Hui-Ping Chuang

Genetic determinants of warfarin dosing in the Han-Chinese population.

UNLABELLED Warfarin, a widely prescribed oral anticoagulant, is used for the prevention of thromboembolism. Polymorphisms in CYP2C9 and VKORC1 have been shown to be associated with warfarin dose requirements. However, it is likely that other genes could also affect warfarin dose. AIMS In this study, we aimed to identify additional genes influencing warfarin dosing in the Han-Chinese population. MATERIALS & METHODS In this study, we screened for SNPs in 13 genes (VKORC1, CYP2C9, CYP2C18, PROC, APOE, EPHX1, CALU, GGCX, ORM1, ORM2, factor II, factor VII and CYP4F2) and tested their associations with warfarin dosing with univariate and multiple regression analysis. RESULTS Polymorphisms in the VKORC1 gene have the strongest effects on warfarin dose, followed by CYP2C9*3. In addition, our results showed that CYP2C18, PROC and EPHX1 have small but significant associations with warfarin dose. In multiple regression analysis, PROC and EPHX1 explained 3% of the dose variation. The incorporation of these two genes into warfarin dosing algorithms could improve the accuracy of prediction in the Han-Chinese population.

Genome-wide expression profiles of subchondral bone in osteoarthritis

IntroductionThe aim of this study was to evaluate, for the first time, the differences in gene expression profiles of normal and osteoarthritic (OA) subchondral bone in human subjects.MethodsFollowing histological assessment of the integrity of overlying cartilage and the severity of bone abnormality by micro-computed tomography, we isolated total RNA from regions of interest from human OA (n = 20) and non-OA (n = 5) knee lateral tibial (LT) and medial tibial (MT) plateaus. A whole-genome profiling study was performed on an Agilent microarray platform and analyzed using Agilent GeneSpring GX11.5. Confirmatory quantitative reverse-transcription polymerase chain reaction (qRT-PCR) analysis was performed on samples from 9 OA individuals to confirm differential expression of 85 genes identified by microarray. Ingenuity Pathway Analysis (IPA) was used to investigate canonical pathways and immunohistochemical staining was performed to validate protein expression levels in samples.ResultsA total of 972 differentially expressed genes were identified (fold change ≥ ± 2, P ≤0.05) between LT (minimal degeneration) and MT (significant degeneration) regions from OA samples; these data implicated 279 canonical pathways in IPA. The qRT-PCR data strongly confirmed the accuracy of microarray results (R2 = 0.58, P <0.0001). Novel pathways were identified in this study including Periostin (POSTN) and Leptin (LEP), which are implicated in bone remodeling by osteoblasts.ConclusionsTo the best of our knowledge, this study represents the most comprehensive direct assessment to date of gene expression profiling in OA subchondral bone. This study provides insights that could contribute to the development of new biomarkers and therapeutic strategies for OA.

Genome-wide association study in NSAID-induced acute urticaria/angioedema in Spanish and Han Chinese populations

AIM Acute urticaria/angioedema (AUA) induced by cross-intolerance to NSAIDs is the most frequent clinical entity in hypersensitivity reactions to drugs. In this work, we conducted a genome-wide association study in Spanish and Han Chinese patients suffering from NSAID-induced AUA. MATERIALS & METHODS A whole-genome scan was performed on a total of 232 cases (112 Spanish and 120 Han Chinese) with NSAID-induced AUA and 225 unrelated controls (124 Spanish and 101 Han Chinese). RESULTS Although no polymorphism reached genome-wide significance, we obtained suggestive associations for three clusters in the Spanish group (RIMS1, BICC1 and RAD51L 1) and one region in the Han Chinese population (ABI3BP). Five regions showed suggestive associations after meta-analysis: HLF, RAD51L1, COL24A1, GalNAc-T13 and FBXL7. A majority of these genes are related to Ca(2+), cAMP and/or P53 signaling pathways. CONCLUSION The associations described were different from those related to the metabolism of arachidonic acid and could provide new mechanisms underlying NSAID-induced AUA.

VKORC1 haplotypes in five East-Asian populations and Indians

AIMS Warfarin, a widely prescribed oral anticoagulant, is used for the prevention of thromboembolism. Several polymorphisms in VKORC1 have been shown to be associated with warfarin dose requirements. The frequencies of these VKORC1 polymorphisms display population differences; however, this has not been examined in many populations. In this study, we examined VKORC1 polymorphisms in five East-Asian populations (Han Chinese, Indonesian, Filipino, Thai and Vietnamese) and Indians. MATERIALS & METHODS A total of six SNPs in the VKORC1 gene (-1639G>A, 497T>G, 1173C>T, 1542T>G, 2255C>T and 3730G>A) were genotyped. Frequencies, linkage disequilibrium and haplotype structures of these six VKORC1 SNPs were analyzed. RESULTS Our data showed that 497T>G is only polymorphic in the Indian population. The 497G allele is very rare in the East-Asian populations (frequency < 1%). The remaining SNPs demonstrated high linkage disequilibrium and had similar frequencies and haplotype structures in all but the Indian population. The Indian population is mostly made up of the H7 haplotype (76%) while the rest of the recruited populations consisted of the H1 haplotype (> 80%).

