Characterization of two highly polymorphic human tryptase loci and comparison with a newly discovered monkey tryptase ortholog

Abstract

Tryptases are serine proteases involved in mast cell-mediated inflammatory responses which represent potential targets of drugs against diseases such as asthma, arthritis and inflammatory bowel disease. In order to interpret pharmacodynamic data on the tryptase inhibitors undergoing clinical trials, we defined the genetic variability of the tryptase 1 (TPS1) and tryptase 2 (TPS2) loci by screening a reference population of 32 individuals representing three major ethnic groups (Caucasian, African American, Asian). Using overlapping PCR products, we resequenced the entire tryptase genes with the only exclusion of TPS2 intron 1 and 20 bp of TPS2 5' untranslated region included in exon 1 and we identified 21 novel single nucleotide polymorphisms in TPS1 and 17 single nucleotide polymorphisms plus a large polymorphic deletion in the TPS2 gene. We also compared the type, frequency and distribution of single nucleotide polymorphisms in TPS1 and TPS2 and we observed that the polymorphism frequency within these two loci is unexpectedly high (approximately 1 SNP every 90 bp) and that some of the allele frequencies differ significantly among the three ethnic groups. Based on differences observed in preclinical studies using a cynomolgus monkey (Macaca fascicularis) asthma model system, we investigated the difference between monkey and human tryptase genes in order to better understand the mechanism of action of our tryptase inhibitors.

Effect of sex and haplotype on plasma tryptase levels in healthy adults

“…This technique yielded genotype frequencies that were consistent with the ßß and ßa haplotypes previously predicted (1:2:1 bb/bb:bb/ba:ba/ba) and reported. 8,15,16 The percentage of subjects who were a-tryptasee deficient (26%) was comparable with the 29% (n = 274), 8 20% (n = 60), 7 and 26% (n = 109) 3 values previously reported. Importantly, small but statistically significant effects of tryptase haplotype and sex on the plasma total tryptase level were noted, with the ßa haplotype and female sex giving higher values.…”

“…In fact, approximately 25% of subjects are a-tryptasee deficient. 3,7,8 The effect of haplotype on total tryptase levels has been partially assessed in 109 healthy subjects, and no significant difference was found between the median levels of those with (5.2 ng/mL) and those without (4.7 ng/ mL) an a-tryptase gene. 3 However, the technique used to assess tryptase genes in that study did not distinguish between the haplotypes of subjects with a:ß gene ratios of 2:2 and 1:3, ie, those with 1 or both haplotypes bearing a-tryptase and ß-tryptase genes, potentially obscuring a gene-dosage effect.…”

Current Options in the Treatment of Mast Cell Mediator-Related Symptoms in Mastocytosis

“…Approximately 25% of people are -tryptase-deficient [84][85][86]. Both -tryptase and -tryptase mRNAs are expressed in all types of human mast cells [87,88].…”

Mast Cell Tryptase β as a Target in Allergic Inflammation: An Evolving Story

“…Interestingly, TPSAB1 can harbor either or tryptase alleles ( [13], see below). The tryptase loci are highly polymorphic [14], and allelic variants of each tryptase that encode isoenzymes (e.g. 1a, 1b, 2,…”