Sequence variants in IL10, ARPC2 and multiple other loci contribute to ulcerative colitis susceptibility

Inflammatory bowel disease (IBD) typically manifests as either ulcerative colitis (UC) or Crohn's disease (CD). Systematic identification of susceptibility genes for IBD has thus far focused mainly on CD, and little is known about the genetic architecture of UC. Here we report a genome-wide association study with 440,794 SNPs genotyped in 1,167 individuals with UC and 777 healthy controls. Twenty of the most significantly associated SNPs were tested for replication in three independent European case-control panels comprising a total of 1,855 individuals with UC and 3,091 controls. Among the four consistently replicated markers, SNP rs3024505 immediately flanking the IL10 (interleukin 10) gene on chromosome 1q32.1 showed the most significant association in the combined verification samples (P = 1.35 x 10(-12); OR = 1.46 (1.31-1.62)). The other markers were located in ARPC2 and in the HLA-BTNL2 region. Association between rs3024505 and CD (1,848 cases, 1,804 controls) was weak (P = 0.013; OR = 1.17 (1.01-1.34)). IL10 is an immunosuppressive cytokine that has long been proposed to influence IBD pathophysiology. Our findings strongly suggest that defective IL10 function is central to the pathogenesis of the UC subtype of IBD.     

Single-copy insertion of transgenes in Caenorhabditis elegans

At present, transgenes in Caenorhabditis elegans are generated by injecting DNA into the germline. The DNA assembles into a semistable extrachromosomal array composed of many copies of injected DNA. These transgenes are typically overexpressed in somatic cells and silenced in the germline. We have developed a method that inserts a single copy of a transgene into a defined site. Mobilization of a Mos1 transposon generates a double-strand break in noncoding DNA. The break is repaired by copying DNA from an extrachromosomal template into the chromosomal site. Homozygous single-copy insertions can be obtained in less than 2 weeks by injecting approximately 20 worms. We have successfully inserted transgenes as long as 9 kb and verified that single copies are inserted at the targeted site. Single-copy transgenes are expressed at endogenous levels and can be expressed in the female and male germlines.     

Identification of ten loci associated with height highlights new biological pathways in human growth

Height is a classic polygenic trait, reflecting the combined influence of multiple as-yet-undiscovered genetic factors. We carried out a meta-analysis of genome-wide association study data of height from 15,821 individuals at 2.2 million SNPs, and followed up the strongest findings in >10,000 subjects. Ten newly identified and two previously reported loci were strongly associated with variation in height (P values from 4 x 10(-7) to 8 x 10(-22)). Together, these 12 loci account for approximately 2% of the population variation in height. Individuals with < or =8 height-increasing alleles and > or =16 height-increasing alleles differ in height by approximately 3.5 cm. The newly identified loci, along with several additional loci with strongly suggestive associations, encompass both strong biological candidates and unexpected genes, and highlight several pathways (let-7 targets, chromatin remodeling proteins and Hedgehog signaling) as important regulators of human stature. These results expand the picture of the biological regulation of human height and of the genetic architecture of this classical complex trait.     

Mutations in different components of FGF signaling in LADD syndrome

Lacrimo-auriculo-dento-digital (LADD) syndrome is characterized by lacrimal duct aplasia, malformed ears and deafness, small teeth and digital anomalies. We identified heterozygous mutations in the tyrosine kinase domains of the genes encoding fibroblast growth factor receptors 2 and 3 (FGFR2, FGFR3) in LADD families, and in one further LADD family, we detected a mutation in the gene encoding fibroblast growth factor 10 (FGF10), a known FGFR ligand. These findings increase the spectrum of anomalies associated with abnormal FGF signaling.     

