Sodium absorption by an amiloride-sensitive channel is the main driving force of lung liquid clearance at birth and lung edema clearance in adulthood. In this study, we tested whether tumor necrosis factor-α (TNF-α), a proinflammatory cytokine involved in several lung pathologies, could modulate sodium absorption in cultured alveolar epithelial cells. We found that TNF-α decreased the expression of the α-, β-, and γ-subunits of epithelial sodium channel (ENaC) mRNA to 36, 43, and 16% of the controls after 24-h treatment and reduced to 50% the amount of α-ENaC protein in these cells. There was no impact, however, on α1and β1Na+-K+-ATPase mRNA expression. Amiloride-sensitive current and ouabain-sensitive Rb+uptake were reduced, respectively, to 28 and 39% of the controls. A strong correlation was found at different TNF-α concentrations between the decrease of amiloride-sensitive current and α-ENaC mRNA expression. All these data show that TNF-α, a proinflammatory cytokine present during lung infection, has a profound influence on the capacity of alveolar epithelial cells to transport sodium.

We have reported that TNF, a proinflammatory cytokine present in several lung pathologies, decreases the expression and activity of the epithelial Na+channel (ENaC) by ∼70% in alveolar epithelial cells. Because dexamethasone has been shown to upregulate ENaC mRNA expression and is well known to downregulate proinflammatory genes, we tested if it could alleviate the effect of TNF on ENaC expression and activity. In cotreatment with TNF, we found that dexamethasone reversed the inhibitory effect of TNF and upregulated α, β, and γENaC mRNA expression. When the cells were pretreated for 24 h with TNF before cotreatment, dexamethasone was still able to increase αENaC mRNA expression to 1.8-fold above control values. However, in these conditions, β and γENaC mRNA expression was reduced to 47% and 14%, respectively. The potential role of TNF and dexamethasone on αENaC promoter activity was tested in A549 alveolar epithelial cells. TNF decreased luciferase (Luc) expression by ∼25% in these cells, indicating that the strong diminution of αENaC mRNA must be related to posttranscriptional events. Dexamethasone raised Luc expression by fivefold in the cells and augmented promoter activity by 2.77-fold in cotreatment with TNF. In addition to its effect on αENaC gene expression, dexamethasone was able to maintain amiloride-sensitive current as well as the liquid clearance abilities of TNF-treated cells within the normal range. All these results suggest that dexamethasone alleviates the downregulation of ENaC expression and activity in TNF-treated alveolar epithelial cells.

We confirm the T1D association with rs10774671, but we conclude that it cannot be attributed (solely) to the splicing variant rs10774671. A serine/glycine substitution in OAS1 exon 3 is more likely a functional variant.

Susceptibility to type 1 diabetes (T1D) is a complex trait, involving several loci. One of these putative loci, insulin-dependent diabetes mellitus-8 (IDDM8) at 6q, has been found to be subject to parental effects, suggesting the involvement of an imprinted gene. IGF-II receptor (IGF2R), the best-studied imprinted gene in the IDDM8 region, encodes the IGF-2 receptor, a protein involved in many biological processes, including immune function and beta-cell regeneration. Mice express only the maternal allele. In humans, the molecular IGF2R imprint (maternal-specific methylation) is present, but it affects expression in only a small subset of individuals. To examine whether IGF2R might contribute to the IDDM8 effect, we examined transmission distortion at several single nucleotide polymorphisms (SNPs) in 404 parent-offspring trios. After correcting for multiple testing, significant distortion was found at only one silent SNP on exon 16 (P = 0.002). SNPs upstream and downstream showed weak linkage disequilibrium and no transmission distortion, localizing the association to a 53-kb block within IGF2R. Interestingly, the exon 16 SNP association was limited to maternally inherited alleles. SLC22A2 and SLC22A3, two genes downstream of IGF2R that are imprinted in the mouse, showed no T1D association. Thus, we present evidence that maternal alleles at an IGF2R polymorphism are associated with T1D. It is thus possible that at some tissue or developmental stage not yet examined, IGF2R is universally imprinted.

