Variation in optineurin (OPTN) allele frequencies between and within populations.

PURPOSE: To evaluate the extent to which mutations in the optineurin (OPTN) glaucoma gene play a role in glaucoma in different populations. METHODS: Case-controlled study of OPTN sequence variants in individuals with or without glaucoma in populations of different ancestral origins and evaluate previous OPTN reports. We analyzed 314 subjects with African, Asian, Caucasian and Hispanic ancestries included 229 cases of primary open-angle glaucoma, 51 cases of juvenile-onset open-angle glaucoma, 33 cases of normal tension glaucoma, and 371 controls. Polymerase chain reaction-amplified OPTN coding exons were resequenced and case frequencies were compared to frequencies in controls matched for ancestry. RESULTS: The E50K sequence variant was identified in one individual from Chile with normal tension glaucoma, and the 691_692insAG variant was found in one Ashkenazi Jewish individual from Russia. The R545Q variant was found in two Asian individuals with primary open-angle glaucoma; one of Filipino ancestry and one of Korean ancestry. In addition to presenting OPTN allele frequencies for Caucasian and Asian populations that have been the subject of previous reports, we also present information for populations of Hispanic and black African ancestries. CONCLUSIONS: Our study contributes additional evidence to support the previously reported association of the OPTN E50K mutation with glaucoma. After finding an additional 691_692insAG OPTN variant, we can still only conclude that this variant is rare. Combined analysis of our data with data from more than a dozen other studies indicates no association of R545Q with glaucoma in most populations. Those same studies disagree in their conclusions regarding the role of M98K in glaucoma. Our analysis of the combined data provides statistically significant evidence of association of M98K with normal tension glaucoma in Asian populations, but not in Caucasian populations; however, the validity of this conclusion is questionable because of large differences in allele frequencies between and within populations. It is currently not possible to tell how much of the underlying cause of the allele frequency difference is attributable to demographic, technical, or ascertainment differences among the studies.

Evaluation of the beta2-adrenergic receptor gene as a candidate glaucoma gene in 2 ancestral populations.

OBJECTIVE: To determine whether the beta(2)-adrenergic receptor (ADRB2) gene is a glaucoma susceptibility locus. DESIGN AND METHODS: The design was an association study stratified by ancestry (white vs black African) and disease (primary open-angle glaucoma vs control subjects). The ADRB2 single nucleotide polymorphisms were determined by sequencing, and the haplotypes of the common single nucleotide polymorphisms affecting codons 16 and 27 were phased by allele-specific polymerase chain reaction and restriction enzyme digestion. We analyzed the association of single nucleotide polymorphisms and haplotypes by ancestry and disease with the Fisher exact test, chi(2) test, and standardized Pearson residual. RESULTS: A total of 583 subjects underwent genotyping (156 white subjects with primary open-angle glaucoma; 143 subjects of black African ancestry with primary open-angle glaucoma; 148 white controls; and 136 controls of black African ancestry). There were no differences in ADRB2 alleles and haplotypes between the primary open-angle glaucoma and control groups, whether analyzed together or by ancestry. Previously described ancestry-based differences in allele frequencies were found. We also found ancestry-based differences in ADRB2 haplotypes. CONCLUSION: The ADRB2 gene was not a glaucoma susceptibility locus in our study population. CLINICAL RELEVANCE: Because this gene is not a disease locus, we can now study the role of ADRB2 haplotypes in the glaucoma risk factor of intraocular pressure fluctuation and variation in intraocular pressure response to beta-blockers.

Ordered subset analysis supports a glaucoma locus at GLC1I on chromosome 15 in families with earlier adult age at diagnosis.

