Publications by authors named "Yuet Ping Yuen"

26 Publications

  • Page 1 of 1

In-house multiplex ligation-dependent probe amplification assay for citrin deficiency: analytical validation and novel exonic deletions in SLC25A13.

Pathology 2021 Dec 25;53(7):867-874. Epub 2021 May 25.

Kowloon West Cluster Laboratory Genetic Service, Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong, China. Electronic address:

Citrin deficiency is one of the most common inborn errors of metabolism in East Asians, which may manifest as neonatal cholestasis, failure to thrive and dyslipidaemia, or recurrent hyperammonaemic encephalopathy. Its molecular diagnosis requires confirmation of the presence of biallelic pathogenic variants in SLC25A13 gene by sequencing, and analysis for a common insertion IVS16ins3kb. However, patients with compatible biochemical features but only one monoallelic pathogenic variant have remained a diagnostic challenge. Here we report the development, validation and application of a multiplex ligation-dependent probe amplification (MLPA) assay using an in-house oligonucleotide probemix and a customised Coffalyer.NET worksheet for detection of exonic copy number variations in SLC25A13. With this MLPA assay, we successfully identified the presence of a heterozygous exonic deletion in SLC25A13 in three of 15 (20%) unrelated individuals with only one monoallelic pathogenic variant detected using conventional methods. Three exonic deletions, two novel involving exon 14 and one reported involving exon 5, were subsequently confirmed with Sanger sequencing. In summary, we developed, evaluated, and demonstrated the clinical utility of an in-house MLPA assay to look for exonic deletions in SLC25A13 in patients with citrin deficiency. With the discovery of novel deletions, MLPA should be considered a test of choice for molecular diagnosis of citrin deficiency when the sequencing result is inconclusive.
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http://dx.doi.org/10.1016/j.pathol.2021.02.010DOI Listing
December 2021

BRAT1 encephalopathy: a recessive cause of epilepsy of infancy with migrating focal seizures.

Dev Med Child Neurol 2020 09 23;62(9):1096-1099. Epub 2019 Dec 23.

Division of Genetic Medicine, Department of Pediatrics, University of Washington, Seattle, WA, USA.

Epilepsy of infancy with migrating focal seizures (EIMFS), one of the most severe developmental and epileptic encephalopathy syndromes, is characterized by seizures that migrate from one hemisphere to the other. EIMFS is genetically heterogeneous with 33 genes. We report five patients with EIMFS caused by recessive BRAT1 variants, identified via next generation sequencing. Recessive pathogenic variants in BRAT1 cause the rigidity and multifocal seizure syndrome, lethal neonatal with hypertonia, microcephaly, and intractable multifocal seizures. The epileptology of BRAT1 encephalopathy has not been well described. All five patients were profoundly impaired with seizure onset in the first week of life and focal seizure migration between hemispheres. We show that BRAT1 is an important recessive cause of EIMFS with onset in the first week of life, profound impairment, and early death. Early recognition of this genetic aetiology will inform management and reproductive counselling.
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http://dx.doi.org/10.1111/dmcn.14428DOI Listing
September 2020

A Hong Kong Chinese kindred with familial hypocalciuric hypercalcaemia caused by mutation.

F1000Res 2019 9;8:1612. Epub 2019 Sep 9.

Department of Chemical Pathology, Prince of Wales Hospital, Shatin, Hong Kong.

