NPHP4 is necessary for normal photoreceptor ribbon synapse maintenance and outer segment formation, and for sperm development.
Won J, Marín de Evsikova C, Smith RS, Hicks WL, Edwards MM, Longo-Guess C, Li T, Naggert JK, Nishina PM. Hum Mol Genet. 2011 Feb 1; 20(3):482-96. Epub 2010 Nov 15.