PKD1 and Isolated polycystic liver disease: Notably, the observation that Sec63 has a preference for multispanning MPs (seen in Figure 6D) is consistent with the fact that the two previously identified clients of Sec63 that are responsible for the disease phenotype of disturbed planar cell polarity in SEC63-linked polycystic liver disease, polycystins 1 and 2, are multispanning MPs in the plasma membrane [168,169,177].