Identification of a Hereditary Pancreatitis Mutation in Four West Virginia Families

Abstract

Hereditary pancreatitis (HP) is the second most common cause of chronic childhood pancreatitis in the United States. Mutations in the cationic trypsinogen gene on chromosome 7 are known to cause HP. We identified four families in West Virginia with symptoms consistent with HP. To determine whether members of these families had defects in the trypsinogen gene, we tested for linkage between the HP gene and simple tandem repeat markers on chromosome 7q and screened for a specific mutation in the cationic trypsinogen gene. Two-point linkage analysis indicated that the disease gene is closely linked to three 7q markers (D7S661, D7S2511, and D7S1805). Restriction fragment length polymorphism analysis showed that all clinically affected members and nonpenetrant carriers from the four families carried a G to A mutation in the third exon of the trypsinogen gene. These findings indicate that this mutation is the cause of HP in the families in our study. The observation that most individuals who carry the mutation have symptoms of HP is consistent with the high but incomplete penetrance of the trait. The presence of a single mutation and a common linked haplotype indicates that the defective allele arose in an ancestor common to all four families.

Molecular basis of hereditary pancreatitis

“…Since a single G > A nucleotide change creates a novel Alf III site (A ᭢ CRYGT), the amplification of exon 3 followed by Alf III digestion 7 has been widely adopted to screen for the R122H mutation. [16][17][18][19]21 Obviously, if R122H mutation arose as a result of a gene conversion event, it would not be detected by this simple method.…”

“…7,[16][17][18][19][20][21][22][23][24][25][26] Whilst no one doubts its disease-causing role in HP, some 27 do argue that 'self-destruct' mechanism proposed for R122H 7 has not yet been proven. In our opinion, however, this may be due to inadequate evaluation rather than a lack of good supporting data and, accordingly, we wish to highlight several issues.…”

“…Transgenic models are attractive but certainly will be confounded by the existence of multiple functional trypsinogen genes and different protective mechanisms against trypsinogen activation in mice. The R122H mutation, in most cases, 7,[16][17][18][19][20][21][22][23][24][25][26] resulted from a single G > A (CGC > CAC) transition, which most probably occurred as a spontaneous deamination of 5-methylcytosine to give thymine in the CpG dinucleotides on the opposite strand. Interestingly, we identified a GC > AT (CGC > CAT) 2 bp nucleotide substitution, which also resulted in a R122H mutation but clearly arose via a different genetic mechanism -gene conversion.…”

Mutations of the Cationic Trypsinogen Gene in Hereditary and Non-Hereditary Pancreatitis

“…A single A–T transversion mutation (N29I) in exon 2 results in an asparagine to isoleucine substitution. These mutations have since been identified in HP families from France [11], Germany [12, 13], the UK [14, 15], the USA [16, 17]and Japan [18]. …”

Molecular pathology and evolutionary and physiological implications of pancreatitis-associated cationic trypsinogen mutations

“…80% (Bell et al 1998;Creighton et al 2000;Dasouki et al 1998;Elitsur et al 1998;Ferec et al 1999;Gress et al 1998;Howes et al 2001;Nishimori et al 1999;Teich et al 1999;Pandya et al 1997Pandya et al -1998Truninger et al 2001;Weber et al 1999;Whitcomb et al 1996). Several lines of good evidence, particularly that the R122 residue was identified to be the primary autolysis site of human cationic trypsin (Gaboriaud et al 1996), and that histidine is not cleaved by trypsin, lend strong support to the theory that the R122H mutation would disrupt an important "fail-safe" or "self-destruct" defensive mechanism against premature trypsin activation within the pancreas, which could lead to autodigestion of the pancreas itself (Whitcomb et al 1996).…”