Functional studies of Ci-Gsx gene in the developing central nervous system of Ciona intestinalis

Esposito, Rosaria (2014). Functional studies of Ci-Gsx gene in the developing central nervous system of Ciona intestinalis. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000d5b9

Abstract

Gsx genes encode for members of ParaHox family of transcription factor and are highly conserved throughout the animal kingdom. They are expressed mainly in the developing CNS in members of all major groups of metazoans. Gsx function, in the few organisms in which it has been investigated, is related re the specification of neural progenitors and in the regulation of the dorso-ventral patterning of the vertebrate neural rube.

In the ascidian Ciona inlesrinalis, the model organism used in this work, a single Gsx ortholog has been identified, named Ci-gsx, whose zygotic expression is localized in the developing CNS, including the precursors of the ocellus photoreceptor cells. Clana ocellus, a pigmented multicellular photoreceptive organ, despite its simplicity, possesses functional and molecular similarities to vertebrate eye, thus representing a valuable tool to study the basic mechanisms of eye development.

The aim of my PhD work has been the investigation of Ci-gsx function in the early specification of photoreceptor cells in Ciona intestinalis. To this end, I used targeted perturbation of Ci-gsx: activity. This study indicated that Ci-gsx is actually involved in the molecular pathway controlling photoreceptor cells differentiation, upstream of Ci-Rx, a key gene for ocellus development. In addition, a detailed analysis of the 5' Ci-gsx regulatory region allowed me to identify the minimal promoter region responsible for Ci-gsx expression. Furthermore, I demonstrated that a member of Sox. family is likely involved in Ci-gsx transcriptional activation. I also identified Ci-msxb as a possible repressor of Ci-gsx extpression in pigment cell lineage.

My data insert a new piece in the genetic cascade controlling early specification of Ciona sensory organs and represent a first evidence of a potential implication of a Gsx ParaHox. gene in this process, thus opening new perspectives OD the role. still controversial. of Gsx gene in the ancestor of bilaterians.

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