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PubMed2003

l(3)malignant brain tumor and three novel genes are required for Drosophila germ-cell formation.

To identify genes involved in the process of germ-cell formation in Drosophila, a maternal-effect screen using the FLP/FRT-ovoD method was performed on chromosome 3R. In addition to expected mutations in the germ-cell determinant oskar and in other genes known to be involved in the process, several novel mutations caused defects in germ-cell formation. Mutations in any of three genes [l(3)malignant brain tumor, shackleton, and out of sync] affect the synchronous mitotic divisions and nuclear migration of the early embryo. The defects in nuclear migration or mitotic synchrony result in a reduction in germ-cell formation. Mutations in another gene identified in this screen, bebra, do not cause mitotic defects, but appear to act upstream of the localization of oskar. Analysis of our mutants demonstrates that two unique and independent processes must occur to form germ cells-germ-plasm formation and nuclear division/migration.

Animals↗
PubMed1998

The evolutionary history of Drosophila buzzatii. XXXIV. The distribution of the retrotransposon Osvaldo in original and colonizing populations.

The frequency distribution of the retrotransposon Osvaldo in the haploid genome of Drosophila buzzatii has been studied in five natural populations from the Iberian Peninsula and six natural populations from Argentina. In Iberian populations, Osvaldo insertion sites do not follow a Poisson distribution, most probably due to eight euchromatic sites with high occupancy, found in all populations. The estimated alpha and beta parameters, which measure the relative importance of drift and negative selection in shaping frequency distributions, indicate that drift is the main force acting upon the distribution of Osvaldo in natural populations of D. buzzatii in the Iberian Peninsula. On the other hand, Osvaldo distribution in populations from Argentina is similar to the distribution of elements with low copy numbers, such as those described for Drosophila melanogaster and Drosophila simulans: there are no indications for deviation from a Poisson distribution, there is a low occupancy per insertion site, and genetic drift has no apparent effect on the frequency distribution. We propose that the unusual distribution found in the populations from the Iberian Peninsula is a consequence of the colonization process. Iberian Peninsula populations suffered a genomic redistribution of Osvaldo, most probably after a founder effect. Consequently, certain copies that arrived at high frequencies are showing a high occupancies today, and the mean copy number of Osvaldo is higher in Iberian Peninsula populations than in populations from Argentina. All other copies are the result of recent (after colonization) transposition events.

Animals↗
PubMed2001

A novel polymorphism in the PTC gene allows easy identification of allelic loss in basal cell nevus syndrome lesions.

Basal cell nevus syndrome (BCNS; also nevoid basal cell carcinoma syndrome [NBCCS]; Gorlin's syndrome) is an autosomal dominant syndrome characterized by multiple basal cell carcinomas, keratocysts, and developmental skeletal defects. Mutation of the human homologue of Drosophila patched (PTC) gene is considered to be the molecular defect in BCNS. PTC mutations have been observed in sporadic tumors including basal cell and ovarian carcinomas and medulloblastoma. The authors report a novel C/T polymorphism in the PTC gene. Forty-eight normal blood samples were screened for the presence of the polymorphism using direct radioactive and automated sequencing of polymerase chain reaction (PCR) products and restriction enzyme digestion. Results demonstrated 20 homozygous T (43%), 11 homozygous C (23%), and 17 heterozygous C/T (35%). The presence of this polymorphism has permitted us to directly detect allelic loss in BCNS, sporadic keratocysts, and basal cell carcinoma (BCC). Further, four BCNS keratocysts and two BCNS-BCC and three non-BCNS keratocysts showed allelic loss of complementary DNA from lesions when compared with their corresponding blood genomic DNA.

Basal Cell Nevus Syndrome↗
PubMed1990

Evidence for chromosomal transmission of polydnavirus DNA.

Heterogeneity in polydnavirus DNA was exploited as a means of following the transmission of viral genomes in parasitoid populations. Parasitoid lines isogenic for viral DNA markers were established from both a braconid (Cotesia melanoscela) and an ichneumonid (Hyposoter fugitivus) species. In crossing experiments these markers routinely segregated in Mendelian (chromosomal) fashion, suggesting that the structure of polydnavirus genomes is probably determined by the integrated form of viral DNA, rather than by extrachromosomal molecules.

Animals↗
PubMed1992

Nucleotide sequence of the tick-borne orthomyxo-like Dhori/India/1313/61 virus membrane protein gene.

