No abstract

Current debate focuses on the relevance of linkage disequilibrium (LD), ethnicity and underlying haplotype structure to the search for genes involved in complex disorders. The recently described association between single nucleotide polymorphisms (SNPs) of the CARD15 (NOD2) gene and Crohn's disease (CD) in populations of north-European descent provides a test case that we have subjected to detailed SNP haplotype based analyses. We examined 23 SNPs spanning 290 kb, including CARD15, in large North-European and Korean samples of patients with Crohn's disease and normal controls. In Europeans we confirmed that the three disease-associated SNPs occur independently but share a common background haplotype. This suggests a common origin and the possibility of an undiscovered more strongly predisposing mutation. Korean CD patients present a phenotype identical to the European patients and have not previously been screened for CARD15. The three disease-associated SNPs were absent and there was no evidence of association between CARD15 and CD. Consequently, the diseaseassociated mutations in the Europeans, which are rare, have arisen recently (after the Asian -European split). Our results highlight important issues relevant to mapping the genes that predispose to complex disorders. First, although ethnically divergent populations may present identical phenotypes they do not necessarily share the same set of predisposing genes. Second, although single-locus tests of association showed consistent association with markers throughout the gene, pair-wise LD between markers (r 2 and D') yielded very little information about actual disease-association. Third, a population comparative approach allowed refining of the marker set through the examination of shared polymorphisms and common LD-groups. This approach, in conjunction with the examination of the mutational steps in a haplotype network, allows unambiguous identification of the potentially causative mutations.

1 TRPM2 is a Ca 2 þ -permeable nonselective cation channel activated by intracellular ADP-ribose (ADPR) and by hydrogen peroxide (H 2 O 2 ). We investigated the modulation of TRPM2 activity by N-(p-amylcinnamoyl)anthranilic acid (ACA). ACA has previously been reported to inhibit phospholipase A 2 (PLA 2 ). 2 Using patch-clamp and calcium-imaging techniques, we show that extracellular application of 20 mM ACA completely blocked ADPR-induced whole-cell currents and H 2 O 2 -induced Ca 2 þ signals (IC 50 ¼ 1.7 mM) in HEK293 cells transfected with human TRPM2. Two other PLA 2 inhibitors, p-bromophenacyl bromide (BPB; 100 mM) and arachidonyl trifluoromethyl ketone (20 mM), had no significant effect on ADPR-stimulated TRPM2 activity. 3 Inhibition of TRPM2 whole-cell currents by ACA was voltage independent and accelerated at decreased pH. ACA was ineffective when applied intracellularly. The single-channel conductance was not changed during ACA treatment, suggesting a reduction of TRPM2 open probability by modulating channel gating. 4 ACA (20 mM) also blocked currents through human TRPM8 and TRPC6 expressed in HEK293 cells, while BPB (100 mM) was ineffective. TRPC6-mediated currents (IC 50 ¼ 2.3 mM) and TRPM8-induced Ca 2 þ signals (IC 50 ¼ 3.9 mM) were blocked in a concentration-dependent manner. 5 ADPR-induced currents in human U937 cells, endogeneously expressing TRPM2 protein, were fully suppressed by 20 mM ACA. 6 Our data indicate that ACA modulates the activity of different TRP channels independent of PLA 2 inhibition. Owing to its high potency and efficacy ACA can serve, in combination with other blockers, as a useful tool for studying the unknown function of TRPM2 in native cells.

By circumventing the malformed middle ear and directly stimulating the cochlea, the VSB provides a new rehabilitation option for atresia patients. We conclude that the procedure is safe and effective and can be implemented in combination with outer ear reconstruction.

Somatic sensation relies on the transduction of physical stimuli into electrical signals by sensory neurons of the dorsal root ganglia. Little is known about how and when during development different types of sensory neurons acquire transduction competence. We directly investigated the emergence of electrical excitability and mechanosensitivity of embryonic and postnatal mouse sensory neurons. We show that sensory neurons acquire mechanotransduction competence coincident with peripheral target innervation. Mechanotransduction competence arises in different sensory lineages in waves, coordinated by distinct developmental mechanisms. Sensory neurons that are mechanoreceptors or proprioceptors acquire mature mechanotransduction indistinguishable from the adult already at E13. This process is independent of neurotrophin-3 and may be driven by a genetic program. In contrast, most nociceptive (pain sensing) sensory neurons acquire mechanosensitive competence as a result of exposure to target-derived nerve growth factor. The highly regulated process of mechanosensory acquisition unveiled here, reveals new strategies to identify molecules required for sensory neuron mechanotransduction.

Hearing and touch are genetically related, and people with excellent hearing are more likely to have a fine sense of touch and vice versa.

Heritable predisposition to inflammatory bowel disease (IBD) has been demonstrated by epidemiological and genetic analysis. Linkage of IBD to broad regions of chromosome 16 has been established by analysis of multiple populations. NOD2, located on proximal 16q, was recently identified as an IBD gene. As the linkage regions on chromosome 16 are large, we have investigated the possibility that NOD2 is not the only IBD gene located on this chromosome. A high-density experiment using 39 microsatellite markers was performed to identify additional regions of association, and to indicate areas of interest for further investigation. A triple-peaked configuration of the linkage curve with peak logarithm of odds (lod) scores of 2.7, 3.2, and 3.1 was observed on proximal 16p, proximal 16q, and central 16q, respectively. The cohort was stratified by coding individuals carrying the NOD2 single nucleotide polymorphism (SNP)8 and SNP13 ''unknown.'' Significance at the central peak, corresponding to the genomic location of NOD2, then decreased from 3.2 to 1.2. The maximal lod scores on the proximal p-arm (lod ‫؍‬ 2.1) and central q-arm (lod ‫؍‬ 2.6) changed only moderately. An exploratory association analysis (TRANSMIT) yielded a strong lead at D16S3068 (P ‫؍‬ 0.00028). The region around this marker was further investigated by using anonymous SNPs. An associated haplotype containing three SNPs was identified (peak significance P ‫؍‬ 0.00027, IBD phenotype). On stratification based on NOD2 genotype, this significance increased to P ‫؍‬ 0.0001. These results confirm the importance of NOD2 and provide evidence for a second IBD gene located on chromosome 16p.

No abstract