Open angle glaucoma (OAG) is a complex disorder with varying etiologies due to multiple genes and environmental effects. This genetic heterogeneity can confound efforts to map loci. Increased homogeneity in a sample can be achieved using either ordered subset analysis (OSA) which groups families, or individual OSA (IOSA), which groups individuals based on disease related covariates. Recently, GLC1I was mapped to 15q11-13 in families with early adult onset of OAG. We tested for linkage to GLC1I in an independent sample of 167 individuals in 25 multiplex OAG families of European descent. We carried out nonparametric linkage analysis on the complete set of 25 families and obtained a maximum LOD score of 1.00 at 9.0 cM. Using mean age at diagnosis (AAD) across the affected individuals within each family to order the families as a proxy for age at onset, we found a maximum OSA LOD score of 2.09 (p=0.021) at 26.1 cM. The mean (+/-s.d.) AAD across the 14 earlier AAD families that contributed to the OSA LOD score was 50.6 years (+/-5.38); the mean AAD for the other 1210 later AAD families that did not contribute to the OSA LOD score (the high-AAD) was 61.7 years (+/-3.50). We also ran IOSA on our families using AAD as our covariate on which to subset affected individuals. The maximum LOD score was 1.01 at 14.3 cM when ordering subjects from early to late AAD. Ordered subset analysis of this sample has provided evidence of linkage close to the previously identified GLC1I glaucoma locus on 15q11-13 in families with middle-aged mean age at diagnosis.

Mutations in TCF8 cause posterior polymorphous corneal dystrophy and ectopic expression of COL4A3 by corneal endothelial cells.

Posterior polymorphous corneal dystrophy (PPCD, also known as PPMD) is a rare disease involving metaplasia and overgrowth of corneal endothelial cells. In patients with PPCD, these cells manifest in an epithelial morphology and gene expression pattern, produce an aberrant basement membrane, and, sometimes, spread over the iris and nearby structures in a way that increases the risk for glaucoma. We previously mapped PPCD to a region (PPCD3) on chromosome 10 containing the gene that encodes the two-handed zinc-finger homeodomain transcription factor TCF8. Here, we report a heterozygous frameshift mutation in TCF8 that segregates with PPCD in the family used to map PPCD3 and four different heterozygous nonsense and frameshift mutations in TCF8 in four other PPCD probands. Family reports of inguinal hernia, hydrocele, and possible bone anomalies in affected individuals suggest that individuals with TCF8 mutations should be examined for nonocular anomalies. We detect transcripts of all three identified PPCD genes (VSX1, COL8A2, and TCF8) in the cornea. We show presence of a complex (core plus secondary) binding site for TCF8 in the promoter of Alport syndrome gene COL4A3, which encodes collagen type IV alpha 3, and we present immunohistochemical evidence of ectopic expression of COL4A3 in corneal endothelium of the proband of the original PPCD3 family. Identification of TCF8 as the PPCD3 gene provides a valuable tool for the study of critical gene regulation events in PPCD pathology and suggests a possible role for TCF8 mutations in altered structure and function of cells lining body cavities other than the anterior chamber of the eye. Thus, this study has identified TCF8 as the gene responsible for approximately half of the cases of PPCD, has implicated TCF8 mutations in developmental abnormalities outside the eye, and has presented the TCF8 regulatory target, COL4A3, as a key, shared molecular component of two different diseases, PPCD and Alport syndrome.

A locus for posterior polymorphous corneal dystrophy (PPCD3) maps to chromosome 10.

Posterior polymorphous corneal dystrophy (PPCD) is an autosomal dominant disorder characterized by corneal endothelial abnormalities, which can lead to blindness due to loss of corneal transparency and sometimes glaucoma. We mapped a new locus responsible for PPCD in a family in which we excluded the previously reported PPCD locus on 20q11, and the region containing COL8A2 on chromosome 1. Results of a 317-marker genome scan provided significant evidence of linkage of PPCD to markers on chromosome 10, with single-point LOD scores of 2.63, 1.63, and 3.19 for markers D10S208 (at (circumflex)theta = 0.03), D10S1780 (at (circumflex)theta = 0.00), and D10S578 (at (circumflex)theta = 0.06). A maximum multi-point LOD score of 4.35 was found at marker D10S1780. Affected family members shared a haplotype in an 8.55 cM critical interval that was bounded by markers D10S213 and D10S578. Our finding of another PPCD locus, PPCD3, on chromosome 10 indicates that PPCD is genetically heterogeneous. Guttae, a common corneal finding sometimes observed along with PPCD, were found among both affected and unaffected members of the proband's sib ship, but were absent in the younger generations of the family. Evaluation of phenotypic differences between family members sharing the same affected haplotype raises questions about whether differences in disease severity, including differences in response to surgical interventions, could be due to genetic background or other factors independent of the PPCD3 locus.

A novel mutation in the PITX2 gene in a family with Axenfeld-Rieger syndrome.

