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Retinitis pigmentosa (RP) comprises a clinically and genetically heterogeneous group of diseases that afflicts approximately 1.5 million people worldwide. Affected individuals suffer from a progressive degeneration of the photoreceptors, eventually resulting in severe visual impairment. To isolate candidate genes for chorioretinal diseases, we cloned cDNAs specifically or preferentially expressed in the human retina and the retinal pigment epithelium (RPE) through a novel suppression subtractive hybridization (SSH) method. One of these cDNAs (RET3C11) mapped to chromosome 1q31-q32.1, a region harbouring a gene involved in a severe form of autosomal recessive RP characterized by a typical preservation of the para-arteriolar RPE (RP12; ref. 3). The full-length cDNA encodes an extracellular protein with 19 EGF-like domains, 3 laminin A G-like domains and a C-type lectin domain. This protein is homologous to the Drosophila melanogaster protein crumbs (CRB), and denoted CRB1 (crumbs homologue 1). In ten unrelated RP patients with preserved para-arteriolar RPE, we identified a homozygous AluY insertion disrupting the ORF, five homozygous missense mutations and four compound heterozygous mutations in CRB1. The similarity to CRB suggests a role for CRB1 in cell-cell interaction and possibly in the maintenance of cell polarity in the retina. The distinct RPE abnormalities observed in RP12 patients suggest that CRB1 mutations trigger a novel mechanism of photoreceptor degeneration.

The gene for autosomal recessive retinitis pigmentosa (RP12) with preserved para-arteriolar retinal pigment epithelium was previously mapped close to the F13B gene in region 1q31-->q32.1. A 4-Mb yeast artificial chromosome contig spanning this interval was constructed to facilitate cloning of the RP12 gene. The contig comprises 25 sequence-tagged sites, polymorphic markers, and single-copy probes, including five newly obtained probes. The contig orders the F13B and HF1 genes, as well as five expressed sequence tags, with respect to the integrated genetic map of this region. Homozygosity mapping resulted in refinement of the candidate gene locus for RP12 to a 1. 3-cM region. Currently, approximately 1 Mb of the contig is represented in P1-derived artificial chromosome (PAC) clones. Direct screening of a cDNA library derived from neural retina with PACs resulted in identification of the human elongation factor 1alpha pseudogene (EEF1AL11) and a human ribosomal protein L30 pseudogene (RPL30). A physical and genetic map covering the entire RP12 candidate gene region was constructed.

Retinitis pigmentosa (RP) denotes a group of hereditary retinal dystrophies, characterized by the early onset of night blindness followed by a progressive loss of the visual field. The primary defect underlying RP affects the function of the rod photoreceptor cell, and, subsequently, mostly unknown molecular and cellular mechanisms trigger the apoptotic degeneration of these photoreceptor cells. Retinitis pigmentosa is very heterogeneous, both phenotypically and genetically. In this review we propose a tentative classification of RP based on the functional systems affected by the mutated proteins. This classification connects the variety of phenotypes to the mutations and segregation patterns observed in RP. Current progress in the identification of the molecular defects underlying RP reveals that at least three distinct functional mechanisms may be affected: 1) the daily renewal and shedding of the photoreceptor outer segments, 2) the visual transduction cascade, and 3) the retinol (vitamin A) metabolism. The first group includes the rhodopsin and peripherin/RDS genes, and mutations in these genes often result in a dominant phenotype. The second group is predominantly associated with a recessive phenotype that results, as we argue, from continuous inactivation of the transduction pathway. Disturbances in the retinal metabolism seem to be associated with equal rod and cone involvement and the presence of deposits in the retinal pigment epithelium.

The Axenfeld-Rieger anomaly is a defect of the anterior chamber of the eye affecting the angle structures. If accompanied by hypodontia, midface hypoplasia, and umbilical anomalies, the designation "Rieger syndrome" is appropriate. Both conditions are autosomal dominant traits. The Axenfeld-Rieger anomaly is also known to occur in a variety of other syndromes. We report on two sisters, born to consanguineous parents, who presented with Axenfeld-Rieger anomaly, hydrocephalus, leptomeningeal calcifications, and mild mental retardation. Their height was on and just below the 3rd centile, respectively. One of them suffered from epilepsy and the other from sensorineural hearing loss. Two of their brothers died at young ages of hydrocephalus and possibly had intracranial calcifications as well. The differential diagnosis is discussed. Of the known syndromes associated with Axenfeld-Rieger anomaly, none could be convincingly applied to the propositae. Possibly, they represent a previously unreported autosomal recessive syndrome.