Familial hypocalciuric hypercalcaemia (FHH) is a genetic disorder of altered calcium homeostasis. Mutations in the , and genes have been reported to cause FHH. We report a Hong Kong Chinese kindred with FHH type 3 (FHH3) caused by mutations in . The proband, a 51-year-old woman with hypercalcaemia, was initially diagnosed to have primary hyperparathyroidism but repeated parathyroidectomy failed to normalize her plasma calcium concentrations. Later, FHH was suspected and yet no mutations were identified in the gene which causes FHH type 1 (FHH1), the most common form of FHH. Genetic testing of revealed a heterozygous c.43C>T (p.Arg15Cys) mutation, confirming the diagnosis of FHH3. The elder brother and niece of the proband, who both have hypercalcaemia, were found to harbour the same mutation. To our knowledge, this is the first Chinese kindred of FHH3 reported in the English literature.
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http://dx.doi.org/10.12688/f1000research.20344.1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6826774PMC
June 2020

An unusual case of undescended testis: type II persistent Müllerian duct syndrome.

Pathology 2019 Apr 7;51(3):335-336. Epub 2019 Mar 7.

Department of Chemical Pathology, Prince of Wales Hospital, Shatin, Hong Kong, China.

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http://dx.doi.org/10.1016/j.pathol.2018.10.023DOI Listing
April 2019

Adverse Effects of Azathioprine in a Child and Her Mother with Eczema.

Indian J Pediatr 2018 Oct 12;85(10):918-919. Epub 2018 May 12.

School of Biomedical Sciences, The Chinese University of Hong Kong, Shatin, Hong Kong.

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http://dx.doi.org/10.1007/s12098-018-2687-zDOI Listing
October 2018

NMR-based urinalysis for rapid diagnosis of β-ureidopropionase deficiency in a patient with Dravet syndrome.

Clin Chim Acta 2015 Feb 25;440:201-4. Epub 2014 Oct 25.

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Background: Beta-ureidopropionase deficiency is a rare inborn error of metabolism (IEM) affecting pyrimidine metabolism. To-date, about 30 genetically confirmed cases had been reported. The clinical phenotypes of this condition are variable; some patients were asymptomatic while some may present with developmental delay or autistic features. In severe cases, patients may present with profound neurological deficit including hypotonia, seizures and mental retardation. Using NMR-based urinalysis, this condition can be rapidly diagnosed within 15 min.

Case: An 11-month-old Chinese boy had dual molecular diagnoses, β-ureidopropionase deficiency and Dravet syndrome. He presented with intractable and recurrent convulsions, global developmental delay and microcephaly. Urine organic acid analysis using GC-MS and NMR-based urinalysis showed excessive amount of β-ureidopropionic acid and β-ureidoisobutyric acid, the two disease-specific markers for β-ureidopropionase deficiency. Genetic analysis confirmed homozygous known disease-causing mutation UPB1 NM_016327.2: c.977G>A; NP_057411.1:p.R326Q. In addition, genetic analysis for Dravet syndrome showed the presence of heterozygous disease-causing mutation SCN1A NM_001165963.1:c.4494delC; NP_001159435.1:p.F1499Lfs*2.

Conclusions: The differentiation between Dravet syndrome and β-ureidopropionase deficiency is clinically challenging since both conditions share overlapping clinical features. The detection of urine β-ureidoisobutyric and β-ureidopropionic acids using NMR or GC-MS is helpful in laboratory diagnosis of β-ureidopropionase deficiency. The disease-causing mutation, c.977G>A of β-ureidopropionase deficiency, is highly prevalent in Chinese population (allele frequency=1.7%); β-ureidopropionase deficiency screening test should be performed for any patients with unexplained neurological deficit, developmental delay or autism.
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http://dx.doi.org/10.1016/j.cca.2014.10.030DOI Listing
February 2015

Online Diagnosis System: a webserver for analysis of Sanger sequencing-based genetic testing data.

Methods 2014 Oct 22;69(3):230-6. Epub 2014 Jul 22.

