The Omicron variant of COVID-19 and its association with croup in children: a single-centre study in Hong Kong.

INTRODUCTION: The fifth wave of the coronavirus disease 2019 (COVID-19) pandemic in Hong Kong was dominated by the Omicron variant, which may cause more upper airway involvement in children. This study was performed to identify any associations between the Omicron variant of COVID-19 and croup in children. METHODS: This retrospective study reviewed the electronic medical records of patients admitted to Tuen Mun Hospital in Hong Kong from 1 January 2018 to 31 March 2022 under the diagnostic code for croup (J05.0 in the International Classification of Diseases 10th Edition). Patients were categorised into three groups according to their admission periods, namely, non-COVID-19, COVID-19-pre-Omicron, and COVID-19-Omicron groups. Disease associations and severity were compared according to incidence, Westley Croup Score, length of hospital stay, medication use, respiratory support, and intensive care unit admissions. RESULTS: The COVID-19 incidence among patients with croup was significantly higher in the COVID-19-Omicron group than in the COVID-19-pre-Omicron group (90.0% vs 2.0%; P<0.001). Compared with patients in the COVID-19-pre-Omicron and non-COVID-19 groups, patients in the COVID-19-Omicron group also had a higher Westley score (moderate and severe disease in the COVID-19-Omicron group: 56.7%; COVID-19-pre-Omicron group: 22.0%, P=0.004; non-COVID-19 group: 24.8%, P<0.001), longer median hospital stay (COVID-19-Omicron group: 3.00 days; COVID-19-pre-Omicron group: 2.00 days, P<0.001; non-COVID-19 group: 2.00 days, P=0.034), and higher mean dexamethasone requirement (COVID-19-Omicron group: 0.78 mg/kg; COVID-19-pre-Omicron group: 0.49 mg/kg, P<0.001; non-COVID-19 group: 0.58 mg/kg, P=0.001). CONCLUSION: The Omicron variant of COVID-19 is associated with croup and can cause more severe disease in Hong Kong children.

Epidemiology and risk factors for severe respiratory syncytial virus infections requiring pediatric intensive care admission in Hong Kong children.

PURPOSE: Respiratory syncytial virus (RSV) is a common cause of lower respiratory tract infection in young children. However, there are limited data on severe RSV infection requiring pediatric intensive care unit (PICU) admission. This retrospective study described features of RSV-associated PICU admissions in Hong Kong and investigated factors for mortality and duration of PICU stay. METHODS: Children with laboratory-confirmed RSV infection and admitted to the PICUs of all eight government hospitals in Hong Kong between January 2009 and June 2011 were identified from computerized auditing systems and PICU databases. RSV in respiratory samples was detected by direct immunofluorescence and/or viral culture. The relationships between mortality and PICU duration and demographic and clinical factors were analyzed. RESULTS: A total of 118 (2.4 %) PICU admissions were identified among 4,912 RSV-positive pediatric cases in all hospitals. Sixty-five (55.6 %) patients were infants. PICU admissions were higher between October and March. Eight (6.8 %) patients died, but only two were infants. RSV-associated mortality was related to prior sick contact, presence of older siblings, neurodevelopmental conditions, chromosomal and genetic diseases, and bacterial co-infections, but none was significant following logistic regression analyses (odds ratio 9.36, 95 % confidence interval 0.91-96.03 for prior sick contact, p = 0.060). Chronic lung disease was the only risk factor for the duration of PICU admission (ß = 0.218, p = 0.017). CONCLUSIONS: The majority of RSV-infected children do not require PICU support. There is winter seasonality for RSV-associated PICU admission in Hong Kong. Prior sick contact is the only risk factor for RSV-associated mortality, whereas the presence of chronic lung disease is associated with longer PICU stay. The current risk-based approach of RSV prophylaxis may not be effective in reducing severe RSV infections.

Vigabatrin-induced visual dysfunction in Chinese patients with refractory epilepsy.

