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C M Lewis

Publications and source records attributed to C M Lewis.

At least 37 records · Page 2Linked to original sources

Mutation of Tec family kinases alters T helper cell differentiation.

The Tec kinases Rlk and Itk are critical for full T cell receptor (TCR)-induced activation of phospholipase C-gamma and mitogen-activated protein kinase. We show here that the mutation of Rlk and Itk impaired activation of the transcription factors NFAT and AP-1 and production of both T helper type 1 (TH1) and TH2 cytokines. Consistent with these biochemical defects, Itk-/- mice did not generate effective TH2 responses when challenged with Schistosoma mansoni eggs. Paradoxically, the more severely impaired Rlk-/-Itk-/- mice were able to mount a TH2 response and produced TH2 cytokines in response to this challenge. In addition, Rlk-/-Itk-/- cells showed impaired TCR-induced repression of the TH2-inducing transcription factor GATA-3, suggesting a potential mechanism for TH2 development in these hyporesponsive cells. Thus, mutations that affect Tec kinases lead to complex alterations in CD4+ TH cell differentiation.

Animals↗

Biochemical and genetic analyses of the Tec kinases Itk and Rlk/Txk.

The Tec kinases have been implicated as important components of signalling pathways downstream of lymphocyte antigen receptors. Activation of these kinases requires two steps: (i) phosphorylation by Src family kinases and (ii) plasma membrane localization, which is mediated by interaction between the pleckstrin homology (PH) domains of Tec kinases and the products of phosphoinositide-3 kinase (PI-3K). Itk and Rlk/Txk are Tec kinases expressed in T-lymphocytes. Despite similarity to other Tec kinases, Rlk/Txk lacks a PH domain and instead possesses a palmitoylated cysteine-string motif. We have found that both Rlk/Txk and Itk are phosphorylated in response to T-cell receptor stimulation and can be activated by phosphorylation by Src family kinases. However, consistent with its lack of PH domain, Rlk/Txk is phosphorylated independent of PI-3K activity. Furthermore, we demonstrated that like Itk, Rlk/Txk is associated with lipid RAFTs (detergent-insoluble, cholesterol-rich regions of the membrane), but unlike Itk, Rlk/Txk's RAFT association is independent of PI-3K activity. Despite these differences, Rlk/Txk partially compensates for loss of Itk in gene-targeted animals, suggesting overlapping functions for these kinases.

Animals↗

Familial clustering of polymorphic light eruption in relatives of patients with lupus erythematosus: evidence of a shared pathogenesis.

BACKGROUND: Abnormal photosensitivity is a common feature of many forms of lupus erythematosus (LE). OBJECTIVES: To examine the role of polymorphic light eruption (PLE) as a possible predisposing factor for cutaneous forms of LE. METHODS: Eighty-five patients with well-characterized subacute cutaneous LE (SCLE) and discoid LE (DLE) were recruited from outpatient clinics, and the prevalence of PLE determined by detailed interview and clinical examination. RESULTS: Symptoms consistent with PLE were reported in 61% and 55% of SCLE and DLE patients, respectively; this was significantly higher than the overall population prevalence of 13.6% (P < 0.001), giving a relative risk (RR) for PLE in SCLE patients of 3.37 (95% confidence interval, CI 2.46--4.28) and DLE patients of 3.11 (95% CI 2.31--3.91). PLE developed before the onset of LE in 61% of cases (median interval 12 years, range 1--40), concomitantly in 24%, and subsequently in a further 15% (median interval 3.5 years, range 1--25). To delineate the relationship between PLE and LE further, the prevalence of PLE was determined in 103 otherwise unaffected first-degree relatives of SCLE and DLE probands; we had previously demonstrated clustering of PLE in families, reflecting a strong genetic component. We found a significantly higher PLE prevalence in relatives of the LE probands than in the general population (P < 0.001), giving an RR for PLE of 2.29 (95% CI 1.55--3.03) and 2.61 (95% CI 1.32--3.89) for female and male relatives, respectively. CONCLUSIONS: The high prevalence of PLE in LE patients, together with clustering of PLE among first-degree relatives of SCLE and DLE probands, suggests that there may be a shared pathogenetic basis for PLE and cutaneous LE. We propose that predisposition to PLE may contribute to the LE phenotype in otherwise susceptible individuals.