Department of Chemical Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong Special Administrative Region; Li Ka Shing Institute of Health Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong Special Administrative Region. Electronic address:

Sanger sequencing is a well-established molecular technique for diagnosis of genetic diseases. In these tests, DNA sequencers produce vast amounts of data that need to be examined and annotated within a short period of time. To achieve this goal, an online bioinformatics platform that can automate the process is essential. However, to date, there is no such integrated bioinformatics platform available. To fulfill this gap, we developed the Online Diagnosis System (ODS), which is a freely available webserver and supports the commonly used file format of Sanger sequencing data. ODS seamlessly integrates base calling, single nucleotide variation (SNV) identification, and SNV annotation into one single platform. It also allows laboratorians to manually inspect the quality of the identified SNVs in the final report. ODS can significantly reduce the data analysis time therefore allows Sanger sequencing-based genetic testing to be finished in a timely manner. ODS is freely available at http://sunlab.lihs.cuhk.edu.hk/ODS/.
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http://dx.doi.org/10.1016/j.ymeth.2014.07.002DOI Listing
October 2014

Potential effects of NPC1L1 polymorphisms in protecting against clinical disease in a chinese family with sitosterolaemia.

J Atheroscler Thromb 2014 24;21(9):989-95. Epub 2014 Jul 24.

Department of Medicine and Therapeutics, Prince of Wales Hospital, The Chinese University of Hong Kong.

Sitosterolaemia is caused by mutations in either ABCG5 or ABCG8. Chinese and Japanese individuals usually have mutations in ABCG5. We herein report a known and a novel mutation in ABCG8 and their potential interaction with NPC1L1 polymorphisms in a Chinese family with sitosterolaemia. We sequenced ABCG5 and ABCG8 and measured the levels of plasma plant sterols in a 15-year-old Chinese girl with clinical sitosterolaemia (xanthomas with elevated low-density lipoprotein cholesterol (LDL-C) and plant sterols) and her apparently healthy family members. NPC1L1 was sequenced in the genetically affected sibling and other family members. A known mutation, c.490C>T (p. Arg164(*)), in exon 4 and a novel mutation, c.1949T>G (p.Leu650Arg), in exon 13 of ABCG8 were detected in the proband and her sister, who had elevated sterols but low LDL-C levels and no xanthomas. The genetically affected sister, but not the proband, carried two additional heterozygous changes in NPC1L1 (rs2072183 C>G, rs2301935 A>C), which were inherited from the mother, who also had a low LDL-C level. In this study, we detected a known and a novel mutation in ABCG8 in a Chinese patient with sitosterolaemia. The same mutations were found in her clinically normal sister, suggesting that the contrasting features with the proband may be related to different variants in NPC1L1 and/or some other undetermined lipid-related genetic factors.
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http://dx.doi.org/10.5551/jat.24679DOI Listing
June 2015

The first report of a Chinese family with McLeod syndrome.

BMJ Case Rep 2014 Jun 3;2014. Epub 2014 Jun 3.

Department of Medicine and Geriatrics, Tuen Mun Hospital, Hong Kong, Hong Kong.

We report the first case of a Chinese family with McLeod syndrome (MLS). The two affected brothers show significant phenotypic heterogeneity. The index case has peripheral acanthocytosis, choreoathetosis of his feet, a slowly progressive neuropathy and myopathy, and an elevated serum creatine kinase (CK) level. His elder brother has more prominent chorea of the shoulders, epilepsy, a rapidly progressive neuropathy and normal serum CK. The diagnosis of MLS was confirmed by a genetic test which showed a hemizygous frameshift mutation in the XK gene.
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http://dx.doi.org/10.1136/bcr-2013-202785DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4054476PMC
June 2014

Isolated persistent elevation of alanine transaminase for early diagnosis of pre-symptomatic Wilson's disease in Chinese children.

World J Pediatr 2013 Nov 21;9(4):361-4. Epub 2013 Oct 21.

Department of Pediatrics, The Chinese University of Hong Kong, Hong Kong, China,

Background: Recent studies presented a contradictory approach for the investigation of pediatric patients with an isolated increase in alanine transaminase. While classical teaching advised for a thorough investigation, recent studies suggested the yield on further investigation was low and thus not necessary. Yet the approach to the same clinical problem may need to be different due to variable disease prevalence rates among different ethnic populations. For the population with a higher prevalence rate of genetic liver diseases like Wilson's disease, an abnormal liver function may be the first presenting feature for some patients.