The transporter 2, ATP-binding cassette, subfamily B (TAP2) is involved in the transport of antigenic peptides to HLA molecules. Coding TAP2 polymorphisms shows a strong association with type 1 diabetes, but it is not clear whether this association may be entirely due to linkage disequilibrium with HLA DR and DQ. Functionally, rat Tap2 nonsynonymous single-nucleotide polymorphisms (nsSNPs) confer differential selectivity for antigenic peptides, but this was not shown to be the case for human TAP2 nsSNPs. In the human, differential peptide selectivity is rather conferred by two splicing isoforms with alternative carboxy terminals. Here, we tested the hypothesis that alleles at the coding SNPs favor different splicing isoforms, thus determining peptide selectivity indirectly. This may be the basis for independent contribution to the type 1 diabetes association. In RNA from heterozygous lymphoblastoid lines, we measured the relative abundance of each SNP haplotype in each isoform. In isoform NM_000544, the G (Ala) allele at 665 Thr>Ala (rs241447) is more than twice as abundant as A (Thr) (GA ‫؍‬ 2.2 ؎ 0.4, P ‫؍‬ 1.5 ؋ 10 ؊4 ), while isoform NM_018833 is derived almost exclusively from chromosomes carrying A (AG ‫؍‬ 18.1 ؎ 5.6, P ‫؍‬ 2.04 ؋ 10 ؊7 ). In 889 Canadian children with type 1 diabetes, differential transmission of parental TAP2 alleles persisted (P ‫؍‬ 0.011) when analysis was confined to chromosomes carrying only DQ*02 alleles, which mark a conserved DR-DQ haplotype, thus eliminating most of the variation at DR-DQ. Thus, we present evidence of TAP2 association with type 1 diabetes that is independent of HLA DR-DQ and describe a plausible functional mechanism based on allele dependence of splicing into isoforms known to have differential peptide selectivities. Diabetes 56: 270 -275, 2007

GH plays an essential role in the growing child by binding to the growth hormone receptor (GHR) on target cells and regulating multiple growth promoting and metabolic effects. Mutations in the GHR gene coding regions result in GH insensitivity (dwarfism) due to a dysfunctional receptor protein. However, children with idiopathic short stature (ISS) show growth impairment without GH or GHR defects. We hypothesized that decreased expression of the GHR gene may be involved. To test this, we investigated whether common genetic variants (microsatellites, SNPs) in regulatory regions of the GHR gene region were associated with the ISS phenotype. Genotyping of a GT‐repeat microsatellite in the GHR 5′UTR in a Montreal ISS cohort (n = 37 ISS, n = 105 controls) revealed that the incidence of the long/short (L/S) genotype was 3.3× higher in ISS children than controls (P = 0.04, OR = 3.85). In an Italian replication cohort (n = 143 ISS, n = 282 controls), the medium/short (M/S) genotype was 1.9× more frequent in the male ISS than controls (P = 0.017, OR = 2.26). In both ISS cohorts, logistic regression analysis of 27 SNPs showed an association of ISS with rs4292454, while haplotype analysis revealed specific risk haplotypes in the 3′ haploblocks. In contrast, there were no differences in GT genotype frequencies in a cohort of short stature (SS) adults versus controls (CARTaGENE: n = 168 SS, n = 207 controls) and the risk haplotype in the SS cohort was located in the most 5′ haploblock. These data suggest that the variants identified are potentially genetic markers specifically associated with the ISS phenotype.

Aims/hypothesis: The association between IL4R and type 1 diabetes has been tested in many studies in recent years, with contradictory results. The aim of this study was to re-evaluate the genetic association in type 1 diabetic nuclear families of mixed European background. Subjects, materials and methods: We genotyped six nonsynonymous single-nucleotide polymorphisms (SNPs) of the IL4R gene in 830 nuclear families as specified above, including a French Canadian subset. Results: No association between type 1 diabetes and any SNP or haplotype was found by the transmission disequilibrium test.

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