Genetic Dissection of the Drosophila Nervous System by means of Mosaics

Given a mutant having abnormal behavior, the anatomical domain responsible for the deficit may be identified by the use of genetic mosaicism. Individuals may be produced in which a portion of the body is mutant male while the rest is normal female. In such sex mosaics, or gynandromorphs, the division line between normal and mutant parts can occur in various orientations. Mutants of five different genes (cistrons) on the X-chromosome of Drosophila melanogaster, having various abnormalities in visual function, have been tested by this method. All of these have been found to be autonomous, i.e., a mutant eye always functions abnormally, regardless of the amount of normal tissue present elsewhere, indicating that the primary causes of the behavioral deficits in these mutants are within the eye

Neurophysiological defects in temperature-sensitive paralytic mutants of Drosophila melanogaster

A new temperature-sensitive paralytic mutant of Drosophila, comatose, is compared behaviorally and physiologically with the previously known types, para and shi. All three have different properties with respect to kinetics of paralysis at high temperature and recovery from paralysis; com is hypersensitive to paralysis by cooling. Neurophysiological experiments indicate different mechanisms for paralysis in each of the mutants

Courtship in Drosophila Mosaics: Sex-Specific Foci for Sequential Action Patterns

Mosaic fate mapping is used to locate the foci determining sex-specific steps in the mating behavior of Drosophila. Male performance of following females and displaying wing vibration toward them requires that a focus inside the head be constituted of male tissue, regardless of the sex of the head sense organs, the legs, the wings, or the thoracic ganglion. For attempted copulation to occur, a second focus in the thoracic region must also be male. Courtship by males is induced by a posteriorly located focus in the female, but an anterior female focus determines receptivity to attempted copulation. The interplay of male and female foci in the complex behavioral sequence is delineated

On the Species Specificity of Acceptor RNA and Attachment Enzymes

One of the steps in protein biosynthesis appears to be the attachment of each amino acid to a specific acceptor (SRNA) molecule. According to the adaptor hypothesis, each SRNA molecule would then fit to a specific complementary base sequence on a linear RNA template, specifying the sequence of amino acids in the resultant protein [1,2]. An adaptor molecule thus could have two specificities: one recognizing the correct amino acid and activating enzyme; the other, the proper position on the template. The correctness of the amino-acid sequence therefore would depend upon the precision and constancy of the adaptors. However, the structures of the enzymes and adaptors are presumably under the genetic control of the organism and might be subject to heritable modifications. It is therefore conceivable that one or both ends of an adaptor might change sufficiently to cause occasional errors and, in the long run, an alteration of the genetic code might evolve. This notion, prompted by genetic observations [3] which suggested that mutation of a bacterium might modify its translation of genetic information, lead to the present comparison of the specificities of the acceptor RNA and activating enzymes of different organisms. Several differences in specificity have been reported previously. Berg et al. [4] demonstrated that SRNA from Escherichia coli contains two distinguishable acceptors for methionine. An enzyme prepared from yeast could attach methionine to one of these, while the enzyme from E. coli could attach to both. Webster found, in pig liver, a difference between the nuclear and cytoplasmic attachment enzymes for alanine. Rendi and Ochoa [6] noted that, for leucine, the enzymes in yeast and in E. coli could attach only to their homologous SRNA. Furthermore, in the case of leucine, rat liver enzyme and SRNA were interchangeable with those from E. coli. The observations presented below show that whether the enzymes and/or acceptors from two organisms are interchangeable depends upon not only the organisms in question but also the particular amino aci

Suppression of polyglutamine toxicity by a Drosophila homolog of myeloid leukemia factor 1

The toxicity of an abnormally long polyglutamine [poly(Q)] tract within specific proteins is the molecular lesion shared by Huntington's disease (HD) and several other hereditary neurodegenerative disorders. By a genetic screen in Drosophila, devised to uncover genes that suppress poly(Q) toxicity, we discovered a Drosophila homolog of human myeloid leukemia factor 1 (MLF1). Expression of the Drosophila homolog (dMLF) ameliorates the toxicity of poly(Q) expressed in the eye and central nervous system. In the retina, whether endogenously or ectopically expressed, dMLF co-localized with aggregates, suggesting that dMLF alone, or through an intermediary molecular partner, may suppress toxicity by sequestering poly(Q) and/or its aggregates

