[An experiment in genetic control of Culex pipiens in the area of Montpellier].
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Chromosome Aberrations↗
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Genetic nomenclature guide. Drosophila melanogaster.
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Animals↗
The human ribosomal protein S7-encoding gene: isolation, structure and localization in 2p25.
We have identified a gene encoding the human ribosomal protein (r-protein) S7. The S7 gene contains seven exons and six introns spanning about 6 kb. Organization of the gene is similar to that of Xenopus laevis S8, the only homologous intron-containing gene isolated so far. An mRNA transcribed from this gene has an open reading frame (ORF) of 582 nucleotides (nt), which encodes a protein of 194 amino acids (22.1 kDa). The transcription start point (tsp) was mapped by a primer extension assay to a C residue within a pyrimidine-rich tract. Human S7 (hS7) is identical to rat S7 (rS7) and exhibits significant similarity with the X. laevis, insect and plant homologs. We have used fluorescence in situ hybridization (FISH) to localize S7 to chromosome 2p25.
Amino Acid Sequence↗
Signal transduction downstream from Ras in Drosophila.
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Animals↗
Gambol and Tc1 are two distinct families of DD34E transposons: analysis of the Anopheles gambiae genome expands the diversity of the IS630-Tc1-mariner superfamily.
Tc1 is a family of DNA transposons found in diverse organisms including vertebrates, invertebrates and fungi. Tc1 belongs to the IS630-Tc1-mariner superfamily, which is characterized by common 'TA' target site and conserved D(Asp)DE(Glu) or DDD catalytic triad. All functional Tc1-like transposons contain a transposase with a DD34E catalytic triad. We conducted a systematic analysis of DD34E transposons in the African malaria mosquito, Anopheles gambiae, using a reiterative and exhaustive search program. In addition to previously described Tc1-like elements, we uncovered 26 new DD34E transposons including a novel family that we named gambol. Designation of family status to gambol is based on phylogenetic analyses of transposase sequences that showed gambol and Tc1 transposons as distinct clades that were separated by mariner and other families of the IS630-Tc1-mariner superfamily. The distinction between Tc1 and gambol is also consistent with the unique TIRs in gambol elements and the presence of a 'W[I/L/V]DEDC' signature near their N-termini. This signature is predicted as part of the 'RED' domain, a component of the 'PAI' and 'RED' DNA binding domains in Tc1 and possibly mariner. Although gambol appears to be related to a few DD34E transposons from cyanobacteria and fungi, no gambol has been reported in any other insects or animals thus far. Several gambol and Tc1 elements have intact ORFs and different genomic copies with high sequence identity, which suggests that they may have been recently active.
Amino Acid Sequence↗
Brainiac encodes a novel, putative secreted protein that cooperates with Grk TGF alpha in the genesis of the follicular epithelium.
brainiac (brn) is involved in a number of developmental events. In addition to being required zygotically for segregation of neuroblasts from epidermoblasts, it is essential for a series of critical steps during oogenesis which also depend upon gurken (grk), a TGF alpha homolog. Animals harboring strong mutations of either grk or EGF receptor tyrosine kinase (Egfr) or doubly mutant for brn and weak grk or Egfr mutations produce ovarian follicles with multiple sets of nurse cell-oocyte complexes. These follicles frequently have discontinuities in the follicular epithelium that uncover nurse cells but not the oocyte. Gaps first appear in the germarium, suggesting that some nurse cells lack affinity for invading prefollicular cells. This is the first evidence that grk, in addition to its involvement in the genesis of anterior-posterior and dorsal-ventral polarity, is also required for Egfr-dependent development of the follicular epithelium that surrounds each nurse cell/oocyte cluster to form an egg chamber. We have used restriction fragment length polymorphisms to localize brn to a 10-kb region within a 300-kb stretch of DNA on the X-chromosome, and we have identified the brn gene by means of RNA rescue. brn codes for a putative secreted protein. brn is expressed in germ cells at the time follicle cells first surround the nurse cell-oocyte complex. Our genetic data suggest that brn acts in a parallel, but partially overlapping pathway to the Grk-Egfr signaling pathway. The brn pathway may help to provide specificity to TGF alpha -Egfr function during oogenesis.