Confidence Intervals↗

A candidate gene analysis of three related photosensitivity disorders: cutaneous lupus erythematosus, polymorphic light eruption and actinic prurigo.

BACKGROUND: Polymorphic light eruption (PLE) is a common inherited photosensitivity disorder, which may predispose to several related but distinct conditions, including subacute cutaneous lupus erythematosus (SCLE), discoid lupus erythematosus (DLE) and actinic prurigo (AP). OBJECTIVES: To examine specific candidate genes for shared susceptibility alleles between these related phenotypes. METHODS: Eighty-five caucasian patients with annular SCLE or DLE were recruited, in addition to 102 first-degree relatives. The prevalence of PLE in both the patient and relative groups was determined by detailed interview and clinical examination. Eighty-five patients with pure PLE and 59 patients with AP were also recruited. Candidate genes were analysed by typing of single nucleotide polymorphisms of IL10 (-1082 G/A and -819 C/T), FCGR2A (131 R/H), SELE (128 S/R), ICAM1 (241 G/R and 469 E/K), IL1A (+ 4845 G/T), IL1B (-511 C/T and + 3954 C/T), IL1RN (+ 2018 T/C) and TNF (-308 G/A) using polymerase chain reaction (PCR) with sequence-specific primers and 5'-nuclease PCR. RESULTS: A significant association was found between SCLE and the rare TNF -308 A allele when compared with patients with DLE (P = 0.043), PLE (P = 0.001), AP (P < 0.001) and healthy controls (P < 0.001). However, there was strong linkage disequilibrium between TNF -308 A and the HLA A*01, B*08, DRB1*0301 haplotype. A negative association was also found between SCLE and the IL1B + 3954 T allele (P = 0.039), but the significance was lost on correction for multiple testing. CONCLUSIONS: We have demonstrated the association of SCLE with the rare TNF -308 A allele, which may be pathogenic or, alternatively, a marker allele for the extended HLA A*01, B*08, DRB1*0301 haplotype that is associated with a number of autoimmune conditions. Although many of the other loci that we chose failed to demonstrate an association, a candidate gene approach remains the most logical one, and the most likely to yield positive results in the future.

Alleles↗

Controlling misdiagnosis errors in preimplantation genetic diagnosis: a comprehensive model encompassing extrinsic and intrinsic sources of error.

We have developed a mathematical model to explore accuracy of preimplantation genetic diagnosis (PGD) using single cell polymerase chain reaction (PCR). The model encompasses both extrinsic technical errors and intrinsic errors related to nuclear and chromosomal abnormalities. Using estimates for these errors, we have calculated the probability of a serious error (affected embryo diagnosed as unaffected) using a variety of strategies designed to increase the accuracy of PGD. Additional information from genotyping a linked marker or a second biopsied cell reduces the probability of replacing an affected embryo, while ensuring that sufficient unaffected embryos can be replaced. For a recessive disease, two genotypes are required to ensure a low probability of replacing an affected embryo (<1%) with a high proportion of unaffected embryos eligible for replacement (68%). These genotypes may be from a single cell with linked marker, or disease genotypes from two cells. PGD of a dominant disease is more difficult, as it relies on the amplification of a single copy of the mutation. Genotypes from two biopsied cells are required to ensure that a high proportion of unaffected embryos are eligible for replacement. This model can be used as a clinical tool to prioritize embryos for transfer in a PGD cycle.

Bayes Theorem↗

Outcome in patients with end-stage renal disease following heart or heart--lung transplantation receiving peritoneal dialysis.