Methods: We reviewed 10 Chinese children with Wilson's disease who were diagnosed at a presymptomatic stage because of an isolated persistent elevation of alanine transaminase.

Results: All 10 patients did not have overt symptoms of liver impairment or neurological deficit. They were picked up incidentally with an abnormal liver function test. All patients were started on treatment shortly after diagnosis, and they remained well and symptom-free on the latest follow-up.

Conclusions: This case series illustrated that an isolated persistent elevation of alanine transaminase is an important clue to the early diagnosis of pre-symptomatic Wilson's disease. It is particularly relevant in the Asian population where the disease is more prevalent.
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http://dx.doi.org/10.1007/s12519-013-0436-yDOI Listing
November 2013

Non-invasive urinary screening for aromatic L-amino acid decarboxylase deficiency in high-prevalence areas: a pilot study.

Clin Chim Acta 2012 Jan 21;413(1-2):126-30. Epub 2011 Sep 21.

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Background: The diagnosis of aromatic L-amino acid decarboxylase (AADC) deficiency, one of the pediatric neurotransmitter disorders, is classically made with plasma enzyme level or cerebrospinal fluid (CSF) neurotransmitter profile, while both are technically demanding and the latter requires the invasive lumbar puncture. So far less than 100 cases have been reported worldwide with 20% from Taiwan. It was postulated that the condition might have been under-diagnosed among Chinese populations and a non-invasive screening tool should be developed in areas with high prevalence.

Methods: Urine metabolic profiles performed by gas chromatography-mass spectrometry (GC-MS) in a 31-month period were retrospectively reviewed: those with vanilmandelic acid concentration lower than one percentile plus the presence of 3-o-methyldopa were defined as positive and the patients were further evaluated.

Results: Among 1046 metabolic profiles (from 845 patients) reviewed, 3 profiles from 2 patients were screened positive: both cases had compatible CSF neurotransmitter profiles and the diagnosis was further confirmed by genetic analysis of DDC gene. 13 negative urinary metabolic profiles from 7 patients who had CSF neurotransmitters analyzed were identified as controls: all 7 CSF neurotransmitter profiles were not compatible for AADC deficiency.

Conclusions: The GC-MS-based urine metabolic profiling was shown to be a satisfactory screening tool for AADC deficiency. Further confirmation can be performed by mutation analysis in the DDC gene, thus avoiding risks of lumbar puncture. We advocate all ethnic Chinese patients presenting with dystonia have their urine organic acids analyzed before proceeding to CSF neurotransmitters analysis.
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http://dx.doi.org/10.1016/j.cca.2011.09.008DOI Listing
January 2012

Fatal viral infection-associated encephalopathy in two Chinese boys: a genetically determined risk factor of thermolabile carnitine palmitoyltransferase II variants.

J Hum Genet 2011 Aug 23;56(8):617-21. Epub 2011 Jun 23.

Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong SAR, China.

