Machado-Joseph disease with retinal degeneration and dementia

OBJECTIVES

To clarify the phenotypic varieties in Machado-Joseph disease (MJD).

MATERIALS AND METHODS

We studied a 64-year-old man with ataxia, retinal degeneration and dementia neurologically, ophthalmologically and genetically.

RESULTS

The patient noted dysesthesia of his hands at age 57 and later had memory disturbance. He had gait disturbance and needed a wheelchair at age 64. His total IQ was 61 on the WAIS-R. He had loss of central vision, ophthalmoplegia, hearing impairment, dysarthria, truncal and limb ataxia, sensory disturbance, and mild weakness of the extremities. Electrophysiologically he was suspected to have polyneuropathy. Brain MRI showed marked atrophy of the cerebellum and pons with mild cerebral atrophy. Ophthalmologic evaluation revealed multiple chorioretinal atrophy. Expanded CAG repeat numbers in MJD1 were 64.

CONCLUSION

These findings indicate that the clinical features of MJD might cover a wider spectrum than previously expected, though it is possible that these complications, namely retinal degeneration and dementia, were incidental findings in this patient.

Retinopathy associated with Machado--Joseph disease (spinocerebellar ataxia 3) with CAG trinucleotide repeat expansion

PURPOSE

To report characteristic atrophic maculopathy in a patient with Machado--Joseph disease (spinocerebellar ataxia 3) caused by trinucleotide repeat expansion of the relevant gene.

METHODS

Case report.

RESULTS

A 64-year-old Japanese man had suffered from slurred speech and gait disturbance since 57 years of age. Cerebellar ataxia, extensor plantar response, and other neurological signs were compatible with features of Machado--Joseph disease. Magnetic resonance imaging showed atrophies of cerebellum and cerebral cortex. Family history suggested an autosomal dominant inheritance of the disease. The patient presented with gaze-evoked nystagmus and limitations of eye movement in all directions. Ophthalmoscopy and fluorescein angiogram revealed symmetric changes in the posterior fundi, which consisted of patchy atrophies at the level of the retinal pigment epithelium. Scotopic electroretinogram showed no abnormalities with normal oscillatory potentials. Polymerase chain reaction analysis of the Machado--Joseph disease gene identified a heterozygous trinucleotide (CAG) repeat expansion.

CONCLUSION

This case illustrates a rare association of atrophic maculopathy and external ophthalmoplegia in Machado--Joseph disease, contrasted with the common occurrence of retinal degeneration in spinocerebellar ataxia 7. Dystrophic changes in the retinal pigment epithelium have rarely been described but may be one of the characteristic complications of Machado--Joseph disease.

Cytochrome P450 1B1 gene mutations in Japanese patients with primary congenital glaucoma(1)

PURPOSE

To report a novel missense mutation and DNA polymorphism of the CYP1B1gene in Japanese patients with primary congenital glaucoma.

METHODS

A series of 11 unrelated patients with primary congenital glaucoma was examined. Patients were followed in the Kagoshima University Hospital between 1979 and 1998. DNA was extracted from leukocytes of the patients, their families, and unrelated healthy individuals. Amplicons spanning the coding regions of the CYP1B1 gene were examined by direct sequencing and enzyme-restriction detection.

RESULTS

In the 11 unrelated patients, besides the previously reported insertional mutation (1620 ins G), a novel missense mutation was identified at codons 444 to replace arginine with glutamine (R444Q) in one patient. The novel missense mutation cosegregated in the relevant family as an autosomal recessive pattern and was not found in other patients or control individuals. In addition, five polymorphic sites were found at codons 48, 119, 330, 432, and 449. These polymorphic alleles did not cosegregate with the disease, and they were found in healthy individuals as well.

CONCLUSIONS

Approximately 20% of Japanese patients with primary congenital glaucoma may be affected by mutations in the CYP1B1 gene. Further studies are justified to explore whether a relationship exists between the phenotypic expressivity of the disease and the type of mutation.

Genetic association of manganese superoxide dismutase with exudative age-related macular degeneration

PURPOSE

To elucidate whether any polymorphic genes for xenobiotic-metabolizing and antioxidant enzymes are associated with the development of exudative age-related macular degeneration.

METHODS

A hospital-based case-control study was performed on a consecutive series of 102 Japanese patients with the exudative form of age-related macular degeneration who were recruited between 1993 and 1998 in the Kagoshima University Hospital. Controls were 200 systemically healthy individuals who had no senescent ocular disorders and were over 50 years of age. There was no evidence of age-related macular degeneration in the 200 controls. Genomic DNA from peripheral bloods was examined using polymerase chain reaction and defined for the genetic polymorphisms of cytochrome P-450 1A1, glutathione S-transferases, microsomal epoxide hydrolase, and manganese superoxide dismutase.

