*15.1. Phosphatases and Inherited Retinopathies*

Inherited defects in the phosphoinositide phosphatase, INPP5E, are associated with the multi-syndromic ciliopathies, Joubert syndrome and Bardet–Biedl syndrome [147–150], and with retinal degeneration. The substrates for this phosphatase are PI(4,5)P2 and PI(3,4,5)P3, and its critical role in the cilia suggests that regulating levels of PI(4,5)P2 may be important in ciliogenesis and cilium stability.

Synaptojanins are phosphoinositide phosphatases associated with synaptic function [151–153], including vesicle uncoating and endocytosis. Synaptojanin-1 deficiency causes severe cone defects in zebrafish and has been implicated in the regulation of autophagy in cones [45,46,75].

Defects in another phosphoinositide phosphatase, OCRL, are associated with a severe ciliopathy, oculocerebrorenal syndrome of Lowe [136]. Symptoms of this disease include glaucoma, a disease of the retina.
