Immunological development and cardiovascular function are normal in annexin VI null mutant mice

Annexins are calcium-binding proteins of unknown function but which are imp licated in important cellular processes, including anticoagulation, ion flu x regulation, calcium homeostasis, and endocytosis. To gain insight into th e function of annexin VI, we performed targeted disruption of its gene in m ice. Matings between heterozygous mice produced offspring with a normal Men delian pattern of inheritance, indicating that the loss of annexin VI did n ot interfere with viability in utero. Mice lacking annexin VT reached sexua l maturity at the same age as their normal littermates, and both males and females were fertile. Because of interest in the role of annexin VI in card iovascular function, we examined heart rate and blood pressure in knockout and wild-type mice and found these to be identical in the two groups. Simil arly, the cardiovascular responses of both sets of mice to septic shock wer e indistinguishable. We also examined components of the immune system and f ound no differences in thymic, splenic, or bone marrow lymphocyte levels be tween knockout and wild-type mice, This is the first study of annexin knock out mice, and the lack of a clear phenotype has broad implications for curr ent views of annexin function.