Influenza-associated encephalopathy (IAE) is a potentially fatal neurological complication of influenza infection usually in the presence of high and persistent fever. Thermolabile carnitine palmitoyltransferase II enzyme (CPT-II) predisposes IAE, so far only described in Japanese. As the genetic origins of Japanese and Chinese are alike, similar genetic risk factors in CPT-II are expected. We report the first two unrelated Chinese patients of thermolabile CPT-II variants that underlain the persistent high fever-triggered viral infection-associated encephalopathy, multi-organ failure and death. Elevated (C16:0+C18:1)/C2 acylcarnitines ratio and the CPT2 susceptibility variant allele [p.Phe352Cys; p.Val368Ile] were detected. The asymptomatic family members of one patient also had abnormal long-chain acylcarnitines. In our experience of biochemical genetics, the elevated (C16:0+C18:1)/C2 acylcarnitines ratio is unusual and specific for thermolabile CPT-II variants. Allele frequency of [p.Phe352Cys; p.Val368Ile] among Hong Kong Chinese was 0.104, similar to Japanese data, and [p.Phe352Cys] has not been reported in Caucasians. This may explain the Asian-specific phenomenon of thermolabile CPT-II-associated IAE. We successfully demonstrated the thermolabile CPT-II variants in patients with viral infection-associated encephalopathy in another Asian population outside Japanese. The condition is likely under-recognized. With our first cases, it is envisaged that more cases will be diagnosed in subsequent years. The exact pathogenic mechanism of how other factors interplay with thermolabile CPT-II variants and high fever leading to IAE, is yet to be elucidated. Fasting and decreased intake during illness may aggravate the disease. Further studies including high risk and neonatal screening are warranted to investigate its expressivity, penetrance and temperature-dependent behaviors in thermolabile CPT-II carriers. This may lead to discovery of the therapeutic golden window by aggressive antipyretics and L-carnitine administration in avoiding the high mortality and morbidity of IAE.
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http://dx.doi.org/10.1038/jhg.2011.63DOI Listing
August 2011

Analysis of inborn errors of metabolism: disease spectrum for expanded newborn screening in Hong Kong.

Chin Med J (Engl) 2011 Apr;124(7):983-9

Chemical Pathology Laboratory, Department of Pathology, Princess Margaret Hospital, Hong Kong SAR, China.

Background: Data of classical inborn errors of metabolism (IEM) of amino acids, organic acids and fatty acid oxidation are largely lacking in Hong Kong, where mass spectrometry-based expanded newborn screening for IEM has not been initiated. The current study aimed to evaluate the approximate incidence, spectrum and other characteristics of classical IEM in Hong Kong, which would be important in developing an expanded newborn screening program for the local area.

Methods: The laboratory records of plasma amino acids, plasma acylcarnitines and urine organic acids analyses from year 2005 to 2009 inclusive in three regional chemical pathology laboratories providing biochemical and genetic diagnostic services for IEM were retrospectively reviewed.

Results: Among the cohort, 43 patients were diagnosed of IEM, including 30 cases (69%) of amino acidemias (predominantly citrin deficiency, hyperphenylalaninemia due to 6-pyruvoyl-tetrahydropterin synthase deficiency and tyrosinemia type I), 5 cases (12%) of organic acidemias (predominantly holocarboxylase synthetase deficiency) and 8 cases (19%) of fatty acid oxidation defects (predominantly carnitine-acylcarnitine translocase deficiency). The incidence of classical IEM in Hong Kong was roughly estimated to be at least 1 case per 4122 lives births, or 0.243 cases per 1000 live births. This incidence is similar to those reported worldwide, including the mainland of China. The estimated incidence of hyperphenylalaninemia was 1 in 29 542 live births.

Conclusions: Our data indicate that it is indisputable for the introduction of expanded newborn screening program in Hong Kong. Since Hong Kong is a metropolitan city, a comprehensive expanded newborn screening program and referral system should be available to serve the neonates born in the area.
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April 2011

Molecular basis of von Hippel-Lindau syndrome in Chinese patients.

Chin Med J (Engl) 2011 Jan;124(2):237-41

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Background: Von Hippel-Lindau (VHL) syndrome is an autosomal dominant familial cancer syndrome predisposing the affected individuals to multiple tumours in various organs. The genetic basis of VHL in Southern Chinese is largely unknown. In this study, we characterized the mutation spectrum of VHL in nine unrelated Southern Chinese families.

Methods: Nine probands with clinical features of VHL, two symptomatic and eight asymptomatic family members were included in this study. Prenatal diagnosis was performed twice for one proband. Two probands had only isolated bilateral phaeochromocytoma. The VHL gene was screened for mutations by polymerase chain reaction, direct sequencing and multiplex ligation-dependent probe amplification (MLPA).

