Franck Girard

Sox neuro, a new Drosophila Sox gene expressed in the developing central nervous system.

We describe the identification and detailed expression pattern of a second Drosophila Sox gene, SoxNeuro (SoxN), highly related to mammalian group B Sox1, 2, 3 genes. SoxN is expressed in a highly dynamic pattern during embyogenesis, being associated with the development of the central nervous system (CNS), from the early steps onwards. We present strong evidence that the early SoxN neuroectoderm expression is controlled by the zygotic dorso-ventral patterning genes (dpp, sog, brk, twi).

In vivo analysis of scaffold‐associated regions in Drosophila: a synthetic high‐affinity SAR binding protein suppresses position effect variegation

Scaffold‐associated regions (SARs) were studied in Drosophila melanogaster by expressing a synthetic, high‐affinity SAR‐binding protein called MATH (multi‐AT‐hook), which consists of reiterated AT‐hook peptide motifs; each motif is known to recognize a wide variety of short AT‐rich sequences. MATH proteins were expressed specifically in the larval eye imaginal discs by means of the tetracycline‐regulated transactivation system and tested for their effect on position effect variegation (PEV). MATH20, a highly potent SAR ligand consisting of 20 AT‐hooks, was found to suppress whitemottled 4 variegation. This suppression required MATH20 expression at an early larval developmental stage. Our data suggest an involvement of the high AT‐rich SARs in higher order chromatin structure and gene expression.

Genome-wide analysis of Sox genes in Drosophila melanogaster

Genes of the Sox family encode evolutionarily conserved HMG box containing transcription factors, which play key roles in various events of cell determination/differentiation during development. The total number of Sox genes in Drosophila melanogaster was estimated to be eight, after classical molecular cloning approaches and exhaustive screening of the complete Drosophila genome. Here we report the embryonic and larval expression pattern of four previously uncharacterized Sox genes, through antibody staining and in situ hybridization experiments.

Genome-wide identification of in vivo Drosophila Engrailed-binding DNA fragments and related target genes.

Chromatin immunoprecipitation after UV crosslinking of DNA/protein interactions was used to construct a library enriched in genomic sequences that bind to the Engrailed transcription factor in Drosophila embryos. Sequencing of the clones led to the identification of 203 Engrailed-binding fragments localized in intergenic or intronic regions. Genes lying near these fragments, which are considered as potential Engrailed target genes, are involved in different developmental pathways, such as anteroposterior patterning, muscle development, tracheal pathfinding or axon guidance. We validated this approach by in vitro and in vivo tests performed on a subset of Engrailed potential targets involved in these various pathways. Finally, we present strong evidence showing that an immunoprecipitated genomic DNA fragment corresponds to a promoter region involved in the direct regulation of frizzled2 expression by engrailed in vivo.

Functional analysis of the chicken delta1-crystallin enhancer activity in Drosophila reveals remarkable evolutionary conservation between chicken and fly.

Functional conservation of enhancers among evolutionarily diverged organisms is a powerful way to identify basic regulatory circuits and key developmental regulators. This is especially applicable to Crystallin genes. Despite unexpected heterogeneity and diversity in their DNA sequences, many studies have revealed that most of the Crystallin genes are regulated by a relatively small set of developmentally important transcription factors. The chicken δ1-crystallin is one of the best-characterized Crystallin genes. Its lens-specific regulation is governed by a 30 bp long DC5 fragment present in the third intron of the gene. DC5 contains PAX6 and SOX2 binding sites, and its activity depends on the cooperative binding of these two transcription factors. To test the idea that Pax6 and Sox2, together with the DC5 enhancer, could form a basic regulatory circuit functional in distantly related animals, we introduced the DC5 fragment into Drosophila and studied its activation pattern and regulation. The results show that the DC5 enhancer is not only active in the compound eye but, remarkably, is specifically active in those cells responsible for Crystallin secretion in Drosophila, i.e. the cone cells. However, regulation of the DC5 enhancer is carried out not by Pax6, but by Pax2 (D-Pax2; shaven – FlyBase) in combination with the Sox2 homologue SoxN. Both proteins (D-PAX2 and SOXN) bind cooperatively to the DC5 fragment and activate the enhancer synergistically. As PAX6 and PAX2 proteins derive from the same ancestor, we propose that during evolution Pax6 function in vertebrate lens development was retained by Pax2 in Drosophila.

Expression pattern of the Sox31 gene during Zebrafish embryonic development

We have identified a novel Sox gene in zebrafish (Danio rerio), Sox31, closely related to mammalian group B Sox genes. The gene is maternally expressed. Zygotic transcription starts at gastrulation, in the presumptive neuroectoderm. Later, expression is restricted to the developing central nervous system, including forebrain, midbrain, hindbrain and spinal cord.

SNCF, a SoxNeuro interacting protein, defines a novel protein family in Drosophila melanogaster

The involvement of the Sox family of transcription factors in the development of the central nervous system (CNS) appears to be conserved in invertebrates and vertebrates. In Drosophila, SoxNeuro (SoxN) was recently shown to be involved in the formation of neuroblasts [Development 129 (2002) 4193; Development 129 (2002) 4219]. Through a yeast two-hybrid assay searching for proteins interacting with SoxN, we have isolated a novel protein in Drosophila, SoxNeuro Co-Factor (SNCF). The expression of the SNCF gene was detected during early embryogenesis at the blastoderm stages, and stopped just at the beginning of gastrulation. In transfected cells, the protein localised to nuclei, and strongly accumulated in nucleoli. SNCF was able to enhance SoxN mediated transcriptional activity in transfected cells, suggesting that SNCF might act as a SoxN co-activator. Finally, data are presented showing the existence in Drosophila of several proteins with a domain of homology to SNCF, which are all expressed early in embryogenesis at the blastoderm stage.

La modification par SUMO réprime l’activité transcriptionnelle des protéines Sox

917 M/S n° 11, vol. 21, novembre 2005 teurs musculaires et nous avons montré qu’elles contribuent majoritairement à la croissance des muscles embryonnaires et fœtaux (Figure 1B). Nous avons également montré que des cellules exprimant la GFP et présentant des caractéristiques de cellules satellites étaient présentes chez le fœtus. Pour quantifier la contribution de ce compartiment somitique à la population de cellules satellites chez l’adulte, nous avons alors remplacé le dermomyotome central de somites de poulet par une région équivalente de somite de caille. L’analyse de chimères avant ou après éclosion montre que, dans la région de la greffe, environ 95 % des cellules satellites sont d’origine caille. Nos observations permettent donc de répondre aux questions évoquées ci-dessus, en démontrant qu’il existe, lors du développement normal des embryons des vertébrés, une source unique de progéniteurs musculaires, le dermomyotome central, dont sont issus les progéniteurs musculaires embryonnaires et fœtaux ainsi que la quasi totalité des cellules souches musculaires de l’adulte [13] (Figure 1C). La démonstration selon laquelle les cellules satellites et les progéniteurs musculaires embryonnaires partagent une origine commune ouvre d’importantes perspectives d’application en thérapie cellulaire. Les progéniteurs musculaires embryonnaires étant plus accessibles que les cellules souches musculaires adultes, il est envisageable de les prélever et d’étudier leur propriétés régénératives afin de les utiliser en remplacement des cellules souches adultes. ◊ A common somitic origin for embryonic muscle progenitors