Investigation of the contribution from peripheral GnRH-like immunoreactive ‘neuroblasts’ to the regenerating central nervous system in the protochordateCiona intestinalis

Abstract

The neural ganglion of the ascidian iona intestinalis regenerates in its entirety within a few weeks of ablation. Here we investigate the role of gonadotropin-releasing hormone-like immunoreactive (GnRHli) cells in regeneration. Immunocytochemical studies show that in addition to a previously described plexus of GnRH-like neurones located in association with the dorsal strand, the normal adult brain contains GnRH-li neurones. These are predominantly localized to the ventral cortical rind at the posterior of the ganglion. Following ablation, non-process bearing GnRH-li cells appear in the regenerating area within two days. By day 8 post-ablation, process bearing GnRH-li cells are detected close to the regenerating brain. The number of these cells increases at later stages. GnRH-li cells are first detected within the regenerating brain at 14 days post-ablation and their number subsequently increases. These cells are initially concentrated along the ventral surface of the regenerating brain near to the dorsal strand. Double labelling studies with bromodeoxyuridine show that none of the GnRH-li cells are labelled at any stage of regeneration. The data are consistent with a sub-population of the new neurones being derived from GnRH-li neuroblasts born prior to ablation, which migrate from the dorsal strand complex into the regenerating ganglion. * Author for correspondence : (m.thorndyke!rhbnc.ac.uk).

Conduction and coordination in deganglionated ascidians

“…This is in marked contrast to Ciona intestinalis and Ascidia mentula, which regenerate their ganglia after 3-5 weeks (Schultze 1900;Day 1919;Lender and Bouchard-Madrelle 1964), a process that is explored in several recent articles, most recently by Bollner et al (1997). We used electrophysiology to verify the earlier descriptions of peripheral conduction in the body wall both before and after deganglionation.…”

Formation of Nervous Systems and Neural Stem Cells in Ascidians

“…This morphological relationship may partly explain the observation that the brain of H. roretzi easily reverts from a thin, cord-like structure (after breeding season, in winter) to the normal brain shape via migration of neurons from the dorsal strand. Similar phenomena are observed during regeneration of other brain structures; for example, after extirpation of the brain in C. intestinalis, the regenerating brain contains GnRH neurons, suggesting that GnRH neurons originate in the dorsal strand and subsequently migrate into the regenerating brain (Bollner et al, 1997). Together with the previous demonstration which GnRH neurons are generated in the dorsal strand and migrate into the brain (Terakado, 2009), the current results reveal that PRL-like neurons are generated in the dorsal strand and migrate into the brain during normal development.…”

“…The regenerated central nervous system may also acquire the anterior-posterior axis identical to that of normal development. In the regenerating brain, no mitotic figures were detected, indicating that migration of post-mitotic cells to the site of ganglion regeneration (Bollner et al, 1995(Bollner et al, , 1997. Initial concentration of GnRH-like cells along the ventral surface of the regenerating brain in C. intestinalis (Bollner et al, 1997) suggests that these cells originate in the dorsal strand and migrate to the surface of regenerating brain as those in normal development.…”

“…In the regenerating brain, no mitotic figures were detected, indicating that migration of post-mitotic cells to the site of ganglion regeneration (Bollner et al, 1995(Bollner et al, , 1997. Initial concentration of GnRH-like cells along the ventral surface of the regenerating brain in C. intestinalis (Bollner et al, 1997) suggests that these cells originate in the dorsal strand and migrate to the surface of regenerating brain as those in normal development. Because the adult brain possesses various types of neurons (cholinergic, GABAergic, glycinergic, and glutamatergic ones), trans-differentiation of the cells from existing tissue must be involved in brain regeneration.…”

“…The anterior-posterior axis of the larval central nervous system is also inherited to form the adult central nervous system, indicating that the anterior-posterior axis of the central nervous system is already determined by developmental regulatory genes (Wada et al, 1998;Horie et al, 2011). Experimental ablation of the cerebral ganglion in C. intestinalis, it regenerates in its entirety within a few weeks (Bollner et al, 1997). This indicates that the regeneration of the adult central nervous system does not require preexisting cells (neurons and glial cells) from the central nervous system; i.e., it accomplishes entirely by cell supply from other tissues and organs than those of the central nervous system.…”