The complete nucleotide sequence of the sixth largest segment of ssRNA (RNA-6) of the tick-borne orthomyxo-like Dhori/India/1313/61 virus was determined by using cloned cDNA derived from infected cell mRNA and dideoxynucleotide sequencing of viral RNA. RNA-6 contains 962 nucleotides and is predicted to encode a protein of 270 amino acids with an M(r) of 30,498 in its first open reading frame (ORF). This protein is likely to represent the viral membrane (M1) protein, based on its predicted M(r) of 29,000 (estimated by PAGE), its relatively high abundance in infected cells and amino acid composition analysis. In addition, a second ORF was found which overlaps the M1 protein gene sequence by 327 nucleotides. This additional reading frame, in the +3 frame, potentially can encode a protein of 141 amino acids. However, S1 nuclease analysis of RNA-6 mRNA from infected cells indicated that there was only a single abundant RNA species corresponding in size to the full-length genomic RNA (0.96 kb). Further studies are needed to determine whether expression of the second ORF occurs and how that expression might arise.

Amino Acid Sequence↗
PubMed1998

windbeutel, a gene required for dorsoventral patterning in Drosophila, encodes a protein that has homologies to vertebrate proteins of the endoplasmic reticulum.

The formation of the dorsoventral axis of the Drosophila embryo depends on cell-cell interactions that take place in the female ovary and involve the activation of transmembrane receptors by secreted ligands. The gene windbeutel functions in the somatic follicle cells of the ovary and is required for the generation of a signal that will determine the ventral side of the embryo. This signal originates in the follicle cells during oogenesis, but its actions are only manifested after fertilization, when the egg has already been laid. We have performed a molecular analysis of windbeutel. We have found that windbeutel encodes a putative resident protein of the endoplasmic reticulum, and has homologs in rats and humans. The gene is expressed for a brief period of time in the follicle cells of the ovary, at around the time when the dorsoventral axis of the egg chamber is first established. We propose that Windbeutel is responsible for the folding and/or modification of a specific factor that is secreted from the follicle cells and participates in the activation of the ventralizing signal.

Amino Acid Sequence↗
PubMed1993

Torso, a receptor tyrosine kinase required for embryonic pattern formation, shares substrates with the sevenless and EGF-R pathways in Drosophila.

The maternally expressed Drosophila gene torso (tor) is a receptor tyrosine kinase that, when activated, initiates a signal transduction cascade that is responsible for the proper differentiation of the terminal, nonsegmented regions of the embryo. l(1)pole hole, the Drosophila raf-1 serine-threonine kinase homolog, and corkscrew, a tyrosine phosphatase, have been shown previously to function in this signal transduction pathway. We have identified other products in this pathway by carrying out a mutagenesis screen for dominant suppressors of a tor gain-of-function allele. More than 40 mutations, some of which fall into seven complementation groups, have been characterized genetically. Two of these correspond to mutations in ras-1 and Son of sevenless (Sos), which also function in the sevenless and EGF receptor (Der) tyrosine kinase pathways. The phenotypes of several other Su(tor) mutations suggest that they also function in other receptor tyrosine kinase-activated pathways at different times during Drosophila development.

Alleles↗
PubMed2000

Construction and transposition of a 100-kilobase extended P element in Drosophila.

We have used P element deletion derivatives at defined locations in the Drosophila genome to construct a 100-kb extended P element more than twice the size of any previously available. We demonstrate that this prototypical extended P element is capable of transposition to new sites in the genome. The structural and functional integrity of a transposed extended P element was confirmed using molecular, genetic, and cytogenetic criteria. This is the first method shown to be capable of producing large, unlinked transpositional duplications in Drosophila. The ability to produce functional transposable elements from half-elements is novel and has many potential applications for the functional analysis of complex genomes.

Animals↗
PubMed2002

Genome-wide analysis of the odorant-binding protein gene family in Drosophila melanogaster.

Olfaction is of considerable importance to many insects in behaviors critical for survival and reproduction, including location of food sources, selection of mates, recognition of colony con-specifics, and determination of oviposition sites. An ubiquitous, but poorly understood, component of the insect's olfactory system is a group of odorant-binding proteins (OBPs) that are present at high concentrations in the aqueous lymph surrounding the dendrites of olfactory receptor neurons. OBPs are believed to shuttle odorants from the environment to the underlying odorant receptors, for which they could potentially serve as odorant presenters. Here we show that the Drosophila genome carries 51 potential OBP genes, a number comparable to that of its odorant-receptor genes. We find that the majority (73%) of these OBP-like genes occur in clusters of as many as nine genes, in contrast to what has been observed for the Drosophila odorant-receptor genes. Two of the presumptive OBP gene clusters each carries an odorant-receptor gene. We also report an intriguing subfamily of 12 putative OBPs that share a unique C-terminal structure with three conserved cysteines and a conserved proline. Members of this subfamily have not previously been described for any insect. We have performed phylogenetic analyses of the OBP-related proteins in Drosophila as well as other insects, and we discuss the duplication and divergence of the genes for this large family. [The sequence data from this study have been submitted to FlyBase. Annotations for these sequences are available as supplementary material at http://www.genome.org.]

