Calretinin immunoreactivity in the developing retina of sharks: Comparison with cell proliferation and GABAergic system markers

• Published in: Experimental eye research Vol. 91; no. 3; pp. 378 - 386
• Main Authors: Ferreiro-Galve, Susana, Rodríguez-Moldes, Isabel, Candal, Eva
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.09.2010
• Subjects: Amacrine Cells - metabolism; Animals; Biomarkers - metabolism; Calbindin 2; calcium-binding protein; Cell Differentiation; Cell Proliferation; development; Dogfish - embryology; Dogfish - growth & development; elasmobranch; Elasmobranchii; evolution; Fluorescent Antibody Technique, Indirect; GAD; gamma-Aminobutyric Acid - metabolism; Glutamate Decarboxylase - metabolism; Haploblepharus fuscus; Immunoenzyme Techniques; Marine; PCNA; Proliferating Cell Nuclear Antigen - metabolism; Retina - embryology; Retina - growth & development; Retina - metabolism; Retinal Ganglion Cells - metabolism; Retinal Horizontal Cells - metabolism; retinogenesis; S100 Calcium Binding Protein G - metabolism; Scyliorhinus canicula; INLi; development; calcium-binding protein; PCNA; IPL; Scyliorhinus canicula; INL; TZ; INLo; OPL; GAD; evolution; ONL; retinogenesis; CR; HCL; CMZ; GCL; elasmobranch; nl; ON
• ISSN: 0014-4835; 1096-0007
• DOI: 10.1016/j.exer.2010.06.011

The calcium-binding protein calretinin (CR) has been widely used as a marker of neuronal differentiation. In the present study we analyzed the distribution of CR-immunoreactive (CR-ir) elements in the embryonic and postembryonic retina of two elasmobranchs, the lesser spotted dogfish ( Scyliorhinus canicula) and the brown shyshark ( Haploblepharus fuscus). We compared the distribution of CR with that of a proliferation marker (the proliferating cell nuclear antigen, PCNA) in order to investigate the time course of CR expression during retinogenesis and explored the relationship between CR and glutamic acid decarboxylase (GAD), the synthesizing enzyme of the gamma-aminobutyric acid (GABA), which has been reported to play a role in shark retinogenesis. The earliest CR immunoreactivity was concurrently observed in subsets of: a) ganglion cells in the ganglion cell layer; b) displaced ganglion cells in the inner plexiform layer and inner part of the inner nuclear layer (INLi); c) amacrine cells in the INLi, and d) horizontal cells. This pattern of CR distribution is established in the developing retina from early stage 32, long after the appearance of a layered retinal organization in the inner retina, and coinciding with photoreceptor maturation in the outer retina. We also demonstrated that CR is expressed in postmitotic cells long after they have exited the cell cycle and in a subset of GABAergic horizontal cells. Overall our results provide insights into the differentiation patterns in the elasmobranch retina and supply further comparative data on the development of CR distribution in the retina of vertebrates. This study may help in understanding the possible involvement of CR in aspects of retinal morphogenesis.