Expression patterns of connexin genes in mouse retina

To analyze the molecular basis of gap junctional communication in mouse ret ina, we examined the expression pattern of the following 13 connexin (Cx) g enes: Cx26, Cx30, Cx30.3, Cx31, Cx31.1, Cx32, Cx36, Cx37, Cx40, Cx43, Cx45, Cx46, and Cx50. By using reverse transcriptase-polymerase chain reactions with primer oligonucleotides to murine connexin genes, we detected mRNAs of Cx26, Cx31, Cx32, Cx36, Cx37, Cx40, Cx43, Cx45, and Cx50. Retinae from het erozygous mice with targeted replacement of most of the Cx45 open reading f rame by a lacZ reporter gene showed Cx45 promoter activity in somata of the ganglion cell layer and the inner nuclear layer. Immunoblot and immunofluo rescence analyses with antibodies generated to murine connexin epitopes rev ealed the presence of Cx36, Cx37, Cx43, and Cx45 proteins: The outer and in ner plexiform layer were immunopositive for Cx36 and Cx45. Cx37 immunoreact ivity was found in blood vessels of the inner retina. Cx43 immunolabeling w as detected in the ganglion cell layer and nerve fiber layer where it was l argely colocalized with immunostaining of glial fibrillary acidic protein s uggesting that Cx43-positive cells could be of glial origin. No Cx26 protei n was detected in retina by using Cx26 antibodies for immunoblot analyses o r confocal microscopy. Furthermore, comparative immunofluorescence analyses of retinae from mice deficient for Cx31, Cx32, or Cx40 with retinae of wil d-type mice revealed no specific immunostaining. Our results demonstrate re gional specificity in expression of connexin genes in mouse retina and, thu s, provide a basis for future assignments of functional defects in connexin -deficient mice to cells in different regions of the retina. J. Comp. Neuro l. 425:193-201, 2000. (C) 2000 Wiley-Liss, Inc.