Germline KRAS mutations cause Noonan syndrome

Noonan syndrome (MIM 163950) is characterized by short stature, facial dysmorphism and cardiac defects. Heterozygous mutations in PTPN11, which encodes SHP-2, cause approximately 50% of cases of Noonan syndrome. The SHP-2 phosphatase relays signals from activated receptor complexes to downstream effectors, including Ras. We discovered de novo germline KRAS mutations that introduce V14I, T58I or D153V amino acid substitutions in five individuals with Noonan syndrome and a P34R alteration in a individual with cardio-facio-cutaneous syndrome (MIM 115150), which has overlapping features with Noonan syndrome. Recombinant V14I and T58I K-Ras proteins show defective intrinsic GTP hydrolysis and impaired responsiveness to GTPase activating proteins, render primary hematopoietic progenitors hypersensitive to growth factors and deregulate signal transduction in a cell lineage-specific manner. These studies establish germline KRAS mutations as a cause of human disease and infer that the constellation of developmental abnormalities seen in Noonan syndrome spectrum is, in large part, due to hyperactive Ras.     

Gain-of-function RAF1 mutations cause Noonan and LEOPARD syndromes with hypertrophic cardiomyopathy

Noonan and LEOPARD syndromes are developmental disorders with overlapping features, including cardiac abnormalities, short stature and facial dysmorphia. Increased RAS signaling owing to PTPN11, SOS1 and KRAS mutations causes approximately 60% of Noonan syndrome cases, and PTPN11 mutations cause 90% of LEOPARD syndrome cases. Here, we report that 18 of 231 individuals with Noonan syndrome without known mutations (corresponding to 3% of all affected individuals) and two of six individuals with LEOPARD syndrome without PTPN11 mutations have missense mutations in RAF1, which encodes a serine-threonine kinase that activates MEK1 and MEK2. Most mutations altered a motif flanking Ser259, a residue critical for autoinhibition of RAF1 through 14-3-3 binding. Of 19 subjects with a RAF1 mutation in two hotspots, 18 (or 95%) showed hypertrophic cardiomyopathy (HCM), compared with the 18% prevalence of HCM among individuals with Noonan syndrome in general. Ectopically expressed RAF1 mutants from the two HCM hotspots had increased kinase activity and enhanced ERK activation, whereas non-HCM-associated mutants were kinase impaired. Our findings further implicate increased RAS signaling in pathological cardiomyocyte hypertrophy.     

Revised rates for the stellar triple-alpha process from measurement of 12C nuclear resonances

In the centres of stars where the temperature is high enough, three alpha-particles (helium nuclei) are able to combine to form 12C because of a resonant reaction leading to a nuclear excited state. (Stars with masses greater than approximately 0.5 times that of the Sun will at some point in their lives have a central temperature high enough for this reaction to proceed.) Although the reaction rate is of critical significance for determining elemental abundances in the Universe, and for determining the size of the iron core of a star just before it goes supernova, it has hitherto been insufficiently determined. Here we report a measurement of the inverse process, where a 12C nucleus decays to three alpha-particles. We find a dominant resonance at an energy of approximately 11 MeV, but do not confirm the presence of a resonance at 9.1 MeV (ref. 3). We show that interference between two resonances has important effects on our measured spectrum. Using these data, we calculate the triple-alpha rate for temperatures from 10(7) K to 10(10) K and find significant deviations from the standard rates. Our rate below approximately 5 x 10(7) K is higher than the previous standard, implying that the critical amounts of carbon that catalysed hydrogen burning in the first stars are produced twice as fast as previously believed. At temperatures above 10(9) K, our rate is much less, which modifies predicted nucleosynthesis in supernovae.     

A contractile nuclear actin network drives chromosome congression in oocytes

Chromosome capture by microtubules is widely accepted as the universal mechanism of spindle assembly in dividing cells. However, the observed length of spindle microtubules and computer simulations of spindle assembly predict that chromosome capture is efficient in small cells, but may fail in cells with large nuclear volumes such as animal oocytes. Here we investigate chromosome congression during the first meiotic division in starfish oocytes. We show that microtubules are not sufficient for capturing chromosomes. Instead, chromosome congression requires actin polymerization. After nuclear envelope breakdown, we observe the formation of a filamentous actin mesh in the nuclear region, and find that contraction of this network delivers chromosomes to the microtubule spindle. We show that this mechanism is essential for preventing chromosome loss and aneuploidy of the egg--a leading cause of pregnancy loss and birth defects in humans.