RESULTS

We found a significant association of manganese superoxide dismutase gene polymorphism, valine/alanine polymorphism at the targeting sequence of the enzyme, with age-related macular degeneration. The patients had an increased frequency of alanine allele and alanine/alanine genotype (odds ratio = 10.14, 95% confidence interval = 4.84 to 2.13; P =.0005 after Bonferroni correction). We also observed a weak association of microsomal epoxide hydrolase exon-3 polymorphism with age-related macular degeneration (odds ratio = 2.20, 95% confidence interval = 4. 02 to 1.20; P =.020 after Bonferroni correction). Cytochrome P-450 1A1, glutathione S-transferases, and microsomal epoxide hydrolase exon-4 were polymorphic, but their genotype frequency distributions did not show a statistically significant difference between the patients and controls.

CONCLUSIONS

The results suggest that manganese superoxide dismutase gene polymorphism is associated with exudative age-related macular degeneration. Microsomal epoxide hydrolase is another enzyme that may be associated with the disease. The exudative form of age-related macular degeneration may have genetic risk factors against oxidative stress and/or effects of xenobiotics. Further association studies in other polymorphic genes for xenobiotic-metabolizing enzymes are needed to elucidate the environmental-genetic interaction in the underlying cause of age-related macular degeneration.

Histopathological analysis of four autopsy cases of HTLV-I-associated myelopathy/tropical spastic paraparesis: inflammatory changes occur simultaneously in the entire central nervous system

Although brain lesions have been described in some cases with HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), little is known about the nature of brain lesion and its relation to the spinal cord lesion. In the present study, we performed histopathological analysis of the brain and the spinal cord of four autopsied cases with HAM/TSP to clarify the relationship between the brain and the spinal cord lesions. In two cases with active-chronic inflammation in the spinal cord, perivascular inflammatory infiltration was also seen in the brain, and the composition of cell subsets was similar both in the spinal cord and in the brain. No active inflammatory change was seen in the brain in two cases with inactive-chronic spinal cord lesions. Inflamed vessels were distributed mainly in the deep white matter and in the area between cerebral cortex and white matter of the brain. In the spinal cord inflamed vessels were mainly seen in the bilateral lateral and the ventral posterior columns. Parenchymal infiltration was diffused in the spinal cord but very sparse in the brain, suggesting the importance of parenchymal infiltration in the destruction of tissues. These results suggest that inflammatory changes occurred simultaneously in the spinal cord and in the brain, and that distribution of inflamed vessels closely correlated with the characteristics of vascular architecture of the brain and the spinal cord, which lead to a slow blood flow. This study may help promote a better understanding of the pathogenesis of HAM/TSP.

Diagnostic potential of mitochondrial DNA assessment in patients with optic neuropathy

OBJECTIVE

To study the primary mutations of mitochondrial DNA (mtDNA) associated with Leber's hereditary optic neuropathy (LHON) in patients with optic neuropathy.

METHODS

Seventy-nine patients with a variety of bilateral optic neuropathies were examined. Mutations at np3460, np11,778 and np14,484 of mtDNA were tested by PCR-restriction detection in peripheral blood DNA from 16 cases of clinically probable LHON, 44 cases of possible LHON, 2 cases of alcohol amblyopia, 4 cases of multiple sclerosis, 5 cases of autosomal dominant optic atrophy, 4 cases of primary open-angle glaucoma, 3 cases of spinocerebellar degeneration, and 1 case of ethambutol-induced optic neuropathy.

RESULTS

The mutation at np11778 was identified in 31 cases (39.2%) to establish LHON, which consisted of: all 16 of clinically probable LHON cases, 13 cases (29.5%) of possible LHON, and 2 cases of alcohol amblyopia. The remaining 48 cases were negative for mtDNA mutations at np3460, np11 778, and np14,484.

CONCLUSION

Assessment of mtDNA provides a useful diagnostic aid in the definition and exclusion of LHON, in particular family history-negative, otherwise undefined bilateral optic nerve inflammatory disease.

A novel PAX6 gene mutation (P118R) in a family with congenital nystagmus associated with a variant form of aniridia

BACKGROUND

A variety of PAX6 gene mutations were identified in patients with aniridia and/or allied ocular dysgenesis such as keratopathy, Peters' anomaly, foveal hypoplasia, and nystagmus. To scrutinize the etiology of a four-generation Japanese family with autosomal dominant nystagmus associated with anterior and posterior segment anomalies, the PAX6 gene was examined.

