and molting. A thorough understanding of the regulation of the synthesis, inactivation, and degradation of biogenic amines in the nervous system is mandatory for the elucidation of their roles in the neurophysiology and behavior of any organism. The availability of mutations that interrupt biogenic-amine metabolism in an experimentally suitable organism such as Drosophila should provide powerful analytical tools for neurochemists, neurophysiologists, and behavioral biologists. To facilitate and stimulate research on biogenic amines and sclerotization, this chapter discusses some known facts about the genetics and biochemistry of biogenic amines and sclerotization in Drosophila .

The Genetics Of Biogenic Amine Metabolism, Sclerotization, And Melanization In Drosophila Melanogaster*

Antibodies made against serotonin (5HT) were used to identify the serotonin neuronal system in the developing and adult nervous system of Drosophila melanogaster. The 5HT neuronal pattern is composed of a small number of neurons, 84 in larvae and 106 in adults, distributed in clusters composed of one to five neurons in the CNS; 5HT immunoreactive (5HT-IR) neurons appear to be predominantly intrasegmental interneurons; however, intersegmental 5HT-IR fibers are observed and at least some neurons send peripheral fibers. Acquisition of 5HT immunoreactivity in the CNS occurs late in embryogenesis, by 16-18 hours, and most if not all the 5HT neurons appear to persist into adulthood. During early metamorphosis, the intensity of 5HT-IR neuropil transiently decreases. Other changes in the CNS during this period are reflected in the appearance of two new 5HT clusters and 5HT-IR neuropil in the developing optic lobes. Comparison of the 5HT-IR pattern with other transmitter systems in Drosophila as well as comparison of the 5HT-IR pattern within different insect species is presented.

Serotonin-containing neurons in Drosophila melanogaster: development and distribution

The development of catecholamine-containing neurons (CA neurons) in the fruit fly Drosophila melanogaster was studied. Glyoxylic-acid-induced histofluorescence and antibodies against dopamine and tyrosine hydroxylase were used to describe catecholamine distribution in the larval central nervous system (CNS). The three techniques gave rise to a similar pattern of distribution of putative CA neurons. At all developmental stages CA neurons were distributed widely throughout the CNS but represented only a small fraction of all CNS neurons. Catecholamine-containing processes were confined to the CNS. The CA neurons are first discerned at about 18 hours of embryonic development. We suggest that these larval CA neurons are maintained throughout the ontogeny of the fly and that the adult CA pattern is composed of embryonic neurons and neurons that differentiate during metamorphosis.

Catecholamine‐containing neurons in Drosophila melanogaster: Distribution and development

Publisher Summary Drosophila melanogaster provides one of the most powerful experimental systems for studying genetic and molecular aspects of nervous system physiology and development. This chapter summarizes studies of compounds that are postulated to mediate or modulate neurotransmission in Drosophila with an emphasis on the genetic approaches used to study them. The premise is that the classical and molecular genetics have the potential to enhance biochemical, immunochemical, and physiological studies of neurotransmitter and neuromodulator function. This chapter covers four major classes of putative neurotransmitters or neuromodulators: (1) acetylcholine (Ach), (2) biogenic amines, (3) amino acids, and (4) neuropeptides. In no instance is there incontrovertible evidence for a role in neurotransmission, although the case for glutamate at the neuromuscular junction is quite strong. For acetylcholine, there is a great deal of circumstantial evidence that is often derived from genetic analyses. In other cases, postulated roles are based solely on analogies with work in other species.

Molecular and genetic approaches to neurotransmitter and neuromodulator systems in Drosophila.

Catecholamine- and serotonin-containing neurons were studied in pale, a Drosophila third-chromosome recessive lethal mutant. Using histofluorescent and immunocytochemical techniques, we show that this mutation only alters catecholamine levels in the CNS. Both the presence of catecholamine-neurons and the expression of serotonin are not affected by the mutation. Furthermore, we show that normal characteristics of catecholamine neurons, such as the presence of the enzyme DOPA decarboxylase and the selective uptake properties are normal in pale mutants. We suggest that pale is either the tyrosine hydroxylase structural gene, or a gene controlling tyrosine hydroxylase activity in Drosophila. The similar genetic location of the putative tyrosine hydroxylase gene and the mutation pale supports the former suggestion.

Genetic dissection of dopamine and serotonin synthesis in the nervous system of Drosophila melanogaster

An unstable Ring-X chromosome, Ddc+ -Ring-X carrying a cloned Dopa decarboxylase (Ddc) encoding segment was constructed. The construction involved a double recombination event between the unstable Ring-X, R(1)wvC and a Rod-X chromosome which contained a P-element mediated Ddc+ insert. The resulting Ddc+ -Ring-X chromosome behaves similarly to the parent chromosome with respect to somatic instability. The Ddc+ -Ring-X chromosome was used to generate Ddc mosaics. Analyses of Ddc mosaics revealed that while there was no absolute requirement for the Ddc+ expression in either the epidermis or the nervous system, very large mutant clones did affect the viability of the mosaic.

https://www.genetics.org/content/genetics/115/2/305.full.pdf

Deborah L. Bordne

Papers

Construction of an unstable Ring-X chromosome bearing the autosomal dopa decarboxylase gene in Drosophila melanogaster and analysis of Ddc mosaics