PURPOSE: To determine the underlying genetic cause of Axenfeld-Rieger syndrome (ARS) in a three-generation family. INTRODUCTION: ARS is a multisystem, autosomal dominant disorder characterized by specific ocular and non-ocular anomalies sometimes caused by mutations in the transcription factor gene, PITX2. METHODS: The three coding exons of the PITX2 gene, i.e., exons 2, 3, and 4, in affected and unaffected subjects were amplified by polymerase chain reaction (PCR) and sequenced. The PCR products of exon 4 were subcloned and sequenced to confirm the nature of the mutation. RESULTS: A deletion of thymine (T) 1261 was identified, creating a frameshift mutation in codon 227. This change is predicted to create 11 novel amino acids downstream, followed by premature truncation of the protein. CONCLUSIONS: This mutation highlights the functional importance of a conserved 14-amino acid sequence at the C-terminus of the protein thought to be important in repressing DNA binding and in protein-protein interactions.

Mutation of the FOXC2 gene in familial distichiasis.

OBJECTIVE: To examine the FOXC2 gene in a family with hereditary distichiasis. BACKGROUND: Distichiasis, ie, a second row of eyelashes arising from the meibomian glands of the eyelids, can be inherited either alone (Online Mendelian Inheritance in Man [OMIM] no. 126300) or, more commonly, as part of the lymphedema-distichiasis (LD) syndrome (OMIM no. 153400). More than 45 families with mutations in the FOXC2 gene and LD have been described. Both lymphedema and distichiasis are highly penetrant. Distichiasis without lymphedema is not commonly seen. METHODS: We examined three generations of a family (N = nine members) with hereditary distichiasis but without lymphedema or other features of LD syndrome. The FOXC2 gene was polymerase chain reaction--amplified from genomic DNA from all family members and examined for mutations. RESULTS: Clinical examination showed distichiasis of all four lids in two affected family members across two generations. There were no other consistent ophthalmologic abnormalities in the family. A cytosine-to-adenine transversion was identified in DNA from affected study participants at nucleotide position 1076, which would be predicted to cause truncation of the protein at codon 359. This change was not observed in any of the nine unaffected family members participating. CONCLUSIONS: This finding suggests that hereditary distichiasis and LD may not be separate genetic disorders but different phenotypic expressions of the same underlying disorder. Ophthalmologists should be aware that LD may present as distichiasis alone and counsel and refer their patients appropriately.

Septuagenarian's phenotype leads to ascertainment of familial MYOC gene mutation.

PURPOSE: To report a family with a myocilin (MYOC) gene mutation ascertained on the basis of the phenotype of the 71-year-old proband with juvenile-onset primary open-angle glaucoma (JOAG). PATIENTS AND METHODS: A thorough patient history of the proband and review of medical records revealed that a filtering procedure performed 50 years before had controlled the intraocular pressure (IOP) and prevented optic disc damage and visual field loss until the bleb failed after cataract surgery. Patient characteristics and history led to suspicion of a mutation in the MYOC gene. Mutation screening and clinical evaluation of the proband and family members were undertaken. RESULTS: A Val426Phe mutation was found in the JOAG proband and in 3 other blood relatives with glaucoma. The mutation was not present in unaffected relatives. CONCLUSIONS: A functioning filtering procedure performed 50 years before the current study was all that was needed to prevent glaucomatous damage and control IOP in the proband. Once the bleb failed, increased IOP led to damage in a relatively brief period of time. Although not every JOAG patient has the MYOC mutation, there is a somewhat typical MYOC phenotype that may predict an increased chance of harboring a MYOC mutation. Use of such phenotype information in evaluating whether to screen older patients can lead to identification of families at risk for open-angle glaucoma.

Clinicopathologic correlation and genetic analysis in a case of posterior polymorphous corneal dystrophy.

