Biomedical subjects

Pui-Yan Kwok

Publications and source records attributed to Pui-Yan Kwok.

41 records · Page 3Linked to original sources

PubMed2002

Novel immunoglobulin superfamily gene cluster, mapping to a region of human chromosome 17q25, linked to psoriasis susceptibility.

Chromosome 17q25 harbors a susceptibility locus for psoriasis ( PSORS2). This locus may overlap with loci for atopic dermatitis and rheumatoid arthritis. To further refine the location of PSORS2, we genotyped 242 primarily nuclear families for 15 polymorphic microsatellites mapping to chromosome 17q23-q25. Non-parametric linkage analysis revealed a linkage peak lying close to a novel cluster of genes from the immunoglobulin (Ig) superfamily. This cluster spans >250 kb and harbors five CMRF35-like genes and a sixth inhibitory receptor ( CMRF35H) with three ITIM motifs that is transcribed in the opposite direction from the rest. The Ig domains encoded by these genes are most similar to those of the TREM (triggering receptor expressed selectively in myeloid cells) molecules, NKp44 and the polymeric immunoglobulin receptor. CMRF35-like genes are only expressed in sub-populations of cells of the myeloid lineage. In order to investigate the association of this region with psoriasis, we genotyped the families for 13 novel microsatellites and 19 SNPs from the region of linkage. A maximum NPL of 1.6 ( P=0.05) was obtained within the interval. Two SNP-based haplotypes revealed some evidence for association with psoriasis. One spanned CMRF35H and includes a non-synonymous polymorphism within CMRF35H (R111Q) (TDT P=0.03). The second was a three-locus haplotype lying within the first intron of CMRF35A2 ( TREM5) (TDT P=0.04). The novel markers described here will facilitate additional linkage and association studies between the CMRF35 family and disease.

Adult↗

PubMed2002

SNP genotyping with fluorescence polarization detection.

When a fluorescent molecule is excited by plane polarized light, the fluorescence emitted is also polarized. The degree of fluorescence polarization (FP) detected, under constant temperature and solvent viscosity, is proportional to the molecular weight of the dye molecule. By monitoring the FP of a fluorescent dye, one can detect significant changes in the molecular weight of the molecule without separation or purification. Because the size of the probe is altered in the course of a number of single nucleotide polymorphism (SNP) genotyping reactions, FP is therefore an excellent detection mechanism for these assays. Indeed, FP detection can be used in SNP genotyping with the primer extension TaqMan((R)) and Invader((R)) assays. Use of FP detection makes it possible to reduce the cost of TaqMan((R)) and Invader((R)) probes by abrogating the need for a fluorescence quencher. Moreover, inexpensive, unpurified, and unlabeled probes are used in the primer extension reaction with FP detection. As an end-point detection mechanism, FP detection is suitable for high-throughput SNP genotyping.

DNA Mutational Analysis↗

PubMed2002

Paternal origins of complete hydatidiform moles proven by whole genome single-nucleotide polymorphism haplotyping.

Complete hydatidiform moles (CHMs) are diploid tumors that result from fertilization of an empty ovum by a haploid 23,X sperm. In most cases, the resulting duplication of the genome gives rise to a 46,XX genotype and is thought to be androgenetic in origin. If this hypothesis is correct, then the genotypes of all polymorphic markers in CHMs should be homozygous. We used a dense set of single-nucleotide polymorphism (SNP) markers, evenly spaced throughout the genome, to definitively test this hypothesis. We genotyped genomic DNA samples from five CHMs and their corresponding maternal samples with 1494 SNP markers using high-density microarrays (HuSNP). As predicted, the maternal samples were heterozygous at >25% of the markers, which is consistent with the expected average heterozygosity of this panel of SNPs. In contrast, the five CHM samples were heterozygous at <0.75% of the SNP markers, which shows that these diploid tumors consist of a duplicated set of chromosomes. Because the CHM genotypes represent the haplotypes of their genomes, our results show that long-range haplotypes can be obtained easily with this resource and that a collection of such samples is a simple way to obtain reference haplotypes for association studies in various populations.

Female↗

PubMed2002

Making 'random amplification' predictable in whole genome analysis.

One of the remaining obstacles to large-scale genetic mapping is the lack of an efficient way to genotype hundreds of thousands of genetic markers. Recently Jordan et al. reported that the 'random' sequences amplified by degenerate oligonucleotide primer (DOP)-PCR can be precisely mapped onto the human genome sequence and that it is possible to predict which DNA sequences will be amplified by a particular degenerate primer.

DNA Primers↗

PubMed2002

Primer design for PCR and sequencing in high-throughput analysis of SNPs.

To achieve high-throughput analysis of allele frequencies in human SNPs, we have developed automated methodsfor designing PCR and DNA sequencing primers. We found we could run the PCR assays at quite stringent, uniform conditions. The design process used freely available databases, including dbSNP, SNPper, and TSC, and publicly available software including RepeatMasker and Primer3. We describe parameters for the software and other considerations that increase experimental success. As anticipated. some assays filed at the design stage due primarily to the genomic locations of repetitive sequences, extreme GC content regions, or lack of sufficient sequence. However, over 23,000 assays, including 96% of those recently analyzed, have been experimentally successfuL Similar design methods could be usedfor PCR assays in any organism with substantial available sequence.

DNA Mutational Analysis↗