PURPOSE: Bilateral visual field constriction has been reported following the use of the antiepileptic drug (AED) vigabatrin. The incidence of retinal toxicity is variable and there are limited data in Asian populations. The authors report the results of ophthalmologic examination in Chinese patients taking this drug. METHODS: The authors identified two groups of patients with refractory epilepsy: one group on vigabatrin and another cohort of patients taking other AEDs. The authors recorded the medical history and performed visual acuity testing, intraocular pressure measurement, slit lamp biomicroscopy, and conventional automated perimetry with Humphrey Visual Field Analyzer II in all patients. RESULTS: Eighteen patients--8 men and 10 women--with a mean age of 23.8 years who were taking vigabatrin were reviewed. Length of treatment with this drug ranged from 13 months to 5 years and the mean daily dosage was 1581 mg. None of the patients in either group had a history of coexisting optic nerve diseases or other neurotoxic drug use. Twenty of 36 (55.6%) eyes of the vigabatrin users showed significant bilateral visual field defects with 80% showing a concentric pattern, compared with none in the control group. CONCLUSIONS: The authors confirmed a high prevalence of visual field constriction associated with vigabatrin in Chinese patients. The use of alternative novel techniques such as measurement of the retinal nerve fibre layer thickness and perimetry may detect early retinal damage and result in even higher incidences. Visual field monitoring is recommended in patients who continue to take this drug.

Genomic annotation of 15,809 ESTs identified from pooled early gestation human eyes.

To complement cDNA libraries from the human eye at early gestation and to discover candidate genes associated with early ocular development, we used freshly dissected human eyeballs from week 9-14 of gestation to construct the early human fetal eye cDNA library. A total of 15,809 clones were isolated and sequenced from the unamplified and unnormalized library. We screened 11,246 good-quality ESTs, leading to the identification of 5,534 nonredundant clusters. Among them, 4,010 (72%) genes matched in the human protein database (Ensembl). The remaining 28% (1,524) corresponded to potentially novel or previously unidentified ESTs. We used BLASTX to compare our EST data with eight organisms and found common expression of a high portion of genes: Caenorhabditis briggsae (26%), Caenorhabditis elegans (27%), Anopheles gambiae (37%), Drosophila melanogaster (32%), Danio rerio (42%), Fugu rubripes (49%), Rattus norvegicusvalitus (52%), and Mus musculus (59%). Nevertheless, 48% (2,680 of 5,534) of the genes expressed in the early developing eye were not shared with current NEIBank human eye cDNA data. In addition, eight known retinal disease genes existed in our ESTs. Among them, six (COL11A1, BBS5, PDE6B, OAT, VMD2, and PGK1) were conserved among the genomes of other organisms, indicating that our annotated EST set provides not only a valuable resource for gene discovery and functional genomic analysis but also for phylogenetic analysis. Our foremost early gestation human eye cDNA library could provide detailed comparisons across species to identify physiological functions of genes and to elucidate evolutionary mechanisms.

Molecular characterization of the developmental gene in eyes: through data-mining on integrated transcriptome databases.

OBJECTIVES: Our aim was to utilize publicly available and proprietary sources to discover candidate genes important for ocular development. DESIGN AND METHODS: The collated information on our 5092 non-redundant clusters was grouped and functional annotation was conducted using gene ontology (FatiGO) for categorizing them with respect to molecular function. The web-based viewer technological platform (H-InvDB) was employed for transcription analyses of in-house high quality fetal eye Expressed Sequence Tags (ESTs). Eye-specific ESTs were also analyzed across species by using EMBEST. RESULTS: According to adult eye cDNA libraries, nucleic acid binding and cell structure/cytoskeletal protein genes were the most abundant among the ESTs of fetal eyes. Using cDNA assembly in H-InvDB, 20 (80%) of the 25 most commonly expressed genes in the human eye are also expressed in extraocular tissues. The crystalline gamma S gene is highly expressed in the eye, but not in other tissues. We used EMBEST to compare human fetal eye and octopus eye ESTs and the expression similarity was low (1.6%). This indicated that our fetal eye library contains genes necessary for the developmental process and biological function of the eye, which may not be expressed in the fully developed octopus eyes. The human fetal eye cDNA library also contained highly abundant eye tissue genes, including alphaA-crystallin, eukaryotic translation elongation factor 1 alpha 1 (EEF1A1), bestrophin (VMD2), cystatin C, and transforming growth factor, beta-induced (BIGH3). CONCLUSIONS: Our annotated EST set provides a valuable resource for gene discovery and functional genomic analysis. This display will help to appreciate the strengths and weaknesses of the different technological platforms, so that in future studies the maximum amount of beneficial information can be derived from the appropriate use of each method.

