Abstract
Purpose: :
Gap–junction channels formed by connexins (Cx) may play essential roles in some processes that occur during retinal development, such as apoptosis and calcium wave spread. The present study was undertaken to determine the distribution pattern of Cx36, Cx43 and Cx45 by immunofluorescence, as well as their gene expression levels by quantitative PCR during postnatal development of the mouse retina.
Methods: :
C57BL/6J mice were sacrificed at postnatal days 5 (P5), P9, P11, P15, P21 and P60. Their eyes were enucleated and retinas were processed for Real–time PCR and immunofluorescence for Cx36, Cx43 and Cx45.
Results: :
Our results showed an increased expression of neuronal Cx36 from P1 until P10, when this Cx reached adult levels and it was mainly distributed in the outer and inner plexiform layers. In turn, Cx43 was almost absent in retinal progenitor cells at P1, it became more visible in glial cell processes about P10, and did not change until adulthood. Double–labeling studies in situ and in vitro with anti–vimentin, a Müller cell marker, confirmed that Cx43 was expressed by these cells. In addition, quantitative PCR showed that Cx43 and vimentin shared very similar temporal expression pattern. Finally, in contrast to Cx36 and Cx43, Cx45 mRNA was strongly down–regulated during development. In early postnatal days, Cx45 was seen ubiquitously distributed throughout the retina in cells undergoing proliferation and differentiation, as well in differentiated neurons. In adult retina, this protein had a more restricted distribution both in neurons and glial cells, as confirmed in situ and in vitro.
Conclusions: :
We observed a distinct temporal expression pattern for Cx36, Cx43, and Cx45, which is probably related to particular roles in retinal function and maintenance of homeostasis during development of the mouse retina.
Keywords: gap junctions/coupling • development • Muller cells