Amino Acid Sequence↗
PubMed2006

Chromosomal variation and genome size support existence of cryptic species of Triatoma dimidiata with different epidemiological importance as Chagas disease vectors.

The wide geographical distribution of Triatoma dimidiata, one of the three major vectors of Chagas disease, ranges from Mexico to northern Peru. Since this species occupies a great diversity of artificial and natural ecotopes, its eradication is extremely difficult. In order to assist control efforts, we used chromosome analyses and DNA amount as taxonomic markers to study genetic variability in populations of T. dimidiata from Mexico, Guatemala, El Salvador and Colombia. We differentiated three groups or cytotypes defined by characteristic chromosome C-banding patterns and genome size measured by flow cytometry. The three cytotypes are restricted to different geographic locations. Cytotype 1 occurs in Mexico (excluding Yucatán), Guatemala (excluding Petén), El Salvador and Colombia. Cytotype 2 occurs in Yucatán and cytotype 3 occurs in Petén. Cytotype 1, commonly associated with domestic and peridomestic environments but also inhabiting sylvatic ecotopes, is the most widespread and with major epidemiological significance. In contrast, the Yucatán cytotype inhabits wild ecotopes but increasingly enters houses, while the Petén cytotype appears exclusively sylvatic. We suggest that these cytotypes represent cryptic species of T. dimidiata with different epidemiological relevance as Chagas disease vectors. Poor ability to colonize human dwellings, together with their restricted geographic distribution, indicate that the Yucatán and Petén putative species probably have much less epidemiological significance than cytotype 1. Thus, the genetic markers we describe are powerful tools to differentiate cryptic species in T. dimidiata with different epidemiological significance, contributing to planning the most effective control measures.

Animals↗
PubMed1991

The major serum protein of Drosophila larvae, larval serum protein 1, is dispensable.

Null alleles of all three genes (alpha, beta and gamma) coding for the major serum protein of Drosophila larvae, larval serum protein 1, have been characterized at the protein level and by analysis of their RNA and DNA. Each allele completely lacks one polypeptide chain. beta shows an unaltered gene but reduced levels of RNA, alpha shows restriction-fragment-length polymorphism and shows low levels of transcript, while gamma is a deletion. The three null alleles have been combined to give a strain without the gene for larval serum protein 1 which survives.

Alleles↗
PubMed1997

Genetic and phenotypic analysis of the genes of the elbow-no-ocelli region of chromosome 2L of Drosophila melanogaster.

The elbow locus is found to be two genes elA and elB, each of which has a distinct phenotype when mutant. Mutations of the elA gene have a strong phenotype where the wing is markedly disrupted. Mutations of elB are weak, mainly affecting the alula and the wing bristles. The two genes are dominant enhancers of each other. Homozygous deletion of the complete elbow region results in lethality. Situated between the elbow genes is the pupal gene and a locus which when deleted causes a crippled leg phenotype. This locus may be a control region for elbow. Immediately adjacent on the proximal side of elA is the no-ocelli locus. The phenotypes of noc alleles vary from extreme, where the ocelli and associated bristles are absent, to weak where these structures are disrupted. The various noc phenotypes are associated with genetically distinct gene regions, mutations of which act as enhancers of each other. Alleles of el and noc show partial failure of complementation, heterozygotes having weak el or weak noc phenotypes. Alleles of both these genes interact with the antimorphic noc allele Sco.

Alleles↗
PubMed2006

Gene transposition as a cause of hybrid sterility in Drosophila.

We describe reproductive isolation caused by a gene transposition. In certain Drosophila melanogaster-D. simulans hybrids, hybrid male sterility is caused by the lack of a single-copy gene essential for male fertility, JYAlpha. This gene is located on the fourth chromosome of D. melanogaster but on the third chromosome of D. simulans. Genomic and molecular analyses show that JYAlpha transposed to the third chromosome during the evolutionary history of the D. simulans lineage. Because of this transposition, a fraction of hybrids completely lack JYAlpha and are sterile, representing reproductive isolation without sequence evolution.