We describe an extended Dutch family with a new hereditary disorder: autosomal dominant vascular retinopathy, migraine and Raynaud's phenomenon. Information was obtained on 289 family members (151 males, 138 females), of whom 198 were personally interviewed. Retinopathy was found in 20 (6.9%) of the family members, migraine in 65 (22.5%) and Raynaud's phenomenon in 50 (17.3%). A combination of all three symptoms was found in 11 subjects. In a genetic linkage analysis we firstly excluded several candidate loci. Subsequently, 75% of the autosomal genome was excluded in a genome-wide search. The following conclusions were drawn. First, genetic factors are involved in Raynaud's phenomenon. Secondly, the genetic linkage of migraine with vascular retinopathy and Raynaud's phenomenon supports a vascular aetiology of this disorder. Finding the gene for this family may help to elucidate the genetic background of migraine and of vascular disorders in general.

Leber hereditary optic neuropathy (LHON) is a maternally inherited disorder, associated with mutations in the mitochondrial DNA, which is notorious for its aspecific presentations. Two pedigrees are described with cases that are atypical for LHON with respect to sex, age of onset, interval between the eyes becoming affected, course of the disease, concomitant disorders, additional test results, final visual acuity, and/or results of mtDNA analysis. Moreover, the pedigrees themselves did not suggest maternal inheritance. We analysed the diagnostic and clinical genetic difficulties related to the atypical aspects of these pedigrees. We conclude that mtDNA analysis is justified in every case of optic nerve atrophy with no clear cause. Identification of one of the three LHON specifically associated mtDNA mutations is essential to confirm the diagnosis.

Audiograms were traced or additionally performed on 23 Usher's syndrome patients in 10 Dutch multi-affected families, all linked to chromosome 1q (USH2A locus). Serial audiograms, available in 13 patients, were used for a regression analysis of binaural pure tone average on age (follow-up, 9 to 32 years) to test for "significant progression," ie, a significant regression coefficient, here called the "annual threshold increase" (ATI, expressed in decibels per year). A significant ATI (> 1 dB/y) was observed in 3 patients. Analysis of variance of ATI demonstrated significant heterogeneity; hearing loss was either stable or progressive. This implies a significant clinical heterogeneity. A similar analysis performed on our progressive USH2A cases and "type III" cases previously reported by others (ATI of 1 to 5 dB/y), some of which were recently linked to chromosome 3q (USH3 locus), failed to show any significant heterogeneity in the progression of hearing loss.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder of the optic nerves. It has been proposed that the specific mutations in the mitochondrial DNA (mtDNA) that are associated with LHON require and X-chromosomally encoded permissive factor in order to become expressed. This would explain both the preponderance of male patients and the fact that most carriers of specific mtDNA mutations remain unaffected. Although linkage studies have been negative so far, the existence of such a factor has not been ruled out. We investigated the genealogical data of 24 large LHON pedigrees and concluded that the presumed X-linked factor would be recessively inherited and that at least 57% of the affected females would be heterozygous. Therefore, these females must be the victim of nonrandom X-chromosomal inactivation (skewed lyonization). However, analysis of X-chromosomal methylation patterns in 16 LHON-affected females revealed substantial skewing in only 15%-20% of cases, which is not significantly different from the patterns in 49 controls. Moreover, we found the frequency of LHON in daughters of affected heterozygous females to be twice to three times as high as in daughters of unaffected heterozygous females, which cannot be explained by an X-chromosomally inherited factor. We concluded that the results of our investigations do not support the hypothesis that LHON is a digenic disease with an X-linked factor being the main cause of loss of vision in the presence of relevant mtDNA mutations.