PATIENTS AND METHODS

A Japanese family showed a variant aniridia phenotype in four successive generations. Affected individuals had congenital nystagmus, microcornea with shortened axial length, superficial peripheral corneal opacification with pannus formation, dislocated pupil, and foveal hypoplasia. Analysis of the PAX6 gene mutation was performed in affected and unaffected individuals.

RESULTS

A novel missense mutation in the PAX6 gene was found in all affected individuals examined, but neither in unaffected individuals nor in unrelated healthy individuals. This mutation predicted a proline to arginine change at codon 118 (P118R) in the paired domain of PAX6 protein.

CONCLUSION

The reported family illustrates that mutations in the PAX6 gene, in particular missense mutations, may manifest atypical clinical expression or forme fruste of aniridia.

Sorsby's fundus dystrophy in two Japanese families with unusual clinical features

PURPOSE

To describe two Japanese families with Sorsby's fundus dystrophy (SFD) with unusual clinical features.

METHODS

Two families from Kagoshima Prefecture with senile-onset macular dystrophy were examined. Three affected individuals through three successive generations of one family and three affected siblings in another family were examined and followed.

RESULTS

The initial symptom of these patients was a rapid or slow central visual loss that occurred at an average age of 67.4 years. The major ophthalmoscopic changes consisted of soft drusen and hemorrhagic or atrophic lesions in the macula, which were progressive and ultimately led to disciform scarring. They had no difficulty with night vision. All the patients had normal peripheral retina with intact peripheral fields. They maintained good ambulatory vision and could walk unguided until late in life. These patients had a novel mutation in the tissue inhibitor of the metalloproteinases-3 (TIMP3) gene.

CONCLUSIONS

This is the first report of SFD from the East. Its clinical features differ from those of SFD patients of the West, appearing closer to features of age-related macular degeneration. These two unrelated Japanese families with an identical mutation in the TIMP3 gene might be descendants of a common ancestor who carried the mutant gene.

[Clinical and genetic features of choroideremia]

BACKGROUND

Choroideremia is an X-linked hereditary eye disease that causes progressive degeneration of the choroid and retina and frequently leads to legal blindness in later life. Recent molecular genetic studies have revealed mutations involving the Rab escort protein (REP-1) gene localized at Xq 21.

CLINICAL FEATURES

The clinical picture and rate of progression may vary among affected individuals in different families and within the same family. Usually, hemizygous males develop night blindness in their teenage years, followed by progressive peripheral visual field constriction and visual disability in late age. Heterozygous female carriers are mostly asymptomatic, but their fundi show characteristic pigment changes in the midperiphery closely resembling the fine mottling observed in the initial stage of the disease in males.

MOLECULAR GENETICS

Assessment of the REP-1 gene in European and Japanese choroideremia patients has revealed a wide variety of mutations, including gross deletions and point mutations such as nonsense, frameshift, and splice-site mutations. All these mutations are thought to fail in intact REP-1 protein synthesis.

CONCLUSIONS

The recent molecular studies may open a new chapter in the research on choroideremia and provide the groundwork for therapeutic potential as well as diagnosis and genetic counseling.

Molecular pathologic analysis of the tonsil in HTLV-I-infected individuals

Little is known about the role of the tonsils in HTLV-I infection. We performed molecular pathologic studies of tonsils in individuals positive or negative for anti-HTLV-I antibodies (HTLV-I-Ab) to clarify histologic characteristics of tonsils in HTLV-I infection. We collected tonsils and peripheral blood samples from patients who underwent tonsillectomy in a prospective manner. HTLV-I-Ab in serum was examined and presence of HTLV-I provirus was detected by polymerase chain reaction (PCR) in extracted DNA of both peripheral blood and tonsils. Histopathologic and immunohistochemical evaluations of tonsils were performed. HTLV-I seropositivity and PCR detection of HTLV-I provirus matched perfectly. Tonsil samples from seropositive individuals showed atrophy of the mantle zone and high numbers of T cells in the marginal zone compared with findings in HTLV-I-negative samples. HTLV-I provirus could be detected only from extracted DNA of extrafollicular areas. PCR in situ hybridization also showed positive signals in some mononuclear cells located in the marginal zone. There was a significant correlation between HTLV-I proviral load in tonsils and in peripheral blood. These results suggest the presence of characteristic histologic changes and deviated localization of HTLV-I-infected cells in the tonsils of individuals positive for HTLV-I.

