Trypsinogen Genes: Insights into Molecular Evolution from the Study of Pathogenic Mutations

Abstract

The basic fuel for evolution is genetic variation that is subsequently acted on by natural selection. Selection may either act conservatively so as to ensure that features of structural or functional importance are retained (purifying selection), or it may act so as to favour those changes, which confer some advantageous characteristics (positive selection). Insights into these divergent evolutionary processes are sometimes generated through the study of pathogenic mutations, an archetypal example being the human trypsinogen genes. The integration of data gleaned from the functional characterisation of pathogenic missense mutations in the human cationic trypsinogen gene (PRSS1) with information obtained from comparative sequence analysis has provided evidence for stepwise selective pressures acting against prematurely activated trypsin within the human pancreas. Studies of PRSS1 mutations have also revealed evidence for past gene conversion events between the various trypsinogen gene family members and have helped to improve our understanding of the evolutionary history of these genes.

Key Concepts:

  • Trypsinogen plays an important role in digestion.

  • Prematurely activated trypsin within the pancreas, if not inhibited and/or inactivated, has the potential to trigger the pancreatic zymogen activation cascade, leading to pancreatic autodigestion and pancreatitis.

  • Gain‐of‐function mutations in the human cationic trypsinogen gene (PRSS1) cause chronic pancreatitis.

  • Pathogenic PRSS1 mutations have been exploited to understand the molecular evolution of the human trypsinogen family.

  • Pathogenic mutations in PRSS1 have revealed the molecular footprints of gene conversion occurring between the highly homologous human trypsinogen genes.

  • The integration of data gleaned from the functional characterisation of pathogenic PRSS1 missense mutations with information obtained from comparative sequence analysis has provided evidence for stepwise selective pressures acting against prematurely activated trypsin within the human pancreas.

  • Genetic data have also helped to improve our understanding of the evolutionary history of the different human trypsinogen genes.

Keywords: chronic pancreatitis; gene conversion; gene formation; missense mutation; natural selection; trypsinogen gene family; molecular evolution

Figure 1.

Genomic organisation of the human trypsinogen gene family. The divergently evolved T1, T2 and T3 genes (Rowen et al., ) are not shown. T5 and T7 are pseudogenes (Rowen et al., ), whereas T6 is annotated as an expressed pseudogene (Chen et al., ). Official gene symbols of the three functional genes and abundance of their encoded proteins in the human pancreatic juices are also shown. Adapted from Chen and Férec, .

Figure 2.

Amino acid sequences of the three functional human trypsinogen isoforms. Signal peptide is highlighted in blue. The amino acid residues of the activation peptide are highlighted in red and numbered P1, P2, P3, etc., from the scissile bond towards the N terminus (Berger and Schechter, ). The disease‐causing mutations in the cationic trypsinogen gene (PRSS1) that shed light on the stepwise selective pressures acting on trypsinogen gene products against premature activation of trypsin within human pancreas are indicated. The amino acid sequence predicted from T6 is also shown; the presence of His instead of Arg at position 122 (Arg122 is the primary autolysis site of mammalian trypsin(ogens)) being underlined.

Figure 3.

Trypsinogen, a double‐edged sword. (a) Illustration of the physiological role of trypsinogen in digestion. (b) Illustration of the pathogenic role of prematurely activated trypsinogen within the pancreas. Normally, prematurely activated trypsin within the pancreas can be inhibited by the human pancreatic secretory trypsin inhibitor and/or degraded by chymotrypsinogen C and trypsin itself. A defect in one or a combination of these defence mechanisms may trigger the zymogen activation cascade leading to pancreatic autodigestion. Adapted from Chen and Férec, .

Figure 4.

Gene conversion‐like mutations causing chronic pancreatitis in the human cationic trypsinogen gene (PRSS1). (a) The p.Arg122His missense mutation caused by a double nucleotide substitution in exon 3 of PRSS1. (b) The p.Ala16Val, p.Asn29Ile and p.Asn29Thr missense mutations in exon 2 of PRSS1. In (a) and (b), the most likely ‘donor’ sequences for the gene conversion events are shown in shaded colours. (c) The gene conversion event involving the replacement of the entire exon 2 of PRSS1 by that of PRSS2. The two vertical bars delimit the maximal converted tract of the p.Asn29Ile gene conversion‐like event illustrated in (b). Dashes indicate identity with the T4 sequence. Exons are in upper case, introns in lower case.

Figure 5.

Multiple alignment of the partial amino acid sequences of vertebrate trypsinogens around residue 29. Note that Asn (N) and Ile (I) at residue 29 (highlighted in bold) are human cationic‐ and anionic‐trypsinogen specific, respectively.