Amino Acid Sequence↗
Bm kettin, homologue of the Drosophila kettin gene, is located on the Z chromosome in Bombyx mori and is not dosage compensated.
In Bombyx mori, the female is the heterogametic sex and the sex determining system is referred to as ZZ/ZW. In a previous study, we found that this insect does not show dosage compensation at the transcriptional level. To confirm the validity of our conclusion, we investigated whether or not another sex-linked gene is dosage compensated. To identify new Z-linked genes, total RNA from reciprocal hybrid females between the silkworm strains p50 and C108 was compared using the differential display technique. Nine cDNA fragments corresponding to several differentially expressed mRNAs were cloned and sequenced. The analysis of nucleotide sequence polymorphisms confirmed that one of these cDNAs, ZDD4, originated from the Z chromosome. The amino acid sequence deduced from ZDD4 has homology with kettin, a modular protein in the Z-disc of Drosophila melanogaster muscles. On immunoblots of Bombyx larval muscle proteins a polypeptide of 380 kDa was labelled with antibody to the ZDD4 peptide. We considered that the gene corresponding to ZDD4 encodes a kettin homologue in the silkworm, and denote it as Bm kettin. By a three-point cross, Bm kettin was mapped at 40.0 CM on the Z chromosome. Southern blot analysis revealed that Bm kettin was present at one copy in the genome. Northern blot analysis showed that Bm Kettin mRNA was 9.1kb in length, and that the level of the mRNA in males was two times greater than that of females. Taken together with our previous observations, the present data suggest that lack of dosage compensation is a general rule in B. mori. Moreover, the twofold difference in Bm kettin expression between males and females may help explain the sexual difference in the wing flapping activity observed in some groups of Lepidoptera.
Amino Acid Sequence↗
The SON gene encodes a conserved DNA binding protein mapping to human chromosome 21.
We report the identification and characterization of a clone for the DNA binding protein SON, which we have isolated from a human keratinocyte cDNA library. Using this clone we have found that the SON gene is expressed in different cell types and that homologous sequences can be detected in vertebrate and insect genomic DNA. Using the polymerase chain reaction (PCR) to amplify SON sequences from a panel of somatic cell hybrids we have assigned the gene encoding human SON to chromosome 21. By use of hybrids containing regions of chromosome 21 the localization has been refined to 21q 22.1-q22.2.
Amino Acid Sequence↗
Hybrid lethal systems in the Drosophila melanogaster species complex. I. The maternal hybrid rescue (mhr) gene of Drosophila simulans.
Hybrid females from Drosophila simulans females x Drosophila melanogaster males die as embryos while hybrid males from the reciprocal cross die as late larvae. The other two classes are sterile adults. Letting C, X, and Y designate egg cytoplasm, X, and Y chromosomes, respectively, and subscripts m and s stand for melanogaster and simulans, CmXmYs males are lethal in the larval stage and are rescued by the previously reported genes, Lhr (Lethal hybrid rescue) in simulans or Hmr (Hybrid male rescue) in melanogaster. We report here another rescue gene located on the second chromosome of simulans, mhr (maternal hybrid rescue) that, when present in the mother, rescues CsXmXs females from embryonic lethality. It has been postulated that the hybrids not carrying the Xs like CmXmYs males are larval lethal and that the hybrids carrying both the Cs and the Xm like CsXmXs females are embryonic lethal. According to these postulates CsXmYs males (obtained by mating attached-X simulans females to melanogaster males) should be doubly lethal, at both embryo and larval stages. When both rescuing genes are present, Hmr in the father and mhr in the mother, males of this genotype are fully viable, as predicted.
Animals↗
Molecular karyotype and chromosomal localization of genes encoding beta-tubulin, cysteine proteinase, hsp 70 and actin in Trypanosoma rangeli.