PURPOSE: To evaluate the clinical history, histopathology, and genetics of posterior polymorphous corneal dystrophy (PPMD) in a woman with a prominent retrocorneal membrane. DESIGN: Observational case report and genetic analysis of her family, UM:139. METHODS: Records were reviewed from a case and associated family members. The diagnosis of PPMD was based on clinical examination, immunohistochemical staining, electron microscopy, and screening of genetic markers from regions previously reported to be associated with PPMD. RESULTS: Over 17 years, the proband with PPMD had 25 ocular procedures performed for glaucoma, cataract, cornea, retina, and postoperative problems. A prominent retrocorneal membrane grew onto the crystalline lens and intraocular lens (IOL). Histopathology revealed stratified epithelial-like cells on iris from an iridectomy and stratified corneal endothelium on a corneal button. Electron microscopy on the cornea revealed microvilli, tonofilaments, and desmosomes consistent with endothelial transformation, which was confirmed by positive anticytokeratin (CK) AE1/AE3 and CAM 5.2 immunoreactivity. Negative immunoreactivity in epithelium and positive in endothelium with anti-CK 7 supported the diagnosis of PPMD rather than epithelial downgrowth. Multiple relatives were affected with PPMD with apparent autosomal dominant inheritance, but surprisingly, the PPMD, congenital hereditary endothelial dystrophy 1 (CHED1) and CHED2 loci on chromosome 20 and the collagen, type VIII, alpha-2 (COL8A2) gene were excluded by linkage and haplotype analyses. CONCLUSIONS: We are unaware of previous PPMD reports describing the unusual feature of a retrocorneal membrane extending onto the crystalline lens and IOL. In addition, this family suggests another PPMD locus.

Characterization of a stapes ankylosis family with a NOG mutation.

OBJECTIVE: To characterize the otologic phenotype in a family with autosomal dominant stapes ankylosis, hyperopia, and skeletal abnormalities caused by a mutation in the noggin gene (NOG). STUDY DESIGN: Case series. SETTING: Academic tertiary care center. PATIENTS: Eight affected and 3 unaffected family members. MAIN OUTCOME MEASURES: History, physical and radiologic examination, and surgical outcomes. RESULTS: Although affected members were initially presumed to have typical nonsyndromic otosclerosis, the clinical data were most consistent with an autosomal dominant congenital stapes ankylosis syndrome. Eight of eight affected family members had bilateral low-frequency conductive hearing loss. Six of eight underwent fenestration procedures and/or stapedectomies. All members with initial postoperative closure of the air-bone gap returned to their baseline conductive loss within 2 years. Two affected family members had documented maximal conductive hearing loss by age 4, and two members without previous otologic surgery have not experienced sensorineural hearing loss. High-resolution temporal bone computed tomography showed stapes ankylosis and indistinction of the incudomalleal junction bilaterally and bony regrowth over the stapedotomy for those with stapedectomies. Detailed physical and radiologic examination identified multiple other skeletal abnormalities. CONCLUSIONS: Although this phenotype may present as classic otosclerosis to the otolaryngologist, detailed investigation revealed a congenital stapes ankylosis syndrome. Because is essential in regulating normal bone development and maturation, mutations in this gene may be associated with excessive bony overgrowth and refixation of the stapes footplate after initial successful surgery. Patients with hereditary conductive hearing loss should be assessed to rule out subtle features of a skeletal syndrome.

Autosomal dominant stapes ankylosis with broad thumbs and toes, hyperopia, and skeletal anomalies is caused by heterozygous nonsense and frameshift mutations in NOG, the gene encoding noggin.

Although fixation of the stapes is usually progressive and secondary to otosclerosis, it may present congenitally, with other skeletal manifestations, as an autosomal dominant syndrome-such as proximal symphalangism (SYM1) or multiple-synostoses syndrome (SYNS1), both of which are caused by mutations in NOG, the gene encoding noggin. We describe a family that was ascertained to have nonsyndromic otosclerosis but was subsequently found to have a congenital stapes ankylosis syndrome that included hyperopia, a hemicylindrical nose, broad thumbs and great toes, and other minor skeletal anomalies but lacked symphalangism. A heterozygous nonsense NOG mutation-c.328C-->T (Q110X), predicted to truncate the latter half of the protein-was identified, and a heterozygous insertion in NOG-c.252-253insC, in which the frameshift is predicted to result in 96 novel amino acids before premature truncation-was identified in a previously described second family with a similar phenotype. In contrast to most NOG mutations that have been reported in kindreds with SYM1 and SYNS1, the mutations observed in these families with stapes ankylosis without symphalangism are predicted to disrupt the cysteine-rich C-terminal domain. These clinical and molecular findings suggest that (1) a broader range of conductive hearing-loss phenotypes are associated with NOG mutations than had previously been recognized, (2) patients with sporadic or familial nonsyndromic otosclerosis should be evaluated for mild features of this syndrome, and (3) NOG alterations should be considered in conductive hearing loss with subtle clinical and skeletal features, even in the absence of symphalangism.