Results: The nine probands and the two symptomatic family members carried heterozygous germline mutations. Eight different VHL mutations were identified in the nine probands. One splicing mutation, NM_000551.2: c.463+1G > T, was novel. The other seven VHL mutations, c.233A > G [p.Asn78Ser], c.239G > T [p.Ser80Ile], c.319C > G [p.Arg107Gly], c.481C > T [p.Arg161X], c.482G > A [p.Arg161Gln], c.499C > T [p.Arg167Trp] and an exon 2 deletion, had been previously reported. Three asymptomatic family members were positive for the mutation and the other five tested negative. In prenatal diagnosis, the fetuses were positive for the mutation.

Conclusions: Genetic analysis could accurately confirm VHL syndrome in patients with isolated tumours such as sporadic phaeochromocytoma or epididymal papillary cystadenoma. Mutation detection in asymptomatic family members allows regular tumour surveillance and early intervention to improve their prognosis. DNA-based diagnosis can have an important impact on clinical management for VHL families.
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January 2011

Role of postmortem genetic testing demonstrated in a case of glutaric aciduria type II.

Diagn Mol Pathol 2010 Sep;19(3):184-6

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Glutaric aciduria type II, or multiple acyl-CoA dehydrogenase deficiency, is a rare metabolic disorder inherited in an autosomal recessive manner. The condition can be caused by mutations in at least 3 genes, including ETFA, ETFB, and ETFDH. When this potentially lethal disorder is known for its clinical and biochemical heterogeneity, mutation analysis will be an invaluable part of diagnosis. We here described a Chinese adolescent boy who enjoyed good health earlier and presented at the age of 14 years with severe vomiting. His condition deteriorated rapidly and he succumbed shortly after. With a travel history before presentation and the late age of onset, diagnosis was particularly difficult. Findings in perimortem biochemical investigations and postmortem autopsy were guiding but not diagnostic. The diagnosis of glutaric aciduria type II was finally confirmed by mutation analysis performed by direct sequencing on genomic DNA from peripheral blood, which identified 2 different unreported missense mutations, c.502G>T (p.V168F) and c.786A>G (p.Q262R), in ETFA. The father and the mother were found to be heterozygous for the 2 mutations in ETFA respectively. Subsequent molecular family screening also ruled out the disease in his elder sister, who had a history of convulsion and a suspicious plasma acylcarnitine profile, and freed her from life-long supplementation. The case showed that molecular autopsies should be part of routine postmortem examination of unexplained sudden death in all age groups and DNA-friendly samples should be routinely collected and archived. In the era of personalized medicine with the power of modern genetics, molecular diagnosis should be obtained for heterogeneous diseases with different genetic defects but sharing similar clinical and/or biochemical phenotypes.
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http://dx.doi.org/10.1097/PDM.0b013e3181c9a8a8DOI Listing
September 2010

Maternally inherited Leigh syndrome: an unusual cause of infantile apnea.

Sleep Breath 2010 Jun 11;14(2):161-5. Epub 2009 Aug 11.

Department of Paediatrics & Adolescent Medicine, The University of Hong Kong, Queen Mary Hospital, Hong Kong, China.

Introduction: Leigh Syndrome is an uncommon cause of infantile apnea.

Case Summary: We report a 5-month-old girl with sudden respiratory arrest followed by episodic hyper- and hypo-ventilation, encephalopathy, and persistent lactic acidosis. Computed tomography of the brain revealed symmetric low densities over the basal ganglia, internal capsule, thalami, and midbrain. Cardiac echocardiogram was suggestive of hypertrophic cardiomyopathy.

