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R Ollo

Publications and source records attributed to R Ollo.

13 recordsLinked to original sources
PubMed1999

Identification and characterization of a putative sevenless homologue in the malaria vector Anopheles gambiae.

Tyrosine kinase sequences were identified and characterized in Anopheles gambiae, the major vector of malaria in subsaharan Africa. One of these sequences has the characteristics expected for a homologue of the Drosophila sevenless gene, which is necessary for R7 photoreceptor cell fate determination in the developing compound eye. The putative Anopheles sevenless gene homologue is located in a telomeric region of the X chromosome and is expressed in the head of late larval and pupal stage mosquitoes. Identification of the Anopheles homologue of the sevenless gene is a first step towards the development of a dominant phenotypic marker that could be used for detecting transformed Anopheles mosquitoes in a wide variety of genetic backgrounds and, as such, could be used in the development of transgenic mosquitoes for the control of parasite transmission. Preliminary evidence for sevenless sequences were also found in DNA from blackfly, Mediterranean fruit fly and the honeybee.

Amino Acid Sequence↗
PubMed1996

A new Drosophila Ca2+/calmodulin-dependent protein kinase (Caki) is localized in the central nervous system and implicated in walking speed.

Calcium/calmodulin-dependent protein kinases (CaM kinases) have been reported to be involved in neuroplasticity. We have cloned a new Drosophila CaM kinase gene named caki. We describe the molecular characterization of caki and a behavioral effect of its elimination. The caki gene is extremely large; comparison of the genomic and cDNA sequences reveals that the caki transcription unit is at least 150 kb. The catalytic domain of this new CaM kinase protein shares homology (41%) with type II CaM kinases, while the C-terminal part is divergent. Constitutively expressed Caki protein is enzymatically active since it causes a 3-fold increase in the level of the Rous sarcoma virus long terminal repeat (RSV LTR) promoter in a co-transfusion assay. In situ hybridization shows that during embryogenesis, larval and pupal life, transcription of caki is restricted almost exclusively to the central nervous system. In the adult head, immunohistochemistry reveals Caki protein in the lamina, the neuropil of the medulla, lobula, lobula plate and in the central brain. Mutant caki flies show reduced walking speed in 'Buridan's paradigm'.

Amino Acid Sequence↗
PubMed1994

Terminal pattern elements in Drosophila embryo induced by the torso-like protein.

The genes torso (tor) and torso-like (tsl) are two of the Drosophila maternal group genes implicated in a receptor tyrosine kinase signalling pathway that specifies terminal cell fate (reviewed in ref. 3). Loss-of-function mutations in these loci cause an identical phenotype in which pattern elements from the anterior (acron) and posterior (telson) ends have been deleted. We have cloned the tsl gene and demonstrate here that, in agreement with previous genetic data, it encodes a protein that is secreted and whose transcription is restricted to specialized categories of follicle cells localized at the poles of the egg chamber. At early blastoderm stage, tsl protein forms a symmetrical concentration gradient at the poles on the surface of the devitellinized embryo. Unrestricted expression of the tsl protein in tsl female mutants induces terminal pattern elements and suppresses the formation of abdomen in embryos. These results suggest that the tsl protein is the ligand that binds to the torso receptor.

Amino Acid Sequence↗
PubMed1993

Structure and expression in baculovirus of the Mokola virus glycoprotein: an efficient recombinant vaccine.

The sequence of the glycoprotein gene of the Mokola virus, the more divergent element of the Lyssavirus genus, has been determined and the predicted protein structure compared to its counterpart in rabies vaccine strains. A global similarity of 54.3% was observed. The divergence affects particularly the rabies antigenic sites involved in the B-cell response. This provides a molecular basis for the absence of cross-protection between Mokola and rabies viruses and argues for the necessity of a specific anti-Mokola vaccine. Toward this goal, a cDNA copy of the glycoprotein gene was cloned into the baculovirus and expressed in Spodoptora frugiperda cells. A recombinant protein was produced in substantial amounts at the surface of the insect cells. Although less strongly glycosylated than the native viral glycoprotein produced in BHK-21 cells, the recombinant protein is antigenically and immunologically similar, it is recognized by specific monoclonal antibodies, and protects mice against an intracerebral challenge with Mokola virus. It therefore constitutes the first experimental genetically engineered vaccine against a rabies-related virus, and fulfills the international standard for protection.

