title: Intragenic duplication: a novel mutational mechanism in hereditary pancreatitis.
abstract: OBJECTIVE
  In a hereditary pancreatitis family from Denmark, we identified a novel intragenic duplication of 9 nucleotides in exon-2 of the human cationic trypsinogen (PRSS1) gene (c.63_71dup) which at the amino-acid level resulted in the insertion of 3 amino acids within the activation peptide of cationic trypsinogen (p.K23_I24insIDK). The aim of the present study was to characterize the effect of this unique genetic alteration on the function of human cationic trypsinogen.
  
  
  METHODS
  Wild-type and mutant cationic trypsinogens were produced recombinantly and purified to homogeneity. Trypsinogen activation was followed by enzymatic assays and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Trypsinogen secretion was measured from transfected HEK 293T cells.
  
  
  RESULTS
  Recombinant cationic trypsinogen carrying the p.K23_I24insIDK mutation exhibited greater than 10-fold increased autoactivation. Activation by human cathepsin B also was accelerated by 10-fold. Secretion of the p.K23_I24insIDK mutant from transfected cells was diminished, consistent with intracellular autoactivation.
  
  
  CONCLUSIONS
  This is the first report of an intragenic duplication within the PRSS1 gene causing hereditary pancreatitis. The accelerated activation of p.K23_I24insIDK by cathepsin B is a unique biochemical property not found in any other pancreatitis-associated trypsinogen mutant. In contrast, the robust autoactivation of the novel mutant confirms the notion that increased autoactivation is a disease-relevant mechanism in hereditary pancreatitis.
authors.affiliation: Department of Medical Gastroenterology, Odense University Hospital, University of Southern Denmark, Odense, Denmark. maiken.t.joergensen@ouh.regionsyddanmark.dk
authors.forename: Maiken T
authors.initials: MT
authors.lastname: Joergensen
authors.forename: Andrea
authors.initials: A
authors.lastname: Geisz
authors.forename: Klaus
authors.initials: K
authors.lastname: Brusgaard
authors.forename: Ove B
authors.initials: OB
authors.lastname: Schaffalitzky de Muckadell
authors.forename: Péter
authors.initials: P
authors.lastname: Hegyi
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Gerdes
authors.forename: Miklós
authors.initials: M
authors.lastname: Sahin-Tóth
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D015153:Blotting, Western; D002401:Cathepsin B / Q000378:metabolism; D003718:Denmark; D004789:Enzyme Activation / Q000235:genetics; D005192:Family Health; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D009154:Mutation; D050500:Pancreatitis, Chronic / Q000201:enzymology / Q000235:genetics; D010375:Pedigree; D020449:Repetitive Sequences, Amino Acid / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D014357:Trypsin / Q000235:genetics* / Q000378:metabolism
chemical_list: C489303:PRSS1 protein, human; D014357:Trypsin; D002401:Cathepsin B