title: Msxb is a core component of the genetic circuitry specifying the dorsal and ventral neurogenic midlines in the ascidian embryo.
abstract: The tail ascidian larval peripheral nervous system is made up of epidermal sensory neurons distributed more or less regularly in ventral and dorsal midlines. Their formation occurs in two-steps: the ventral and dorsal midlines are induced as neurogenic territories by Fgf9/16/20 and Admp respectively. The Delta2/Notch interaction then controls the number of neurons that form. The genetic machinery acting between the inductive processes taking place before gastrulation and neuron specification at tailbud stages are largely unknown. The analysis of seven transcription factors expressed in the forming midlines revealed an unexpected complexity and dynamic of gene expression. Their systematic overexpression confirmed that these genes do not interact following a linear cascade of activation. However, the integration of our data revealed the distinct key roles of the two upstream factors Msxb and Nkx-C that are the earliest expressed genes and the only ones able to induce neurogenic midline and ESN formation. Our data suggest that Msxb would be the primary midline gene integrating inputs from the ventral and dorsal inducers and launching a pan-midline transcriptional program. Nkx-C would be involved in tail tip specification, in maintenance of the pan-midline network and in a posterior to anterior wave controlling differentiation.
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, F-66650 Banyuls/Mer, France.
authors.forename: Agnès
authors.initials: A
authors.lastname: Roure
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, CNRS, Biologie Intégrative des Organismes Marins (BIOM), Observatoire Océanologique, F-66650 Banyuls/Mer, France. Electronic address: sebastien.darras@obs-banyuls.fr.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Darras
mesh_terms: D000818:Animals; D019521:Body Patterning / Q000235:genetics*; D019070:Cell Lineage; D002938:Ciona intestinalis / Q000196:embryology* / Q000235:genetics*; D004625:Embryo, Nonmammalian / Q000378:metabolism*; D004817:Epidermis / Q000196:embryology / Q000378:metabolism; D004843:Epistasis, Genetic; D025461:Feedback, Physiological; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D055495:Neurogenesis / Q000235:genetics*; D011984:Sensory Receptor Cells / Q000166:cytology / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism
chemical_list: D018398:Homeodomain Proteins; D014157:Transcription Factors
keywords: Ascidian; Gene regulatory network; Neurogenic; Peripheral nervous system; Transcription factors