BACKGROUND: End-stage renal disease (ESRD) complicates 5--10% of heart and heart--lung transplant patients. We report our experience of peritoneal dialysis (PD) in 17 such patients. METHODS: Between March 1995 and February 1999, 13 heart transplant and four heart--lung transplant patients (11 male, 6 female) joined our PD programme (10 continuous ambulatory PD, seven automated PD). Median time from heart or heart--lung transplantation to ESRD was 9 years (range 1--13 years), and median age at introduction of renal replacement therapy was 51 years (range 23--66 years). The frequency of exit-site infections, peritonitis, and PD survival (including technique failure and death) in the transplant group (TxP) was calculated retrospectively. These were compared with two contemporary control groups: PD patients immunosuppressed for other indications (ISP, n=19) and, all other patients recruited onto the PD programme (NISP, n=132). RESULTS: Median follow-up was 10 months (range 2--27 months) for TxP, 7 months (range 2--29 months) for ISP, and 14 months (range 1--48 months) for NISP groups. The frequency of exit-site infections was similar in each group: 1 in 26 months for TxP; 1 in 30 months for ISP, and 1 in 27 months for NISP (P=NS). The frequency of peritonitis was greater in the TxP group at 1 in 15 months, compared with 1 in 20 months for ISP and 1 in 29 months for NISP (TxP vs NISP, P<0.05). PD failure following infection was 23.5% for TxP, 10.5% for ISP, and 12.9% for NISP. Actuarial PD survival at 24 months was only 25.2% in the TxP group compared with 79% in the NISP group. There were no deaths related to immediate complications of PD. CONCLUSIONS: Increased risk of PD peritonitis and reduced PD survival is reported in this cohort of 17 heart and heart--lung recipients with ESRD. Nevertheless, for patients with severely impaired cardiac function, PD may still offer therapeutic advantage.

Adolescent↗

Polymorphic light eruption and the HLA DRB1*0301 extended haplotype are independent risk factors for cutaneous lupus erythematosus.

Recent evidence suggests that polymorphic light eruption (PLE) is an inherited photosensitivity disorder which may predispose to cutaneous lupus erythematosus (LE). In this study we examine the relative risk (RR) attributable to the presence of PLE, together with the effect of the major histocompatibility complex (MHC) in the development of cutaneous LE. Eighty-five Caucasian patients with annular subacute cutaneous LE (SCLE) and discoid LE (DLE) were recruited, together with 102 first degree relatives and 200 healthy local Caucasian controls. Symptoms suggestive of PLE were elicited in patients and relatives, and human leukocyte antigen (HLA) typing determined by PCR-SSP. Standard association analysis and family transmission disequilibrium testing (TDT) were then used to compare the HLA frequencies between groups. We found a significant (P < 0.05) association of the HL4 A*01, B*08, DRB1*0301 extended haplotype with both SCLE and DLE and also significant association of DLE with the HLA A*03, B*07, DRB1*15 haplotype, with a possible protective effect in SCLE for HLA B*44 and DRB1*04 (P=0.002 and 0.001 respectively). Association was observed between PLE and cutaneous LE (P < 0.001), but not between PLE and any HLA allele. From these figures we estimate, for the general population, that the RR of developing SCLE given the presence of (a) PLE, (b) DRB1*0301 and (c) both PLE and DRB1*0301 is 3.37, 5.45 and 12.03, respectively. For DLE, equivalent RRs are 3.11, 2.15 and 6.94. In conclusion, these data imply the involvement of both PLE and HLA DRB1*0301 in the development of SCLE and DLE. They form a basis for examining the genetic architecture of photosensitivity, some aspects of which may be common to both cutaneous LE and PLE.

Alleles↗

Multipoint linkage analysis of a candidate gene locus in rheumatoid arthritis demonstrates significant evidence of linkage and association with the corticotropin-releasing hormone genomic region.

OBJECTIVE: Rheumatoid arthritis (RA) is the most common disabling autoimmune disease, affecting approximately 1% of the population. The disease etiology is unknown, but it involves inflammation and immune dysregulation and is influenced by genetic variation at both HLA and other, as-yet-unidentified genetic loci. Corticotropin-releasing hormone (CRH; or corticotropin-releasing factor), a primary regulator of the hypothalamic-pituitary-adrenal axis and a key element in the response to stress and inflammation, is a strong candidate gene for RA. We examined the role of DNA variation across the region containing this gene in multicase families with RA. METHODS: We genotyped fluorescently labeled simple tandem repeat genetic markers from chromosome 8q13 in 295 families with multiple cases of RA. Singlepoint and multipoint nonparametric linkage analysis and association analysis using transmission disequilibrium testing (TDT) were also used. RESULTS: Single-point linkage analysis using a microsatellite within 30 kb of the CRH locus (CRH.PCR at position 8q13) showed a significant excess of allele sharing in 295 United Kingdom RA families with at least 2 affected members (MapMaker/Sibs logarithm of odds [LOD] 1.4; P = 5.5x10(-3); mean identity by descent [ibd] sharing 55.9%). To provide a more detailed linkage map, a multipoint analysis was conducted with an additional 7 dinucleotide microsatellite markers (average heterozygosity 0.75) flanking the CRH locus. Significant linkage was detected over a 22-cM region between D8S285 and D8S530, with the maximum singlepoint LOD score of 1.77 at D8S1723 (MapMaker/Sibs P = 2.2x10(-3); mean ibd sharing 59.3%). Multipoint analysis showed strongest evidence for linkage at the same marker (multipoint LOD 1.78, P = 2.1x10(-3), mean ibd sharing 55.8%). TDT analysis showed significant association at the CRH locus (P = 2.6x10(-3)). CRH has a sibling relative risk of 1.14, and contributes <10% to the sibling relative risk of RA. CONCLUSION: With the exception of HLA, this is the strongest evidence yet of a genetic locus that is both linked to and associated with RA, and provides an avenue for further genetic characterization and potentially novel therapeutic intervention.