The molecular karyotype of nine Trypanosoma rangeli strains was analyzed by contour-clamped homogeneous electric field electrophoresis, followed by the chromosomal localization of beta-tubulin, cysteine proteinase, 70 kDa heat shock protein (hsp 70) and actin genes. The T. rangeli strains were isolated from either insects or mammals from El Salvador, Honduras, Venezuela, Colombia, Panama and southern Brazil. Also, T. cruzi CL-Brener clone was included for comparison. Despite the great similarity observed among strains from Brazil, the molecular karyotype of all T. rangeli strains analyzed revealed extensive chromosome polymorphism. In addition, it was possible to distinguish T. rangeli from T. cruzi by the chromosomal DNA electrophoresis pattern. The localization of beta-tubulin genes revealed differences among T. rangeli strains and confirmed the similarity between the isolates from Brazil. Hybridization assays using probes directed to the cysteine proteinase, hsp 70 and actin genes discriminated T. rangeli from T. cruzi, proving that these genes are useful molecular markers for the differential diagnosis between these two species. Numerical analysis based on the molecular karyotype data revealed a high degree of polymorphism among T. rangeli strains isolated from southern Brazil and strains isolated from Central and the northern South America. The T. cruzi reference strain was not clustered with any T. rangeli strain.
Actins↗
Dosage compensation in birds.
The Z and W sex chromosomes of birds have evolved independently from the mammalian X and Y chromosomes [1]. Unlike mammals, female birds are heterogametic (ZW), while males are homogametic (ZZ). Therefore male birds, like female mammals, carry a double dose of sex-linked genes relative to the other sex. Other animals with nonhomologous sex chromosomes possess "dosage compensation" systems to equalize the expression of sex-linked genes. Dosage compensation occurs in animals as diverse as mammals, insects, and nematodes, although the mechanisms involved differ profoundly [2]. In birds, however, it is widely accepted that dosage compensation does not occur [3-5], and the differential expression of Z-linked genes has been suggested to underlie the avian sex-determination mechanism [6]. Here we show equivalent expression of at least six of nine Z chromosome genes in male and female chick embryos by using real-time quantitative PCR [7]. Only the Z-linked ScII gene, whose ortholog in Caenorhabditis elegans plays a crucial role in dosage compensation [8], escapes compensation by this assay. Our results imply that the majority of Z-linked genes in the chicken are dosage compensated.
Aconitate Hydratase↗
The Drosophila GAGA factor is required for dosage compensation in males and for the formation of the male-specific-lethal complex chromatin entry site at 12DE.
Drosophila melanogaster males have one X chromosome, while females have two. To compensate for the resulting disparity in X-linked gene expression between the two sexes, most genes from the male X chromosome are hyperactivated by a special dosage compensation system. Dosage compensation is achieved by a complex of at least six proteins and two noncoding RNAs that specifically associate with the male X. A central question is how the X chromosome is recognized. According to a current model, complexes initially assemble at approximately 35 chromatin entry sites on the X and then spread bidirectionally along the chromosome where they occupy hundreds of sites. Here, we report that mutations in Trithorax-like (Trl) lead to the loss of a single chromatin entry site on the X, male lethality, and mislocalization of dosage compensation complexes.
Animals↗
Insertion sequence elements in Bacillus thuringiensis subsp. darmstadiensis.
Two variants of insertion sequence IS231, named IS231G and H, were isolated from Bacillus thuringiensis subsp. darmstadiensis 73-E-10-2 (BTD2), an isolate toxic to dipteran insects, and characterized by DNA sequence analysis. They are encoded consecutively as direct repeats on an EcoRI fragment of 5.6 kilo base pairs. Direct tandem repeats of IS231 elements have not been previously reported. Both elements are closely related to other members of the IS231 family that have been isolated from B. thuringiensis strains toxic to lepidopteran as well as to dipteran insects. A close correlation exists between the evolutionary relationships of the IS231 sequences determined to data and the toxicity spectrum of the host cell. Probing of BTD2 DNA with a radiolabeled IS231G fragment demonstrated that IS231 elements are located on 55- and 34-MDa plasmids as well as on chromosomal DNA. Chromosomal DNA, but not plasmids, from BTD2 also hybridizes to another, unrelated insertion sequence, IS240, from B. thuringiensis subsp. israelensis, an isolate toxic to dipteran insects. BTD2, therefore, contains IS elements once thought to reside exclusively in either dipteran- or lepidopteran-specific subspecies of B. thuringiensis.
