Functional characterization of the 5' flanking region of human ubiquitin fusion degradation 1 like gene (UFD1L)

A family- and population-based study of the UFD1L gene for schizophrenia

The present work was undertaken to investigate the association of the UFD1L locus with schizophrenia among 304 Chinese family trios of Han descent. We detected four single nucleotide polymorphisms (SNPs) in the 5'-end region of the UFD1L gene. The transmission disequilibrium test (TDT) revealed allelic associations for rs5746744 (chi(2) = 8.02, P = 0.005) and rs1547931 (chi(2) = 7.18, P = 0.007), but failed to replicate disease association for rs5992403 present in the promoter region, which was initially found in Italian and Canadian samples. The allelic association for rs5746744 and rs1547931 was replicated with independently recruited case-control samples. The 2-SNP haplotype analysis showed an association for the rs5992403-rs5746744 haplotypes (chi(2) = 18.92, df = 3, P = 0.0003), the rs5746744-rs1547931 haplotypes (chi(2) = 11.06, df = 3, P = 0.011) and the rs1547931-rs2238769 haplotypes (chi(2) = 18.88, df = 3, P = 0.0003). The 4-SNP haplotype analysis also showed strong association with illness (chi(2) = 29.54, df = 9, P = 0.0005) but there were more than one individual haplotypes with a low frequency excessively non-transmitted. The four SNPs tested were not located in the same LD block among the Chinese population. This study raises the possibility that a disease-resistant variant may be carried by two or more haplotypes at the UFD1L locus due to frequent recombination during meiosis.

Interaction of DIO2 T92A and PPARgamma2 P12A polymorphisms in the modulation of metabolic syndrome

Type 2 iodothyronine deiodinase (DIO2) converts thyroid prohormone tetraiodothyronine into the biologically active triiodothyronine hormone, which increases insulin sensitivity at the skeletal muscle level. The DIO2 T92A polymorphism modulates deiodinase activity and has been inconsistently associated with insulin resistance. Also, the P121A polymorphism of the peroxisome proliferator-activated receptor (PPAR) gamma2 gene, which encodes a transcription factor involved in insulin signaling, has been inconsistently associated with insulin resistance. This study was aimed at evaluating the combined effect of DIO2 T92A and PPARgamma2 P12A polymorphisms on insulin resistance-related features in 590 non-diabetic whites. A significant gene-gene interaction was observed in the modulation of systolic (p = 0.01) and diastolic (p = 0.02) blood pressure and metabolic syndrome (p = 0.02), with carriers of both DIO2 A92 and PPARgamma2 A12 variants showing the worst phenotype. This latter interaction was also shown by multifactor dimensionality reduction analysis (p = 0.0045). A peroxisome proliferator response element in the DIO2 promoter was identified by in silico analysis and confirmed by in vitro gel shift mobility assay, thus providing a biological plausibility for the observed gene-gene interaction. If confirmed in other populations, comprising several thousand individuals, these data may help identify individuals at risk for insulin resistance-related abnormalities.

A functional variant of the adipocyte glycerol channel aquaporin 7 gene is associated with obesity and related metabolic abnormalities

Aquaporin 7 (AQP7), the gateway protein controlling glycerol release, has recently emerged as a modulator of adipocyte metabolism. AQP7 knockout mice develop obesity and hyperglycemia. The contribution of AQP7 to these abnormalities in humans is unknown. We examined whether common single nucleotide polymorphisms (SNPs) in the AQP7 gene modulate the risk of obesity and related abnormalities. Among several SNPs we identified, A-953G in the AQP7 promoter was associated with type 2 diabetes in 977 (530 female/447 male) Caucasians: odds ratio for XG (i.e., AG+GG) versus AA individuals was 1.36 (95% CI 1.01-1.84), P = 0.04. This finding was entirely due to the association among females (1.8 [1.2-2.6], P = 0.004), which was no longer significant when adjusted for BMI. In fact, BMI was higher in XG than in AA females (30.8 +/- 6.6 vs. 28.9 +/- 5.2, P = 0.002). This association was confirmed in independent case-control study (n = 299 female subjects) for morbid obesity (1.66 [1.01-2.74], P = 0.04). Luciferase and mobility shift assays showed that, compared with -953A, the -953G promoter had reduced transcriptional activity (P = 0.001) and impaired ability to bind CCAAT/enhancer binding protein (C/EBP)beta transcription factor (P = 0.01). Finally, AQP7 expression in adipose tissue decreased from AA to AG to GG individuals (P = 0.036). These data strongly suggest that AQP7 downregulation is pathogenic for obesity and/or type 2 diabetes.

Global changes in STAT target selection and transcription regulation upon interferon treatments

The STAT (signal transducer and activator of transcription) proteins play a crucial role in the regulation of gene expression, but their targets and the manner in which they select them remain largely unknown. Using chromatin immunoprecipitation and DNA microarray analysis (ChIP-chip), we have identified the regions of human chromosome 22 bound by STAT1 and STAT2 in interferon-treated cells. Analysis of the genomic loci proximal to these binding sites introduced new candidate STAT1 and STAT2 target genes, several of which are affiliated with proliferation and apoptosis. The genes on chromosome 22 that exhibited interferon-induced up- or down-regulated expression were determined and correlated with the STAT-binding site information, revealing the potential regulatory effects of STAT1 and STAT2 on their target genes. Importantly, the comparison of STAT1-binding sites upon interferon (IFN)-gamma and IFN-alpha treatments revealed dramatic changes in binding locations between the two treatments. The IFN-alpha induction revealed nonconserved STAT1 occupancy at IFN-gamma-induced sites, as well as novel sites of STAT1 binding not evident in IFN-gamma-treated cells. Many of these correlated with binding by STAT2, but others were STAT2 independent, suggesting that multiple mechanisms direct STAT1 binding to its targets under different activation conditions. Overall, our results reveal a wealth of new information regarding IFN/STAT-binding targets and also fundamental insights into mechanisms of regulation of gene expression in different cell states.