Patcharee Lertrit’s research while affiliated with Mahidol University and other places

Background: This study aimed to explore clinical and molecular factors that cause discordance for clinical expression of Leber's hereditary optic neuropathy (LHON) in a pair of identical twins with the 14484 point mutation. Case summary: Twin patients with the 14484 point mutation were studied for zygosity by using the Short Tandem Repeats Typing system. For the monozygotic twins, the radioactive restriction and densitometric analyses were used to quantitate the heteroplasmy level for the 14484 point mutation. The mitochondrial genome was analyzed to determine influential factors by mitochondrial deoxyribonucleic acid (DNA) sequencing, denaturing high-performance liquid chromatography and next generation sequencing. For the dizygotic twins, the nuclear DNA was analyzed. The twins with 14484 LHON were monozygotic with homoplasmy. No difference in the point mutation in mitochondrial DNA was found. No modifying genes that potentially influenced the disparity in phenotypic expression of LHON were detected in these twins. Conclusion: This 11-year follow-up of monozygotic twins showed additional genetic modifications and epigenetic factors are possibly associated with discordance for LHON.

Background Cyclic vomiting syndrome (CVS) is a functional gastrointestinal disorder characterized by recurrent stereotypic episodes of vomiting. The pathophysiology of CVS remains obscure. Previous studies have supported the hypotheses of mitochondrial dysfunction. However, data on association studies between mitochondrial DNA (mtDNA) polymorphisms and pediatric-onset CVS are limited and inconsistent. The aims of this study were to describe clinical characteristics, evaluate association of mtDNA polymorphisms 16519T and 3010A with pediatric-onset CVS and identify new mtDNA candidate variants. Methods This study involved Thai patients diagnosed with CVS according to the Rome III or IV criteria before the age of 15 years. Patients' demographic data, clinical characteristics, previous investigations and treatment outcomes were obtained. Blood samples were collected for next-generation (whole exome) sequencing, followed by analysis of chromosome M (mitochondrial. Variants were filtered according to clinical significance using ClinVar and MITOMAP. mtDNA polymorphisms in 148 normal Thai individuals were used as controls. Results Forty-eight children were enrolled in the clinical study, and 30 participated in the genetic analysis. The median age at onset and median age at diagnosis was 3.0 (1.5–5.6) and 6.3 (3.0–8.6) years, respectively. Maternal history of migraine was positive in 16.7%. About 45.7% (21 of 46) of the patients achieved complete clinical remission, with the mean symptom duration of 5.9 ± 3.3 years. The prevalence of mtDNA variants 16519T and 3010A among the patient group and Thai general population (control) were as follows: 40.0% (12/30) vs. 27.7% ( P = 0.18) and 6.7% (2/30) vs. 0.7% ( P = 0.07), respectively. Five known pathogenic variants were identified in 6 patients, including mtDNA 8528C in one patient who also had infantile hypertrophic cardiomyopathy. Six likely pathogenic variants were found but without statistical significance. We identified 11 variants with significant prevalence in the patient group. Though, these variants were classified as variants of unknown significance (VUS), several of them were located in mt functional regions and therefore they deserve further investigations as new candidates for association with pediatric CVS. Conclusion There were no associations of mtDNA polymorphisms 16519T and 3010A with CVS in our pediatric cohort. Five pathogenic variants and 11 VUS were found associated with pediatric-onset CVS.

Background Leber’s inherited optic neuropathy (LHON) is well known for incomplete penetrance. A pair of monozygotic twins carrying 14484T > C LHON mutation: one displayed LHON characteristics (affected LHON) and the other twin was an unaffected LHON carrier, were studied to identify possible modifier(s) for LHON manifestation. Methods Primary fibroblasts from affected and unaffected monozygotic twins with 14484T > C LHON mutation were treated with different insults to differentiate cellular phenotype between the two fibroblasts. RNA sequencing of the fibroblasts indicated differentially expressed genes and whole genome sequencing was used to identify candidates for disease modifier. Results Our results suggested that fibroblast from unaffected carrier was able to adapt to galactose and hydrogen peroxide insult, while affected fibroblasts were not. We found reduced expression of total SOD2 with high proportion of inactive SOD2 (acetylated SOD2) in affected LHON fibroblast, while decreased expression of SIRT3 was detected in affected LHON fibroblasts treated with combination of insults. Differential expression indicated enrichment of a pathway relating to negative regulator of cell death pathway in unaffected carrier fibroblast. Expression of receptor for prostaglandin E receptor (PTGER3) was found to be affected by two SNPs. Unaffected LHON fibroblast possessed rs75523942 that indicates a positive effect on PTGER3 expression, while affected LHON fibroblast possessed rs496483 that indicates a negative effect on PTGER3 expression. Discordant SNPs on prostaglandin E receptor 3 (PTGER3) were identified as eQTL. Conclusions This study indicates that prostanoid receptor could be a possible modifier for LHON manifestation of these twins.