Bacillus thuringiensis↗
Insect immunity. Characterization of a Drosophila cDNA encoding a novel member of the diptericin family of immune peptides.
Drosophila shows an immune response when challenged by injection of low doses of bacteria. To date, the molecules involved in this immune reaction have remained elusive, with the exception of cecropins (4-kDa antibacterial peptides initially isolated from the moth Hyalophora cecropia) for which three closely related genes have been characterized recently. We report the molecular cloning and sequencing of a cDNA from a library of immune Drosophila which encodes a novel member of the family of diptericins (9-kDa antibacterial peptides initially isolated from the fly Phormia terranovae). Transcripts for the Drosophila diptericin are detected 2 h after injection of bacteria. They are apparently derived from a single gene mapping at position 56 A on the right arm of the second chromosome. We discuss the existence of a distant relationship between the diptericins and two other groups of anti-bacterial insect proteins, the attacins, and the sarcotoxins II.
Amino Acid Sequence↗
Molecular cloning of ID4, a novel dominant negative helix-loop-helix human gene on chromosome 6p21.3-p22.
Transcription factors containing a basic helix-loop-helix (bHLH) motif regulate the expression of tissue-specific genes in a number of mammalian and insect systems. DNA-binding activity of the bHLH proteins is dependent upon formation of homo- and/or heterodimers. Dominant negative HLH proteins (Id-related genes) also contain the HLH-dimerization domain but lack the DNA-binding basic domain. Consequently, Id proteins inhibit binding to DNA and transcriptional transactivation by heterodimerization with bHLH proteins. We report here the cDNA sequence of a novel human HLH gene (HGMW-approved symbol ID4) that lacks the basic domain. ID4 is differentially expressed in adult organs in four mRNA molecules, which are presumably a result of differential splicing and/or alternative usage of the polyadenylation sites. Transfection experiments indicated that enforced expression of Id-4H protein inhibits the trans-activation of the muscle creatine kinase E-box enhancer by MyoD. Finally, we localized the ID4 gene to the chromosome 6p21-p22 region.
Amino Acid Sequence↗
A genetic screen of the Drosophila X chromosome for mutations that modify Deformed function.
We have screened the Drosophila X chromosome for genes whose dosage affects the function of the homeotic gene Deformed. One of these genes, extradenticle, encodes a homeodomain transcription factor that heterodimerizes with Deformed and other homeotic Hox proteins. Mutations in the nejire gene, which encodes a transcriptional adaptor protein belonging to the CBP/p300 family, also interact with Deformed. The other previously characterized gene identified as a Deformed interactor is Notch, which encodes a transmembrane receptor. These three genes underscore the importance of transcriptional regulation and cell-cell signaling in Hox function. Four novel genes were also identified in the screen. One of these, rancor, is required for appropriate embryonic expression of Deformed and another homeotic gene, labial. Both Notch and nejire affect the function of another Hox gene, Ultrabithorax, indicating they may be required for homeotic activity in general.
Animals↗
Rearrangements at a hobo element inserted into the first intron of the singed gene in the unstable sn49 system of Drosophila melanogaster.
The cytological structure of the X chromosome and the DNA organisation of the singed locus were examined in five singed bristle mutants of Drosophila melanogaster. These mutants are all derived from the unstable mutant singed-49, isolated from a wild population in the Russian Far East in 1975. Rearrangements were found at a site within the first intron of the singed gene, where a hobo element is inserted in these mutants. One rearrangement, which is associated with a strong bristle phenotype, has an inversion between 2D and the location of singed at 7D, which separates the singed promoter from the singed coding region. Two phenotypically wild-type derivatives have smaller rearrangements within the first intron which do not appear to interfere with singed expression. Two derivatives with bristle phenotypes have more complex rearrangements, and one of them shows a dominant or antimorphic phenotype. DNA blotting and in situ hybridisation experiments show that, in addition to these rearrangements at a hobo element inserted at singed, other hobo elements in these strains have been mobilised. This system is therefore similar to others in which functional hobo elements continue to transpose, resulting in elevated rates of mutation and chromosome rearrangement.
Animals↗
Targeting dosage compensation to the X chromosome of Drosophila males.
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Animals↗