Nephronophthisis (NPH) is an autosomal recessive cystic kidney disease that leads to renal failure in childhood or adolescence. Most NPHP gene products form molecular networks. We have identified ANKS6 as a new NPHP family member that connects NEK8 (NPHP9) to INVERSIN (INVS, NPHP2) and NPHP3 to form a distinct NPHP module. ANKS6 localizes to the proximal cilium and knockdown experiments in zebrafish and Xenopus confirmed a role in renal development. Genetic screening identified six families with ANKS6 mutations and NPH, including severe cardiovascular abnormalities, liver fibrosis and situs inversus. The oxygen sensor HIF1AN (FIH) hydroxylates ANKS6 and INVS, while knockdown of Hif1an in Xenopus resembled the loss of other NPHP proteins. HIF1AN altered the composition of the ANKS6/INVS/NPHP3 module. Network analyses, uncovering additional putative NPHP-associated genes, placed ANKS6 at the center of the NPHP module, explaining the overlapping disease manifestation caused by mutations of either ANKS6, NEK8, INVS or NPHP3.

Autosomal recessive polycystic kidney disease (ARPKD), usually considered to be a genetically homogeneous disease caused by mutations in PKHD1, has been associated with ciliary dysfunction. Here, we describe mutations in the DAZ interacting protein 1-like (DZIP1L) gene in patients with ARPKD, findings we have further validated by loss-of-function studies in mice and zebrafish. DZIP1L localizes to centrioles and at the distal end of basal bodies, and interacts with septin2, a protein implicated in maintenance of the periciliary diffusion barrier at the ciliary transition zone. Consistent with a defect in the diffusion barrier, we found that the ciliary membrane translocation of the PKD proteins, polycystin-1 and −2, is compromised in DZIP1L mutant cells. Together, these data provide the first conclusive evidence that ARPKD is not a homogeneous disorder, and establishes DZIP1L as a second gene involved in its pathogenesis.

Key Words: Rac1 Ⅲ ELMO1 Ⅲ DOCK180 Ⅲ vascular morphogenesis Ⅲ zebrafish A ngiogenesis, the formation of blood vessels from preexisting ones, is a crucial process during embryonic development as well as in several pathological conditions such as during tumor growth and in ischemic diseases. 1 Angiogenesis is activated by angiogenic growth factors, such as vascular endothelial growth factor (VEGF), leading to the formation of endothelial sprouts. 1 During the last few years it has been shown that angiogenic sprouts consist of 3 types of functionally different endothelial cell types, namely the tip cells, the stalk cells and the phalanx cells. 2 The tip cells are migratory cells at the leading front of the forming angiogenic sprouts; stalk cells are primarily formed by cell proliferation, and phalanx cells represent a more quiescent endothelium. Endothelial cell proliferation and migration have been intensively studied, and several important major signaling cascades have been identified. Based on the recognition of novel molecules regulating these major pathways 3 it is becoming increasingly important to identify and functional characterize the regulators for blood vessel formation. The small GTPases RhoA, Rac1, and Cdc42 have been shown to regulate migration of endothelial cells during angiogenesis. 4 -8 Rac1 is an essential factor during embryonic development as its endothelial specific deletion leads to an early embryonic vascular lethal phenotype. 7 Rac1 is ubiquitously expressed in 20 hpf zebrafish embryos 9 at the start phase of intersomitic vessel formation. 10 Therefore, a specific temporal and spatial regulation of Rac1 activation in the vascular system implies the existence of additional regulators for Rac1. Several important questions regarding the regulation and function of Rac1 in the embryonic and adult vasculature remain unanswered. Little is known about (1) which intracellular proteins modulate the activation of Rac1; (2) the upstream regulators of Rac1 in vivo are; and (3) the functions of these regulators in the vasculature in vivo are.The ELMO1/DOCK180 (engulfment and cell motility 1/dedicator of cytokinesis 180; also known as DOCK1) complex is an unusual GEF for Rac1 regulating cell migration in Caenorhabditis elegans, Drosophila melanogaster, and glioblastomas. 11,12 ELMO1 contains a pleckstrin homology domain for interaction with DOCK180. 13 DOCK180 uses a conserved "Docker" or "CZH2" domain to mediate the nucleotide exchange on Rac1. 11 Binding of ELMO1 to DOCK180 induces a conformational change releasing the DOCK180 self inhibitory loop. Consequently, the activated ELMO1/DOCK180 complex stabilizes Rac1 in its nucleotide free transition state and regulates its localization. 11 has not yet been reported. The aim of this study was to analyze the function of the ELMO1/DOCK180 complex in vascular development and to identify the upstream regulators of the bipartite GEF ELMO1/ DOCK180 in the vascular system. We report a strong, temporally controlled vascular expression of elmo1 in zebrafis...