Adult↗

Analysis of single-nucleotide polymorphisms in the interleukin-4 receptor gene for association with inflammatory bowel disease.

Genetic linkage analysis in families with multiple cases of inflammatory bowel disease (IBD) has mapped a gene which confers susceptibility to IBD to the pericentromeric region of chromosome 16 (IBD1). The linked region includes the interleukin(IL)-4 receptor gene (IL4R). Since IL-4 regulation and expression are abnormal in IBD, the IL4R gene is thus both a positional and functional candidate for IBD1. We screened the gene for single-nucleotide polymorphisms (SNPs) by fluorescent chemical cleavage analysis, and tested a subset of known and novel SNPs for allelic association with IBD in 355 families, which included 435 cases of Crohn's disease and 329 cases of ulcerative colitis. No association was observed between a haplotype of four SNPs (val50ile, gln576arg, A3044G, G3289A) and either the Crohn's disease or ulcerative colitis phenotypes using the transmission disequilibrium test. There was also no evidence for association when the four markers were analyzed individually. The results indicate that these variants are not significant genetic determinants of IBD, and that the IL4R gene is unlikely to be IBD1. Linkage disequilibrium analyses showed that the val50ile and gln576arg variants are in complete equilibrium with each other, although they are separated by only about 21 kilobases of genomic DNA. This suggests that a very dense SNP map may be required to exclude or detect disease associations with some candidate genes.

Alleles↗

A screen of random sequences for those that alter the trafficking of the influenza virus hemagglutinin in vivo.

In order to determine if the sequence patterns known to specify internalization represent the majority of possible internalization signals, we identified random sequences capable of causing a reporter protein to be internalized at least several-fold faster than the rate of non-selective internalization of membrane by clathrin-coated pits. A library of influenza hemagglutinin (HA) proteins, bearing short random sequences in place of the wild-type cytoplasmic domain, was prepared in recombinant SV40 virus. The library was expressed and screened for HAs that could internalize anti-HA antibody from the medium. The cytoplasmic sequences of the selected proteins were determined. From a small sample of sequences we detected several that did not resemble those previously identified. The known internalization signals must represent only a subset of the sequences that can serve as internalization signals.

Amino Acid Motifs↗

Genetic modeling of abnormal photosensitivity in families with polymorphic light eruption and actinic prurigo.

Actinic prurigo and polymorphic light eruption are two of the so-called idiopathic photodermatoses, resulting from abnormal cutaneous responses to ultraviolet radiation (photosensitivity). Whereas they are clinically distinct in most cases, there are sufficient similarities between them to suggest they may be related conditions. To take this further, we examined the prevalence of polymorphic light eruption in families ascertained through actinic prurigo probands, as evidence of a shared pathogenesis. We then determined the heritability of photosensitivity in 420 individuals from families ascertained through polymorphic light eruption and actinic prurigo probands using segregation analysis. Across 58 pedigrees the prevalence of photosensitivity in first-degree relatives was 20.9% compared with a population prevalence of 13.6%, giving a relative risk of 1.5 (confidence interval 1.15-2.0) and providing evidence of clustering within families. The prevalence of photosensitivity (predominantly polymorphic light eruption) in relatives of actinic prurigo probands was 23.7%, with a relative risk of 1.74 (confidence interval 1.24-2.36). Modeling for polymorphic light eruption across all pedigrees revealed a strong genetic component with polymorphic light eruption showing a dominant mixed mode of inheritance. The model parameters estimate that 72% of the U.K. population carry a low penetrance polymorphic light eruption susceptibility allele, but that among this highly prevalent genotype only 24% of susceptible females and 13% of susceptible males will have polymorphic light eruption. Expression of polymorphic light eruption in genetically susceptible individuals (intergenotype variance) is determined in large part by a polygenic component, with an important additional environmental component. In summary, this study provides clear evidence that polymorphic light eruption is an inherited condition. It also suggests that polymorphic light eruption and actinic prurigo share a common genetic background, supporting the view that actinic prurigo may represent a human leukocyte antigen-restricted subset of polymorphic light eruption.

