Sylvie Schneider-Maunoury

Pattern of expression of the transcription factor Krox-20 in mouse hair follicle

We examined the pattern of expression in hair follicles of the transcription factor gene Krox-20. During embryogenesis, Krox-20 is first expressed in the upper portion of the hair bud, then in the hair canal, in the sebaceous glands and in the outer root sheath. In the mature follicles, Krox-20, like Shh and TGFbetaRII, is also expressed in a sub-population of matrix keratinocytes located in a ring-like fashion in vibrissal follicles and clustered on one side of the papilla in pelage follicles. This polarized pattern rotates around the papilla as a result of sequential gene expression by individual groups of matrix cells. This peculiar pattern is not linked to follicle angling.

Sequence and expression pattern of ziro7, a novel, divergent zebrafish iroquois homeobox gene.

We have isolated the zebrafish ziro7 gene, a novel, divergent member of the Iroquois family. ziro7 is expressed at early epiboly stages in the dorsal half of the zebrafish embryo, with a higher level in the dorso-lateral margin. From mid-gastrulation stages onward, ziro7 is expressed in a large transversal stripe in the future neural plate, which subsequently divides into thinner stripes located in the diencephalon, midbrain and hindbrain.

Cloning of vertebrate Protogenin (Prtg) and comparative expression analysis during axis elongation.

A murine cDNA encoding Protogenin, which belongs to the DCC/Neogenin family, was cloned in a screen performed to identify novel cDNAs regionally expressed in the neural plate. Isolation of the putative zebrafish orthologues allowed a comparative analysis of the expression patterns of Protogenin genes during embryogenesis in different vertebrate species. From mid‐gastrulation to early somite stages, Protogenin expression is restricted to posterior neural plate and mesoderm, with an anterior limit at the level of the rhombencephalon in mouse, chicken, and zebrafish. During somitogenesis, the expression profiles in the three species share features in the neural tube but present also species‐specific characteristics. The initiation of Protogenin expression just before somitogenesis and its maintenance in the neural tube and paraxial mesoderm during this process suggest a conserved role in axis elongation. Developmental Dynamics 235:2836–2844, 2006.

Multiple Developmental Functions of the Zinc Finger Gene Krox-20 Are Revealed by Targeted Insertion of the E. coli lacZ Coding Sequence

The inactivation of the Krox-20 gene in the mouse has allowed us to study the involvement of this gene in the regulation of several processes as diverse as hindbrain segmentation, peripheral nervous system (PNS) myelination and endochondral bone formation (Schneider-Maunoury et al. 1993; Topilko et al. 1994; Levi et al. 1996). The aim of the present chapter is to describe the procedure we selected to inactivate the Krox-20 gene and to show how this strategy, which involved the use of a lacZ tracer gene, has helped us in understanding the phenotypes associated with the mutation and has enabled us to discover novel Krox-20 functions.

Contrôle génétique de la morphogenèse du rhombencéphale des vertébrés

Au cours du developpement embryonnaire des vertebres, le rhombencephale est sujet a un processus de segmentation transitoire, qui gouverne lorganisation ulterieure de cette region du systeme nerveux central. Des progres recents ont permis daborder letude du reseau de regulation genetique qui controle la delimitation des segments successifs le long de la plaque neurale et la specification de leur identite, en fonction de leur position le long de laxe antero-posterieur.