Animals↗
PubMed1995

Positional cloning and sequence analysis of the Drosophila clock gene, timeless.

The Drosophila genes timeless (tim) and period (per) interact, and both are required for production of circadian rhythms. Here the positional cloning and sequencing of tim are reported. The tim gene encodes a previously uncharacterized protein of 1389 amino acids, and possibly another protein of 1122 amino acids. The arrhythmic mutation tim01 is a 64-base pair deletion that truncates TIM to 749 amino acids. Absence of sequence similarity to the PER dimerization motif (PAS) indicates that direct interaction between PER and TIM would require a heterotypic protein association.

Amino Acid Sequence↗
PubMed1991

Evidence for a chromosomal location of polydnavirus DNA in the ichneumonid parasitoid Hyposoter fugitivus.

Evidence is presented in support of a chromosomal location for sequences homologous to polydnavirus DNA in the ichneumonid parasitoid Hyposoter fugitivus. In this study, four different viral genome segments were cloned and used as probes against genomic DNA extracted from male parasitoids and digested with a variety of restriction enzymes. Each probe typically identified a single off-size fragment (OSF) in the case of enzymes not cutting viral genome segments, while two OSFs were generated by enzymes cutting at one and two sites. While extra OSFs were occasionally observed, these were invariably found to be due to the presence of polymorphic restriction sites in flanking chromosomal DNA. Analysis of these data suggests that a single, stable chromosomal locus exists for sequences homologous to each viral genome segment; the data also indicate that viral and cognate parasitoid genomic DNAs are largely if not entirely colinear.

Animals↗
PubMed1993

The dynamics of chromatin condensation: redistribution of topoisomerase II in the 87A7 heat shock locus during induction and recovery.

We have examined the in vivo sites of action for topoisomerases II in the 87A7 heat shock locus as a function of gene activity. When the hsp70 genes are induced, there is a dramatic redistribution of topoisomerase II in the locus which parallels many of the observed alterations in chromatin structure. In addition to changes in the topoisomerase II distribution within the locus, we find topoisomerase II localized around the putative domain boundaries scs and scs'. During recovery, when the chromatin fiber of the locus recondenses, the major sites of action for topoisomerase II appear to be located within the two hsp70 genes and in the intergenic spacer separating the two genes.

Animals↗
PubMed1994

The SR protein B52/SRp55 is essential for Drosophila development.

B52, also called SRp55, is a 52-kDa member of the Drosophila SR protein family of general splicing factors. Escherichia coli-produced B52 is capable of both activating splicing and affecting the alternative splice site choice in human in vitro splicing reactions. Here we report the isolation of a B52 null mutant generated by remobilizing a P element residing near the B52 gene. The resulting deletion, B52(28), is confined to the B52 gene and its neighbor the Hrb87F gene. Second-instar larvae homozygous for the deletion are deficient in both B52 mRNA and protein. The B52 null mutant is lethal at the first- and second-instar larval stages. Germ line transformation of Drosophila flies with B52 genomic DNA rescues this lethality. Thus, B52 is an essential gene and has a critical role in Drosophila development. Larvae deficient in B52 are still capable of splicing the five endogenous pre-mRNAs tested here, including both constitutively and alternatively spliced genes. Therefore, B52 is not required for all splicing in vivo. This is the first in vivo deficiency analysis of a member of the SR protein family.

Animals↗
PubMed1996

att, a target for regulation by tra2 in the testes of Drosophila melanogaster, encodes alternative RNAs and alternative proteins.

We have identified a gene, alternative testis transcripts (att), which is alternatively expressed, at both the RNA and protein levels, in testes and somatic tissues. The testis-specific RNA differs from somatic RNAs in both promoter usage and RNA processing and is dependent on the function of the transformer 2 gene. The differences between the somatic and testis RNAs have substantial consequences at the protein level. The somatic RNAs encode a protein with homology to the mammalian Graves' disease carrier proteins. The testis RNA lacks the initiation codons used in somatic tissue and encodes two different proteins. One of these begins in a testis-specific exon, uses a reading frame different from that for the somatic protein, and is completely novel. The other protein initiates translation in the frame of the somatic RNA at a Len CUG codon which is within the open reading frame for the somatic protein. This produces a novel truncated version of the Graves' disease carrier protein-like protein that lacks all sequences N terminal to the first transmembrane domain.

Alternative Splicing↗