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References

Baptista AM, Jonson PH, Hough E and Petersen SB (1998) The origin of trypsin: evidence for multiple gene duplications in trypsins. Journal of Molecular Evolution 47(3): 353–362.

Berger A and Schechter I (1970) Mapping the active site of papain with the aid of peptide substrates and inhibitors. Philosophical Transactions of the Royal Society. Series B Biological Sciences 257(813): 249–264.

Casola C, Zekonyte U, Phillips AD, Cooper DN and Hahn MW (2012) Interlocus gene conversion events introduce deleterious mutations into at least 1% of human genes associated with inherited disease. Genome Research 22(3): 429–435.

Chen JM and Férec C (2000a) Wanted: a consensus nomenclature for cationic trypsinogen mutations. Gastroenterology 119(1): 277–278.

Chen JM and Férec C (2000b) Origin and implication of the hereditary pancreatitis‐associated N21I mutation in the cationic trypsinogen gene. Human Genetics 106(1): 125–126.

Chen JM and Férec C (2000c) Gene conversion‐like missense mutations in the human cationic trypsinogen gene and insights into the molecular evolution of the human trypsinogen family. Molecular Genetics and Metabolism 71(3): 463–469.

Chen JM and Férec C (2003) Trypsinogen genes: evolution. In: Cooper DN (ed.) Nature Encyclopedia of the Human Genome, vol. 5, pp. 645–650. London, UK: Nature Publishing Group.

Chen JM and Férec C (2009) Chronic pancreatitis: genetics and pathogenesis. Annual Review of Genomics and Human Genetics 10: 63–87.

Chen JM, Cooper DN, Chuzhanova N, Férec C and Patrinos GP (2007) Gene conversion: mechanisms, evolution and human disease. Nature Reviews Genetics 8(10): 762–775.

Chen JM, Kukor Z, Le Maréchal C et al. (2003a) Evolution of trypsinogen activation peptides. Molecular Biology and Evolution 20(11): 1767–1777.

Chen JM, Le Maréchal C, Lucas D, Raguénès O and Férec C (2003b) ‘Loss of function’ mutations in the cationic trypsinogen gene (PRSS1) may act as a protective factor against pancreatitis. Molecular Genetics and Metabolism 79(1): 67–70.

Chen JM, Montier T and Férec C (2001) Molecular pathology and evolutionary and physiological implications of pancreatitis‐associated cationic trypsinogen mutations. Human Genetics 109: 245–252.

Chen JM, Radisky ES and Férec C (2013) Human trypsins. In: Rawlings ND and Salvesen GS (eds) Handbook of Proteolytic Enzymes, 3rd edn, pp. 2600–2609. Oxford: Academic Press.

Chen JM, Raguénès O, Férec C, Deprez PH and Verellen‐Dumoulin C (2000) A CGC>CAT gene conversion‐like event resulting in the R122H mutation in the cationic trypsinogen gene and its implication in the genotyping of pancreatitis. Journal of Medical Genetics 37(11): E36.

Chimpanzee Sequencing and Analysis Consortium (2005) Initial sequence of the chimpanzee genome and comparison with the human genome. Nature 437(7055): 69–87.

Craik CS, Largman C, Fletcher T et al. (1985) Redesigning trypsin: alteration of substrate specificity. Science 228(4697): 291–297.

Férec C, Raguénès O, Salomon R et al. (1999) Mutations in the cationic trypsinogen gene and evidence for genetic heterogeneity in hereditary pancreatitis. Journal of Medical Genetics 36(3): 228–232.

Fleming MA, Potter JD, Ramirez CJ, Ostrander GK and Ostrander EA (2003) Understanding missense mutations in the BRCA1 gene: an evolutionary approach. Proceedings of the National Academy of Sciences of the USA 100(3): 1151–1156.

Gaboriaud C, Serre L, Guy‐Crotte O et al. (1996) Crystal structure of human trypsin 1: unexpected phosphorylation of Tyr151. Journal of Molecular Biology 259(5): 995–1010.

Gorry MC, Gabbaizedeh D, Furey W et al. (1997) Mutations in the cationic trypsinogen gene are associated with recurrent acute and chronic pancreatitis. Gastroenterology 113(4): 1063–1068.

Joergensen MT, Geisz A, Brusgaard K et al. (2011) Intragenic duplication: a novel mutational mechanism in hereditary pancreatitis. Pancreas 40(4): 540–546.

Kassell B and Kay J (1973) Zymogens of proteolytic enzymes. Science 180(4090): 1022–1027.

Nakanishi J, Yamamoto M, Koyama J, Sato J and Hibino T (2010) Keratinocytes synthesize enteropeptidase and multiple forms of trypsinogen during terminal differentiation. Journal of Investigative Dermatology 130(4): 944–952.

