NPHP1 and ciliopathy: For example, although the absence of individual ciliopathy genes encoding MKS/MKSR proteins or NPHP proteins (NPHP-1, NPHP-4) does not result in serious cilia defect, the loss of nphp-4 (the ortholog of human NPHP4) in combination with mks-6 (the ortholog of human CC2D2A) causes more severe cilia-related defects (transition zone membrane association defects) (Williams et al, 2011).