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Chapter 3

Protein Kinase C Regulates Rod Photoreceptor

Differentiation Through Modulation of STAT3

Signaling

Carolina Pinzon-Guzman, Samuel Shaomin Zhang, and Colin J. Barnstable

Abstract The molecular signals governing retinal development remain poorly understood, but some key molecules that play important roles have been identified. Activation of STAT3 by cytokines such as LIF and CNTF specifically blocks differentiation of rod photoreceptors. Here we test the hypothesis that PKC activation promotes development of rod photoreceptors by inhibiting STAT3. Explant cultures of mouse retina were used to study the effects of PKC activation on rod development. The expression of opsin, a rod specific marker, is induced at an early stage in retina explants cultured in the presence of PMA and this effect is prevented by the PKC inhibitor Go7874. Histological experiments show that there is expression of PKC beta1, but not PKC-alpha in the outer nuclear layer between E17.5 and PN5. In vitro data derived from cell lines shows that activation of PKC results in reduction of STAT3 phosphorylation. In addition, inhibition of PKC results in increase STAT3 phosphorylation. We suggest that cross talk of signals between STAT3 and PKC may determine the differentiation of rods from retinal progeitors.

3.1 Introduction

Rod photoreceptors are among the last cell types to differentiate from multipotential retinal progenitors. Much of the information necessary to generate rod photoreceptors is intrinsic to the retinal epithelium since explants of embryonic retinas are capable of forming all the major classes of cells (Sparrow et al. 1990). Within the retinal epithelium, however, photoreceptor differentiation can clearly be influenced by a number of cell interactions mediated by either direct cell-cell contacts or through soluble factors released from cells (Watanabe and Raff 1990; 1992; Reh 1992; Altshuler and Cepko 1992). Several of these factors have been

C.J. Barnstable (B)

Department of Neural and Behavioral Sciences, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA

e-mail: cbarnstable@psu.edu

R.E. Anderson et al. (eds.), Retinal Degenerative Diseases, Advances in Experimental

21

Medicine and Biology 664, DOI 10.1007/978-1-4419-1399-9_3,

C Springer Science+Business Media, LLC 2010