The Gja4 gene encodes an intercellular channel forming protein, also known as Connexin 37, that is a component of gap junctions. These mice carry a knock out mutation of the Gja4 gene in which a PGK-NEO cassette replaces almost the entire coding region. Homozygous females are viable but infertile due to absence of ovulation (oocyte and ovarian follicle development arrest). Homozygous males and heterozygous females are viable and fertile. No gene product (mRNA or protein) is detected by RT-PCR of heart tissue from homozygous E11.5 embryos, immunohistochemical analysis of oocytes, aorta tissue, kidney, and platelets, and by Western blot analysis of aortic endothelial lysates, from homozygotes. Homozygous animals have increased numbers of collateral blood vessels and recover more quickly from experimental hindlimb ischemic injury, and exhibit enhanced ischemia-induced collateral remodeling and angiogenesis, compared to wildtype controls. In addition, arteriolar conducted vasoconstriction in the cremaster muscle is reduced. Bleeding time is reduced in homozygotes, with more rapid thrombus formation and increased platelet aggregation. Homozygous embryos exhibit enlarged jugular lymph sacs (at E13.5), and have fewer numbers of lymphatic valves at later stages. Adult homozygotes have a deficiency in lymphatic valves, including thoracic duct valves, and exhibit lymphatic dysfunction (as measured by Evans Blue dye assay). Venous valves are absent in peripheral veins of homozygous mice. During backcrossing, the Y chromosome may not have been fixed to the C57BL/6 genetic background. Male mice that are homozygous for the targeted mutation are viable and fertile.