In a previous study on a large pedigree from a genetically isolated population in the Netherlands, we localized a gene for autosomal recessive retinitis pigmentosa with paraarteriolar preservation of the retinal pigment epithelium (PPRPE) on the long arm of chromosome 1. In this study, we present an integrated genetic map of the target region. The resulting genetic order of the markers was used to construct haplotypes and to screen for key-recombinants in the pedigree. The obligate RP12 region was reduced from 16 cM to 5 cM between the markers D1S533 and CACNL1A3. The CACNL1A3 and phosducin (PDC) genes were placed outside the candidate gene region, thereby excluding the involvement of these genes in retinitis pigmentosa with PPRPE. Our data result in the following order of the markers and genes in the region 1q31 --> q32.1: cen-D1S158-(D1S238-D1S422)/PDC- D1S533-RP12/(F13B-D1S413)-CACNL1A3-DIS4 77-D1S306-D1S53-tel.

Thirty-seven patients, comprising 24 familial cases and 13 isolated patients with Usher syndrome type II (USH2), underwent ophthalmologic examination. Based on the degree of hearing loss, normal vestibular function, and gene-linkage analysis, familial cases were assumed to have USH2A. An analysis of genetic heterogeneity failed to reveal the presence of a second locus in the Dutch population. Although the patients appear to belong to a genetically homogeneous group, remarkable ophthalmologic variability was found. Corrected visual acuity decreased with age and remarkable differences in visual acuity were found within one family. Fundoscopic findings were classified as type A if attenuated vessels and bone corpuscles in all quadrants were found or as type B if findings other than these were found. The prevalence of type A significantly increased with age.

The electron transfer activity of Complex I of the respiratory chain and Complex I-linked ATP synthesis were investigated in leukocytes of four males affected by Leber hereditary optic neuropathy and a mutation in the ND6 gene at nucleotide position 14,484 of mtDNA. The electron transfer activity in leukocytes of the patients was about 35% of that in control leukocytes, whereas the Complex I-linked ATP synthesis showed a decrease of only about 20%. This demonstrates that all three mtDNA mutations that are clearly associated with Leber hereditary optic neuropathy result in deficiency of Complex I. However, the relationship between these mtDNA mutations, the function of Complex I and the phenotypic profile remains elusive.

Leber hereditary optic neuropathy (LHON) is a heritable disorder, clinically characterized by rapidly progressive loss of central vision due to severe bilateral optic atrophy. The disease predominantly occurs in men. The clinical picture shows marked interpersonal variation. Recently it has been established that LHON is associated with at least three specific mutations in the mitochondrial DNA, which explains the non-Mendelian, strictly maternal inheritance. The presence of different mutations implies that there is not only clinical but also genetical heterogeneity. Since all matrilinear family members carry the mtDNA mutation involved, but only 30-50% of males and 5-15% of the females develop LHON, other etiological factors, hereditary or exogenous, remain to be discovered. Identification of these factors is of major importance to understand the pathogenesis and to explore the possibilities for therapy and prevention of LHON.

Batten disease, or the juvenile form of neuronal ceroid lipofuscinosis, is an autosomal recessive neurodegenerative disorder manifesting with progressive blindness, seizures, and dementia, leading to an early death. The CLN3 locus which is involved in Batten disease had been localized to chromosome 16p11.2. Linkage disequilibrium has been observed between CLN3 and polymorphic microsatellite markers D16S288, D16S299, and D16S298, making carrier detection and prenatal diagnosis by haplotype analysis possible. For the purpose of carrier detection, haplotypes from Dutch Batten patients and their families were constructed. Most patients share the same D16S298 allele, suggesting the presence of a founder effect in the Dutch population. In a large inbred Dutch family, in which Batten disease occurs with high frequency, haplotype analysis has been carried out with high accuracy for carrier detection.