Discussion: Diagnosis of Leigh syndrome due to T8993G mutation was confirmed with polymerase chain reaction and direct DNA sequencing of mitochondrial genome. To our knowledge, this is the first report of proven maternally inherited Leigh syndrome in Hong Kong.
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http://dx.doi.org/10.1007/s11325-009-0288-9DOI Listing
June 2010

WITHDRAWN: Novel missense mutation (Y24H) in the G6PT1 gene causing glycogen storage disease type 1b.

Mol Genet Metab 2009 Mar 23. Epub 2009 Mar 23.

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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http://dx.doi.org/10.1016/S1096-7192(02)00057-4DOI Listing
March 2009

Missense mutation Leu72Pro located on the carboxyl terminal amphipathic helix of apolipoprotein C-II causes familial chylomicronemia syndrome.

Clin Chim Acta 2006 Feb 8;364(1-2):256-9. Epub 2005 Sep 8.

Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.

Background: Chylomicronemia syndrome can be caused by 2 autosomal recessive disorders - lipoprotein lipase (LPL) deficiency and apolipoprotein C-II (apo C-II) deficiency.

Methods: We described 2 siblings with chylomicronemia syndrome of a consanguineous family. To determine the molecular basis of chylomicronemia syndrome in this family, we performed direct DNA sequencing of the LPL and APOC2 genes of the proband.

Results: A novel homozygous mutation, Leu72Pro, in the APOC2 gene was found in both siblings whereas their parents were carriers. No LPL mutations were detected in the siblings. Apo C-II contains 3 amphipathic alpha helices; the C-terminal alpha helix is composed of residues 64 to 74. Substitution of residue 72 from a helix former leucine to a helix breaker, proline, is predicted to change the secondary structure of the C-terminal helix and subsequently alter the interaction between apo C-II and LPL.

Conclusions: To our knowledge, Leu72Pro is the first missense mutation identified in the C-terminal of apo C-II. The result is consistent with the current biochemical and structural findings that the C-terminal helix of apo C-II is important for activation of LPL.
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http://dx.doi.org/10.1016/j.cca.2005.07.025DOI Listing
February 2006

Novel mutations in the BCHE gene in patients with no butyrylcholinesterase activity.

Clin Chim Acta 2005 Jan;351(1-2):155-9

Department of Pathology, Queen Elizabeth Hospital, Hong Kong, China.

Background: Butyrylcholinesterase (BCHE) deficiency is characterized by prolonged apnea after the use of certain muscle relaxants with the genetic defect lying in the BCHE gene.

Methods: Two Chinese patients with no serum BCHE activity were studied. The BCHE genes were screened for mutations by polymerase chain reaction and direct DNA sequencing.

Results: Of the four mutations detected, two novel mutations were identified in the two patients, i.e., F474L, and an insertion of an adenine between nucleotide positions 395 and 396. This information was used to screen the immediate families of the patients for carrier status.

Conclusions: We established the molecular basis of butyrylcholinesterase deficiency in two Chinese patients. The developed mutation detection assay provides a reliable method for identifying mutant BCHE carriers.
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http://dx.doi.org/10.1016/j.cccn.2004.09.004DOI Listing
January 2005

Novel mutations of the AGXT gene causing primary hyperoxaluria type 1.

J Nephrol 2004 May-Jun;17(3):436-40

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

Background: Primary hyperoxaluria type 1 (PH1), an inherited cause of nephrolithiasis, is due to a functional defect of the liver-specific peroxisomal enzyme alanine:glyoxylate aminotransferase (AGT). A definitive PH1 diagnosis can be established by analyzing AGT activity in liver tissue or mutation analysis of the AGXT gene.

Methods: The molecular basis of PH1 in three Chinese patients, two with adult-onset and one with childhood-onset recurrent nephrolithiasis, was established by analyzing the entire AGXT gene.