Amino Acid Sequence↗
PubMed1991

Analysis of Krüppel control elements reveals that localized expression results from the interaction of multiple subelements.

The Drosophila gap gene Krüppel (Kr) displays a complex spatiotemporal pattern of expression during embryogenesis. Using P-element transformation experiments, we demonstrate that control elements guiding Kr expression in the central or in the anterior domain at the blastoderm stage are each composed of multiple subelements that interact synergistically. We provide evidence that bicoid (bcd) and hunch-back (hb) gene products, as well as at least one other activator, are needed to activate Kr expression in the central domain. We localize and describe regulatory elements within the 4.1-kilobase region proximal to the Kr promoter that are responsible for expression in the ectoderm, mesoderm, amnioserosa, and nervous system. Finally, a protein instability motif encoded in the second exon appears to be important for resetting the dynamic Kr pattern.

Animals↗
PubMed1987

Drosophila Krüppel gene product produced in a baculovirus expression system is a nuclear phosphoprotein that binds to DNA.

The product of the Drosophila segmentation gene Krüppel was produced in cultured insect cells using the baculovirus expression system. When a cloned Krüppel cDNA sequence was inserted into the viral genome downstream from the promoter of the polyhedrin gene, a polypeptide with an apparent molecular weight of approximately equal to 72,000 was observed in the nuclei of infected cells. Antibodies were raised against this protein and used to detect Krüppel in Drosophila embryos. Characterization of the Krüppel protein extracted from infected cells showed that it is tightly bound to the nucleus, it binds to calf thymus DNA-cellulose, and it is phosphorylated. These results support the hypothesis that Krüppel is a regulatory protein that acts by binding DNA.

Animals↗
PubMed1984

Evolution of aspartyl proteases by gene duplication: the mouse renin gene is organized in two homologous clusters of four exons.

Overlapping recombinant clones that appear to encompass the entire renin gene, named Ren 1, have been isolated from a library of BALB/c mouse genomic DNA fragments. Based on restriction endonuclease mapping and DNA sequence analysis, Ren 1 spans 9.6 kb and contains nine exons interrupted by eight intervening sequences of highly variable size. The first exon, encoding the signal peptide of preprorenin, is separated from the eight following exons by a 3-kb intron. These eight exons are organized into two clusters of four separated by a 2-kb intron. DNA stretches encoding the aspartyl residues, which are part of the active site of renin, are located at homologous positions in both clusters. Our results show that aspartyl protease genes have arisen by duplication and fusion of an ancestral gene containing five exons. The estimated date of the duplication event of the mouse renin genes Ren 1 and Ren 2 is discussed.

Amino Acid Sequence↗
PubMed1983

Structural relationships among mouse and human immunoglobulin VH genes in the subgroup III.

The mouse VHIII subgroup is composed of four families which share sequence homology. We isolated a VH germ-line genomic clone, which cross hybridizes with a cDNA probe from one of these families, derived from a myeloma secreting an antigalactan antibody. We report here the nucleotide sequence of the cross hybridizing gene and show that very likely it has an anti-sheep red blood cell specificity. Comparison of its nucleotide sequence with those of the three other VHIII families shows that these genes share segmental homologies of variable lengths. This suggests that interchanges of sequence blocks between VH genes could be an important evolutionary mechanism for diversifying the germ-line repertoire. The strong homology (82%) with human VHIII genes suggests that efficient antibody sequences are strongly conserved. This conservation of homology is particularly striking when compared to the more limited homology (63%) between mouse and human C kappa genes.

Animals↗
PubMed1983

Gene conversion and polymorphism: generation of mouse immunoglobulin gamma 2a chain alleles by differential gene conversion by gamma 2b chain gene.