Retinitis pigmentosa with preserved para-arteriolar retinal pigment epithelium is a rare form of retinitis pigmentosa that starts early in life with preservation of retinal pigment epithelium adjacent to and under the retinal arterioles and that has hitherto been described as an isolated form. We examined 22 patients from one large family, together with two isolated patients, and confirmed the presumed autosomal recessive mode of inheritance in this type of retinitis pigmentosa. New findings associated with retinitis pigmentosa with preserved para-arteriolar retinal pigment epithelium were asteroid hyalosis in four (17%) of 24 patients, tortuosity of retinal arterioles in 11 (46%) of 24 patients, peripheral regions of opacified vessels in eight (33%) of 24 patients, and preservation not only of the para-arteriolar pigment epithelium, but also of the peripheral retinal pigment epithelium in 13 (54%) of 24 patients. Previously reported signs present in these patients were nystagmus in six (25%) of 24 patients, hypermetropia in 23 (96%) of 24 patients, optic nerve head drusen in nine (38%) of 24 patients, vascular sheathing in 11 (46%) of 24 patients, maculopathy in all 24 patients (100%), yellow round deposits in the posterior pole in nine (38%) of 24 patients, exudates resembling those in Coats' disease in two (8%) of 24 patients, visual field defects in all 24 patients (100%), and nondeductible electroretinograms in 21 (91%) of 23 patients. Linkage analysis carried out in the large family resulted in the assignment of a gene for retinitis pigmentosa with preserved para-arteriolar retinal pigment epithelium to chromosome 1q31-q32.1.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease of the optic nerves associated with various mitochondrial DNA (mtDNA) mutations. Four of these mutations, at nucleotide positions (np) 3460, 11778, 14484 and 15257, have been postulated to be of primary pathogenetical importance. Previously, we described the molecular and clinical findings in patients with the 11778 and 14484 mutations. Here we describe the molecular and clinical findings of patients in eight pedigrees with the 3460 mutation and in three pedigrees with the 15 257 mutation. In all three 15257 positive pedigrees the 3460, the 11778 or the 14484 mutation was also found. The first combination has not been reported before. We compared the clinical findings in these pedigrees with those of the 3460, 11778 and 14484 positive pedigrees that lack the 15257 mutation. No significant differences were found with respect to the age of onset, visual outcome or the probability of developing LHON. We conclude that there is no evidence that the 15257 mutation, which has been reported in normal controls, has primary causal significance, because it may coincide with the 3460, 11778 and 14484 mutations. We presume that the 15257 mutation has no secondary pathogenic importance, since it has no clear contribution to the degree or the probability of phenotypic expression.

A mother and daughter with autosomal dominant retinitis pigmentosa (adRP) were found to carry a cytosine-to-adenine transversion mutation at codon 4 of the rhodopsin gene. This mutation predicts a substitution of lysine for threonine at one of the glycosylation sites in the rhodopsin molecule (Thr4Lys). Both patients presented with a similar phenotype including a tigroid pattern of the posterior pole and a regional predilection for degenerative pigmentary changes in the inferior retina with corresponding visual field defects. The electroretinographic pattern was suggestive of RP of the cone-rod type. This report documents the clinical findings associated with this defined mutation of the rhodopsin gene.

Linkage analysis was carried out in a Dutch family with Nance-Horan (NH) syndrome. Close linkage without recombination between NH and the Xp loci DXS207, DXS43, and DXS365 (zmax = 3.23) was observed. Multipoint linkage analysis and the analysis of recombinations in multiple informative meioses suggest the genetic order Xcen-DMD (exon 49)-DXS451-(NH, DXS207, DXS365, DXS43)-(STS, DXF30)-Xpter. These data refine the localization of the NH locus on the distal Xp.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disease associated with mitochondrial DNA (mtDNA) mutations. We describe the distribution of seven different mtDNA mutations and the clinical findings in 334 LHON patients belonging to 29 families. Mutations described only in LHON at nucleotide positions 11778, 3460, and 14484 were found in 15, two, and nine families respectively. In three families none of these mutations was found. Mutations described in LHON but also in controls at nucleotide positions 15257, 13708, 4917, and 4216 were found in one, 10, three and 12 families respectively. Combinations of mtDNA mutations were found in most families. The patient population mainly consisted of 79.2% to 89.5% males except for one family with only 10 of 17 patients being males (58.9%, p approximately 0.036). In 11 families only the 11778 mutation was found; in this group (WX) the affected males had a mean age of onset of 29.2 years and a mean visual outcome of 0.113. In seven families the 14484, 13708, and 4216 mutations were found; in this group (MA) the affected males had a mean age of onset of 22.0 years and a mean visual outcome of 0.442. In two families no mutation was found at all; in this group (YX) the affected males had a mean age of onset of 18.9 years and a mean visual outcome of 0.167. The mean age of onset in the WX group is significantly higher than in the MA group (p < or = 0.001) and in the YX group (p approximately 0.01). The mean visual outcome in the MA group is significantly better than in the WX group (p

