Immunofluorescence analyses of the tubby mutant retina. (A) The WT tubby protein migrates at approximately 60 kDa by immunoblotting, but tubby protein expression is absent in the mutant tissues indicating that the mutation is a functional null allele. The lower panel shows the actin immunoblotting results as a loading control. (B) Rhodopsin is localized primarily in photoreceptor outer segments in WT but is severely mislocalized to the cell body in the tubby mutant at one month of age. Similarly, blue and green cone opsins are normally localized to the cone outer segments in WT but are also mislocalized to the cell body and synaptic terminals in the tubby mutant retina. (C) In contrast to rhodopsin and cone opsins, peripherin/RDS and GRK, which are also integral membrane proteins, do not show mislocalization in the tubby mutant. Rod PDE and RP1 protein, which are membrane and cytoskeleton associated proteins, respectively, also manifest normal outer segment localization. IS, inner segment; ONL, outer (photoreceptor) nuclear layer; OPL, outer plexiform layer; OS, outer segment. Cell nuclei were counter stained blue by DAPI.