Indocyanine green staining and removal of internal limiting membrane in macular hole surgery: histology and outcome

PURPOSE

To report the surgical technique, outcome, and histologic findings involving indocyanine green staining and removal of internal limiting membrane in primary macular hole surgery.

METHODS

Prospectively, consecutive patients with idiopathic macular hole or myopic macular hole with retinal detachment were recruited. After pars plana vitrectomy and epiretinal membrane removal, the internal limiting membrane was stained and removed. The specimens were stained using hematoxylin and eosin and periodic acid-Schiff. Immunohistochemical staining was also performed for glial fibrillary acidic protein, vimentin, type I and type IV collagen, and actin.

RESULTS

Among 10 patients (10 eyes) in the study, nine eyes had stage 3 or 4 macular hole. Four of them had chronic macular hole. The tenth patient had retinal detachment resulting from a myopic macular hole. Postoperatively, all cases had closure of macular hole without an elevated edge and the retina was attached. Seven patients had improvement of 2 or more Snellen lines, whereas visual acuity remained the same for the other three patients. In six eyes in which complete histologic examinations were feasible, internal limiting membrane was confirmed and two eyes also had a small amount of epiretinal membrane. Myofibrocytes in internal limiting membrane, either scattered or as a single layer, were found in three cases.

CONCLUSIONS

Removal of indocyanine green--stained internal limiting membrane around idiopathic macular hole or myopic macular hole with retinal detachment is confirmed with histology and may contribute to macular hole closure and retinal reattachment.

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.

The miracle of microarray data analysis

A report on the tenth Annual Bioinformatics and Genome Research meeting of the Cambridge Healthtech Institute's Beyond Genome 2001 series, San Francisco, USA, 17-19 June 2001.

Genetic imbalances in pT2 breast cancers of southern Chinese women

While much information has been reported on the genetic alterations in breast cancers of Caucasians, little is known about the Oriental populations where breast cancers currently rank the second most common neoplasm. As a first step toward understanding the underlying genetics changes in this population, we used comparative genomic hybridization (CGH) to the genome-wide analysis of forty pT2 tumors from patients of a racially homogenous population in southern China. A complex pattern of genetic alterations emerged with the commonest chromosomal gains identified on 1q (58%), 8q (55%), 11q13 (25%), 16p (28%), 17q (53%) and 20q (35%), and frequent losses on 8p (38%), 11q (28%), 13q (30%) and 18q (25%). When breast cancers with and without lymph-node metastasis were compared, a higher copy gain of 10p was identified in the node-positive group (P=.036). An overall increase in the average number of genetic aberrations was also identified in the late onset group (>45 years)(P=.042) with a higher incidence of genetic losses noted (P=.035). In particular, losses on 16q were detected in 30% of the late onset patients but none in the early onsets (P=0.049). In this study, we have illustrated the pattern of genetic changes in breast tumors of southern Chinese females. While frequent 1q, 8q, 17q and 20q gains, and common 8p and 13q deletions detected were consistent to those aberrations reported from the Caucasian populations, the difference in genetic changes associated in lymph-node metastasis and age of onset identified should provide the basis for additional investigations into the underlying tumorigenesis in the Oriental population.

Absence of trabecular meshwork-inducible stretch response (TISR)/oculomedin gene and proximal promoter mutation in primary open angle glaucoma patients

We investigated the coding exon and promoter sequence in the trabecular meshwork-inducible stretch response (TISR)/oculomedin gene for mutations in Chinese primary open angle glaucoma (POAG) subjects. The entire TISR/oculomedin coding sequence, together with 138 bp of promoter sequence 5' to the start codon and 170 bp of the 3' untranslated region in 110 Chinese POAG patients and 108 unrelated control subjects without glaucoma, aged 50 years or above, were screened for alterations by DNA sequencing. One heterozygous sequence alteration, K28E, was identified in one control subject, and two homozygous sequence alterations, K28K and 135+36delC, were universally found in every sample. As a result, no common TISR/ oculomedin coding sequence nor any proximal promoter mutation that causes POAG was found. The effect of TISR/ oculomedin in glaucoma has yet to be established.

