Abstract
Calcium-binding proteins (CaBPs) form a subfamily of calmodulin-like proteins that were cloned from the retina. CaBP4 and CaBP5 have been shown to be important for normal visual function. Although CaBP1/caldendrin and CaBP2 have been shown to modulate various targets in vitro, it is not known whether they contribute to the transmission of light responses through the retina. Therefore, we generated mice that lack CaBP2 or CaBP1/caldendrin (Cabp2–/– and Cabp1–/–) to test whether these CaBPs are essential for normal retinal function. By immunohistochemistry, the overall morphology of Cabp1–/– and Cabp2–/– retinas and the number of synaptic ribbons appear normal; transmission electron microscopy shows normal tethered ribbon synapses and synaptic vesicles as in wild-type retinas. However, whole-cell patch clamp recordings showed that light responses of retinal ganglion cells of Cabp2–/– and Cabp1–/– mice differ in amplitude and kinetics from those of wild-type mice. We conclude that CaBP1/caldendrin and CaBP2 are not required for normal gross retinal and synapse morphology but are necessary for the proper transmission of light responses through the retina; like other CaBPs, CaBP1/caldendrin and CaBP2 likely act by modulating presynaptic Ca2+-dependent signaling mechanisms.
Footnotes
The authors report no conflict of interest.
The research was supported by a University of Washington Royalty Research Fund, University of Washington bridge funding, and National Institutes of Health (NIH) grant R01 EY020850 to F.H.; the Howard Hughes Medical Institute and NIH grant EY11850 to F.R.; NIH grants NS084190 and DC009433 and a Carver Research Program of Excellence to A.L.; and a long-term fellowship by Human Frontier Science Program to R.S.
This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International, which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.