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P Laurenti

Publications and source records attributed to P Laurenti.

7 recordsLinked to original sources
PubMed1997

GIF-DB, a WWW database on gene interactions involved in Drosophila melanogaster development.

GIF-DB (Gene Interactions in the Fly Database) is a new WWW database (http://www-biol.univ-mrs.fr/ approximately lgpd/GIFTS_home_page. html ) describing gene molecular interactions involved in the process of embryonic pattern formation in the flyDrosophila melanogaster. The detailed information is distributed in specific lines arranged into an EMBL- (or SWISS-PROT-) like format. GIF-DB achieves a high level of integration with other databases such as FlyBase, EMBL and SWISS-PROT through numerous hyperlinks. The original concept of interaction databases examplified by GIF-DB could be extended to other biological subjects and organisms so as to study gene regulatory networks in an evolutionary perspective.

Animals↗
PubMed1995

Genetic and molecular analysis of terminal deletions of chromosome 3R of Drosophila melanogaster.

Terminal deletions of chromosome 3R are induced at a high frequency (3.2 x 10(-3)) by irradiating 45-4 Drosophila melanogaster females with a low dose of X-rays. The 45-4 line carries a white transgene inserted at 16 kb from the terminus and is homozygous for the mu-2 mutation, a gene involved in the repair of double-strand DNA breaks. Four of the 51 recovered deleted strains have lost modulo, the distalmost essential gene on chromosome 3R. Breakpoints of 22 deletions have been localised in a single hybridisation step, using pulsed-field gel electrophoresis to separate genomic DNA fragments obtained from digestion with a rare-cutter restriction enzyme. Breaks do not occur at random, but are rather clustered in three susceptible chromosomal domains. Backcross experiments resulting in transheterozygous (deleted chromosome/45-4) animals indicate that the activity of the white transgene is enhanced when the DNA break has occurred proximal to a critical position. This suggests that homologous chromosomal pairing distal to the critical position results in the definition of a more compact chromatin structure and, due to position effect, in the silencing of white.

Animals↗
PubMed1995

DWnt-4, a novel Drosophila Wnt gene acts downstream of homeotic complex genes in the visceral mesoderm.

Wnt genes encode putative cell signalling proteins which play crucial roles during development. From a library of DNA fragments associated, in vivo, with Ultrabithorax proteins, we isolated a novel Drosophila Wnt gene, DWnt-4. Neither a paralog nor an ortholog of the gene exist in the current repertoire of full-length Wnt sequences. DWnt-4 maps close (30 kb) to wingless, suggesting that the two Wnt genes derive from a duplication that occurred early in evolution, since they are significantly diverged in sequence and structure. Developmental expression of DWnt-4 partially overlaps that of wingless. The gene is transcribed following a segment polarity-like pattern in the posterior-most cells of each parasegment of the ectoderm, and at two locations that correspond to parasegments 4 and 8 of the visceral mesoderm. The control of DWnt-4 expression in the visceral mesoderm involves a network of regulatory molecules that includes Ultrabithorax and other proteins from the homeotic complex (HOM-C), as well as the TGF-beta decapentaplegic gene product.

Animals↗
PubMed1994

The modifier of variegation modulo gene acts downstream of dorsoventral and HOM-C genes and is required for morphogenesis in Drosophila.

Growing evidence involves chromatin structural flexibility in gene regulation during development. modulo is a dominant suppressor of position effect variegation, suggesting the participation of its product in the assembly of higher order chromatin structures. Here we report the patterns of modulo expression and regulation during embryogenesis, analyzed in correlation with phenotypical defects resulting from the amorphic mutation of the gene. Zygotic expression of modulo depends on the activity of genes which pattern the embryo along dorsoventral and anteroposterior axes and specify diversified morphogenesis, dorsal and the mesoderm-specific genes twist and snail direct modulo expression in the presumptive mesoderm. The homeotic genes Sex combs reduced and Ultrabithorax positively regulate the gene in the ectoderm of parasegment 2 and abdominal mesoderm, respectively, modulo mutants exhibit aberrant morphogenesis of tissues originating from those embryonic primordia which normally express the gene, but do not show defect in cell fate specification. We propose that down-stream of pattern-forming genes modulo controls, via chromatin structural changes, genes critical for the process of morphogenesis of several tissue types.

Animals↗
PubMed1992

Homeotic control in Drosophila; the scabrous gene is an in vivo target of Ultrabithorax proteins.

The regulatory functions of transcription factors encoded by the Ultrabithorax (Ubx) gene initiate genetic programmes essential for segmental identity and morphogenesis in Drosophila. Based on the formation of DNA-protein adducts in intact nuclei and immunoselection procedure, we cloned genomic targets for Ubx proteins. One clone was studied in detail. It encompasses parts of the last intron and exon of the scabrous (sca) gene, which encodes a secreted protein involved in cellular communication during neurogenesis. Five motifs, presenting the ATTA core, which is shared by most homeodomain binding sites, were found in the nucleotide sequence of this clone. We detail here the dynamic pattern of sca transcript accumulation during embryogenesis and show that mutation of Ubx results in the ectopic transcription of sca in the first abdominal segment. We propose that a direct interaction of Ubx with cis-acting elements in sca negatively regulates the gene. Transcript localization in several combinations of deficiencies in the Bithorax complex (BX-C) indicates that sca is downregulated by abdominal A (abdA) and Abdominal B (AbdB), and suggests that it is a common target of the three genes of BX-C.

Animals↗
PubMed1992

Cell lineage-specific expression of modulo, a dose-dependent modifier of variegation in Drosophila.

Variegation in Drosophila is a manifest illustration of the important role played by chromatin structure in gene expression. We have isolated mutants of modulo (mod) and shown that this gene is a dominant suppressor of variegation. Null mutants are recessive lethal with a melanotic tumour phenotype. The mod protein directly binds DNA, which indicates that it may serve to anchor multimeric complexes promoting chromatin compaction and silencing. Using a specific monoclonal antibody we examined by immunocytochemistry the accumulation pattern of mod protein during embryogenesis. The protein is first detected before the blastoderm cellularization in all somatic nuclei, precisely when pericentromeric heterochromatin becomes visible. After the first cell division, mod protein is expressed in lineages of specific embryonic primordia. Based on its dominant phenotype, expression pattern and DNA-binding activity of its product, we propose that mod regulates chromatin structure and activity in specific cell lineages.

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