Decreasing efficacy of repeated intravitreal triamcinolone injections in diabetic macular oedema.

BACKGROUND/AIM: Intravitreal triamcinolone (IVTA) results in transient improvements in diabetic macular oedema (DMO), necessitating repeated injections. The authors report a case series of 10 eyes of 10 patients with DMO, who received a repeat injection of 4 mg IVTA, at least 26 weeks after the first injection of the same dose. METHOD: Pre-injection and at 2, 4, 9, and 17 weeks post-injection, best corrected visual acuity (BCVA) and central foveal thickness (CFT) on optical coherence tomography, after the first and repeat injections, were compared using paired t test. Side effects were monitored. RESULTS: BCVA, CFT, intraocular pressure (IOP), and cataract scores were not significantly different before initial and repeat injections (given at 32.5 (SD 3.5) weeks after the first injection). Transient improvements of BCVA and CFT were achieved after both injections. However, after the repeat injection, the BCVA was significantly worse at all time points (p<0.05) and so were the best achieved CFT and the CFT at 4 weeks post-injection (p = 0.034 and 0.011 respectively), compared with the initial injection. Post-injection maximum IOPs and increase in cataract scores were not significantly different between the two injections. CONCLUSION: A repeat injection of 4 mg of IVTA may not be as effective as an initial injection for the treatment of DMO.

Combined photodynamic therapy and intravitreal triamcinolone injection for the treatment of subfoveal choroidal neovascularisation in age related macular degeneration: a comparative study.

AIM: To evaluate the outcomes of combined intravitreal triamcinolone (IVTA) and photodynamic therapy (PDT) with verteporfin in the treatment of subfoveal choroidal neovascularisation (CNV) caused by age related macular degeneration (AMD). METHODS: 48 eyes from 48 patients with subfoveal CNV caused by AMD were prospective recruited, with 24 eyes treated with combined PDT with IVTA and compared with a control group of 24 eyes which received PDT monotherapy. In the combined treatment group, IVTA was performed immediately after PDT as an outpatient procedure. The mean number of treatments, mean logMAR best corrected visual acuity (BCVA), mean line of visual acuity changes, and proportion of patients without moderate visual loss at 1 year were compared between the combined and monotherapy groups. RESULTS: At 1 year the logMAR BCVA for the PDT with IVTA group changed from 0.88 to 0.95 (p = 0.32 compared with baseline), whereas the logMAR BCVA for the monotherapy group reduced from 0.74 to 1.09 (p<0.001 compared with baseline). A significantly higher proportion of patients who had PDT with IVTA did not develop moderate visual loss at 1 year compared with the monotherapy group (70.8% and 33.3% respectively, p = 0.009). Eyes which had combined treatment had significantly fewer lines lost compared with monotherapy alone (0.7 and 3.5 lines respectively, p = 0.015). Subgroup analysis showed that PDT with IVTA is effective in preventing visual loss in both predominately classic and occult CNV groups. The mean number of treatments for the combined and monotherapy groups was 1.5 and 1.96 respectively (p = 0.076). CONCLUSIONS: Combined PDT with IVTA appeared more effective statistically at 12 months for stabilisation of vision (<3 logMAR lines change) compared with PDT monotherapy. Further randomised control trials might be justified to conclude the efficacy of PDT with IVTA.

