The granzyme B gene is highly polymorphic in wild mice but essentially invariant in common inbred laboratory strains.
Granzyme B is a 247 amino acid pro-apoptotic protease secreted by effector lymphocytes for the purpose of killing virus-infected cells. While the capacity of granzyme B to potently induce caspase-dependent apoptosis has long been recognized, it has only recently been found that human and mouse granzyme B activate overlapping but distinct apoptotic pathways. To investigate a possible evolutionary basis for this observation, we sequenced the exons and flanking intronic sequences of the mouse Gzmb gene from a variety of inbred laboratory strains and wild mice. The sequences of 12/13 inbred strains encoded identical proteins, the exception being DBA/2, whose sequence varied at two amino acids. By contrast with the laboratory strains, there was extensive polymorphism in the Gzmb gene of 54 wild mice and 28 wild-derived inbred mice examined, resulting in 2-18 amino acid differences in the predicted proteins, a discrepancy rate of up to 7.3%. Many of these amino acid variations were found in rat and/or human granzyme B. The granzyme B allotype of inbred laboratory strains could be identified in only one of three geographically dispersed clans of wild mice and was absent from all 28 wild-derived inbred strains. The Gzmb gene of Mus musculus castaneus, a close relative of laboratory mice, encoded six amino acid differences compared with the laboratory strains, all of which were also found in corresponding positions in the granzyme B molecules of wild mice. Unlike the protease, the extended granzyme B recognition and cleavage site in Bid, a key pro-apoptotic substrate, was invariant.
Thia
Kevin Y T
KY
Cancer Immunology Program, Peter MacCallum Cancer Centre, St Andrew's Place, A'Beckett Street, East Melbourne 8006, Australia.
Trapani
Joseph A
JA
D000595:Amino Acid Sequence; D000818:Animals; D014644:Genetic Variation; D053804:Granzymes / Q000235:genetics*; D051379:Mice; D008805:Mice, Inbred A; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008811:Mice, Inbred DBA; D016688:Mice, Inbred NOD; D008814:Mice, Inbred NZB; D008969:Molecular Sequence Data; D018807:Polymorphism, Single-Stranded Conformational
D053804:Granzymes