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Integrative Biology of Marine Organisms
UMR 7232

Master 2 internship proposal:telencephalon evolutionary origins.

Anterior forebrain or telencephalon is a higly developped structure in vertebrates and contains the olfactory bulb and regions that control higher-order brain functions. Understanding its evolutionary origins is a long standing question in evo-devo, but no equivalent region has been so far identified in the vertebrate sister groups, the invertebrate chordates, ascidians and amphioxus. A recent single cell-RNAseq study in ascidian has identified a cell population that is closely related to telencephalon by transcription profiling (1). These cells form a sensory organ of ectodermal origin, the palps, that is located at the anterior-most part of the embryo. It is not part of the central nervous system but forms at the anterior neural plate border. Our group has produced published and unpublished data that show that palps formation is under the control of three signaling pathways, Wnt, Bmp and Nodal (2). Interestingly, in vertebrates, the early specification of the telencephalon is achieved through the triple inhibition of these pathways (3).

The goal of the internship is to identify genes specific for the telencephalon/palps in chordates and determine whether their expression is regulated by Wnt, Bmp and Nodal signals. Under the supervision of a PhD student currently performing a comparative approach between ascidians and amphioxus on the roles of Bmp and Wnt, the student will undertake the follwing tasks:

- identify candidate palps/telencephalon genes in both ascidians and amphioxus using already available RNA-seq and scRNA-seq data

- determine their expression patterns by in situ hybridization during the embryogenesis of ascidians and amphioxus

- determine the function of 1-2 validated candidates by CRISPR inactivation in ascidians

 

1.   Cao C, Lemaire LA, Wang W, Yoon PH, Choi YA, Parsons LR, et al. Comprehensive single-cell transcriptome lineages of a proto-vertebrate. Nature. 2019 Jul 10;1.

2.   Feinberg S, Roure A, Piron J, Darras S. Antero-posterior ectoderm patterning by canonical Wnt signaling during ascidian development. PLOS Genetics. 2019 Mar 29;15(3):e1008054.

3.   Niehrs C. The Spemann organizer and embryonic head induction. The EMBO Journal. 2001 Feb 15;20(4):631–7.

15/06/20

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