Disease-causing mutations in BEST1 gene are associated with altered sorting of bestrophin-1 protein.

Mutations in BEST1 gene, encoding the bestrophin-1 (Best1) protein are associated with macular dystrophies. Best1 is predominantly expressed in the retinal pigment epithelium (RPE), and is inserted in its basolateral membrane. We investigated the cellular localization in polarized MDCKII cells of disease-associated Best1 mutant proteins to study specific sorting motifs of Best1. Real-time PCR and western blots for endogenous expression of BEST1 in MDCK cells were performed. Best1 mutant constructs were generated using site-directed mutagenesis and transfected in MDCK cells. For protein sorting, confocal microscopy studies, biotinylation assays and statistical methods for quantification of mislocalization were used. Analysis of endogenous expression of BEST1 in MDCK cells revealed the presence of BEST1 transcript but no protein. Confocal microscopy and quantitative analyses indicate that transfected normal human Best1 displays a basolateral localization in MDCK cells, while cell sorting of several Best1 mutants (Y85H, Q96R, L100R, Y227N, Y227E) was altered. In contrast to constitutively active Y227E, constitutively inactive Y227F Best1 mutant localized basolaterally similar to the normal Best1 protein. Our data suggest that at least three basolateral sorting motifs might be implicated in proper Best1 basolateral localization. In addition, non-phosphorylated tyrosine 227 could play a role for basolateral delivery.

Transcriptional regulation of PRPF31 gene expression by MSR1 repeat elements causes incomplete penetrance in retinitis pigmentosa.

PRPF31-associated retinitis pigmentosa presents a fascinating enigma: some mutation carriers are blind, while others are asymptomatic. We identify the major molecular cause of this incomplete penetrance through three cardinal features: (1) there is population variation in the number (3 or 4) of a minisatellite repeat element (MSR1) adjacent to the PRPF31 core promoter; (2) in vitro, 3-copies of the MSR1 element can repress gene transcription by 50 to 115-fold; (3) the higher-expressing 4-copy allele is not observed among symptomatic PRPF31 mutation carriers and correlates with the rate of asymptomatic carriers in different populations. Thus, a linked transcriptional modifier decreases PRPF31 gene expression that leads to haploinsufficiency. This result, taken with other identified risk alleles, allows precise genetic counseling for the first time. We also demonstrate that across the human genome, the presence of MSR1 repeats in the promoters or first introns of genes is associated with greater population variability in gene expression indicating that copy number variation of MSR1s is a generic controller of gene expression and promises to provide new insights into our understanding of gene expression regulation.

A Study into the Evolutionary Divergence of the Core Promoter Elements of PRPF31 and TFPT.

Mutations in PRPF31 have been implicated in retinitis pigmentosa, a blinding disease caused by degeneration of rod photoreceptors. The disease mechanism in the majority of cases is haploinsufficiency. Crucially, attempts at generation of animal models of disease have proved unsuccessful, yielding animals with a visual phenotype that does not mirror human disease. This suggests that, in these animals, the transcriptional regulation of PRPF31 is different to humans and compared to other species. Study of the evolution of the PRPF31 core promoter has important implications for our understanding of human disease, as disease phenotype is modified by differentially expressed alleles in the population. PRPF31 lies in a head-to-head arrangement with TFPT, a gene involved in cellular apoptosis. The two genes were shown to share common regulatory elements in the human genome. In this study, the core promoters of PRPF31 and TFPT were characterised by dual-luciferase reporter assay using genomic DNA from the green monkey, domestic dog and house mouse. It was found that the core promoters were conserved between human and monkey. In dog, the TFPT core promoter was conserved, but different PRPF31 gene architecture meant the gene was controlled by a long-range promoter lying some 2000bp from the transcription start site. There was very low level of conservation (<20%) of the PRPF31 5' region between mouse and human. It was shown that mouse populations did not show variable Prpf31 expression levels, revealing a potential explanation for the lack of phenotype observed in the Prpf31 knock-out mouse model.

Lead compound design for TPR/COX dual inhibition.

The modes of action of TxA2 antagonists and COX-2 inhibitors were studied utilizing flexible ligand docking with postdocking minimization and ab initio interaction energy calculations. The resulting increased understanding of their binding interactions led to the design of a lead compound with chemical moieties that allowed efficient binding to both the thromboxane receptor and the COX-2 enzyme. This compound is derived from allicin, a natural component of garlic, and is a good starting point for the development of anti-inflammatory drugs with fewer side effects or improved cardiovascular drugs.

Elevated B-type natriuretic peptide levels in patients undergoing coronary stenting.

BACKGROUND: Release of B-type natriuretic peptide (BNP) may be triggered by tissue hypoxia even in the absence of left ventricular (LV) dysfunction, generating interest in studying changes in levels following percutaneous coronary intervention (PCI). Though the prognostic role of natriuretic peptides following elective PCI has been documented, most studies only assessed single pre-procedural levels. Previous studies assessing BNP rise following balloon angioplasty or coronary stenting have reported conflicting results; most of these studies excluded patients with recent acute coronary syndrome (ACS). RESULTS: We studied the changes in BNP following coronary stenting in 100 patients across the entire spectrum of ACS and observed a significant rise in BNP following stenting. Baseline BNP levels > 100 pg/ml were observed in 31% of patients; following PCI, 45% of patients were noted to have BNP > 100 pg/ml. In patients with baseline BNP < 100 pg/ml, 20% had post-procedure BNP levels > 100 pg/ml. Post-PCI BNP levels were significantly higher in patients with recent ACS (versus those with stable angina), those with LV dysfunction, high baseline troponin I, visible angiographic thrombus and those with post-PCI TIMI 1-2 flow. Patients with post-PCI BNP levels > 100 pg/ml had a trend toward more frequent occurrence of TIMI no reflow following PCI (9.3 versus 1.7%; p = 0.07). CONCLUSION: Recent ACS, raised basal troponin, LV dysfunction, and presence of angiographic thrombus were all associated with high baseline and post-PCI BNP levels. Though recent ACS was the strongest predictor of elevated BNP levels, BNP levels rose following PCI even in patients with chronic stable angina.