Results: Three novel mutations (c2T>C, c817insAG and c844C>T) and two previously reported mutations (c33insC and 679-IVS6+2delAAgt) were identified. c2T>C converts the initiation codon from ATG to ACG, which predicts significant reduction, if not complete abolition, of protein translation. c817insAG leads to a frameshift and changes the amino acid sequence after codon 274. c844C>T changes glutamine at codon 282 to a termination codon, resulting in protein truncation.

Conclusions: This is the first report describing AGXT gene mutations in Chinese patients with PH1. AGXT genotypes cannot fully explain the clinical heterogeneity of PH1, and other factors involved in disease pathogenesis remain to be identified. Our experience emphasizes the importance of excluding PH1 in patients with recurrent nephrolithiasis to avoid delay or inappropriate management.
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October 2004

Ethnic-specific splicing mutation of the carnitine-acylcarnitine translocase gene in a Chinese neonate presenting with sudden unexpected death.

Chin Med J (Engl) 2003 Jul;116(7):1110-2

Department of Chemical Pathology, the Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.

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July 2003

Novel missense mutation (Y24H) in the G6PT1 gene causing glycogen storage disease type 1b.

Mol Genet Metab 2002 Nov;77(3):249-51

Department of Pathology, Princess Margaret Hospital, Hong Kong, China.

We describe a Chinese patient with glycogen storage disease type 1b presenting with failure to thrive and protuberant abdomen. The neutropenia was mild and the patient did not have fasting hypoglycemia. Direct DNA sequencing of the G6PT1 gene revealed the patient to be a compound heterozygote of a novel missense mutation, Y24H, and another missense mutation, P191L, which we had described previously. The mother is heterozygous for the Y24H mutation and the father is heterozygous for the P191L mutation. Y24H and P191L may be ethnic-specific mutations as they have not been reported in other populations. The DNA-based diagnosis of GSD 1b will enable us to make an accurate determination of carrier status and to perform prenatal diagnosis of this disease.
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http://dx.doi.org/10.1016/s1096-7192(02)00110-5DOI Listing
November 2002

DNA-based diagnosis of isolated sulfite oxidase deficiency by denaturing high-performance liquid chromatography.

Mol Genet Metab 2002 Jan;75(1):91-5

Department of Chemical Pathology, The Chinese University of Hong Kong, Prince of Wales Hospital, Hong Kong, China.

Isolated sulfite oxidase deficiency is a rare autosomal recessive disease, characterized by severe neurological abnormalities, seizures, mental retardation, and dislocation of the ocular lenses, that often leads to death in infancy. There is a special demand for prenatal diagnosis, since no effective treatment is available for isolated sulfite oxidase deficiency. Until now, the cDNA sequence of the sulfite oxidase (SUOX) gene has been available, but the genomic sequence of the SUOX gene has not been published. In this study, we have performed a DNA-based diagnosis of isolated sulfite oxidase deficiency in a Chinese patient. To do so, we designed oligonucleotide primers for amplification of the predicted exons and intron-exon boundaries of the SUOX gene obtained from the completed draft version of the human genome. Using overlapping PCR products, we confirmed the flanking intronic sequences of the coding exons and that the entire 466-residue mature peptide is encoded by the last exon of the gene. We then performed mutation detection using denaturing high-performance liquid chromatography (DHPLC). The DHPLC chromatogram of exon 2b showed the presence of heteroduplex peaks only after mixing of the mutant DNA with the wild-type DNA, indicating the presence of a homozygous mutation. Direct DNA sequencing showed a homozygous base substitution at codon 160, changing the codon from CGG to CAG, which changes the amino acid from arginine to glutamine, i.e., R160Q. The DNA-based diagnosis of isolated sulfite oxidase deficiency will enable us to make an accurate determination of carrier status and to perform prenatal diagnosis of this disease. The availability of the genomic sequences of human genes from the completed draft human genome sequence will simplify the development of molecular genetic diagnoses of human diseases from peripheral blood DNA.
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http://dx.doi.org/10.1006/mgme.2001.3267DOI Listing
January 2002
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