Hunting for disease genes in multi-functional diseases

Disease genes may be identified through functional, positional, and candidate gene approaches. Although extensive and often labor-intensive studies such as family linkage analysis, functional investigation of gene products and genome database searches are usually involved, thousands of human disease genes, especially for monogenic diseases with Mendelian transmission, have been identified. However, in diseases caused by more than one gene, or by a combination of genetic and environmental factors, identification of the genes is even more difficult. Common examples include atherosclerosis, cancer, Alzheimer's disease, asthma, diabetes, glaucoma, and age-related macular degeneration. There have been conflicting reports on the roles of associated genes. Even with population-based case-control studies and new statistical methods such as the sib-ship disequilibrium test and the discordant alleles test, there is no agreement on whether alpha2-macroglobulin (A2M) is a gene for Alzheimer's disease. Another example is the inconsistent association between age-related macular degeneration and ATP-binding cassette transporter (ABCR). Ethnic variation causes further complications. In our investigation of LDL-receptor variants in familial hypercholesterolemia, and the trabecular meshwork inducible glucocorticoid response protein, or myocillin (TIGR-MYOC) mutation pattern in primary open angle glaucoma, we did find dissimilar results in Chinese compared to Caucasians. New information from the Human Genome Project and advancements in technologies will aid the search for and confirm identification of disease genes despite such challenges.

Rapid analysis of CGG repeat length in the FMR1 gene

The number of trinucleotide CGG repeats at the 5' untranslated region of the FMR1 gene is associated with the fragile X syndrome of mental retardation. We screened for the CGG repeat length in the FMR1 gene of the X-chromosomes from unrelated normal Chinese subjects recruited in Hong Kong and Dalian, a southern and a northern Chinese city respectively. These cities are about 3000 km apart and the residents have few historical interactions. Genomic DNA was analysed by PCR and detected by Southern hybridisation with a radiolabelled (CGG)5 probe for the CGG repeat number. A different distribution pattern of CGG allele size from the Caucasians is observed. It is a bimodal pattern with the most common CGG repeats allele at 29 against 30 in the Caucasians. Among the Hong Kong subjects, five alleles of more than 50 CGG repeats were detected, and four of those were in heterozygous females. There was no difference in the repeat patterns in subjects from the two cities, suggesting no genotypic variation in FMR1 between northern and southern Chinese.

The apolipoprotein E epsilon4 allele is unlikely to be a major risk factor of age-related macular degeneration in Chinese

Apolipoprotein E (ApoE) is a major transporter of lipids and cholesterol in the nervous system. Age-related macular degeneration (ARMD), characterized by drusen containing lipids, was reported to show a lower frequency of the ApoE epsilon4 allele than control subjects. We sought to examine the association of this polymorphism with ARMD in Hong Kong Chinese. Among 98 ARMD subjects, the frequency of epsilon4 carriers showed a trend toward a decrease compared to controls, but it was not significant (11.2 vs. 15.0%, p < 0.52). The association of epsilon4 with an apparent reduced risk of ARMD was reported previously in the exudative form of the disease, however among 39 exudative ARMD patients there was also no significant difference in epsilon4 frequency (12.8%, p < 0.93). The lack of a statistically significant effect of epsilon4 may be due to the lower frequency of epsilon4 in Chinese than Europeans. Thus we cannot exclude a possible effect of this allele on ARMD risk, but we can conclude that this allele is likely not a major factor influencing ARMD risk in the Chinese.

Roles for lipoprotein lipase in Alzheimer's disease: an association study

Lipoprotein lipase (LPL) assists lipid transport by transferring lipids between lipoprotein particles and cells. LPL binds apolipoprotein E (apoE) lipoprotein particles and a major apoE receptor, low density lipoprotein receptor related protein (LRP). Because apoE and LRP polymorphisms alter Alzheimer's disease (AD) risk, and LPL itself is found in AD amyloid plaques, we examined whether LPL variants also affect AD risk. In case-control studies in the United States and Canada, the frequencies of two LPL alleles known to affect LPL enzymatic activity were measured in Caucasian AD or elderly normal (N) subjects. Pathologically confirmed subjects in both studies exhibited similar trends toward fewer 447Ter and more 291Ser alleles in AD. Combining results from both countries gave allele frequencies for 447Ter of 13.7% (26/190) in N and 9.4% (80/852) in AD (P = 0.10), and for 291Ser of 0.0% (0/184) in N and 1. 3% (8/636) in AD (P = 0.21). The trend appeared even greater for homozygous 447Ter subjects: 4.2% (4/95) of N vs. 1.4% (6/426) of AD (P = 0.09). These trends are consistent with a putative protective effect of 447Ter and causative effect of 291Ser on AD. Furthermore, brains of AD patients with 447Ter showed trends toward fewer plaques, tangles, and glia, and more neurons and cortical thickness than AD patients without 447Ter. Hippocampal plaques were significantly reduced. LPL might affect hippocampal function and thus dementia via its role as supplier of membrane components or antioxidants to neurons. Alternatively, LPL may play a part in plaque formation through its interaction with apoE and LRP.