Family Health↗

A method for meta-analysis of genome searches: application to simulated data.

Genome searches have been performed for many complex traits, and in some cases several searches have been performed in a single disease. Replication of significant results is rare, and a systematic method of reviewing results from a number of searches is needed. A method for meta-analysis is presented which provides a systematic descriptive overview of the separate analyses while dealing with some of the problems specific to meta-analysis of genome searches. The results of two separate meta-analyses correctly indicate the presence of susceptibility loci on chromosomes 1, 3, and 5 in the GAW11 Problem 2 data.

Genetic Linkage↗

Meta-analysis of genome searches.

We have developed a method for meta-analysis of genome scans which allows systematic integration of data from published results. The Genome Search Meta-analysis method (GSMA) uses a non-parametric ranking method to identify genetic regions that show consistently increased sharing statistics or lod scores. The GSMA ranks genetic regions according to the lod score or p-value achieved in each scan. The summed rank across studies is compared to its probability distribution assuming ranks are randomly assigned. The GSMA can confirm evidence for regions highlighted in the original genome scans, and identify novel regions, which did not reach significance in any scan. In this paper, the GSMA was applied to four genome screens in multiple sclerosis and across 11 screens from autoimmune disorders. The GSMA is appropriate for studies with different family ascertainment, markers, and statistical analysis methods. The method increases the power to detect individual linkages in a clinically homogeneous dataset and has the potential to detect susceptibility loci in clinically distinct diseases which show involvement of common pathogenetic pathways.

Autoimmune Diseases↗

DNA variation in a 5-Mb region of the X chromosome and estimates of sex-specific/type-specific mutation rates.

We describe a new approach for the study of human genome variation, based on our solid-phase fluorescence chemical mismatch-cleavage method. Multiplex screening rates >/=80 kb/36-lane gels are achieved, and accuracy of mismatch location is within +/-2 bp. The density of differences between DNA from any two humans is sufficiently low, and the estimate of their position is accurate enough, to avoid sequencing of most polymorphic sites when defining their allelic state. Furthermore, highly variable sequences, such as microsatellites, are distinguished easily, so that separate consideration can be given to loci that do and do not fit the definition of infinite mutation sites. We examined a 5-Mb region of Xq22 to define the haplotypes of 23 men (9 Europeans, 9 Ashkenazim, and 5 Pygmies) by reference to DNA from one Italian man. Fifty-eight 1.5-kb segments revealed 102 segregating sites. Seven of these are shared by all three groups, two by Pygmies and Europeans, two by Pygmies and Ashkenazim, and 19 by Ashkenazim and Europeans. Europeans are the least polymorphic, and Pygmies are the most polymorphic. Conserved allelic associations were recognizable within 40-kb DNA segments, and so was recombination in the longer intervals separating such segments. The men showed only three segregating sites in a 16.5-kb unique region of the Y chromosome. Divergence between X- and Y-chromosome sequences of humans and chimpanzees indicated higher male mutation rates for different types of mutations. These rates for the X chromosomes were very similar to those estimated for the X-linked factor IX gene in the U.K. population.

Animals↗

Mutation rates in humans. I. Overall and sex-specific rates obtained from a population study of hemophilia B.

