Secondary and tertiary structure modeling reveals effects of novel mutations in polycystic liver disease genes PRKCSH and SEC63

Waanders E, Venselaar H, te Morsche RHM, de Koning DB, Kamath PS, Torres VE, Somlo S, Drenth JPH. Secondary and tertiary structure modeling reveals effects of novel mutations in polycystic liver disease genes PRKCSH and SEC63. Polycystic liver disease (PCLD) is characterized by intralobular bile duct cysts in the liver. It is caused by mutations in PRKCSH, encoding hepatocystin, and SEC63, encoding Sec63p. The main goals of this study were to screen for novel mutations and to analyze mutations for effects on protein structure and function. We screened 464 subjects including 76 probands by direct sequencing or conformation‐sensitive capillary electrophoresis. We analyzed the effects of all known and novel mutations using a combination of splice site recognition, evolutionary conservation, secondary and tertiary structure predictions, Poly Phen , and p Mut and sift . We identified a total of 26 novel mutations in PRKCSH (n = 14) and SEC63 (n = 12), including four splice site mutations, eight insertions/ deletions, six non‐sense mutations, and eight missense mutations. Out of 48 PCLD mutations, 13 were predicted to affect splicing. Most mutations were located in highly conserved regions and homology modeling for two domains of Sec63p showed severe effects of the residue substitutions. In conclusion, we identified 26 novel mutations associated with PCLD and we provide in silico analysis in order to delineate the role of these mutations.     

Patients with isolated polycystic liver disease referred to liver centres: clinical characterization of 137 cases

Background and aim: Isolated polycystic liver disease (PCLD) is characterized by the presence of multiple cysts in the liver in the absence of polycystic kidneys. The clinical profile of PCLD is poorly defined and we set up a study for the clinical characteristics of PCLD. Methods: We collected clinical data on 188 PCLD patients (defined as >10 liver cysts) from five tertiary referral centres, and 137 patients were selected for the purpose of this study. We performed molecular analysis of the PCLD associated genes PRKCSH and SEC63 in 91 patients. Results: A total of 118 (86%) patients were female. The majority of patients (88%) had >20 cysts. The median age at diagnosis was 47 years (range 23–84). 37 (41%) patients carried a mutation. Clinical symptoms at presentation were present in 111 (84%) patients. γ‐glutamyl transferase was elevated to 1.4 times upper limit of normal (interquartile range 1.0–2.7). The presence of a mutation and female gender predicted a more severe course: female patients were 9 years younger at the time of diagnosis (47 years; range 23–84) and 91% had symptoms (P<0.01); likewise, mutation carriers were younger at presentation (39 years; range 35–48) and 95% of this cohort had symptoms (P<0.01). During follow‐up [median 8.2 years (range 0–35)], 10% of untreated and 51% of treated patients developed complications. Mortality in this cohort was 8%, but only 2% died of PCLD‐related causes. 58% of patients were treated a median of 2 years (range 0–25) after diagnosis. Conclusion: Symptomatic PCLD patients are mainly females. Females and mutation carriers were younger at diagnosis and had a more severe course of disease.