Safety enhanced photodynamic therapy with half dose verteporfin for chronic central serous chorioretinopathy: a short term pilot study.

AIM: To evaluate short term safety of an enhanced photodynamic therapy (PDT) protocol with half dose verteporfin for treating chronic central serous chorioretinopathy (CSC). METHODS: 20 eyes of 18 patients with symptomatic chronic CSC underwent PDT using 3 mg/m2 verteporfin. Verteporfin was infused over 8 minutes followed by indocyanine green angiography guided laser application 2 minutes later. Serial optical coherence tomography (OCT) and multifocal electroretinography (mfERG) recordings were performed before PDT, at 4 days, 2 weeks, and 1 month after PDT. The best corrected visual acuity (BCVA), OCT central retinal thickness, and mean mfERG response amplitudes and peak latencies were compared longitudinally. Subgroup analysis was further performed for eyes with or without pigment epithelial detachment (PED). RESULTS: At 1 month after PDT, the median BCVA improved from 20/40 to 20/30 (p = 0.001). The mean central retinal thickness also reduced from 276 microm to 158 microm (p < 0.001) and 17 (85%) eyes had complete resolution of serous retinal detachment and/or PED. MfERG showed no significant changes in the mean N1 and P1 response amplitude and latency for all eyes. Subgroup analysis demonstrated that eyes without PED had a significant increase in the mean central mfERG P1 response amplitude with reduction in P1 peak latency at 1 month post-PDT. For eyes with PED, transient reduction in the mean central P1 response amplitude was observed at 4 days post-PDT. CONCLUSIONS: The modified safety enhanced PDT protocol with half dose verteporfin appeared to be a beneficial treatment option for patients with chronic CSC, especially in eyes without serous PED. Further controlled study is warranted to demonstrate the long term safety and efficacy of this treatment option.

Late leakage of filtering bleb in a patient with orbital pseudotumor.

PURPOSE: To report an unusual case of spontaneous late leakage of filtering bleb in a patient with orbital pseudotumor. METHODS: Single case report. RESULTS: A 53-year-old woman developed spontaneous leakage of bleb in her right eye 23 years after trabeculectomy with application of mitomycin-C (MMC). Two weeks later, her symptoms were blurring of vision, increasing redness, and dull ocular pain in the right eye. The inflammatory signs were suggestive of endophthalmitis, orbital cellulites, or pseudo-tumor. Absence of ophthalmoplegia, fever, and raised white cell count, together with the computed tomographic scan finding, confirmed the diagnosis of orbital pseudotumor. She responded well to oral steroids. CONCLUSIONS: Orbital pseudotumor may initially present with spontaneous late leakage in a bleb augmented by MMC. Orbital pseudotumor should be added to the list of differential diagnoses when facing a patient with an inflamed, chemotic, proptotic eye in the presence of a late bleb leak.

Adrenoreceptor-mediated effect of neuropeptide Y decreases cardiac inotropic responses.

The effect of neuropeptide Y on the number and affinity of catecholamine receptors in the ventricular myocardium was investigated. Receptor binding studies showed that incubation of cardiac membrane in the presence of neuropeptide Y (NPY, 10(-7) M) decreased the number of alpha/beta-adrenoceptor binding sites (Bmax) without affecting the affinity (KD) of these receptors. Although not able to modulate the contractility by itself, NPY was able to decrease the positive inotropic effects of phenylephrine and isoproterenol in the isolated, perfused myocardium. Ca2+/Mg(2+)-ATPase activity, measured from the sarcolemma, sarcoplasmic reticulum and myofibrils, was unaltered whereas the activity of sarcolemmal Na+/K(+)-ATPase was decreased when NPY was included in the media. On the other hand, NPY was shown to increase the phosphoinositide-phospholipase C associated with the sarcolemma. These findings support the hypothesis that NPY modulates postsynaptic adrenergic receptors in the myocardium and can affect the adrenergic-induced, inotropic response.