A population-based study of hemophilia B mutations was conducted in the United Kingdom in order to construct a national confidential database of mutations and pedigrees to be used for the provision of carrier and prenatal diagnoses based on mutation detection. This allowed the direct estimate of overall (micro), male (v), and female (u) mutation rates for hemophilia B. The values obtained per gamete per generation and the 95% confidence intervals are micro;=7.73 (6. 29-9.12&parr0;x10-6; v=18.8 (14.5-22.9&parr0;x10-6; and u=2.18 (1. 44-3.16&parr0;x10-6. The ratio of male-to-female mutation rates is 8. 64, with a 95% confidence interval of 5.46-14.5. The higher male rate was not caused by a much higher rate of transition at CpG sites in the male. Attempts to detect evidence of gonadal mosaicism for hemophilia B mutation in suitable families did not detect any instances of ovarian mosaicism in any of 47 available opportunities. This suggests that the risk of a noncarrier mother manifesting as a gonadal mosaic by transmitting the mutation to a second child should be <0.062.

CpG Islands↗

Risk factors for detecting germline BRCA1 and BRCA2 founder mutations in Ashkenazi Jewish women with breast or ovarian cancer.

We ascertained 184 Ashkenazi Jewish women with breast/ovarian cancer (171 breast and 13 ovarian cancers, two of the former also had ovarian cancer) in a self-referral study. They were tested for germline founder mutations in BRCA1 (185delAG, 5382insC, 188del11) and BRCA2 (6174delT). Personal/family histories were correlated with mutation status. Logistic regression was used to develop a model to predict those breast cancer cases likely to be germline BRCA1/BRCA2 mutation carriers in this population. The most important factors were age at diagnosis, personal/family history of ovarian cancer, or breast cancer diagnosed before 60 years in a first degree relative. A total of 15.8% of breast cancer cases, one of 13 ovarian cancer cases (7.7%), and both cases with ovarian and breast cancer carried one of the founder mutations. Age at diagnosis in carriers (44.6 years) was significantly lower than in non-carriers (52.1 years) (p<0.001), and was slightly lower in BRCA1 than BRCA2 carriers. Thirty three percent of carriers had no family history of breast or ovarian cancer in first or second degree relatives. Conversely, 12% of non-mutation carriers had strong family histories, with both a first and a second degree relative diagnosed with breast or ovarian cancer. The predicted values from the logistic model can be used to define criteria for identifying Ashkenazi Jewish women with breast cancer who are at high risk of carrying BRCA1 and BRCA2 mutations. The following criteria would identify those at approximately 10% risk: (1) breast cancer <50 years, (2) breast cancer <60 years with a first degree relative with breast cancer <60 years, or (3) breast cancer <70 years and a first or second degree relative with ovarian cancer.

Adult↗

Receptor-mediated folate uptake is positively regulated by disruption of the actin cytoskeleton.

Receptor-mediated folate uptake is initiated by binding of ligand to a glycosyl phosphatidylinositol-anchored protein, folate receptor alpha (FR alpha). This receptor is expressed in a limited number of normal tissues but is overexpressed in a large number of epithelial malignancies. FR alpha synthesis, at least in part, is regulated by endogenous folate and by hormones in some cells, but much less is known about the control of function. Recently, we showed that phorbol 12-myristate 13-acetate increases the rate of receptor cycling, increases the rate of folate delivery, and causes the majority of the receptor to reside on the cell surface in nonmalignant cells in vitro (C. M. Lewis et al., Biochim. Biophys. Acta, 1401: 157-169, 1998). However, based upon effects (or lack of effects) of specific inhibitors of protein kinase C, the mechanism of action of phorbol 12-myristate 13-acetate is not likely via protein kinase C. Because exo- and endocytosis are controlled by the actin cytoskeleton, we tested cytochalasin D and latrunculin B, actin-disrupting agents, on FR alpha-mediated folate uptake. Disruption of the actin cytoskeleton reversibly increases the proportion of receptors on the cell surface and increases the rate of 5-methyltetrahydrofolate delivery. Disrupting microtubules with nocodazole had no effect. The increased rate of folate delivery caused by cytochalasin D is not observed in FR-negative cell lines. Although we have not yet identified the upstream effectors, likely candidates include small G-proteins such as rho, which are known to cause actin polymerization. In addition to identifying the machinery for receptor-mediated folate uptake, it may be important to integrate this new data into studies of FR alpha as a tumor antigen for imaging or delivering molecules via anti-FR antibodies or compounds coupled to folic acid.

Actins↗