Apolipoprotein E isoforms in Alzheimer's disease pathology and etiology

The apolipoprotein E (apoE) epsilon4 allele increases risk of Alzheimer's disease (AD), perhaps by accelerating plaque formation, or by impairing neuron repair. Considerable evidence supports both mechanisms. AD patients with epsilon4 have more and earlier amyloid deposits than do patients without epsilon4. The same is true of non-demented control subjects. In vitro, all apoE isoforms inhibit amyloid beta protein (Abeta) aggregation, but apoE4 less effectively than apoE3. Transgenic amyloid-producing mice expressing apoE3 or apoE4 develop less Abeta deposition than apoE knockout mice. These observations are consistent with an effect of apoE isoforms on Abeta aggregation in AD. ApoE is important for neurite maintenance since apoE knockout mice lose neurites and suffer behavioral deficits with aging or treatment with excitotoxins. ApoE4 mice show similar defects, but apoE3 mice are normal. AD patients with epsilon4 show more neuritic deficits than epsilon3 carriers. ApoE epsilon4 also worsens neurological impairment in head injury, stroke, and multiple sclerosis. Thus, apoE4 is less effective at neurite maintenance. Perhaps epsilon4 increases AD risk by both mechanisms: allowing amyloid deposition and failing to repair neurites. In either case, introducing apoE3 or apoE2 into the brain, for example by gene therapy or cell grafts, might delay AD progression.

Determinants of umbilical cord arterial 8-iso-prostaglandin F2alpha concentrations

OBJECTIVE

To determine the concentration of 8-isoPGF(2alpha) in cord blood as a measure of oxidative stress during labour, and to compare them with other established parameters of in vivo lipid peroxidation and with the acid-base status of the newborn.

METHOD

Umbilical cord arterial and venous blood samples were collected from 81 singleton term deliveries for determination of 8-isoPGF(2alpha), malondialdehyde and organic hydroperoxides. In addition, metabolites derived from the oxidative metabolism of purines during hypoxia-reoxygenation and routine cord blood of oxygen saturation, pH, pO2, pCO2, HCO3 and base excess were measured.

RESULTS

Arterial concentrations of 8-isoPGF(2alpha) were significantly higher in cases with fetal distress, tight nuchal cord (P < 0.001), the umbilical coiling index, and male sex (P < 0.05) (R2 = 0.48). No correlation was found with any parameter of acid-base status. In arterial and venous blood the concentrations of organic hydroperoxides and hypoxanthine significantly correlated with the fetal nuchal cord (P < 0.001) (R2 = 0.26 and 0.16, respectively).

CONCLUSION

Our findings indicate that 8-isoPGF2(alpha) in cord arterial blood is a suitable parameter to quantify a possible oxidative stress in the fetus during labour. Measurements of the F2-isoprostane concentrations in cord blood at labour provide a clinically useful method to assess the perinatal outcome.

The association between cigarette smoking and ocular diseases

OBJECTIVE

To review the effect of smoking on common ocular disorders.

DATA SOURCES

Medline literature search, 1966 to 1999.

STUDY SELECTION

The following key words were used: smoking; Graves' disease, age-related macular degeneration; glaucoma; cataract.

DATA EXTRACTION

Epidemiological and experimental studies were reviewed.

DATA SYNTHESIS

Cigarette smoking is an important risk factor for cardiovascular, respiratory, and malignant diseases. There is also a strong association between smoking and a number of common eye diseases, which include Graves' ophthalmopathy, age-related macular degeneration, glaucoma, and cataract. Despite the multifactorial aetiology of these ocular syndromes, smoking is an independent risk factor that has dose-response effects. It causes morphological and functional changes to the lens and retina due to its atherosclerotic and thrombotic effects on the ocular capillaries. Smoking also enhances the generation of free radicals and decreases the levels of antioxidants in the blood circulation, aqueous humour, and ocular tissue. Thus, the eyes are more at risk of having free-radical and oxidation attacks in smokers.

CONCLUSION

Smoking, if continued, may perpetuate further ocular damage and lead to permanent blindness. Cessation of smoking and avoidance of passive smoking is advised to minimise the harmful effects of smoking on the eyes.

Truncations in the TIGR gene in individuals with and without primary open-angle glaucoma

PURPOSE

To investigate the coding exons in the trabecular meshwork-induced glucocorticoid response protein (TIGR) gene for mutations in primary open-angle glaucoma (POAG) in Chinese subjects.

METHODS

Ninety-one Chinese patients with POAG and 113 of their family members without glaucoma were screened for sequence alterations in the TIGR gene by polymerase chain reaction, conformation-sensitive gel electrophoresis, and DNA sequencing. One hundred thirty-two unrelated individuals without glaucoma, aged 50 years or more, were studied as control subjects.

RESULTS

Five sequence variants that lead to amino acid changes were identified. One was novel: Arg91Stop in one patient with POAG. Four had been reported: Arg46Stop in subjects with and without POAG, including an unaffected 77-year-old woman homozygous for Arg46Stop; Gly12Arg in subjects without glaucoma; and Asp208Glu and Thr353Ile in subjects with and without POAG. The previously reported 1-83(G-->A) and Arg76Lys polymorphisms were detected in both patients and controls and always occurred together.

