Human mouse mast cell protease 7-like tryptase genes are pseudogenes.
BACKGROUND
Alpha-tryptase and beta-tryptase are important clinical markers for mast cell-dependent disorders. A third family of tryptase genes on human chromosome 16 has been identified and called human mouse mast cell protease 7 (hmMCP-7)-like tryptase.


OBJECTIVE
This study was designed to determine whether these tryptase genes are expressed by human mast cells.


METHODS
A 2842-bp hmMCP-7-like tryptase gene was cloned and sequenced from a human placental genomic library. PCR and RT-PCR procedures, respectively, were used to determine whether this tryptase gene family was present in most genomes and whether it was expressed.


RESULTS
The tryptase clone was almost identical to the hmMCP-7-like tryptase II and I genes, and therefore it was called hmMCP-7-like tryptase III. All such genes encode a Gln(-3) like alpha-tryptase. They also terminate translation after amino acid 235, whereas alpha- and beta-tryptase genes each encode a 275-amino acid protein. In this study, cell lines HMC-1, KU812, and Mono-Mac-6; mast cells derived in vitro from cord blood and fetal liver progenitors; and mast cell-enriched preparations of dispersed skin and lung cells contained hmMCP-7-like tryptases in their genomes by PCR with gene-specific primers. To identify whether such genes were transcriptionally active, RT-PCR revealed alpha- or beta-tryptase products in all mast cell preparations and cell lines and in activated skin-derived mast cells, but no hmMCP-7-like tryptase products.


CONCLUSIONS
These results indicate hmMCP-7-like tryptase (I, II, III) genes are pseudogenes and unlikely to affect measurements of alpha- and beta-tryptases.
Min
H K
HK
Department of Internal Medicine, Virginia Commonwealth University, Richmond 23298, USA.
Kambe
N
N
Schwartz
L B
LB
D000818:Animals; D019976:Cloning, Organism; D005784:Gene Amplification; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011544:Pseudogenes / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012697:Serine Endopeptidases / Q000235:genetics*; D053802:Tryptases
C509190:Tpsb2 protein, mouse; D012697:Serine Endopeptidases; C509222:Tpsab1 protein, mouse; D053802:Tryptases