Ingrowth by photoreceptor axons induces transcription of a retrotransposon in the developing Drosophila brain

The development of the lamina, the first optic ganglion of the fly visual system, depends on inductive cues from the innervating photoreceptor axons. lacZ expression from a P-element insertion, A72, occurs in the anlage of the lamina coincident with axon ingrowth from the eye imaginal disc. In eyeless mutants lacking photoreceptor axons, lacZ expression did not occur. The P-element was found to have inserted within the 3′ long terminal repeat (LTR) of a ‘17.6′ type retrotransposon. The expression pattern of 17.6 transcripts in the brain in wild-type and eyeless mutants paralleled the expression of the lacZ reporter. Analysis of 17.6 cis-regulatory sequences indicates that the lamina-specific expression is due to the combined action of an enhancer element in the LTR and a repressor element within the internal body of the retrotransposon. The regulation of the 17.6 retrotransposon provides a model for the study of innervation-dependent gene expression in postsynaptic cells during neurogenesis

Non-lethal PCR genotyping of single Drosophila

In Drosophila, genetic techniques relying on stochastic chromosomal rearrangements involve the generation and screening of a large number of fly stocks to isolate a few lines of interest. Here, we describe a PCR-based method allowing non-lethal molecular characterization of single flies. Using this procedure, individual candidate recombinant animals can be genotyped and selected one generation earlier than with extant methodology and, importantly, before stocks are established. This advance should significantly facilitate several of the most fundamental and routine techniques in Drosophila genetics

From monoclonal antibody to gene for a neuron-specific glycoprotein in Drosophila

A monoclonal antibody (MAb24B10), derived from mice immunized with Drosophila retina, exclusively stains photoreceptor cells in the retina and their axonal projections to the optic ganglia. The antigen (Ag24B10) is a 160-kDa glycoprotein comprising about 0.8% of the retina protein. By microsequencing, 19 of the first 21 amino acids at the NH2-terminal end of the protein have been determined. Using synthetic oligonucleotide probes corresponding to a portion of this amino acid sequence, we isolated a homologous genomic clone. A partial DNA sequence of this clone, along with blot experiments on genomic DNA and RNA, indicate that this clone is part of the structural gene for Ag24B10. By in situ hybridization, the gene was localized to the tip of chromosome 3R

Multiple-stress analysis for isolation of Drosophila longevity genes

Long-lived organisms tend to be more resistant to various forms of environmental stress. An example is the Drosophila longevity mutant, methuselah, which has enhanced resistance to heat, oxidants, and starvation. To identify genes regulated by these three stresses, we made a cDNA library for each by subtraction of "unstressed" from "stressed" cDNA and used DNA hybridization to identify genes that are regulated by all three. This screen indeed identified 13 genes, some already known to be involved in longevity, plus candidate genes. Two of these, hsp26 and hsp27, were chosen to test for their effects on lifespan by generating transgenic lines and by using the upstream activating sequence/GAL4 system. Overexpression of either hsp26 or hsp27 extended the mean lifespan by 30%, and the flies also displayed increased stress resistance. The results demonstrate that multiple-stress screening can be used to identify new longevity genes

Calx, a Na-Ca exchanger gene of Drosophila melanogaster

We have cloned Calx, a gene that encodes a Na-Ca exchanger of Drosophila melanogaster. Calx encodes two repeated motifs, Calx-α and Calx-β, that overlap domains required for exchanger activity and regulation. Calx has multiple transcripts in adults, including at least one expressed in the retina. The Calx genomic locus comprises ≥35 kb between the Atpα and rudimentary-like genes in chromosomal region 93B. In Xenopus oocytes, microinjected Calx cRNA induces calcium uptake like that of its homolog, the 3Na^+-1Ca^(2+) exchanger of mammalian heart. Implications of Calx-α motifs for the mechanism of Na-Ca exchange are discussed