A novel truncating mutation of cytochrome P4501B1 (CYP1B1) gene in primary infantile glaucoma

PURPOSE

To report a novel mutation of the CYP1B1 gene in a Japanese patient with primary infantile glaucoma.

METHODS

DNA was extracted from leukocytes of six unrelated patients with primary infantile glaucoma. The coding regions of the CYP1B1 gene were amplified by polymerase chain reaction, examined by agarose gel separation and heteroduplex methods, and directly sequenced.

RESULTS

One of the patients with primary infantile glaucoma had a mutation of the CYP1B1 gene, with an abnormal shift in agarose gel separation and heteroduplex analysis. Direct sequencing disclosed a homozygous insertion of guanine at nucleotide 1620 of exon 3, which produced a frameshift leading to premature termination of amino acid translation. The patient was male and had sporadic, classic primary infantile glaucoma. None of the other five patients with infantile glaucoma, the 30 patients with primary adult-onset glaucoma, or the 70 healthy control subjects showed any abnormalities in the CYP1B1 gene.

CONCLUSIONS

This is the first report of CYP1B1 gene mutation in primary infantile glaucoma from the Eastern world. CYP1B1 gene mutation for primary infantile glaucoma spreads worldwide, but its prevalence may have ethnic or geographic differences.

REP-1 gene mutations in Japanese patients with choroideremia

BACKGROUND

Choroideremia (CHM) is an X-linked progressive dystrophy of the choroid, retinal pigment epithelium, and retina. Recently, the REP-1 gene was isolated and the causative mutations in the gene were detected in patients with CHM. In a previous study, we described a Japanese family with CHM who had a mutation in the REP-1 gene. In the present study, we performed extensive analysis of the REP-1 gene in patients with CHM from several institutions in Japan.

METHODS

Twenty-six patients with CHM and 5 unaffected females from 22 independently ascertained families were examined. Exons 1-15 of the REP-1 gene were screened by single-strand conformation polymorphism. The DNA fragments suspected of any variations were directly sequenced.

RESULTS

Fifteen different mutations, including one previously reported mutation, were detected in 18 families. In addition, carrier status was proven in four unaffected females found to be heterozygous for the mutant allele.

CONCLUSIONS

Fifteen different mutations of the REP-1 gene were detected in 18 Japanese families. There were no hot spots for the mutations and no missense mutations. The results show that REP-1 gene defects cause CHM in Japanese patients, and the mutations in these Japanese patients differed from the mutations reported for CHM patients in Europe, Canada, and America except for R267X and 1313delTC. These findings suggest that the mutations occurred independently in the Japanese patients.

[Sorsby's fundus dystrophy: a literature review]

BACKGROUND

Sorsby's fundus dystrophy (SFD) is an autosomal dominant macular dystrophy first described in a 1949 study of five British families, and it has received attention because of its clinical similarity to age-related macular degeneration and recent identification of the pathogenic gene.

CLINICAL FEATURES

To date, about twenty families with SFD have been reported from Europe, North America, South Africa, Australia, and Japan. A review of the literature found that the age of onset is usually during the fourth or fifth decade of life, the prominent ophthalmoscopic finding is hemorrhagic or atrophic lesion in the macula, and functional prognosis is usually unfavorable due to additional peripheral chorioretinal dystrophy, ultimately leading to poor ambulatory vision in the late decades of life.

MOLECULAR GENETICS

Recent molecular studies have identified mutations in the tissue inhibitor of metalloproteinases-3 (TIMP 3) gene as the pathogenic gene defect.

CONCLUSIONS

TIMP 3 gene examinations not only allow accurate diagnosis but also lay the groundwork for future studies of potential therapeutic protocols.

Perivascular T cells are infected with HTLV-I in the spinal cord lesions with HTLV-I-associated myelopathy/tropical spastic paraparesis: double staining of immunohistochemistry and polymerase chain reaction in situ hybridization

HTLV-I-infected cells play an important role in pathogenesis HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Our previous studies of quantitative polymerase chain reaction (PCR) and in situ PCR suggested that T cells infiltrating in the spinal cord lesion were infected with HTLV-I. To elucidate the localization of HTLV-I proviral DNA directly, we performed double staining using immunohistochemistry and PCR in situ hybridization (PCR-ISH). Fresh frozen sections of the spinal cord from four HAM patients taken at autopsy were first immunostained with antibodies to pan T cells (UCHL-1), macrophages (KP-1) and helper/inducer T cells (OPD4). Then PCR-ISH was carried out with specific primers and probe for the HTLV-I pX region. UCHL-1-positive cells were noted around perivascular areas and, to some extent, in the parenchyma. Of the UCHL-1-positive cells, 9.4% (case 1), 9.6% (case 2), 1.1% (case 3) and 6.7% (case 4) became positive in HTLV-I PCR-ISH. UCHL-1-negative cells were HTLV-I PCR-ISH negative and almost all KP-1-positive cells were HTLV-I negative. HTLV-I was localized to OPD4-positive cells in examined lesions of cases 2 and 4. These data are a direct demonstration of HTLV-I proviral DNA localizing to infiltrated T cells in HAM/TSP spinal cord lesions.

