*15.3. PI Binding Proteins*

Proteins with phosphoinositide-binding domains have also been associated with retinal disease. These include the product of the *tub*/*TUB* gene [162,163] and a related protein, TULP1 [47,164–166]. Tub was discovered as the protein encoded by a gene whose mutation in *tubby* mice causes obesity, deafness and blindness. The widely expressed members of the tubby family, including TULP1-TULP4, have a characteristic carboxyl-terminal tubby domain consisting of an alpha helix surrounded by a beta barrel which has been shown to bind to specific phosphoinositides [167]. Both Tub and Tulp1 are expressed in the retina, and TULP1 mutations cause retinitis pigmentosa [47,168].