Pharmacogenetic dosing of warfarin in the Han-Chinese population: a randomized trial

AIM This study aimed to determine clinical utility of genotype-guided dosing for warfarin in Han-Chinese. METHODS A total of 320 patients were randomly assigned International Warfarin Pharmacogenetic Consortium algorithm, Taiwan algorithm and optimal clinical care arms. The primary outcome of the study was the percentage of time in the therapeutic range during the first 90 days of treatment. RESULTS The percentage of time in the therapeutic range of the clinical care group in the first 2 weeks was significantly higher than the algorithm groups. This difference was no longer observed after 4 weeks. No difference in excessive anticoagulation (international normalized ratio ≥4.0) and adverse events was observed. CONCLUSION Genotype-guided dosing did not provide significant benefit. Loading dose with frequent international normalized ratio monitoring could provide sufficient control of anticoagulation.

Determinants of the Over-Anticoagulation Response during Warfarin Initiation Therapy in Asian Patients Based on Population Pharmacokinetic-Pharmacodynamic Analyses

To clarify pharmacokinetic-pharmacodynamic (PK-PD) factors associated with the over-anticoagulation response in Asians during warfarin induction therapy, population PK-PD analyses were conducted in an attempt to predict the time-courses of the plasma S-warfarin concentration, Cp(S), and coagulation and anti-coagulation (INR) responses. In 99 Chinese patients we analyzed the relationships between dose and Cp(S) to estimate the clearance of S-warfarin, CL(S), and that between Cp(S) and the normal prothrombin concentration (NPT) as a coagulation marker for estimation of IC50. We also analyzed the non-linear relationship between NPT inhibition and the increase in INR to derive the non-linear index λ. Population analyses accurately predicted the time-courses of Cp(S), NPT and INR. Multivariate analysis showed that CYP2C9*3 mutation and body surface area were predictors of CL(S), that VKORC1 and CYP4F2 polymorphisms were predictors of IC50, and that baseline NPT was a predictor of λ. CL(S) and λ were significantly lower in patients with INR≥4 than in those with INR<4 (190 mL/h vs 265 mL/h, P<0.01 and 3.2 vs 3.7, P<0.01, respectively). Finally, logistic regression analysis revealed that CL(S), ALT and hypertension contributed significantly to INR≥4. All these results indicate that factors associated with the reduced metabolic activity of warfarin represented by CL(S), might be critical determinants of the over-anticoagulation response during warfarin initiation in Asians. Trial Registration ClinicalTrials.gov NCT02065388

Homozygosity Mapping and Whole-Genome Sequencing Links a Missense Mutation in POMGNT1 to Autosomal Recessive Retinitis Pigmentosa

PURPOSE To identify the genetic cause in five families with autosomal recessive retinitis pigmentosa, a genetic disorder involving retinal degeneration and visual loss with high genetic heterogeneity. METHODS We performed whole-genome single nucleotide polymorphism genotyping on 35 members from the five families to map the region of homozygosity shared by all patients. Whole-genome sequencing was then conducted on one of the patients and a novel variant was identified in POMGNT1 from the homozygous region, which was confirmed by Sanger sequencing and sequenced in all family members. Mutant and wild-type POMGNT1 were expressed in heterologous cells to assess enzyme activity. RESULTS A 1.8-Mb homozygous region was identified at 1p34-p33 shared by all 17 patients. Whole-genome sequencing revealed a novel missense mutation in POMGNT1 (c.359A>C, p.Leu120Arg) from this homozygous region, which was shown to co-segregate with disease phenotype. The mutant protein carrying this missense mutation showed an approximately 80% decrease in POMGNT1 enzyme activity compared with the wild type. CONCLUSIONS We identified a novel mutation in POMGNT1 that causes nonsyndromic autosomal recessive retinitis pigmentosa, adding to the genetic heterogeneity of this retinal disease. POMGNT1 encodes a glycosyltransferase in O-mannosyl glycosylation and was previously found to be responsible for a group of congenital muscular dystrophies called dystroglycanopathies. Our discovery suggests the involvement of O-mannosyl glycosylation in retinitis pigmentosa and presents an instance of POMGNT1 mutation that does not involve muscular dystrophy.

A large kindred of early-onset osteoarthritis of the knee and hip: excluding the link to COL2A1 gene

OBJECTIVES To characterize a large extended family with early-onset OA of the knee and investigate its associations with the COL2A1 gene. METHODS Phenotype assessments were conducted in a six-generation family to identify individuals affected with OA. Short tandem repeat polymorphic (STRP) markers and DNA sequencing were performed to investigate the involvement of the COL2A1 gene in this family. RESULTS The kindred affected with OA showed autosomal dominant inheritance. The mean age of onset was 37.3 +/- 19.2, 29.8 +/- 13.7 and 12.0 +/- 7.2 years for generations IV, V and VI, respectively, and 25 +/- 16.1 years for males and 34.3 +/- 15.5 years for females. The height of the affected males was shorter than the unaffected males (155.9 +/- 11.4 vs 164.5 +/- 16.0 cm, P = 0.010). Arm span in the affected males was also significantly shorter than the unaffected males (158.4 +/- 12.5 vs 165.3 +/- 16.7 cm, P = 0.027). However, both height and arm span were not reduced in the affected female OA patients. STRP markers surrounding COL2A1 locus did not show linkage of the COL2A1 locus with the OA. Sequencing of COL2A1 gene revealed three single nucleotide polymorphisms but no mutation was found in the affected patients. CONCLUSIONS The COL2A1 was not a susceptibility gene responsible for the OA phenotype in a large extended kindred with familial early-onset OA. The availability of DNA samples will allow genome-wide linkage study to identify the susceptibility locus.