Endothelial tubes assemble from intracellular vacuoles in vivo

The formation of epithelial tubes is crucial for the proper development of many different tissues and organs, and occurs by means of a variety of different mechanisms. Morphogenesis of seamless, properly patterned endothelial tubes is essential for the development of a functional vertebrate circulatory system, but the mechanism of vascular lumenization in vivo remains unclear. Evidence dating back more than 100 years has hinted at an important function for endothelial vacuoles in lumen formation. More than 25 years ago, in some of the first endothelial cell culture experiments in vitro, Folkman and Haudenschild described "longitudinal vacuoles" that "appeared to be extruded and connected from one cell to the next", observations confirmed and extended by later studies in vitro showing that intracellular vacuoles arise from integrin-dependent and cdc42/Rac1-dependent pinocytic events downstream of integrin-extracellular-matrix signalling interactions. Despite compelling data supporting a model for the assembly of endothelial tubes in vitro through the formation and fusion of vacuoles, conclusive evidence in vivo has been lacking, primarily because of difficulties associated with imaging the dynamics of subcellular endothelial vacuoles deep within living animals. Here we use high-resolution time-lapse two-photon imaging of transgenic zebrafish to examine how endothelial tubes assemble in vivo, comparing our results with time-lapse imaging of human endothelial-cell tube formation in three-dimensional collagen matrices in vitro. Our results provide strong support for a model in which the formation and intracellular and intercellular fusion of endothelial vacuoles drives vascular lumen formation.     

Meta-analysis identifies 29 additional ulcerative colitis risk loci, increasing the number of confirmed associations to 47

Genome-wide association studies and candidate gene studies in ulcerative colitis have identified 18 susceptibility loci. We conducted a meta-analysis of six ulcerative colitis genome-wide association study datasets, comprising 6,687 cases and 19,718 controls, and followed up the top association signals in 9,628 cases and 12,917 controls. We identified 29 additional risk loci (P < 5 × 10(-8)), increasing the number of ulcerative colitis-associated loci to 47. After annotating associated regions using GRAIL, expression quantitative trait loci data and correlations with non-synonymous SNPs, we identified many candidate genes that provide potentially important insights into disease pathogenesis, including IL1R2, IL8RA-IL8RB, IL7R, IL12B, DAP, PRDM1, JAK2, IRF5, GNA12 and LSP1. The total number of confirmed inflammatory bowel disease risk loci is now 99, including a minimum of 28 shared association signals between Crohn's disease and ulcerative colitis.     

Genome-wide meta-analysis increases to 71 the number of confirmed Crohn's disease susceptibility loci

We undertook a meta-analysis of six Crohn's disease genome-wide association studies (GWAS) comprising 6,333 affected individuals (cases) and 15,056 controls and followed up the top association signals in 15,694 cases, 14,026 controls and 414 parent-offspring trios. We identified 30 new susceptibility loci meeting genome-wide significance (P < 5 × 10??). A series of in silico analyses highlighted particular genes within these loci and, together with manual curation, implicated functionally interesting candidate genes including SMAD3, ERAP2, IL10, IL2RA, TYK2, FUT2, DNMT3A, DENND1B, BACH2 and TAGAP. Combined with previously confirmed loci, these results identify 71 distinct loci with genome-wide significant evidence for association with Crohn's disease.     

Ethanol impairs Rho GTPase signaling and differentiation of cerebellar granule neurons in a rodent model of fetal alcohol syndrome

Developmental exposure to ethanol impairs fetal brain development and causes fetal alcohol syndrome. Although the cerebellum is one of the most alcohol-sensitive brain areas, signaling mechanisms underlying the deleterious effects of ethanol on developing cerebellar granule neurons (CGNs) are largely unknown. Here we describe the effects of in vivo ethanol exposure on neurite formation in CGNs and on the activation of Rho GTPases (RhoA and Rac1), regulators of neurite formation. Exposure of 7-day-old rat pups to ethanol for 3 h moderately increased blood alcohol concentration (BAC) (∼40 mM) and inhibited neurite formation and Rac1 activation in CGNs. Longer exposure to ethanol for 5 h resulted in higher BAC (∼80 mM), induced apoptosis, inhibited Rac1, and activated RhoA. Studies demonstrated a regulatory role of Rho GTPases in differentiation of cerebellar neurons, and indicated that ethanol-associated impairment of Rho GTPase signaling might contribute to brain defects observed in fetal alcohol syndrome. Received 16 July 2006; received after revision 12 September 2006; accepted 13 October 2006     

Cyclin A1 is a p53-induced gene that mediates apoptosis, G2/ M arrest, and mitotic catastrophe in renal, ovarian, and lung carcinoma cells

We were the first to identify cyclin A1 as a p53-induced gene by cDNA expression profiling of p53-sensitive and -resistant tumor cells [Maxwell S. A. and Davis G. E. (2000) Proc. Natl. Acad. Sci. USA 97, 13009–13014]. We show here that cyclin A1 can induce G2 cell cycle arrest, polyploidy, apoptosis, and mitotic catastrophe in H1299 non-small cell lung, TOV-21G ovarian, or 786-0 renal carcinoma cells. More cdk1 protein and kinase activities were observed in cyclin A1-induced cells than in GFP control-induced cells. Thus, cyclin A1 might mediate apoptosis and mitotic catastrophe through an unscheduled or inappropriate activation of cdk1. Two primary renal cell carcinomas expressing mutated p53 exhibited reduced or absent expression of cyclin A1 relative to the corresponding normal tissue. Moreover, renal carcinoma-derived mutant p53s were deficient in inducing cyclin A1 expression in p53-null cells. Cyclin A1 but not cyclin A2 was upregulated in etoposide-treated tumor cells undergoing p53-dependent apoptosis and mitotic catastrophe. Forced upregulation of cyclin A2 did not induce apoptosis. The data implicate cyclin A1 as a downstream player in p53-dependent apoptosis and G2 arrest. Received 1 November 2005; received after revision 17 February 2006; accepted 13 April 2006     

A frameshift mutation in NOD2 associated with susceptibility to Crohn's disease

Crohn's disease is a chronic inflammatory disorder of the gastrointestinal tract, which is thought to result from the effect of environmental factors in a genetically predisposed host. A gene location in the pericentromeric region of chromosome 16, IBD1, that contributes to susceptibility to Crohn's disease has been established through multiple linkage studies, but the specific gene(s) has not been identified. NOD2, a gene that encodes a protein with homology to plant disease resistance gene products is located in the peak region of linkage on chromosome 16 (ref. 7). Here we show, by using the transmission disequilibium test and case-control analysis, that a frameshift mutation caused by a cytosine insertion, 3020insC, which is expected to encode a truncated NOD2 protein, is associated with Crohn's disease. Wild-type NOD2 activates nuclear factor NF-kappaB, making it responsive to bacterial lipopolysaccharides; however, this induction was deficient in mutant NOD2. These results implicate NOD2 in susceptibility to Crohn's disease, and suggest a link between an innate immune response to bacterial components and development of disease.