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Cerebral cavernous malformations (CCMs) are human vascular malformations caused by mutations in three genes of unknown function, KRIT1, CCM2 and PDCD10. Here we show that the HEG1 receptor, linked to CCM genes in zebrafish, is selectively expressed in endothelial cells and that Heg1-/- mice exhibit defective integrity of the heart, blood vessels and lymphatic vessels. In contrast, Heg1-/-;Ccm2+/lacZ and Ccm2lacZ/lacZ mice die early in development due to a failure of nascent endothelial cells to associate into patent vessels, a phenotype shared by deficient zebrafish embryos and reproduced by deficient endothelial cells ex vivo. These cardiovascular defects are associated with abnormal endothelial junctions like those observed in human CCMs, and biochemical and cellular imaging studies identify a cell autonomous pathway in which HEG1 receptors couple to KRIT1 at cell junctions. These studies identify HEG1-CCM signaling as a critical regulator of cardiovascular organ formation and integrity.

The migration patterns of naive and activated T cells are associated with the expression of distinct sets of chemokine receptors, but the molecular basis for this regulation is unknown. Here we identify Krupple-like factor 2 (KLF2) as a key transcriptional factor needed to prevent naive T cells from expressing inflammatory chemokine receptors and acquiring the migration patterns of activated T cells. Lineage-specific deletion of KLF2 resulted in fewer naive T cells in the blood and secondary lymphoid organs, whereas it expanded naive T cell numbers in nonlymphoid tissues; these effects were associated with altered expression of inflammatory chemokine receptors on naive T cells. KLF2 repressed the expression of several chemokine receptors, including CCR3 and CCR5. We thus conclude that KLF2 maintains proper T cell migration patterns by linking T cell movement and transcriptional regulation of chemokine receptor expression patterns.

Cerebral cavernous malformation is a common human vascular disease that arises due to loss-of-function mutations in genes encoding

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