Total aniridia was found in a 2-month-old baby boy. Otherwise the baby was healthy. Ophthalmological examination of the elder sister, parents and paternal grandparents revealed no abnormalities. There was no consanguinity between the parents. Hence, the aniridia was considered sporadic, and the possibility of Wilms' tumour had to be taken into consideration. The chromosomes of the baby were normal, as judged by conventional cytogenetic analysis. In addition, DNA analysis demonstrated that there was no subchromosomal deletion in band 11p13, spanning the aniridia-Wilms' tumour region. Therefore, we conclude that the genetic defect leading to aniridia is confined to the aniridia locus and that the child has no increased risk of developing Wilms' tumour.

Leber's hereditary optic neuropathy (LHON) is characterized by subacute loss of central vision due to bilateral optic nerve atrophy accompanied by several nonspecific clinical findings. The only pathognomonic feature is its strictly maternal inheritance. It was therefore impossible to establish the diagnosis in patients with no known affected matrilinear sibs, until several mutations in the mitochondrial DNA (mtDNA) were discovered in relation to LHON. The authors describe the case histories and the occurrence of six mtDNA mutations in eight presumed singleton LHON patients and discuss the clinical and genetic implications of the results.

Although physical and genetic mapping studies assigned the X-linked ocular albinism gene to Xp22.3, the exact gene order in this region is still unclear. We present additional genetic mapping data concerning X-linked ocular albinism that suggests the consensus order Xpter-STS-DXS237-KAL-(OA1, DXS143)-DXS85-DXS16-Xcen.

Thirteen families with X-linked juvenile retinoschisis (XLRS) were studied in order to evaluate the linkage relationship between the XLRS locus (RS) and seven X-chromosomal DNA markers. Linkage was found between RS and DXS9 (theta max = 0.11, Zmax = 4.17), DXS16 (theta max = 0.06, Zmax = 7.72), DXS41 (theta max = 0.06, Zmax = 8.13) and DXS43 (theta max = 0.03, Zmax = 6.11). Recombinants were found between RS and all loci studied. Multipoint linkage analysis and recombination analysis significantly favour the order of Xpter-(DXS9, (DXS16-DXS43))-RS-DXS41-Xcen.

Mitochondrial DNA (mtDNA) was deleted in a patient with Kearns-Sayre syndrome (KSS) presenting with a choroideremia-like fundus picture instead of pigmentary retinopathy. No evidence for X-linked choroideremia was present, and because of the strong association between KSS and deleted mtDNA, we suggest that choroideremia is a phenocopy and can be part of KSS.

Differential Alu PCR fingerprint cloning was used to isolate a DNA probe from the Xp11.4-->p11.21 region of the human X chromosome. This novel sequence, cpXr318 (DXS742), detects a new submicroscopic deletion interval at the Norrie disease locus (NDP). Combining our data with the consensus genetic map of the proximal short arm of the X chromosome, we propose the physical order Xcen-DXS14-DXS255-(DXS426, TIMP)-(DXS742-([MAOB-MAOA-DXS7], NDP)-DXS77-DXS228)-DXS209-DXS148-DXS196-++ +Xpter. The cpXr318 probe and a subclone from a cosmid corresponding to the DXS7 locus were converted into sequence-tagged sites. Finally, DXS742, DSX7, DXS77, and MAOA were integrated into a physical map spanning the Norrie disease locus.

A retrospective study was performed of patients with retinitis pigmentosa (RP) registered at the Department of Ophthalmogenetics of the Netherlands Ophthalmic Research Institute. The aim was to establish the relative frequencies of the genetic modes and to attempt a clinical subclassification. Of the 575 RP patients, 10.4% were X-linked, 22.4% autosomal dominant, 30.1% autosomal recessive, and 37.1% simplex cases. Clinical classification was inconclusive, and consequently correlation of phenotype to genotype impossible in most cases. One exception was the occurrence of a tapetal reflex, which seemed to differentiate between RP2 and RP3. Gene defects have not been detected so far in Dutch families with either autosomal dominant or autosomal recessive RP. In the future, simplex cases will have to be classified according to their genetic defects. It is probable that results of DNA studies may prove a better basis for classification of RP than clinical data.

