The number of tandem repeats in the carboxyl-ester lipase (CEL) gene as a risk factor in alcoholic and idiopathic chronic pancreatitis.

BACKGROUND/AIMS: The variable number of tandem repeats (VNTR) in the last exon of the carboxyl-ester lipase (CEL) gene has been reported to associate with alcohol-induced chronic pancreatitis (ACP) in a Japanese study. Here, we have investigated the association between the number of CEL VNTR repeats and ACP or idiopathic chronic pancreatitis (ICP) in a cohort of German patients. METHODS: Patients diagnosed with ACP (n = 203) or ICP (n = 64) were genotyped using a screening method consisting of PCR followed by DNA fragment analysis. The allele frequencies of different CEL VNTR lengths were compared to the frequencies in healthy controls (n = 390). RESULTS: We observed no statistical significant associations between CEL VNTR allele frequencies and ACP or ICP. CONCLUSION: This study did not find evidence that supported an association between the common length variations of the CEL VNTR and chronic pancreatitis.

Long-range gene regulation links genomic type 2 diabetes and obesity risk regions to HHEX, SOX4, and IRX3.

Genome-wide association studies identified noncoding SNPs associated with type 2 diabetes and obesity in linkage disequilibrium (LD) blocks encompassing HHEX-IDE and introns of CDKAL1 and FTO [Sladek R, et al. (2007) Nature 445:881-885; Steinthorsdottir V, et al. (2007) Nat. Genet 39:770-775; Frayling TM, et al. (2007) Science 316:889-894]. We show that these LD blocks contain highly conserved noncoding elements and overlap with the genomic regulatory blocks of the transcription factor genes HHEX, SOX4, and IRX3. We report that human highly conserved noncoding elements in LD with the risk SNPs drive expression in endoderm or pancreas in transgenic mice and zebrafish. Both HHEX and SOX4 have recently been implicated in pancreas development and the regulation of insulin secretion, but IRX3 had no prior association with pancreatic function or development. Knockdown of its orthologue in zebrafish, irx3a, increased the number of pancreatic ghrelin-producing epsilon cells and decreased the number of insulin-producing beta-cells and glucagon-producing alpha-cells, thereby suggesting a direct link of pancreatic IRX3 function to both obesity and type 2 diabetes.

Diabetes and pancreatic exocrine dysfunction due to mutations in the carboxyl ester lipase gene-maturity onset diabetes of the young (CEL-MODY): a protein misfolding disease.

CEL-maturity onset diabetes of the young (MODY), diabetes with pancreatic lipomatosis and exocrine dysfunction, is due to dominant frameshift mutations in the acinar cell carboxyl ester lipase gene (CEL). As Cel knock-out mice do not express the phenotype and the mutant protein has an altered and intrinsically disordered tandem repeat domain, we hypothesized that the disease mechanism might involve a negative effect of the mutant protein. In silico analysis showed that the pI of the tandem repeat was markedly increased from pH 3.3 in wild-type (WT) to 11.8 in mutant (MUT) human CEL. By stably overexpressing CEL-WT and CEL-MUT in HEK293 cells, we found similar glycosylation, ubiquitination, constitutive secretion, and quality control of the two proteins. The CEL-MUT protein demonstrated, however, a high propensity to form aggregates found intracellularly and extracellularly. Different physicochemical properties of the intrinsically disordered tandem repeat domains of WT and MUT proteins may contribute to different short and long range interactions with the globular core domain and other macromolecules, including cell membranes. Thus, we propose that CEL-MODY is a protein misfolding disease caused by a negative gain-of-function effect of the mutant proteins in pancreatic tissues.

Nucleosome binding by the bromodomain and PHD finger of the transcriptional cofactor p300.

The PHD finger and the bromodomain are small protein domains that occur in many proteins associated with phenomena related to chromatin. The bromodomain has been shown to bind acetylated lysine residues on histone tails. Lysine acetylation is one of several histone modifications that have been proposed to form the basis for a mechanism for recording epigenetically stable marks in chromatin, known as the histone code. The bromodomain is therefore thought to read a part of the histone code. Since PHD fingers often occur in proteins next to bromodomains, we have tested the hypothesis that the PHD finger can also interact with nucleosomes. Using two different in vitro assays, we found that the bromodomain/PHD finger region of the transcriptional cofactor p300 can bind to nucleosomes that have a high degree of histone acetylation. In a nucleosome retention assay, both domains were required for binding. Replacement of the p300 PHD finger with other PHD fingers resulted in loss of nucleosome binding. In an electrophoretic mobility shift assay, each domain alone showed, however, nucleosome-binding activity. The binding of the isolated PHD finger to nucleosomes was independent of the histone acetylation levels. Our data are consistent with a model where the two domains cooperate in nucleosome binding. In this model, both the bromodomain and the PHD finger contact the nucleosome while simultaneously interacting with each other.