We have determined the complete nucleotide sequence of the C57BL/6 allele of the mouse immunoglobulin gamma 2a chain gene. A comparison with the BALB/c gamma 2a gene for 1912 nucleotides reveals that the two alleles exhibit extensive divergence, since there are 138 single-base-pair differences and 8 insertions or deletions. We have compared the two gamma 2a alleles with the two corresponding gamma 2b alleles, which differ in only 12 positions. It appears that among the 134 differences between the two gamma 2a alleles, 70 are at positions where gamma 2a and gamma 2b are identical in the BALB/c haplotype and 54 are at positions where gamma 2a and gamma 2b are identical in the C57BL/6 haplotype. All these results suggest that nonreciprocal gene conversion between nonallelic genes can introduce sequence homogeneity in linked genes and can generate extensive divergence and polymorphism in allelic genes. We suggest that the gamma 2a and gamma 2b gene ancestors freely diverged after duplication, and that the conversion events were promoted by a deletion shortening the distance between the two loci.

Alleles↗
PubMed1981

Mouse heavy chain variable regions: nucleotide sequence of a germ-line VH gene segment.

We have constructed a library of Balb/c mouse embryo DNA in the vector Charon 4A. The library was searched for sequences homologous to the VH region of a cloned cDNA of the UPC10 heavy chain mRNA. In this paper, we describe the structure and the partial nucleotide sequence of one of such clones (VH441). The nucleotide sequence of this germ-line gene indicates that it encodes amino-acids 1-98 of the X44 and J601 galactan-binding VH regions, but that it differs from the UPC10 VH segment by four single base changes. The VH gene appears to contain a 101 bases long intervening sequence within a precursor sequence identical to the precursor sequence of UPC10. The 3' non coding sequence of the V gene contains the two conserved sequences found in embryonic V DNA segments, CACAGTG and ACATGAACC, separated by 23 nucleotides and a sequence CACTGTG separated by 33 nucleotides from the first heptamer.

Animals↗
PubMed1981

Comparison of mouse immunoglobulin gamma 2a and gamma 2b chain genes suggests that exons can be exchanged between genes in a multigenic family.

A 23-kilobase EcoRI DNA fragment coding for the BALB/c immunoglobulin gamma 2a chain was cloned from mouse embryo DNA in the cosmid pJC74, and a nucleotide sequence of 1904 bases was determined for the entire constant region (CH1, CH2, and CH3), the three intervening sequences (IVS 1, IVS 2, and IVS 3) and the 5' and 3' flanking sequences. When the gamma 2a chain nucleotide sequence was compared with the gamma 2b chain nucleotide sequence, the percent homology of corresponding segments (excluding deletion and insertion) was 82% for the 5' flanking sequence, 87% for CH1, 84% for IVS 1, 96% for the hinge, 95% for IVS 2, 94.6% for CH2, 86% for IVS 3, 74% for CH3, 89% for the 3' untranslated region, and 92% for the 3' flanking region. These findings show that different domains of gamma 2a and gamma 2b have independent rates of evolution and that some of the noncoding segments of the gene are more conserved than are adjacent coding segments. Hypotheses on the possible role of IVS is gene evolution and expression are discussed.

Animals↗
PubMedDate not supplied

Correlation between D region structure and antigen-binding specificity: evidences from the comparison of closely related immunoglobulin VH sequences.

A VH region gene is generated from three gene segments, VH, D and JH, separated on the germline chromosome and rearranged during differentiation to generate an active VH gene. The sequence and length variations of the D region are an important source of the antibody diversification. To investigate their role in the antigen recognition, VH sequences of three myeloma proteins (ABE48, UPC10 and MOPC173) having different antigen specificities and whose VH segments were expected to be highly homologous have been determined: cDNA clones containing the structural gene sequences for the three proteins have been constructed. The nucleotide sequences of the three VH regions have been determined. The deduced amino-acid sequences are compared to those of four other myeloma proteins (J539, X44, X24 and T601). The seven proteins have highly homologous VH segments. The comparison points out the correlation existing between the D-region structure and the antigen-binding specificity.

Amino Acid Sequence↗