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Manjit Kaur

Publications and source records attributed to Manjit Kaur.

7 recordsLinked to original sources
PubMed2025

Epistasis of ERAP1 With 4 Major Histocompatibility Complex Class I Alleles in Frontal Fibrosing Alopecia: A Genome-Wide Association Study Meta-Analysis.

IMPORTANCE: Frontal fibrosing alopecia (FFA) is an inflammatory and scarring form of hair loss of increasing prevalence that most commonly affects women. An improved understanding of the genetic basis of FFA will support the identification of pathogenic mechanisms and therapeutic targets. OBJECTIVE: To identify novel genomic loci at which common genetic variation affects FFA susceptibility and assess nonadditive effects on genetic risk between susceptibility loci. DESIGN, SETTING, AND PARTICIPANTS: Four genome-wide association studies were combined using an SE-weighted meta-analysis. Within the major histocompatibility complex (MHC) locus, stepwise conditional analysis was undertaken to determine independently associated classical MHC class I alleles. Statistical tests for epistatic interaction were performed between risk alleles at the MHC and endoplasmic reticulum aminopeptidase 1 (ERAP1) loci. MAIN OUTCOMES AND MEASURES: Genome-wide significant locus associated with FFA and nonadditive effects on genetic risk between susceptibility loci. RESULTS: Of 6668 included patients, there were 1585 European female individuals with FFA and 5083 controls. Genome-wide significant associations were identified at 4 genomic loci, including a novel susceptibility locus at 5q15, and the association signal could be fine-mapped to a single nucleotide substitution (rs10045403) in the 5' untranslated region of ERAP1 (rs10045403; odds ratio, 1.30; 95% CI, 1.19-1.43; P = 3.6 × 10-8). Within the MHC, FFA risk was statistically independently associated with HLA-A*11:01, HLA-A*33:01, HLA-B*07:02, and HLA-B*35:01. FFA risk was affected by genetic variation at the ERAP1 locus only in individuals who carried at least 1 of the MHC class I risk alleles. CONCLUSIONS AND RELEVANCE: In this genome-wide meta-analysis, a supra-additive effect of genetic variation was found that affected peptide trimming and antigen presentation on FFA susceptibility. Patients with FFA may benefit from emerging therapeutic approaches that modulate ERAP-mediated processes.

Female↗
PubMed2003

Novel amplification of DNA in a hairpin structure: towards a radical elimination of PCR errors from amplified DNA.

Errors introduced during PCR amplification set a selectivity limit for microsatellite analysis and molecular mutation detection methods since polymerase misincorporations invariably get confused with genuine mutations. Here we present hairpin-PCR, a new form of PCR that completely separates genuine mutations from polymerase misincorporations. Hairpin-PCR operates by converting a DNA sequence to a hairpin following ligation of oligonucleotide caps to DNA ends. We developed conditions that allow a DNA hairpin to be efficiently PCR-amplified so that, during DNA synthesis, the polymerase copies both DNA strands in a single pass. Consequently, when a misincorporation occurs it forms a mismatch following DNA amplification, and is distinguished from genuine mutations that remain fully matched. Error-free DNA can subsequently be isolated using one of many approaches, such as dHPLC or enzymatic depletion. We present feasibility for the main technical steps involved in this new strategy, conversion of a sequence to a hairpin that can be PCR-amplified from human genomic DNA, exponential amplification from picogram amounts, conversion of misincorporations to mismatches and separation of homoduplex from heteroduplex hairpins using dHPLC. The present hairpin-PCR opens up the possibility for a radical elimination of PCR errors from amplified DNA and a major improvement in mutation detection.

Artifacts↗
PubMed2002

A PCR-based amplification method retaining the quantitative difference between two complex genomes.

With the increasing emergence of genome-wide analysis technologies (including comparative genomic hybridization (CGH), expression profiling on microarrays, differential display (DD), subtractive hybridization, and representational difference analysis (RDA)), there is frequently a need to amplify entire genomes or cDNAs by PCR to obtain enough material for comparisons among target and control samples. A major problem with PCR is that amplification occurs in a nonlinear manner and reproducibility is influenced by stray impurities. As a result, when two complex DNA populations are amplified separately, the quantitative relationship between two genes after amplification is generally not the same as their relation before amplification. Here we describe balanced PCR, a procedure that faithfully retains the difference among corresponding amplified genes by using a simple principle. Two distinct genomic DNA samples are tagged with oligonucleotides containing both a common and a unique DNA sequence. The genomic DNA samples are pooled and amplified in a single PCR tube using the common DNA tag. By mixing the two genomes, PCR loses the ability to discriminate among the different alleles and the influence of impurities is eliminated. The PCR-amplified pooled samples can be separated using the DNA tag unique to each individual genomic DNA sample. The principle of this method has been validated with synthetic DNA, genomic DNA, and cDNA applied on microarrays. By removing the bias of PCR, this method allows a balanced amplification of allelic fragments from two complex DNAs even after three sequential rounds of PCR. This balanced PCR approach should allow genetic analysis in minute laser-microdissected tissues, paraffin-embedded archived material, or single cells.

