Elsevier

Neuroscience

Volume 122, Issue 1, 20 November 2003, Pages 123-128
Neuroscience

HuC/D confocal imaging points to olfactory migratory cells as the first cell population that expresses a post-mitotic neuronal phenotype in the chick embryo

https://doi.org/10.1016/j.neuroscience.2003.07.004Get rights and content

Abstract

In the present study, the expression of the HuC/D RNA-binding proteins, a marker of neurons that have left the mitotic cycle, in cells migrating from the olfactory neuroepithelium toward the telencephalon in the chick embryo was investigated by means of immunofluorescence and confocal laser microscopy. Results showed that this migratory cell population is early and massively labeled by the a-HuC/D antibody starting from the first olfactory pit stage. At this developmental stage, olfactory migratory cells appeared to be the only neuronal population that expressed the HuC/D antigens in the whole embryo. In following developmental stages, the great majority of migratory cells, the number of which increased progressively, continued to be heavily immunopositive for the a-HuC/D antibody while immunopositivity to this antibody begins to be detected in other regions of the nervous system. HuC/D immunopositivity persisted until stage 30 HH (about 6.5 days), the later developmental stage investigated in this study, when colocalization with GnRH was detected. Negativity to the anti-proliferating cell nuclear antigen (anti-PCNA) immunostaining, a marker of S-phase, showed that migratory olfactory cells have left the mitotic cycle. Altogether, these results suggest that we have identified the first population of post-mitotic neurons in the developing nervous system of the chick embryo.

Section snippets

Experimental procedures

Fertilised chick eggs were kept in a “Covatutto 40” incubator (Novital, Varese, Italy) at 38 °C and 80% relative humidity. Embryos were withdrawn at various developmental stages according to Hamburger and Hamilton (1992): 16 HH (about 51–56 h of incubation), 18 HH (about 65–69 h of incubation), 21 HH (about 3.5 days of incubation), and 30 HH (about 6.5 days of incubation). Approval for this study was obtained from the Animal Care and Ethics Committee of the University of Turin.

Embryos were

Results

Results of the HuC/D immunolabelling are shown in Fig. 1. At stage 16 HH, about 51–56 h of incubation, a cluster of a-HuC/D immuno-positive cells projecting from the olfactory pit to the telencephalic vesicle was detected (Fig. 1a). Only occasional labeled cells were detected in the context of the olfactory neuroepithelium that is just beginning to hollow and to form a pit. High resolution confocal imaging (Fig. 1e) demonstrated the prevailing cytoplasmic location of HuC/D antigens.

At stage 18

Discussion

The main finding of the present study is the identification and description of a nerve cell population that first, and massively, shows immuno-positivity for the anti-HuC/D antibody in comparison to other regions of the developing chick nervous system where immmuno-labeling by the antibody directed against these two RNA-binding proteins appears later (Wakamatsu and Weston, 1997). In the chick embryo, the early stages of olfactory neuroepithelium differentiation are accompanied by migration of

Acknowledgements

This work was supported by grants from the Italian MURST/MIUR.

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