Abstract
Purpose :
Mutations in CEP290 cause Leber congenital amaurosis (LCA). The current study is to determine molecular functions of CEP290 in photoreceptors and identify disease mechanisms of CEP290-associated LCA.
Methods :
Localization of various inner segment- and outer segment-specific proteins was evaluated by immunohistochemistry in Cep290 conditional and rd16 mutant mouse retinas as well as by immunoblot analyses of isolated outer segments. iCre75 transgenic mice were used to inactivate Cep290 expression in rod photoreceptors.
Results :
Localization of most outer segment-specific proteins was not altered in CEP290 deficient photoreceptors. One notable exception was rhodopsin, which showed significant mislocalization in the inner segment at all stages of degeneration. In contrast, mislocalization of inner segment proteins in the outer segment was more pronounced. In particular, depletion of CEP290 caused rapid accumulation of inner segment proteins STX3 and STXBP1, which are known to mislocalize in Bardet-Biedl syndrome (BBS) mutant retinas, in the outer segment. Among STX3 interacting proteins, SNAP25, which normally localizes to the inner segment plasma membrane, also showed significant mislocalization to the outer segment. Other inner segment plasma membrane proteins tested, including IMPG2 and Na+/K+-ATPase1, showed various degrees of mislocalization to the outer segment. In contrast, localization of endomembrane proteins including VAMP2, a v-SNARE protein localizing to secretory vesicles, was not affected.
Conclusions :
Our data indicate that CEP290 is necessary to maintain compartment-specific protein localization in photoreceptors, particularly to prevent mislocalization of inner segment plasma membrane proteins to the outer segment. CEP290 is also needed for outer segment-specific localization of rhodopsin. These data demonstrate that photoreceptor degeneration in CEP290-LCA is associated with disruption of compartmentalized protein localization.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.