Gene mutations in retinitis pigmentosa and their clinical implications.

Retinitis pigmentosa (RP) is a group of inherited progressive retinal diseases affecting about 1 in 3500 people worldwide. So far, there is no prevention or cure, with permanent visual loss or even blindness the ultimate consequence usually after midlife. The genetics of RP are complex. It can be sporadic, autosomal dominant, autosomal recessive, or X-linked. Thirty-two genes are known to be associated with RP, sometimes the same gene gets involved in different inheritance traits. Some RP cases have a digenic cause. About 60% RP cases still have no known genetic cause. A large number of mutations cause RP, and they can be deletions, insertions, or substitutions that cause missense mutations or truncations. The RHO, RP1, and RPGR genes contribute the greatest number of known mutations causative of RP. But there is no single mutation that alone accounts for more than 10% of unrelated patients. Genetic testing for RP therefore requires screening for a group of genes. High-throughput and automated sequence detection technologies are essential. Due to the complexity in phenotype and genetics, and the fact that RP is untreatable, genetic testing for presymptomatic diagnosis of RP is controversial. Meanwhile, new genes are still to be identified, mostly by family linkage and sib-pair analysis. Research on gene therapy for RP requires information on gene mutations causative of RP.

Efficacy of pressure topical anaesthesia in punctal occlusion by diathermy.

AIMS: To prospectively compare the efficacy and safety of pressure topical anaesthesia in punctal occlusion by using cautery in the treatment of dry eye syndrome (DES) with that of conventional treatment by using needle injection of anaesthetic agents. METHODS: In a randomised controlled trial, 18 consecutive adult patients with DES requiring punctal occlusion were recruited over a 10 month period. Consenting patients were randomised into two groups. Group A patients received pressure topical anaesthesia in the right eye followed by injection anaesthesia in the left eye. Group B was vice versa. Punctal occlusion using cautery was performed in each eye after a specified time following the application of anaesthesia. The main outcome measures were the pain experienced during application of anaesthesia and that during punctal occlusion. RESULTS: 36 eyes of 18 patients were randomised to receive injection anaesthesia in one eye and pressure topical anaesthesia in the other. Nine patients (nine females) were in group A and nine patients (seven females, two males) in group B. The mean age of group A patients was 45.3 (SD 13.5) years, and that of group B patients was 55.6 (12.6) years. The two groups were comparable in terms of mean age (p=0.117) and mean pain score for pressure topical anaesthesia application (p=0.612), injection anaesthesia application (p=0.454), diathermy in pressure anaesthetised eyes (p=0.113), and diathermy in injection anaesthetised eyes (p=0.289). Paired t test was used to compare the mean pain score for pressure topical anaesthesia application (16.8 (24.8)) with those for injection anaesthesia application (56.7 (30.0)). 18 eyes of 18 patients were compared with the fellow eye of the same 18 patients. The mean pain score for injection anaesthesia was greater than for pressure topical anaesthesia application (p<0.0001) (statistical power=0.87). No statistically significant difference was found in the mean pain score for diathermy for eyes that received pressure topical anaesthesia (20.5 (27.5)) compared with eyes that received injection anaesthesia (23.1 (26.3)) (p=0.760) (statistical power=0.96). All 18 patients preferred pressure topical anaesthesia to injection anaesthesia. CONCLUSION: Injection anaesthesia for punctal occlusion is more painful than pressure topical anaesthesia application. However, the pain experienced during diathermy application for punctal occlusion is similar between pressure anaesthetised eyes and injection anaesthetised eyes. Pressure topical anaesthesia is a less painful (in terms of anaesthesia application) but equally effective alternative to conventional injection anaesthesia when used for punctal occlusion.

Choroidal neovascularisation in pathological myopia: an update in management.