The authors describe a female patient with unilateral malformations of skin, cerebrum and eye. The symptoms consisted of local skin hypoplasia, skin appendages and lipomatous tissue; cysts, hypoplasia and lipomatosis of the brain; and ocular malformations. In the newborn period the symptoms led to the diagnosis of oculocerebrocutaneous (OCC) syndrome. In the first year of life the clinical course deteriorated and the psychomotor development was progressively retarded. Evaluation at the age of 15 months prompted the authors to change the diagnosis to encephalocraniocutaneous lipomatosis (ECCL). The differential diagnosis of ECCL and OCC syndromes is discussed and a possible common pathogenetic pathway of these two rare disorders is proposed.

A case of partial duplication of chromosome 1 (1q41-qter) and partial deletion of chromosome 9 (9p24-pter) with infantile congenital glaucoma is reported. The histopathology of the eyes is described. The clinical findings ascribed to trisomy 1q and partial monosomy 9p are summarized and compared to this case. As this is the second report of a patient with monosomy 9p24-pter and congenital glaucoma, it may indicate localization of a gene involved in congenital glaucoma in this region of the human genome.

By making use of positional cloning strategies we recently isolated a candidate gene for choroideremia (CHM), which is transcribed in retina, choroid, and/or retinal pigment epithelium. The gene contains an open reading frame that is structurally altered in 10 CHM patients with sizable deletions and in a female patient with a balanced translocation involving the Xq21 band. Employing PCR-SSCP analysis and direct DNA sequencing we have now detected and characterized different point mutations in five patients with CHM. Each of these mutations introduces a termination codon into the open reading frame of the CHM candidate gene, thereby predicting a distinct truncated protein product. Together these findings provide convincing evidence for the candidate gene being identical with the choroideremia gene.

X-linked ocular albinism (XOA) is characterized by anomalies of the eyes and hypopigmentation or absence of pigment in skin, hair and eyes due to a hereditary inborn error of metabolism affecting the pigment cells. The gene of XOA of the Nettleship-Falls type (OA1) has been mapped to Xp22.3, and several closely linked RFLP loci have been identified. Linkage analysis and deletion mapping have established the marker gene order Xpter-STS-DX237-(OA1,DXS143,DXS85)-DXS1 6-DXS43-Xcen. Although the position of OA1 has yet not been fully resolved, we report on the first carrier detections in OXA of the Nettleship-Falls type by DNA analysis using markers which unquestionably flank OA1.

The results of linkage analysis in a family with X-linked retinitis pigmentosa (XLRP) are presented. Probe M27B (DXS255), localized to Xp11.22, was only loosely linked to XLRP, whereas pHOC3 (OTC), in the more distal Xp21.1 region, was tightly linked. In this family, the conditional probability of an RP3 locus (in Xp21.1-p11.4) was found to be 0.978 compared with 0.021 for an RP2 locus (in Xp11.4-p11.2). Risk assessment showed that 2 out of 4 "at risk" females showing no clinical abnormality have a high probability of being genetic carriers of XLRP. Some affected males have recurrent respiratory infections as a result of a condition indistinguishable from the immotile cilia syndrome; indeed, there is an association between XLRP and susceptibility to respiratory infections in the majority of affected males. The possibility that previously observed ciliary abnormalities in XLRP patients might be associated specifically with an RP3 locus abnormality is discussed.

A large family with autosomal dominant aniridia is described. One of the family members presented with reduced visual acuity, nystagmus, slightly distorted macular reflex, but normal irides and clear media. Because of the high variability in expression of aniridia, even within family, a diagnosis of aniridia could not be excluded. However linkage analysis using tightly linked chromosome 11p13 markers flanking the aniridia locus (catalase, D11S151, and D11S325) made it highly unlikely that this patient inherited the aniridia gene from his affected mother.