CONCLUSIONS

A different pattern of TIGR sequence variants exists in the Chinese than in non-Chinese populations. No common TIGR mutation that causes POAG was found. The occurrence of subjects without glaucoma who are heterozygous or homozygous for Arg46Stop suggests that reduction in the amount of TIGR protein does not cause glaucoma. Thus, the TIGR missense mutations known to cause POAG probably do not cause glaucoma by inactivating a normal TIGR function, but rather through the gain of a pathologic function.

The alpha-synuclein gene and Parkinson disease in a Chinese population

OBJECTIVE

To study the Ala53Thr and Ala30Pro mutations of the alpha-synuclein gene in a large number of Chinese patients with Parkinson disease (PD) as well as controls.

METHODS

We recruited 183 Chinese patients with sporadic PD, 17 with younger-onset PD (onset age <50 years), and 7 with PD and a positive family history as well as 227 unaffected Chinese control subjects from the outpatient departments of 2 major hospitals in Hong Kong. All subjects were assessed for the the diagnosis of PD by a consultant neurologist or geriatrician. Subjects were interviewed with a standard questionnaire that also questioned for family history. Venous blood samples were obtained from the subjects and genomic DNA was extracted and studied for the presence of Ala53Thr mutation in exon 4 and Ala30Pro mutation in exon 3 of the alpha-synuclein gene using a polymerase chain reaction restriction fragment length polymorphism method.

RESULTS

None of the Chinese PD patients or controls had either the Ala53Thr (exon 4) or Ala30Pro (exon 3) mutation of the alpha-synuclein gene.

CONCLUSION

We failed to discover Ala53Thr or Ala30Pro mutations in a large number of Chinese patients with PD and control subjects, adding to the emerging consensus that variations in the alpha-synuclein gene are associated with PD in few families worldwide.

Congenital hypertrophy of the retinal pigment epithelium and APC mutations in two Chinese families with familial adenomatous polyposis

PURPOSE

Congenital hypertrophy of the retinal pigment epithelium (CHRPE) exists almost exclusively among familial adenomatous polyposis (FAP) patients with adenomatous polyposis coli (APC) mutations between codon 413 in exon 9 and codon 1387 in exon 15. We investigated the locality of APC mutations in relationship to the occurrence of CHRPE in two Chinese families with FAP.

METHODS

Genomic DNA of available members of two unrelated Chinese FAP families was investigated for sequence alteration in the APC gene by polymerase chain reaction and direct sequencing. All subjects were examined by binocular indirect ophthalmoscopy (BIO) for CHRPE.

RESULTS

A mutation in exon 6, Arg216Stop, was identified in one patient with FAP and CHRPE. An Arg283Stop mutation in exon 8 was found in 5 members in another family; 4 of them had FAP and all had small hypopigmented white lesions, probably a new type of CHRPE.

CONCLUSIONS

We found two mutations, Arg216Stop and Arg283Stop, upstream of codon 413 in FAP patients presenting with CHRPE. Arg283Stop has not previously been reported in such patients. A large-scale study on CHRPE and APC mutations in Chinese FAP patients is required to affirm their inter-relationships and the significance of the hypopigmented white lesions.

The monoamine oxidase B gene GT repeat polymorphism and Parkinson's disease in a Chinese population

Monoamine oxidase B (MAOB) metabolises dopamine and activates neurotoxins known to induce parkinsonism in humans and primates. Therefore the MAOB gene (MAOB; Xp15.21-4) is a candidate gene for Parkinson's disease (PD). Longer length dinucleotide repeat sequences in a highly polymorphic GT repeat region of intron 2 of this gene showed an association with PD in an Australian cohort. We repeated this allele-association study in a population of 176 Chinese PD patients (90 men, 86 women) and 203 agematched controls (99 men, 104 women). Genomic DNA was extracted from venous blood and the polymerase chain reaction was used to amplify the appropriate regions of the MAOB gene. The length of each (GT) repeat sequence was determined by 5% polyacrylamide denaturing gel electrophoresis. There was no significant difference in allele frequencies of the (GT) repeat allelic variation between patients and controls (chi2 = 2.48; df = 5, P<0.75). Therefore the longer length GT repeat alleles are not associated with PD in this Chinese population. Possible reasons for the discrepancy between Chinese and Australian populations include a different interaction between this genetic factor and environmental factors in the two populations and the possibility that the long length GT repeat alleles may represent a marker mutation, genetically linked to another susceptibility allele in whites but not in Chinese. Methodological differences in the ascertainment of cases and controls in this cohort could also explain the observed differences. Further study is required to determine whether the longer length GT repeat alleles are true susceptibility alleles in PD.