Characterization of the annexin I gene and evaluation of its role in type 2 diabetes

Integrative network analysis reveals molecular mechanisms of blood pressure regulation

Genome‐wide association studies (GWAS) have identified numerous loci associated with blood pressure (BP). The molecular mechanisms underlying BP regulation, however, remain unclear. We investigated BP‐associated molecular mechanisms by integrating BP GWAS with whole blood mRNA expression profiles in 3,679 individuals, using network approaches. BP transcriptomic signatures at the single‐gene and the coexpression network module levels were identified. Four coexpression modules were identified as potentially causal based on genetic inference because expression‐related SNPs for their corresponding genes demonstrated enrichment for BP GWAS signals. Genes from the four modules were further projected onto predefined molecular interaction networks, revealing key drivers. Gene subnetworks entailing molecular interactions between key drivers and BP‐related genes were uncovered. As proof‐of‐concept, we validated SH2B3, one of the top key drivers, using Sh2b3^−/− mice. We found that a significant number of genes predicted to be regulated by SH2B3 in gene networks are perturbed in Sh2b3^−/− mice, which demonstrate an exaggerated pressor response to angiotensin II infusion. Our findings may help to identify novel targets for the prevention or treatment of hypertension.

Comprehensive characterization of annexin I alterations in esophageal squamous cell carcinoma

PURPOSE

The purpose is to characterize alterations of the annexin I gene, its mRNA, and protein expression in esophageal squamous cell carcinoma.

EXPERIMENTAL DESIGN

Fifty-six cases of esophageal squamous cell carcinoma were analyzed using four microsatellite markers flanking the annexin I gene (9q11-q21) to identify loss of heterozygosity. In addition, we performed (a) single-strand conformation polymorphism and DNA sequencing along the entire promoter sequence and coding region to identify mutations, (b) real-time quantitative reverse transcription-PCR of RNA from frozen esophageal squamous cell carcinoma tissue (n = 37) and in situ hybridization (n = 5) on selected cases to assess mRNA expression, and (c) immunohistochemistry (n = 44) to evaluate protein expression. The prevalence of the allelic variants identified in the first 56 patients was refined in 80 additional esophageal squamous cell carcinoma patients and 232 healthy individuals.

RESULTS

Forty-six of 56 (82%) esophageal squamous cell carcinoma patients showed loss of an allele at one or more of the four microsatellite markers; however, only one (silent) mutation was seen. Two intragenic variants were identified with high frequency of allelic loss (A58G, 64%; L109L, 69%). Thirty of 37 (81%) esophageal squamous cell carcinoma patients showed reduced annexin I mRNA expression, which was confirmed by in situ hybridization, whereas annexin I protein expression was reduced in 79% of poorly differentiated tumor cell foci but in only 5% of well-differentiated tumor foci, although allelic loss on chromosome 9 was found in both tumor grades.

CONCLUSIONS

Allelic loss of annexin I occurs frequently, whereas somatic mutations are rare, suggesting that annexin I is not inactivated in esophageal squamous cell carcinoma via a two-hit mechanism. A decrease in annexin I protein expression was confirmed, consistent with a quantitative decrease in mRNA expression, and appeared to be related to tumor cell differentiation. We conclude that annexin I is not the tumor suppressor gene corresponding to the high levels of loss of heterozygosity observed on chromosome 9 in esophageal squamous cell carcinoma; however, dysregulation of mRNA and protein levels is associated with this tumor type.