Histopathological and ultrastructural features of feline hereditary cerebellar cortical atrophy: a novel animal model of human spinocerebellar degeneration

Human spinocerebellar degeneration is one of the intractable diseases. We studied the detailed neuropathology of cats with hereditary cerebellar degeneration obtained from the experimental breeding. The findings included almost total loss of Purkinje cells with an increase in Bergmann's glia in the cerebellar hemisphere, preservation of some Purkinje cells in the vermis and moderate neuronal depletion of the olive nucleus. Cerebellar and pontine nuclei were normal. The cerebrum and spinal cord as well as the peripheral nervous system appeared normal. Electron microscopic examination revealed swelling of the distal dendrites of Purkinje cells in the less-affected nodule of the vermis, and clusters of presynaptic boutons without any synaptic contact in the severely affected folia where Purkinje cell bodies and dendrites disappeared. Prolonged existence of presynapses in the molecular and Purkinje cell layers was confirmed by positive immunoreactivity to anti-synaptophysin. Quantitative analysis using electron microscopy demonstrated an apparent increase in the density and mean size of presynapses in the molecular layer of the severely affected folia. These findings indicate that degeneration of Purkinje cells started at the most distal part of the dendrite in this animal model of cerebellar degeneration, and that presynapses, axon terminals of the granular cells and basket cells can exist for a long time even after complete degeneration of the Purkinje cells. Further investigation of this novel animal model may promote a better understanding of pathogenesis of human hereditary cerebellar degeneration.

A novel splice site mutation in the tissue inhibitor of the metalloproteinases-3 gene in Sorsby's fundus dystrophy with unusual clinical features

Sorsby's fundus dystrophy (SFD) is an autosomal dominant macular dystrophy which is developed usually in the third or fourth decade of life, and is characterized by central visual loss and nyctalopia due to fundus changes of exudative or atrophic macular lesions. Its functional prognosis is usually poor because of disciform macular scars and peripheral chorioretinal atrophies. To date, five different mutations in the tissue inhibitor of the metalloproteinases-3 (TIMP3) gene have been identified in families of a wide geographic origin, all of which are missense mutations that cause replacement by cysteine of conserved amino acids in the C-terminus of exon 5 of TIMP3. We have studied two Japanese families with SFD, the first report from the Eastern world, and identified a novel 3' splice site mutation in the TIMP3 gene, namely a single base insertion at the intron 4/exon 5 junction which converts the consensus sequence CAG to CAAG in the splice acceptor site. In addition, our patients displayed a distinctive clinical expression in that they developed macular dystrophies at an approximately 30-year later age of onset and preserved functional vision until later life with essentially uninvolved peripheral retina. The present findings may provide some insight into the genotype-phenotype relationship in SFD.

Analysis of peripherin/RDS gene for Japanese retinal dystrophies

We studied 133 Japanese patients with retinal dystrophies to detect peripherin/RDS (retinal degeneration slow) gene defects. The patients analyzed included 52 with autosomal dominant retinitis pigmentosa, 36 with autosomal recessive retinitis pigmentosa, 3 with simplex retinitis pigmentosa, 12 with cone-rod dystrophy, 5 with rod-cone dystrophy, 3 with vitelliform macular dystrophy (Best's disease), 4 with macular dystrophy, 2 with cone dystrophy, 2 with fundus flavimaculatus, 2 with fundus albipunctatus, and 12 with retinitis pigmentosa with macular degeneration as well as 40 unrelated normal persons. Three exons of the peripherin/RDS gene cut into 150-200 base-pair fragments were amplified by polymerase chain reaction and screened by single-strand conformation polymorphism. The DNA fragments with any suspected variations were directly sequenced. Eight point mutations were detected. Among them, two missense mutations at codons 304 and 338 result in an amino acid substitution of glutamine for glutamic acid and aspartic acid for glycine, respectively. However, they were not cosegregated with the diseases, and these mutations were also commonly found in normal controls. For these controls, the proportion of transversion from G to C at codon 304 (GAG-->CAG) and transition from G to A at codon 338 (GGC-->GAC) were 0.192 +/- 0.045 and 0.173 +/- 0.053, respectively. Our results suggest that a peripherin/RDS gene mutation might be rare in Japanese patients.

