Histone H2AX phosphorylation as a molecular pharmacological marker for DNA interstrand crosslink cancer chemotherapy

The aims of this study were to investigate mechanisms of action involved in H2AX phosphorylation by DNA interstrand crosslinking (ICL) agents and determine whether gamma H2AX could be a suitable pharmacological marker for identifying potential ICL cellular chemosensitivity. In normal human fibroblasts, after treatment with nitrogen mustard (HN2) or cisplatin, the peak gamma H2AX response was detected 2-3 h after the peak of DNA ICLs measured using the comet assay, a validated method for detecting ICLs in vitro or in clinical samples. Detection of gamma H2AX foci by immunofluorescence microscopy could be routinely detected with 6-10 times lower concentrations of both drugs compared to detection of ICLs using the comet assay. A major pathway for repairing DNA ICLs is the initial unhooking of the ICL by the ERCC1-XPF endonuclease followed by homologous recombination. HN2 or cisplatin-induced gamma H2AX foci persisted significantly longer in both, ERCC1 or XRCC3 (homologous recombination) defective Chinese hamster cells that are highly sensitive to cell killing by ICL agents compared to wild type or ionising radiation sensitive XRCC5 cells. An advantage of using gamma H2AX immunofluorescence over the comet assay is that it appears to detect ICL chemosensitivity in both ERCC1 and HR defective cells. With HN2 and cisplatin, gamma H2AX foci also persisted in chemosensitive human ovarian cancer cells (A2780) compared to chemoresistant (A2780cisR) cells. These results show that gamma H2AX can act as a highly sensitive and general marker of DNA damage induced by HN2 or cisplatin and shows promise for predicting potential cellular chemosensitivity to ICL agents. (c) 2008 Elsevier Inc. All rights reserved.

Absence of the 7-repeat variant of the DRD4 VNTR is associated with drifting sustained attention in children with ADHD but not in controls

Many genetic studies have demonstrated an association between the 7-repeat (7r) allele of a 48-base pair variable number of tandem repeats (VNTR) in exon 3 of the DRD4 gene and the phenotype of attention deficit hyperactivity disorder (ADHD). Previous studies have shown inconsistent associations between the 7r allele and neurocognitive performance in children with ADHD. We investigated the performance of 128 children with and without ADHD on the Fixed and Random versions of the Sustained Attention to Response Task (SART). We employed timeseries analyses of reaction-time data to allow a fine-grained analysis of reaction time variability, a candidate endophenotype for ADHD. Children were grouped into either the 7r-present group (possessing at least one copy of the 7r allele) or the 7r-absent group. The ADHD group made significantly more commission errors and was significantly more variable in RT in terms of fast moment-to-moment variability than the control group, but no effect of genotype was found on these measures. Children with ADHD without the 7r allele made significantly more omission errors, were significantly more variable in the slow frequency domain and showed less sensitivity to the signal (d') than those children with ADHD the 7r and control children with or without the 7r. These results highlight the utility of time-series analyses of reaction time data for delineating the neuropsychological deficits associated with ADHD and the DRD4 VNTR. Absence of the 7-repeat allele in children with ADHD is associated with a neurocognitive profile of drifting sustained attention that gives rise to variable and inconsistent performance. (c) 2008 Wiley-Liss, Inc.

Equalisation of time variant multipath channels using amplitude banded LMS algorithms

For the purpose of equalisation of rapidly time variant multipath channels, we derive a novel adaptive algorithm, the amplitude banded LMS (ABLMS); which implements a nonlinear adaptation based on a coefficient matrix. Then we develop the: ABLMS algorithm as the adaptation procedure for a linear transversal equaliser (LTE) and a decision feedback equaliser (DFE) where a parallel adaptation scheme is deployed. Computer simulations demonstrate that with a small increase of computational complexity, the ABLMS based parallel equalisers provide a significant improvement related to the conventional LMS DFE and the LMS LTE in the case of a second order Markov communication channel model.

Amplitude banded RLS approach to time variant channel equalization

This paper proposes a non-linear adaptive algorithm, the amplitude banded RLS (ABRLS) algorithm, as an adaptation procedure for time variant channel equalizers. In the ABRLS algorithm, a coefficient matrix is updated based on the amplitude level of the received sequence. To enhance the capability of tracking for the ABRLS algorithm, a parallel adaptation scheme is utilized which involves the structures of decision feedback equalizer (DFE). Computer simulations demonstrate that the novel ABRLS based equalizer provides a significant improvement relative to the conventional RLS DFE on a rapidly time variant communication channel.

Cannabinoid Receptor influences Chromatin Remodelling in Mouse Spermatids by affecting Content of Transition Protein 2 mRNA and Histone Replacement

Marijuana smokers and animals treated with ?9-tetrahydrocannabinol, THC, the principal component of marijuana, show alterations of sperm morphology suggesting a role for cannabinoids in sperm differentiation and/or maturation. Since the cannabinoid receptor 1 (CNR1) activation appears to play a pivotal role in spermiogenesis, the developmental stage where DNA is remodeled, we hypothesized that CNR1 receptors might also influence chromatin quality in sperm. We used Cnr1 null mutant (Cnr1-/-) mice to study the possible role of endocannabinoids on sperm chromatin during spermiogenesis. We demonstrated that CNR1 activation regulated chromatin remodeling of spermatids by either increasing Tnp2 levels or enhancing histone displacement. Comparative analysis of WT, Cnr1+/- and Cnr1-/- animals suggested the possible occurrence of haploinsufficiency for Tnp2 turnover control by CNR1, while histone displacement was disrupted to a lesser extent. Further, flow cytometry analysis demonstrated that the genetic loss of Cnr1 decreased sperm chromatin quality and was associated with sperm DNA fragmentation. This damage increased during epididymal transit, from caput to cauda. Collectively, our results show that the expression/activity of CNR1 controls the physiological alterations of DNA structure during spermiogenic maturation and epididymal transit. Given the deleterious effects of sperm DNA damage on male fertility, we suggest that the reproductive function of marijuana users may also be impaired by deregulation of the endogenous endocannabinoid system.

