The CTRB1-CTRB2 risk allele for chronic pancreatitis discovered in European populations does not contribute to disease risk variation in the Chinese population due to near allele fixation

We read with great interest the article by Rosendahl et al1 reporting the identification of CTRB1-CTRB2 (chymotrypsin B1 and chymotrypsin B2) as a new chronic pancreatitis (CP) risk locus by means of genome-wide association study, with the lead single nucleotide polymorphism (SNP) rs8055167 having an OR of 1.35. Moreover, they found that a previously reported 16.6 kb inversion in the CTRB1-CTRB2 locus2 was in linkage disequilibrium with the CP-associated SNPs and optimally tagged by rs8048956. Furthermore, they provided in silico and in vivo evidence showing that the inversion variant changes the expression ratio of the CTRB1 and CTRB2 isoforms, the major risk allele being associated with increased CTRB1 and decreased CTRB2 mRNA expression as compared with the minor allele. Finally, they provided in vitro evidence that CTRB1 was less efficient in degrading anionic trypsinogen (PRSS2) than CTRB2 (note that rapid degradation of PRSS2 conferred by a PRSS2 missense variant...

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