Retinal manifestations in mitochondrial diseases associated with mitochondrial DNA mutation

PURPOSE

To scrutinize retinal involvement associated with distinct mitochondrial DNA (mtDNA) defects, we reviewed the records of a consecutive series of patients with various mitochondrial diseases.

METHODS

Clinical, laboratory and mtDNA studies were performed in: five patients with Kearns-Sayre syndrome (KSS); six patients with chronic progressive external ophthalmoplegia (CPEO); three patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episode (MELAS); three patients with myoclonic epilepsy and ragged-red fibers (MERRF); 20 patients with Leber's hereditary optic neuropathy (LHON); 30 patients with simple diabetes mellitus.

RESULTS

All KSS patients with neurologic and cardiac symptoms associated with a deletion of mtDNA in muscle biopsy specimens showed widespread retinal pigmentary changes characterized by salt- and pepper-like appearance of the fundus. Three of six patients with CPEO, a mild variant of KSS, showed subtle defects at the level of retinal pigment epithelium of the posterior pole, although mtDNA deletion was similar to that in KSS. Of three patients with MELAS syndrome, one patient showed juvenile cataract and mild retinal pigmentary defect in the posterior pole. Of three patients with MERRF syndrome associated with a mtDNA mutation at nucleotide position (np) 8344, one patient showed mild pigment disorder in the posterior pole in addition to optic neuropathy. Two of 20 patients with LHON associated with a mtDNA mutation at np 11778 showed mild pigmentary defect in the macula together with typical optic neuropathy. In addition, two of 30 patients with isolated diabetes mellitus showed a mtDNA mutation at np 3243 (MELAS mutation), but they did not present with any other neurologic or multisystem disorder.

CONCLUSION

The retina, in particular the retinal pigment epithelium, is highly vulnerable to be involved by mtDNA defect, and the retinopathy is phenotypically variable and frequently subclinical, depending to some extent on the type or site of mtDNA defect.

Genotypes of aldehyde dehydrogenase and alcohol dehydrogenase polymorphisms in patients with Leber's hereditary optic neuropathy

To define whether alcohol drinking provides a risk for Leber's hereditary optic neuropathy (LHON), the genotypes of low K(m) aldehyde dehydrogenase (ALDH2) and alcohol dehydrogenase type 2 (ADH2), major enzymes involving the alcohol metabolism, were examined in 29 unrelated Japanese patients with LHON associated with mitochondrial DNA 11778 mutation, 24 unrelated asymptomatic carriers with the mutation and 57 normal controls without the mutation. PCR-restriction detection revealed three genotypes of ALDH2 and ADH2. The allele frequencies of either enzyme in LHON patients, asymptomatic carriers, or both, did not differ from those in normal controls. There is no association between LHON and genotypes of alcohol-metabolizing enzymes. However, six of the LHON patients had frequent alcohol consumption, while none of the asymptomatic carriers claimed frequent drinking habit. Thus, we could not make a denial of drinking effects on optic nerve damage in LHON.

Genetic analysis of a clinical isolate of human cytomegalovirus exhibiting resistance against both ganciclovir and cidofovir

Both ganciclovir-sensitive and -resistant human cytomegaloviruses (HCMV) were isolated from a patient with aplastic anemia complicated with CMV retinitis and encephalitis. Ganciclovir-resistant clinical isolate, 93-1R, also showed cross-resistance against (s)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine (cidofovir). Molecular analysis of plaque-cloned strains revealed that a single nucleotide substitution at 2160 (C to T) resulted in amino acid substitution at codon 501 from leucine to phenylalanine in the DNA polymerase gene. This mutation at codon 501 was easily identified by means of AluI digestion of the selected PCR product. The same mutation existed in the DNA fragment amplified from the patient's brain, suggesting that cross-resistant mutant 93-1R caused encephalitis. Furthermore, ganciclovir-resistant 93-1R-3 replicated much faster and was released more efficiently into the culture medium than ganciclovir-sensitive 91-7S-1.

A novel AvaI polymorphism within exon 5 of the rhodopsin gene

We identified a novel AvaI polymorphism within 3' non-coding region within exon 5 of the human rhodopsin gene and determined the allele frequency in a Japanese population. The polymorphism was found to be due to A/G transversion at nucleotide 5510 of the gene.