Choroidal neovascularisation (CNV) secondary to pathological myopia is an important cause of significant visual impairment in young and middle aged adults globally and is particularly prevalent in Asian populations. In the past few years, there have been rapid advancements in the different treatments for myopic CNV. The purpose of this perspective is to give an overview of the natural history of myopic CNV and the various treatment options including laser photocoagulation, photodynamic therapy, sub-macular surgery, and macular translocation surgery. Future directions in the management of myopic CNV are also discussed.

Chloroquine-induced bull's eye maculopathy.

We report the case of a 51-year-old woman who presented with bilateral progressive deterioration in vision after taking chloroquine for severe rheumatoid arthritis for 10 years. She was found to have a bull's eye pattern of depigmentation in the macula of both eyes. Despite cessation of chloroquine, her vision did not improve. The clinical presentation of chloroquine retinopathy is discussed, along with the importance of scheduled eye examination for individuals taking chloroquine or hydroxychloroquine.

Causes of childhood blindness in a school for the visually impaired in Hong Kong.

OBJECTIVE: To identify the causes of blindness in children attending a school for the blind in Hong Kong. DESIGN: Cross-sectional observational study. SETTING: School for blind children in Hong Kong. PARTICIPANTS: Eighty-two blind students at the Ebenezer School and Home for the Visually Impaired were examined between December 1998 and August 1999. MAIN OUTCOME MEASURES: Demographic data were obtained from students and a questionnaire assessment made of their medical and ocular history. Visual acuity was assessed and visual loss classified according to the World Health Organization classification of visual impairment. Complete ophthalmic assessments were performed in all students including slit-lamp examination and dilated binocular indirect ophthalmoscopy. RESULTS: The mean age of the students was 12.2 years. Ten (12.2%) had a family history of eye disease. Major past medical illnesses were reported in 50% with prematurity and diseases of the central nervous system found in 26.8% and 11.0% of students, respectively. The most common anatomical site for visual impairment was the retina (47.6%), followed by diseases of the optic nerve (14.6%), and diseases of the anterior segment and the lens (14.6%). CONCLUSIONS: The pattern of childhood blindness in Hong Kong is similar to that seen in other developed countries. Preventable causes of childhood blindness, such as prematurity and birth asphyxia, were responsible for a large proportion of cases. Early diagnosis and treatment of such conditions may reduce the incidence of childhood blindness in Hong Kong.

Primary immunodeficiency in Hong Kong and the use of genetic analysis for diagnosis.

OBJECTIVES: To review the management of primary immunodeficiency and discuss recent advances in genetic analysis. DESIGN: Retrospective study. SETTING: University teaching hospital, Hong Kong. PATIENTS: Children diagnosed with primary immunodeficiency and followed up in the immunology clinic during the period 1988 to 2003. MAIN OUTCOME MEASURES: Demographic data, co-morbidities and treatment of patients, outcome and complications; identification of disease by genetic mutations. RESULTS: Medical records of a total of 117 patients (72 male, 45 female) diagnosed with primary immunodeficiency in the Department of Paediatrics and Adolescent Medicine, Queen Mary Hospital, Hong Kong during the past 15 years (1988-2003) were reviewed. All patients were followed up in the immunology clinic. Some patients had been referred from the private sector or other hospitals for immunological workup. Six categories of primary immunodeficiency were identified: predominantly humoral defect (n=50), predominantly cellular defect (n=22), combined humoral and cellular defect (n=5), phagocytic defect (n=18), complement disorders (n=4), and others (n=18). Although infection was the underlying cause of most co-morbidities and mortality, autoimmune (n=7) and allergic (n=23) manifestations were common. In addition, three patients developed lymphoma. Recent advances in the genetic diagnosis of several types of primary immunodeficiency were also reviewed: X-linked Wiskott-Aldrich syndrome, X-linked chronic granulomatous disease, X-linked agammaglobulinaemia, X-linked lymphoproliferative syndrome, leukocyte adhesion disease type I, and X-linked hyperimmunoglobulin M syndrome. This provides an invaluable means of understanding the molecular basis of primary immunodeficiency and has important clinical applications. CONCLUSIONS: Co-morbidities like autoimmune disease and allergic disease are common in patients with primary immunodeficiency and should be carefully evaluated. Likewise, a diagnosis of primary immunodeficiency should be considered when evaluating patients with these conditions. Rapid progress in the field of molecular genetics will enable definite and early diagnosis, and more importantly, potential curative therapy to be administered.