DNA, Complementary↗
PubMed2002

Determining the molar mass of a plasma substitute succinylated gelatin by size exclusion chromatography-multi-angle laser light scattering, sedimentation equilibrium and conventional size exclusion chromatography.

The clinical effectiveness of succinylated gelatin as a plasma substitute depends strongly on its molar mass, determined conventionally by size exclusion chromatography (SEC). This study evaluates different SEC calibration standards in comparison with two independent "absolute" methods for determining the weight average molar mass (M(w)) of a succinylated gelatin sample. SEC calibrated using succinylated gelatin fractions correlated well with size exclusion chromatography-multi-angle laser light scattering (SEC-MALLS) and sedimentation equilibrium whereas SEC calibrated with unmodified gelatin, sodium polystyrene sulfonates or pullulans overestimated M(w) by over 20%. Universal calibration was equivocal. The problems associated with the preparation of succinylated gelatin fractions suggest that an absolute method such as SEC-MALLS may be a more suitable choice for determining the M(w) in succinylated gelatins.

Calibration↗
PubMed2002

An amplification and ligation-based method to scan for unknown mutations in DNA.

A new approach is presented for the sensitive and selective scanning for unknown DNA mutations, based on ligation-mediated PCR and the use of the glycosylases TDG and MutY. These two highly selective enzymes together can detect about 70% of commonly observed polymorphisms and mutations in human tumors. DNA is cross-hybridized to form mismatches at the positions of point mutations, de-phosphorylated to eliminate any pre-existing phosphorylated DNA ends, and then exposed to enzymatic treatment to remove mismatched thymidine (TDG) or adenine (MutY). The resulting apurinic/apyrimidinic sites at the position of the mismatches are heat-converted to 5'-phosphate-containing strand breaks, the DNA is denatured, and an oligonucleotide is ligated at the position of the newly created 5'-phosphate-containing DNA ends. The ligated oligonucleotide then participates in a PCR reaction that amplifies exponentially only the mutation-containing fragments. Using this method, A-->G mutations in a p53 (TP53)-containing system, T-->G, G-->A, and C-->A, mutations in the Ku gene (XRCC5), and ATM, gene for a number of patient-derived genomic DNA samples have been successfully screened. This PCR-based assay is capable of detecting one mutated allele in 100 normal alleles and requires 5 to 100 ng of genomic DNA as starting material. The assay allows final visualization of the mutated fragments on a common ethidium gel or biotinylation and use in a capture format, potentially allowing the isolation of diverse mutated DNA fragments simultaneously. This versatile new approach should allow high throughput detection of DNA alterations and application in diverse areas of human mutation research.

Adenine↗
PubMed2002

Ligation of a primer at a mutation: a method to detect low level mutations in DNA.

Detection of low frequency mutations following exposure to mutagens or during the early stages of cancer development is instrumental for risk assessment and molecular diagnosis. We present a sensitive new method to detect trace levels of DNA mutations induced within a large excess of wild-type sequences. The method is based on mutation-induced generation of new restriction enzyme recognition sites. A DNA sequence is amplified from genomic DNA or cDNA using a high fidelity polymerase. The purified PCR product is digested with a restriction enzyme that recognizes the newly generated restriction site, partially dephosphorylated and ligated with an oligonucleotide at the position of the mutation. The ligated oligonucleotide is then utilized in two rounds of PCR to amplify the mutated DNA but not the wild-type allele that contains no restriction site. An A-->T polymorphism in mRNA (tenascin gene, A(2366)-->T, Asn-->Ile) and a G-->A polymorphism in genomic DNA (Ku gene, G(74582)-->A, Val-->Ile), both of which generate a restriction site for the enzyme SAU3A1, demonstrate the application. Eleven patient samples pre-characterized for the G(74582)-->A polymorphism in the repair gene Ku are used to demonstrate the reliability of this approach. This technique quantitatively detects the Ku G-->A polymorphism at a mutant frequency of 1.6x10(-6) relative to the wild-type allele. Mutations in p53 that are frequently induced by mutagens can readily be detected using the present method. As an example, using a second enzyme BbvI, a mutation frequently encountered in human cancers (G(14154)-->A mutation, p53 codon 245, Arg-->Gln) was detected in patient samples. The process does not require radioactivity, utilizes established procedures and overcomes several factors known to produce false positives in RFLP-based assays. The present amplification via primer ligation at the mutation (APRIL-ATM) has potential applications in the detection of mutagen-generated genetic alterations, early detection of tumor marker mutations in bodily discharges and the diagnosis of minimal residual disease.

Adenocarcinoma↗