Ancient migrations in Southeast Asia The past movements and peopling of Southeast Asia have been poorly represented in ancient DNA studies (see the Perspective by Bellwood). Lipson et al. generated sequences from people inhabiting Southeast Asia from about 1700 to 4100 years ago. Screening of more than a hundred individuals from five sites yielded ancient DNA from 18 individuals. Comparisons with present-day populations suggest two waves of mixing between resident populations. The first mix was between local hunter-gatherers and incoming farmers associated with the Neolithic spreading from South China. A second event resulted in an additional pulse of genetic material from China to Southeast Asia associated with a Bronze Age migration. McColl et al. sequenced 26 ancient genomes from Southeast Asia and Japan spanning from the late Neolithic to the Iron Age. They found that present-day populations are the result of mixing among four ancient populations, including multiple waves of genetic material from more northern East Asian populations. Science , this issue p. 92 , p. 88 ; see also p. 31

Two distinct population models have been put forward to explain present-day human diversity in Southeast Asia. The first model proposes long-term continuity (Regional Continuity model) while the other suggests two waves of dispersal (Two Layer model). Here, we use whole-genome capture in combination with shotgun sequencing to generate 25 ancient human genome sequences from mainland and island Southeast Asia, and directly test the two competing hypotheses. We find that early genomes from Hoabinhian hunter-gatherer contexts in Laos and Malaysia have genetic affinities with the Onge hunter-gatherers from the Andaman Islands, while Southeast Asian Neolithic farmers have a distinct East Asian genomic ancestry related to present-day Austroasiatic-speaking populations. We also identify two further migratory events, consistent with the expansion of speakers of Austronesian languages into Island Southeast Asia ca. 4 kya, and the expansion by East Asians into northern Vietnam ca. 2 kya. These findings support the Two Layer model for the early peopling of Southeast Asia and highlight the complexities of dispersal patterns from East Asia.

Purpose: Our goal was to describe the clinical and molecular genetic findings in Thai patients with Leber congenital amaurosis (LCA). Methods: Whole exome sequencing (WES) was performed in eight unrelated patients. All genes responsible for inherited retinal diseases (IRDs) based on RetNet were selected for analysis. Potentially causative variants were filtered through a bioinformatics pipeline and validated using Sanger sequencing. Segregation analysis of the causative genes was performed in family members when available. Results: Eleven deleterious variants, six nonsense and five missense, were identified in seven genes: four LCA-associated genes (CEP290, IQCB1, NMNAT1, and RPGRIP1), one gene responsible for syndromic LCA (ALMS1), and two IRDs-related genes (CTNNA1 and CYP4V2). Clinical reassessment supported the diagnosis of syndromic LCA in those patients harboring potentially pathogenic variants in the ALMS1. Interestingly, two causative genes, CTNNA1 and CYP4V2, previously reported to cause butterfly-shaped pigment dystrophy (BSPD) and Bietti's crystalline dystrophy (BCD), respectively, were detected in two other patients. These two patients developed rapid and severe visual loss in contrast to BSPD and BCD patients in previous studies. The results of this study demonstrate that causative variants identified in the CTNNA1 and CYP4V2 genes are also associated with LCA. Conclusions: This is the first report describing the molecular genetics and clinical manifestations of Thai patients with LCA. The present study expands the spectrum of LCA-associated genes, which is a benefit for molecular diagnosis. The identification of mutations in the CTNNA1 and CYP4V2 genes requires further elucidation in larger cohorts with LCA.