Genetic markers for retinitis pigmentosa.

OBJECTIVE: To review recent advances in the molecular genetics of retinitis pigmentosa with emphasis on the development of genetic markers that aids diagnosis and prognosis. DATA SOURCES AND EXTRACTION: Literature search of MEDLINE from 1988 to 2005 using the following key words: 'retinitis pigmentosa', 'rhodopsin', 'RP1', 'RPGR', and 'genetic counseling'. References of two genes--RHO and RP1--causing retinitis pigmentosa in the Chinese population were reviewed. STUDY SELECTION: Literature and data related to genetic markers for retinitis pigmentosa. DATA SYNTHESIS: The genetics of retinitis pigmentosa is complex. It can be sporadic or familial, with heterogeneous transmission modes. Retinitis pigmentosa is associated with nearly 40 chromosomal loci, where 32 candidate genes have been identified. A large number of mutations are known to cause retinitis pigmentosa. But no single mutation alone accounts for more than 10% of unrelated retinitis pigmentosa patients. Genetic tests for retinitis pigmentosa require screening for a consort of mutations in a large number of genes. High throughput screening technology such as denaturing high performance liquid chromatography and automated DNA sequencing should make such tests feasible. CONCLUSIONS: Rapid developments in the understanding of the genetics of retinitis pigmentosa have helped to establish genetic tests of clinical value. The complex mode of inheritance nonetheless makes genetic counselling difficult, even in the presence of positive genetic screening results.

RP1 in Chinese: Eight novel variants and evidence that truncation of the extreme C-terminal does not cause retinitis pigmentosa.

Heterozygous truncating mutations in the RP1 gene cause approximately 7% of autosomal dominant retinitis pigmentosa (RP) cases. To examine the role of RP1 mutations in RP, we screened 101 unrelated Chinese RP patients (unselected for mode of inheritance) and 190 elderly normal control subjects for sequence changes in the coding exons for the 2156 amino acid RP1 protein. One patient had a mutation, thus RP1 mutations cause about 0.0% to 5.4% (95% confidence interval) of all RP among Chinese. The mutation was R677X, the most common found in Americans. Five other known sequence changes were found. In addition, nine novel sequence alterations were identified: 746G>A (R249H), 1437G>T (M479I), 2116G>C (G706R), 3024G>A (Q1008Q), 3188G>A (Q1063R), 5797C>T (R1933X), 6423A>G (I2141M), and the variants 6542C>T and 6676T>A, both in the 3' untranslated region. One control subject and three members of a non-RP family were heterozygous for R1933X, which is therefore likely to be a non-disease-causing variant. The most C-terminal truncation previously reported was due to Tyr1053 (1-bp del) and occurred in RP patients. Thus the presence of a normal level of at least part of RP1 between amino acids 1052 and 1933 appears necessary to prevent RP. Hum Mutat 17:436, 2001.

High-throughput conformation-sensitive gel electrophoresis for discovery of SNPs.

High-throughput screening for single nucleotide polymorphisms (SNPs) or mutations can be achieved by inexpensive technologies. We modified the original protocols of conformation-sensitive gel electrophoresis (CSGE) to increase throughput several fold to 1.3 samples/min, which is about five times faster than denaturing high-performance liquid chromatography (DHPLC). The modifications include decreasing the gel thickness, increasing the number of lanes to 96, and increasing the number of samples per lane to seven. This high-throughput CSGE method is fast, robust, and as simple as the original protocols. Together with a two-stage strategy for screening homozygotes and the replacement of ethidium bromide with SYBR Gold DNA dye staining, this protocol is a reliable and cost-effective alternative for laboratories that require high-throughput screening.