Erling Tjora1,2, Anny Gravdal3,4, Trond Engjom5,6, Miriam Cnop7,8, Bente B Johansson2, Georg G Dimcevski5,6, Anders Molven3,9, Karianne Fjeld3,4. 1. Department of Pediatrics and Adolescent Medicine, Haukeland University Hospital. 2. Center for Diabetes Research, Department of Clinical Science, University of Bergen. 3. The Gade Laboratory for Pathology, Department of Clinical Medicine, University of Bergen. 4. Department of Medical Genetics, Haukeland University Hospital. 5. Section for Gastroenterology, Department of Clinical Medicine, University of Bergen. 6. Department of Medicine, Haukeland University Hospital, Bergen, Norway. 7. ULB Center for Diabetes Research, Université Libre de Bruxelles. 8. Division of Endocrinology, ULB Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium. 9. Department of Pathology, Haukeland University Hospital, Bergen, Norway.
Abstract
OBJECTIVES: The hybrid allele of the carboxyl ester lipase gene (CEL-HYB1) is a genetic risk factor for chronic pancreatitis (CP) although the mechanism promoting disease development is largely unknown. Here, we aimed to clinically describe subjects carrying the CEL-HYB1 allele and to elucidate why the protein product is pathogenic by analyzing pancreatic secretions and cellular models. METHODS: Norwegian cases (n = 154) diagnosed with recurrent acute pancreatitis or CP were subjected to genetic screening by a CEL-HYB1-specific PCR assay followed by Sanger sequencing. For investigation of CEL-HYB1 protein secretion, duodenal juice samples from cases and controls were analyzed by western blotting. HEK293cells were transfected with constructs expressing CEL-HYB1 or the normal CEL protein (CEL-WT) and analyzed by qPCR, cell fractionation and western blotting. RESULTS: Two CEL-HYB1-positive families were identified. In both pedigrees, CEL-HYB1 did not fully co-segregate with disease. One proband had recurrent acute pancreatitis and was an active smoker. Her mother was a CEL-HYB1 carrier who had suffered from several attacks of acute pancreatitis until she stopped smoking. The other proband was diagnosed with CP and pancreas divisum. Her CEL-HYB1-positive parent was symptom-free but exhibited pancreatic imaging changes. When analyzing the CEL protein in duodenal juice, CEL-WT was readily detectable but no band corresponding to the risk variant was seen. In CEL-HYB1-transfected cells, we observed impaired protein secretion, protein aggregation and endoplasmic reticulum stress. CONCLUSION: Our data suggest that CEL-HYB1, in combination with well-known pancreatitis risk factors, causes disease through the misfolding-dependent pathway of genetic CP risk.
OBJECTIVES: The hybrid allele of the carboxyl ester lipase gene (CEL-HYB1) is a genetic risk factor for chronic pancreatitis (CP) although the mechanism promoting disease development is largely unknown. Here, we aimed to clinically describe subjects carrying the CEL-HYB1 allele and to elucidate why the protein product is pathogenic by analyzing pancreatic secretions and cellular models. METHODS: Norwegian cases (n = 154) diagnosed with recurrent acute pancreatitis or CP were subjected to genetic screening by a CEL-HYB1-specific PCR assay followed by Sanger sequencing. For investigation of CEL-HYB1 protein secretion, duodenal juice samples from cases and controls were analyzed by western blotting. HEK293cells were transfected with constructs expressing CEL-HYB1 or the normal CEL protein (CEL-WT) and analyzed by qPCR, cell fractionation and western blotting. RESULTS: Two CEL-HYB1-positive families were identified. In both pedigrees, CEL-HYB1 did not fully co-segregate with disease. One proband had recurrent acute pancreatitis and was an active smoker. Her mother was a CEL-HYB1 carrier who had suffered from several attacks of acute pancreatitis until she stopped smoking. The other proband was diagnosed with CP and pancreas divisum. Her CEL-HYB1-positive parent was symptom-free but exhibited pancreatic imaging changes. When analyzing the CEL protein in duodenal juice, CEL-WT was readily detectable but no band corresponding to the risk variant was seen. In CEL-HYB1-transfected cells, we observed impaired protein secretion, protein aggregation and endoplasmic reticulum stress. CONCLUSION: Our data suggest that CEL-HYB1, in combination with well-known pancreatitis risk factors, causes disease through the misfolding-dependent pathway of genetic CP risk.