Novel role for polycystin-1 in modulating cell proliferation through calcium oscillations in kidney cells

Objectives: Polycystin-1 (PC1), a signalling receptor regulating Ca2+-permeable cation channels, is mutated in autosomal dominant polycystic kidney disease, which is typically characterized by increased cell proliferation. However, the precise mechanisms by which PC1 functions on Ca2+ homeostasis, signalling and cell proliferation remain unclear. Here, we investigated the possible role of PC1 as a modulator of non-capacitative Ca2+ entry (NCCE) and Ca2+ oscillations, with downstream effects on cell proliferation. Results and discussion: By employing RNA interference, we show that depletion of endogenous PC1 in HEK293 cells leads to an increase in serum-induced Ca2+ oscillations, triggering nuclear factor of activated T cell activation and leading to cell cycle progression. Consistently, Ca2+ oscillations and cell proliferation are increased in PC1-mutated kidney cystic cell lines, but both abnormal features are reduced in cells that exogenously express PC1. Notably, blockers of the NCCE pathway, but not of the CCE, blunt abnormal oscillation and cell proliferation. Our study therefore provides the first demonstration that PC1 modulates Ca2+ oscillations and a molecular mechanism to explain the association between abnormal Ca2+ homeostasis and cell proliferation in autosomal dominant polycystic kidney disease

Common variants at 12p11, 12q24, 9p21, 9q31.2 and in ZNF365 are associated with breast cancer risk for BRCA1 and/or BRCA2 mutation carriers

Abstract Introduction Several common alleles have been shown to be associated with breast and/or ovarian cancer risk for BRCA1 and BRCA2 mutation carriers. Recent genome-wide association studies of breast cancer have identified eight additional breast cancer susceptibility loci: rs1011970 (9p21, CDKN2A/B), rs10995190 (ZNF365), rs704010 (ZMIZ1), rs2380205 (10p15), rs614367 (11q13), rs1292011 (12q24), rs10771399 (12p11 near PTHLH) and rs865686 (9q31.2). Methods To evaluate whether these single nucleotide polymorphisms (SNPs) are associated with breast cancer risk for BRCA1 and BRCA2 carriers, we genotyped these SNPs in 12,599 BRCA1 and 7,132 BRCA2 mutation carriers and analysed the associations with breast cancer risk within a retrospective likelihood framework. Results Only SNP rs10771399 near PTHLH was associated with breast cancer risk for BRCA1 mutation carriers (per-allele hazard ratio (HR) = 0.87, 95% CI: 0.81 to 0.94, P-trend = 3 × 10-4). The association was restricted to mutations proven or predicted to lead to absence of protein expression (HR = 0.82, 95% CI: 0.74 to 0.90, P-trend = 3.1 × 10-5, P-difference = 0.03). Four SNPs were associated with the risk of breast cancer for BRCA2 mutation carriers: rs10995190, P-trend = 0.015; rs1011970, P-trend = 0.048; rs865686, 2df-P = 0.007; rs1292011 2df-P = 0.03. rs10771399 (PTHLH) was predominantly associated with estrogen receptor (ER)-negative breast cancer for BRCA1 mutation carriers (HR = 0.81, 95% CI: 0.74 to 0.90, P-trend = 4 × 10-5) and there was marginal evidence of association with ER-negative breast cancer for BRCA2 mutation carriers (HR = 0.78, 95% CI: 0.62 to 1.00, P-trend = 0.049). Conclusions The present findings, in combination with previously identified modifiers of risk, will ultimately lead to more accurate risk prediction and an improved understanding of the disease etiology in BRCA1 and BRCA2 mutation carriers

Ionic regulation of endonuclease activity in PC12 cells.

We have investigated the Ca2+ dependency of DNA degradation into nucleosome-sized fragments in intact chromaffin-like PC12 cells and PC12 nuclear fractions. In intact cells we were unable to trigger DNA fragmentation by inducing either transient or sustained elevations of cytoplasmic Ca2+ ([Ca2+]i) with the Ca2+ ionophore ionomycin. On the contrary, DNA fragmentation was induced in intact cells by the intracellular Zn2+ chelator NNN'N'-tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN). To characterize further PC12 cell endonuclease activity, we then investigated digestion by purified PC12 cell fractions of exogenously added plasmids. In nuclear fractions two endonuclease activities were identified: an acidic (pH 5.0) endonuclease activity that was fully Ca2+- and Mg(2+)-independent; and a neutral (pH 7.6) endonuclease activity that was Ca(2+)-independent but Mg(2+)-dependent. Both endonuclease activities were inhibited by Zn2+. Nuclear membrane permeabilization greatly enhanced plasmid digestion at pH 7.6, but not at pH 5.0. This suggests that neutral endonuclease was located in a membrane-bound compartment, whereas acidic endonuclease was freely accessible to the substrate even in the presence of an intact nuclear membrane. In intact nuclei, digestion of genomic DNA could not be triggered by increasing the bivalent cation composition of the medium. On the contrary, in hypotonic medium we observed a large spontaneous nucleolytic DNA degradation that was increased by Zn2+ chelation. However, an acidic pH shift was a potent stimulus for DNA fragmentation in isotonic as well as hypotonic medium

Huntington chorea in the province of Ferrara from 1971 to 1987. Descriptive study

The descriptive study analyzes the temporal trend of the incidence rates of Huntington chorea in the province of Ferrara and indicates the fluctuation of the frequency in time. The estimates of the incidence are similar to those obtained in northern Europe