Expression of Beta Subunit 2 of Ca²+/Calmodulin-Dependent Protein Kinase I in the Developing Rat Retina

Expression of beta 2 subunit of Ca²+/calmodulin-dependent protein kinase I (CaMKIβ2) of the rat retina during the developmental period and in the adulthood was studied immunohistochemically. The immunoreactivity of CaMKIβ2 was detected in the earliest development of the primordial retina at embryological day (E) 12. The inner neuroblastic layer from which the presumptive ganglion cells are generated showed the ubiquitous CaMKIβ2 immunoreactivity at E15 and persistently expressed at the same level until postnatal day (P) 0 when the inner neuroblastic layer divides into the ganglionic cell layer and the inner plexiform layer. The strong immunoreactivity was detected in the ganglion cell layer and the moderate one in the internal plexiform layer. CaMKIβ2 immunoreactivities were persistantly expressed throughout the postnatal development at the same level. The low level of intensity was first found in the inner nuclear layer at P7, followed by the outer plexiform, outer nuclear and rod-cone cell layers at the age of P12, respectively. The intensities of CaMKIβ2 immunoreactivities in the inner nuclear and rod-cone cell layers were gradually increased to the strong level by P18 and persisted until adulthood. The present study revealed that the expression of CaMKIβ2 in the retina was detected from the earliest development until adulthood, indicating that CaMKIβ2 may be required in both proliferation and differentiation of the retinal precursor cells and subsequent formation of the functional layers. In addition, CaMKIβ2 immunoreactivity in the rod-cone cell layer implies that this protein may be involved in the visual signaling process.