Familial facioscapulohumeral muscular dystrophy: phenotypic diversity and genetic abnormality

We report two cases showing facioscapulohumeral muscular dystrophy (FSHD) with phenotypic diversity but the same genetic abnormality detected by a p13E-11 probe. The proband, a 26-year-old woman, showed an early onset, tortuosity of retinal arterioles and respiratory failure. The 53-year-old mother of the proband had limb-girdle (L-G) type muscular weakness with very mild facial involvement. Muscle biopsy showed perivascular cell infiltration in both patients. These cases suggest that the phenotypic diversity ranges from L-G type weakness to severe respiratory failure in FSHD family.

[A literature review of Norrie disease]

Norrie disease is a rare genetic disorder characterized by bilateral congenital blindness. The salient clinical feature early in life is a dense, white, vascularized mass behind each lens due to maldeveloped retina. Cataracts and corneal opacities are developed in young childhood, followed by bulbar atrophies. Histopathologic examination suggests primary vitreoretinal dysplasia because of developmental arrest of the retina in the middle embryonic stage. Occasional patients show psychomotor retardation or progressive hearing loss as part of a multisystem disorder. The disease is transmitted by an X-linked recessive form of inheritance, with sons of female carriers having a 50% risk for expressing the disease. In recent years, a candidate gene for Norrie disease has been isolated and characterized, which encompasses 27 kilobases and consists of three exons interspersed by two introns. Microdeletions and a variety of point mutations in the disease gene were identified in Norrie patients, although the genotype-phenotype correlation remains to be defined, and molecular diagnosis is now available for Norrie disease. The encoded protein has homology to a protein domain involving mucins and TGF beta, which may play an essential role in targeting of retinal/neural connections.

[HTLV-I associated retinochoroidal degeneration]

A review of 100 patients with HTLV-I (human T-cell lymphotropic virus type I) associated myelopathy revealed 9 cases (9.0%) of retinochoroidal degeneration. Most of the cases developed the ocular disease at age 50 or older, either preceded or followed by neurologic disease. Ophthalmoscopic abnormalities included classic retinitis pigmentosa and localized degenerative changes of the retina and choroid, with visual disturbance corresponding to the severity of retinal changes. None of the cases showed any contributory family history. In reference to the prevalence of retinitis pigmentosa, these cases were thought to indicate a meaningful rather than coincident association between HTLV-I associated myelopathy and retinochoroidal degeneration. Hence, HTLV-I may involve the underlying etiology of a newly defined disease called HTLV-I associated retinochoroidal degeneration. On the other hand, since HTLV-I seroprevalence in patients with isolated retinitis pigmentosa was comparable with that in the general population, it appears unlikely that the retrovirus may also involve an isolated form of retinochoroidal degenerative disease.

Mutations in the Norrie disease gene: a new mutation in a Japanese family

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Familial mitochondrial encephalomyopathy with deaf-mutism, ophthalmoplegia and leukodystrophy

We report two sisters (32 and 36 years old) with familial deaf-mutism, progressive external ophthalmoplegia, leukodystrophy and mitochondrial myopathy. T2-weighted brain MRI demonstrated diffuse symmetrical high intensity areas in the white matter. Their muscle biopsies showed ragged-red fibers and cytochrome c oxidase (CCO)-negative fibers. CCO activity in biopsied muscle decreased to about 20% of normal control. They had no deletions of the mitochondrial DNA and no point mutations in mitochondrial tRNA. Their brother was diagnosed as having Kugelberg-Welander disease, grand mal seizures and urinary dysfunction. Their parents and grandparents had consanguinity. Three relatives were found to have deaf-mutism without accompanying ophthalmoplegia. This rare combination of mitochondrial encephalomyopathy and familial deaf-mutism might be caused by a nuclear DNA mutation in these sisters.

Novel mutation at the initiation codon in the Norrie disease gene in two Japanese families

We have identified a new mutation of Norrie disease (ND) gene in two Japanese males from unrelated families; they showed typical ocular features of ND but no mental retardation or hearing impairment. A mutation was found in both patients at the initiation codon of exon 2 of the ND gene (ATG to GTG), with otherwise normal nucleotide sequences. Their mothers had the normal and mutant types of the gene, which was expected for heterozygotes of the disease. The mutation of the initiation codon would cause the failure of ND gene expression or a defect in translation thereby truncating the amino terminus of ND protein. In view of the rarity and marked heterogeneity of mutations in the ND gene, the present apparently unrelated Japanese families who have lived in the same area for over two centuries presumably share the origin of the mutation.