An extensive linkage analysis was performed by studying ten Xp22 loci in ten families segregating for X-linked ocular albinism of the Nettleship-Falls type (XOA). Linkage was confirmed between the XOA locus (OA1) and both DXS16 (theta max = 0.10, zeta max = 4.09) and DXS237 (theta max = 0.12, zeta max = 2.53). Linkage was found between OA1 and the loci DXS85 (theta max = 0.00, zeta max = zeta max = 4.37), DXS143 (theta max = 0.04, zeta max = 3.74), STS (theta max = 0.05, zeta max = 2.48), DXF30S1 (DXS278) (theta max = 0.07, zeta max = 8.79) and DXF30S2/3 (DXS278) (theta max = 0.00, zeta max = 14.93). An indication for linkage was found between OA1 and the loci DXS43 (theta max = 0.10, zeta max = 1.58) and DXS31 (theta max = 0.12, zeta max = 1.55). The analysis of multiple informative meioses suggests the order Xpter-(DXS31, DXS89)-(DXF30S1, DXS237)-(DXF30S2/3, OA1)-DXS143-(DXS16, DXS43)-Xcen. Various multipoint linkage analyses using the DNA loci order DXF30S1-STS-DXS237-DXS143-DXS16 significantly favour the position of OA1 between DXS237 and DXS143. These results further determine the genetic map around the XOA locus on the distal Xp and may be useful for DNA diagnosis in families with XOA.

The distal region of human chromosome band 11p13 is believed to contain a cluster of genes involved in the development of the eye, kidney, urogenital tract, and possibly the nervous system. Genetic abnormalities of this region can lead to Wilms tumor, aniridia, urogenital abnormalities, and mental retardation (WAGR syndrome). Using 11 DNA markers covering the entire distal region of 11p13, including the WAGR region, we have carried out molecular studies on 58 patients with one or more features of this syndrome and patients with other diseases or structural cytogenetic abnormalities associated with 11p13. Cytogenetic analyses were performed in all cases. In 12 patients we were able to demonstrate deletions of this region. In 2 patients balanced translocations and in 2 additional patients duplications of this region were characterized. In total, 5 chromosomal breakpoints within 11p13 were identified. One of these breakpoints maps within the smallest region of overlap of WAGR deletions. Moreover, we were unable to demonstrate constitutional deletions in a candidate sequence for the Wilms tumor gene or any other marker in 2 patients with aniridia and urogenital abnormalities, 4 patients with Wilms tumor and urogenital abnormalities, 5 patients with bilateral Wilms tumors, and 3 familial Wilms tumor cases. We suggest that the molecular techniques used here (heterozygosity testing for polymorphic markers mapping between AN2 and WT1 and deletion analysis by dosage, cytogenetic analysis, or in situ hybridization) can be employed to identify sporadic aniridia patients with and without increased tumor risk.

A family with X-linked megalocornea (XMC) is presented. The most typical ocular features of the disease (cornea globosa, arcus lipoides, mosaic dystrophy of the cornea, pigment dispersion, and cataract) are described and their diagnostic value is discussed by reviewing the literature. Linkage data suggest that the XMC locus maps in the region Xq13-q25, most probably in Xq21-q22.

DNA diagnosis of X-linked retinitis pigmentosa (XLRP) is hampered by its genetic heterogeneity, while a clinical subdivision is almost impossible to make. So far, diagnostic services have been offered only to those families in which linkage to one RP locus (RP2 or RP3) has been clearly established. In most families, however, the nature of the XLRP type cannot be distinguished on the basis of linkage analysis. Here the authors describe that in some families DNA diagnosis is nonetheless feasible, when polymorphic DNA markers are used which span the entire Xp21.1-Xcen region and when no recombination between these markers disturbs the phase.

The authors present the results of ocular examination of six children with congenital Marfan syndrome with contractures (CMC syndrome). The ocular and neuroradiological findings of the CMC syndrome are discussed with reference to the literature. The ocular findings are: blue sclerae, megalocorneas, hypoplastic irides with complete translucency, miosis, spherophakia with or without lens dislocation and severe myopia. This study demonstrates that ophthalmological examination of children with congenital contractures and arachnodactyly is very helpful for diagnosis of the CMC syndrome. The authors stressed that ophthalmologists should not only look for luxation of the lens in children who are suspected of having CMC syndrome. Spherophakia was common in the children and could easily be observed through the translucent irides. Biometric evaluation of the eyes is recommended. All of the cases in this paper and reported cases are sporadic. No conclusions have been reached in the literature on whether the CMC syndrome represents the severe expression of the classical Marfan syndrome or a distinct entity. Maybe the answer will remain difficult, until the specific molecular defects in the collagen diseases are discovered. This study demonstrates that ophthalmological examination of the children with congenital contractures and arachnodactyly is very helpful for the diagnosis of CMC syndrome.