Nemoda Z and Sahin‐Tóth M (2005) The tetra‐aspartate motif in the activation peptide of human cationic trypsinogen is essential for autoactivation control but not for enteropeptidase recognition. Journal of Biological Chemistry 280(33): 29645–29652.

Ng PC and Henikoff S (2001) Predicting deleterious amino acid substitutions. Genome Research 11(5): 863–874.

Nyaruhucha CN, Kito M and Fukuoka SI (1997) Identification and expression of the cDNA‐encoding human mesotrypsin(ogen), an isoform of trypsin with inhibitor resistance. Journal of Biological Chemistry 272(16): 10573–10578.

Petronella N and Drouin G (2012) Strong purifying selection against gene conversions in the trypsin genes of primates. Human Genetics 131(11): 1739–1749.

Pfutzer R, Myers E, Applebaum‐Shapiro S et al. (2002) Novel cationic trypsinogen (PRSS1) N29T and R122C mutations cause autosomal dominant hereditary pancreatitis. Gut 50(2): 271–272.

Rinderknecht H, Renner IG, Abramson SB and Carmack C (1984) Mesotrypsin: a new inhibitor‐resistant protease from a zymogen in human pancreatic tissue and fluid. Gastroenterology 86(4): 681–692.

Roach JC (2002) A clade of trypsins found in cold‐adapted fish. Proteins 47(1): 31–44.

Roach JC, Wang K, Gan L and Hood L (1997) The molecular evolution of the vertebrate trypsinogens. Journal of Molecular Evolution 45(6): 640–652.

Rowen L, Koop BF and Hood L (1996) The complete 685‐kilobase DNA sequence of the human β T cell receptor locus. Science 272(5269): 1755–1762.

Rowen L, Williams E, Glusman G et al. (2005) Interchromosomal segmental duplications explain the unusual structure of PRSS3, the gene for an inhibitor‐resistant trypsinogen. Molecular Biology and Evolution 22(8): 1712–1720.

Sahin‐Toth M (2000) Human cationic trypsinogen. Role of Asn‐21 in zymogen activation and implications in hereditary pancreatitis. Journal of Biological Chemistry 275: 22750–22755.

Sahin‐Toth M and Toth M (2000) Gain‐of‐function mutations associated with hereditary pancreatitis enhance autoactivation of human cationic trypsinogen. Biochemical and Biophysical Research Communications 278: 286–289.

Szmola R, Kukor Z and Sahin‐Tóth M (2003) Human mesotrypsin is a unique digestive protease specialized for the degradation of trypsin inhibitors. Journal of Biological Chemistry 278(49): 48580–48589.

Teich N, Nemoda Z, Kohler H et al. (2005) Gene conversion between functional trypsinogen genes PRSS1 and PRSS2 associated with chronic pancreatitis in a six‐year‐old girl. Human Mutation 25(4): 343–347.

Teich N, Ockenga J, Hoffmeister A et al. (2000) Chronic pancreatitis associated with an activation peptide mutation that facilitates trypsin activation. Gastroenterology 119(2): 461–465.

Wang S, Magoulas C and Hickey D (1999) Concerted evolution within a trypsin gene cluster in Drosophila. Molecular Biology and Evolution 16(9): 1117–1124.

Whitcomb DC, Gorry MC, Preston RA et al. (1996) Hereditary pancreatitis is caused by a mutation in the cationic trypsinogen gene. Nature Genetics 14(2): 141–145.

Wiegand U, Corbach S, Minn A, Kang J and Müller‐Hill B (1993) Cloning of the cDNA encoding human brain trypsinogen and characterization of its product. Gene 136(1‐2): 167–175.

Witt H, Luck W and Becker M (1999) A signal peptide cleavage site mutation in the cationic trypsinogen gene is strongly associated with chronic pancreatitis. Gastroenterology 117(1): 7–10.

Witt H, Sahin‐Tóth M, Landt O et al. (2006) A degradation‐sensitive anionic trypsinogen (PRSS2) variant protects against chronic pancreatitis. Nature Genetics 38(6): 668–673.

Further Reading

Chen JM and Férec C (2013a) Cationic trypsin (Human). In: Rawlings ND and Salvesen GS (eds.) Handbook of Proteolytic Enzymes, 3rd edn, pp. 2609–2614. Oxford: Academic Press.

Chen JM and Férec C (2013b) Anionic trypsin (Human). In: Rawlings ND and Salvesen GS (eds) Handbook of Proteolytic Enzymes, 3rd edn, pp. 2614–2616. Oxford: Academic Press.

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Chen, Jian‐Min, Cooper, David N, and Férec, Claude(Feb 2013) Trypsinogen Genes: Insights into Molecular Evolution from the Study of Pathogenic Mutations. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0006140.pub3]