Obesity is a major worldwide health issue, with increasing prevalence in adults and children from developed and developing countries. Obesity causes several chronic diseases, including cardiovascular and respiratory diseases, osteoarthritis, hypertension, stroke, type II diabetes, obstructive sleep apnea, and several types of cancer. Previous genome-wide association studies have identified several genes associated with obesity, including LEP, LEPR, POMC, PCSK1, FTO, MC3R, MC4R, GNPDA2, TMEM18, QPCTL/GIPR, BDNF, ETV5, MAP2K5/SKOR1, SEC16B, SIM1, and TNKS/MSRA. However, most of these variants are found in the intronic or intergenic regions, making it difficult to elucidate the underlying mechanisms. Therefore, in this study, we performed a whole exome sequencing of the protein-coding regions in the total genome (exome) of two obese and one normal subject belonging to the same Thai family to identify the genes responsible for obesity. We identified 709 functional variants that were differentially expressed between obese and normal subjects; of these, 65 were predicted to be deleterious to protein structure or function. The minor allele frequency of 14 of these genes (ALOX5AP, COL9A2, DEFB126, GDPD4, HCRTR1, MLL3, OPLAH, OR4C45, PRIM2, RXFP2, TIGD6, TRPM8, USP49, and ZNF596) was low, indicating causal variants that could be associated with complex traits or diseases. Genotyping revealed HCRTR1, COL9A2, and TRPM8 to be associated with the regulation of feeding behavior and energy expenditure. These genes constituted a network of pathways, including lipid metabolism, signaling transduction, immune, membrane transport, and gene regulation pathways, and seemed to play important roles in obesity.

Purpose: Retinitis pigmentosa (RP) is a clinically and genetically heterogeneous group of inherited retinal degenerations characterized by progressive loss of photoreceptor cells and RPE functions. More than 70 causative genes are known to be responsible for RP. This study aimed to identify the causative gene in a patient from a consanguineous family with childhood-onset severe retinal dystrophy. Methods: To identify the defective gene, whole exome sequencing was performed. Candidate causative variants were selected and validated using Sanger sequencing. Segregation analysis of the causative gene was performed in additional family members. To verify that the mutation has an effect on protein synthesis, an expression vector containing the first ten amino acids of the mutant protein fused with the DsRed2 fluorescent protein was constructed and transfected into HEK293T cells. Expression of the fusion protein in the transfected cells was measured using fluorescence microscopy. Results: By filtering against public variant databases, a novel homozygous missense mutation (c.3G>A) localized in the start codon of the MERTK gene was detected as a potentially pathogenic mutation for autosomal recessive RP. The c.3G>A mutation cosegregated with the disease phenotype in the family. No expression of the first ten amino acids of the MerTK mutant fused with the DsRed2 fluorescent protein was detected in HEK293T cells, indicating that the mutation affects the translation initiation site of the gene that may lead to loss of function of the MerTK signaling pathway. Conclusions: We report a novel missense mutation (c.3G>A, p.0?) in the MERTK gene that causes severe vision impairment in a patient. Taken together with previous reports, our results expand the spectrum of MERTK mutations and extend our understanding of the role of the MerTK protein in the pathogenesis of retinitis pigmentosa.

Purpose: Cisplatin and 5-Fluorouracil are the critical components of therapeutic regimen in a broad range of malignancies. Their therapeutic efficacy is limited due to the development of toxic side effects and drug resistance by the cancer cells. Cisplatin toxic side effects are usually associated with mitochondrial injury in vivo and in vitro. In vitro evidence indicates that cisplatin decreases mitochondrial DNA (mtDNA) copy number. There is limited information on the effect of cisplatin on human mtDNA quantity. In order to clarify the effects of cisplatin and 5-FU on mtDNA in human, this study focused on the changes of mtDNA quantitation in cancer patients who were treated with cisplatin-based regimens. Methods: 24 blood samples from head and neck cancer patients were collected before chemotherapy and after second cycle of chemotherapy. Total DNA was extracted from peripheral blood leukocytes by salting out method. Validation of primer pairs were done by conventional PCR and checked by gel electrophoresis. The relative changes of mtDNA quantity were determined by quantitative PCR targeting Cyt-B genes normalizing with the nuclear gene PARL. Result: Comparing 24 samples, there was an increased mtDNA level after second cycle of chemotherapy, though it did not reach the statistically significant level (P=0.31, Wilcoxon signed ranked test). However, 58% of the total patients had relatively increased mtDNA amount while 42% of the total patients showed decreased mtDNA amount after second cycle of chemotherapy (P<0.05, paired t-test). Conclusion: Overall, Cisplatin-based chemotherapy can affect mtDNA quantity changes in leucocytes of head and neck cancer patients.