Acetylated alpha-tubulin in the connecting cilium of developing rat photoreceptors.

PURPOSE To examine the distribution of acetylated alpha-tubulin in the connecting cilium of rat rod photoreceptors during different stages of photoreceptor development. METHODS An antibody found to be specific for the acetylated form of alpha-tubulin was used in immunoelectron microscopy of retinas from animals of different ages. RESULTS All the microtubules of the connecting cilium, including those of the basal bodies, were found to contain acetylated alpha-tubulin at the earliest stage of outer segment development, before the cilium has begun to grow out from the cell, and at all subsequent stages. CONCLUSIONS These results indicate that the alpha-tubulin of the connecting cilium is acetylated either before, or at least very soon after, its assembly into microtubules. Given that acetylation of alpha-tubulin is correlated with stable microtubules, the results suggest that stable microtubules might be important in creating the foundation for the formation of the outer segment, as well as in helping maintain the polarity of the mature photoreceptor.