[Antibodies to human T-cell lymphotropic virus type 1 in the aqueous humor of HTLV-I associated uveitis]

To elucidate the pathomechanism of human T-cell lymphotropic virus type 1 (HTLV-I) associated uveitis (HAU), we assessed antibodies to HTLV-I and IgG for paired samples of serum and aqueous humor. Seven of 10 samples from HAU patients showed antibodies to HTLV-I in the aqueous humor with antibody titer ranging from 16 to 128, and five of these samples showed significantly high antibody quotients as calculated by reference to the IgG levels in the serum and aqueous humor, hence suggesting local production of antibodies rather than their transfer from the serum. On the other hand, eight of 45 control samples from HTLV-I carriers with senile cataract but without uveitis had antibodies to HTLV-I in the aqueous humor with antibody titer ranging from 8 to 128, but none of these samples showed high antibody quotient. We conclude that, although antibodies to HTLV-I in aqueous humor were detected in those HAU and control cases which showed high antibody titer in the serum, intraocular synthesis of antibodies to HTLV-I may sometimes occur in HAU.

[Ocular manifestations in mitochondrial DNA abnormalities]

We reviewed the ophthalmological and genetic aspects of mitochondrial diseases, a group of multisystem disorders that involve the function and morphology of mitochondria and affect multiple organs including skeletal muscle, central nervous system, heart, and ear. Disease-specific deletion or point mutation of mitochondrial DNA (mtDNA) has been clarified in many clinical entities of the group, and we confirmed that the ocular manifestations, including chronic progressive external ophthalmoplegia, blepharoptosis, retinochoroidal degeneration and optic nerve atrophy, develop in association with either deletion or point mutation of mtDNA. Together with a review of the literature, we describe a case of myoclonic epilepsy and ragged-red fibers with mutation at mtDNA 8344 and insidious bilateral optic atrophy. We also describe cases of myotonic dystrophy which had an abnormal expansion of CTG repeat of chromosome 19 protein kinase gene and showed retinochoroidal degeneration and mitochondrial morphological changes.

Immunohistochemistry of the monkey retina with a monoclonal antibody against subunit V of cytochrome c oxidase

A monoclonal antibody against subunit V of cytochrome c oxidase was newly prepared from purified bovine heart muscle enzyme. This antibody showed cross-reactivity against the bovine and the human cytochrome c oxidase on Western blot. Cytochrome c oxidase in paraffin embedded sections of monkey retinas and optic nerves was examined immunohistochemically using the monoclonal antibody. The inner segment of cone and rod photoreceptors, the inner nuclear layer and the inner plexiform layer showed marked reactivities. The optic nerve fiber axons also showed high reactivities, with more in the unmyelinated fibers peripheral to the lamina cribrosa. These immunohistochemical results using the antibody are mostly agreeable with previously reported histochemical localization of cytochrome c oxidase activity in the retina, but there were some noticeable differences in the plexiform layers.

Identification of essential arginine residue(s) for Mg-ATP binding of human argininosuccinate synthetase

Human argininosuccinate synthetase (ASS) activity was found to be inactivated by alpha-dicarbonyls such as 1,2-cyclohexanedione and phenylglyoxal in accordance with pseudo first-order kinetics. The enzyme was almost completely protected from this inactivation by Mg-ATP and partially by its analogues. The strongest protective effect against inactivation was found with Mg-ATP, followed by Mg-ADP, AMP, adenosine and Mg-inorganic pyrophosphate. These results suggest the importance of arginine residue(s) for Mg-ATP binding. We determined the amino acid sequence of the peptide with the highest specific radioactivity derived from ASS which had been labeled with [14C]phenylglyoxal and then cleaved by cyanogen bromide treatment. The sequence obtained, PEFYNRFKGRNDLM, corresponds to residues 148-161 of the amino acid sequence deduced from the cDNA nucleotide sequence determined by Bock et al. [Nucleic Acids Res 11:6505-6512, 1983], and has a high homology with the sequences of ATP-binding sites proposed for several ATP-requiring enzymes.

Fundus flavimaculatus: polymorphic retinal change in siblings

A 12-year-old boy and an 11-year-old girl, siblings of healthy, consanguineous parents, had a bilateral retinal dystrophy with a gradual loss of vision. The brother showed a bull's eye macular change with sparse fundus flavimaculatus type flecks. The sister had numerous fleck lesions of fundus flavimaculatus throughout the posterior fundus, but there was virtually no macular change. Thus the siblings presented instances of polymorphic expressivity of fundus flavimaculatus.