Linkage analysis was performed in six families segregating for X-linked ocular albinism of the Nettleship-Falls type using four polymorphic DNA markers from the distal Xp. Linkage was found between the disease locus (OA1) and the loci DXS237 (theta max = 0.06, Zmax = 2.82), DXS278 (theta max = 0.03, Zmax = 5.27) and DXS16 (theta max = 0.10, Zmax = 2.33). The analysis of multiple informative meioses suggests that OA1 maps between DXS278/DXS237 and DXS143/DXS16. Multipoint linkage analysis slightly favours the order DXS278/DXS237-OA1-DXS16. These data refine the genetic localization of OA1 and may be useful for carrier detection in X-linked ocular albinism by DNA analysis.

A 7-year-old girl was found to have a progressive axial crystalline cataract located in the embryonal, fetal, and infantile nucleus. She also had the unknown association of crystalline cataract with uncombable hair. Samples of the aspirate after extracapsular cataract extraction (ECCE) showed elongated, trigonal crystals on scanning electron microscopy. On transmission electron microscopy, the crystals were surrounded by a membrane sometimes consisting of up to 30 concentric layers. The crystals were found to contain carbon, oxygen, nitrogen, sulfur, and disulfide bonds. The findings suggest that a major constituent of the crystals was a sulfur-containing aminoacid, probably cystine. Protein analysis of the remaining lens material showed elevated alpha-, beta 2-, and gamma 2- crystallin levels. Analysis of the hair root status showed hair loss in the resting phase of the hair cycle with abnormal sheathing in most hairs that were in the growth phase.

Mitochondrial DNA isolated from white blood cells was investigated in families suffering from Leber's hereditary optic neuropathy. A recently described mutation at nucleotide position 11778 was present in 5 out of 12 families and heteroplasmic mitochondrial DNA was observed in 2 of these 5 families. A rapid shift in genotype was found in one of the families with heteroplasmy: the grandmother had 60 percent mitochondrial DNA mutated at nucleotide position 11778, the mother 55 percent, and the two sons at least 95 percent. These data indicate that the number of mitochondrial DNA molecules transmitted to the progeny passes a developmental bottleneck, as previously proposed to occur in bovine oogenesis.

A progressive demyelinating cerebral disorder is described in a normally-appearing female infant with neonatal seizures, progressive psychomotor deterioration, deafness, retinopathy, peripheral neuropathy and loss of myelin observed on magnetic resonance imaging (MRI) scanning. MRI also showed the absence of macroscopic neocortical dysplasia which is usually found in Zellweger syndrome (ZS). Adrenal cortical function was normal. The patient died at the age of 37 months. Extensive biochemical investigations of peroxisomal functions in the patient revealed an impairment of peroxisomal beta-oxidation resulting in elevated levels of very long (greater than C22) chain fatty acids in plasma and fibroblasts. Moreover, elevated plasma levels of intermediates of bile acid biosynthesis such as tri- and dihydroxycholestanoic acid were found. Other peroxisomal functions were normal. Immunoblotting of the peroxisomal beta-oxidation enzyme proteins in liver from the patient revealed normal responses with antisera against acyl-CoA oxidase, bifunctional protein and thiolase respectively. From these data we conclude that the patient had a deficiency of a single peroxisomal beta-oxidation enzyme at the level of either the bifunctional protein or peroxisomal thiolase with retained immunoreactivity against these enzymes.

Three families with a total of five patients with Lowe's syndrome are described. We tried to trace female heterozygotes by ophthalmological abnormalities in order to realize prevention of this serious X-chromosomal recessive disease. Of the fourteen female relatives examined, eight showed pathological opacities of the lens, two of these being proven heterozygotes. In our opinion, in Lowe's syndrome, examination of the eyes can play an important role in the detection of heterozygotes.

The rhizomelic type of chondrodysplasia punctata (RCDP) is recognizable at birth because of the typical phenotype and radiological features. Most patients die young, some survive until their teens but all are severely retarded. Recent studies showed RCDP to be a peroxisomal disorder. Peroxisomal investigations may be important in defining the prognosis for an individual patient, and are definitely of use in antenatal diagnosis.