Butyrylcholinesterase K variant is genetically associated with late onset Alzheimer's disease in Northern Ireland

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that has been associated, sometimes controversially, with polymorphisms in a number of genes. Recently the butyrylcholinesterase K variant (BCHE K) allele has been shown to act in synergy with the apolipoprotein E epsilon4 (APOE epsilon4) allele to promote risk for AD. Most subsequent replicative studies have been unable to confirm these findings. We have conducted a case-control association study using a clinically well defined group of late onset AD patients (n=175) and age and sex matched control subjects (n=187) from the relatively genetically homogeneous Northern Ireland population to test this association. The BCHE genotypes of patients were found to be significantly different from controls (chi(2)=23.68, df=2, p

A GREM1 gene variant associates with diabetic nephropathy

Gremlin, a cell growth and differentiation factor, promotes the development of diabetic nephropathy in animal models, but whether GREM1 gene variants associate with diabetic nephropathy is unknown. We comprehensively screened the 5' upstream region (including the predicted promoter), all exons, intron-exon boundaries, complete untranslated regions, and the 3' region downstream of the GREM1 gene. We identified 31 unique variants, including 24 with a minor allele frequency exceeding 5%, and 9 haplotype-tagging single nucleotide polymorphisms (htSNPs). We selected one additional variant that we predicted to alter transcription factor binding. We genotyped 709 individuals with type 1 diabetes of whom 267 had nephropathy (cases) and 442 had no evidence of kidney disease (controls). Three individual SNPs significantly associated with nephropathy at the 5% level, and two remained significant after adjustment for multiple testing. Subsequently, we genotyped a replicate population comprising 597 cases and 502 controls: this population supported an association with one of the SNPs (rs1129456; P = 0.0003). Combined analysis, adjusted for recruitment center (n = 8), suggested that the T allele conferred greater odds of nephropathy (OR 1.69; 95% CI 1.36 to 2.11). In summary, the GREM1 variant rs1129456 associates with diabetic nephropathy, perhaps explaining some of the genetic susceptibility to this condition.

Genome-wide association identifies a common variant in the reelin gene that increases the risk of schizophrenia only in women

Sex differences in schizophrenia are well known, but their genetic basis has not been identified. We performed a genome-wide association scan for schizophrenia in an Ashkenazi Jewish population using DNA pooling. We found a female-specific association with rs7341475, a SNP in the fourth intron of the reelin ( RELN) gene (p = 2.9 x 10(-5) in women), with a significant gene-sex effect (p = 1.8 x 10(-4)). We studied rs7341475 in four additional populations, totaling 2,274 cases and 4,401 controls. A significant effect was observed only in women, replicating the initial result (p = 2.1 x 10(-3) in women; p = 4.2 x 10(-3) for gene-sex interaction). Based on all populations the estimated relative risk of women carrying the common genotype is 1.58 (p = 8.8 x 10(-7); p = 1.6 x 10(-5) for gene-sex interaction). The female-specific association between RELN and schizophrenia is one of the few examples of a replicated sex-specific genetic association in any disease.

Clonal characteirization of sporadic cribriform-morular variant of papillary thyroid carcinoma by laser microdissection based APC mutation analysis

Cribriform-morular variant (C-MV) of papillary thyroid carcinoma (PTC) is a rare and unusual neoplasm composed of multiple histologic components, including cribriform, papillary, solid, tall columnar, and morular patterns. Analyses of gross C-MV of PTC lesions has linked adenomatous polyposis coli (APC) mutations to its pathogenesis; however, the extent of involvement of mutations in the development Of individual components is unclear We report on bidirectional sequencing of the mutation cluster region (codons 1032-1565) of the APC gene in individually laser-microdissected components of a previously unreported C-MV of PTC. A silent Thr1493Thr gene variant was found in all tumoral components, whereas a 5-base-pair frameshift deletion at codon 1309 was identified only in the morules. Neither variant was observed in matched normal thyroid tissue. These results show the histologic components of C-MV of PTC to have some common mutational background, although additional somatic mutations may be involved in the development of morular structures.

Inhibition of histone deacetylase 2 increases apoptosis and p21(Cip1/WAF1) expression, independent of histone deacetylase 1

Histone deacetylases ( HDACs) 1 and 2 share a high degree of homology and coexist within the same protein complexes. Despite their close association, each possesses unique functions. We show that the upregulation of HDAC2 in colorectal cancer occurred early at the polyp stage, was more robust and occurred more frequently than HDAC1. Similarly, while the expression of HDACs1 and 2 were increased in cervical dysplasia and invasive carcinoma, HDAC2 expression showed a clear demarcation of high-intensity staining at the transition region of dysplasia compared to HDAC1. Upon HDAC2 knockdown, cells displayed an increased number of cellular extensions reminiscent of cell differentiation. There was also an increase in apoptosis, associated with increased p21(Cip1/WAF1) expression that was independent of p53. These results suggest that HDACs, especially HDAC2, are important enzymes involved in the early events of carcinogenesis, making them candidate markers for tumor progression and targets for cancer therapy.