MYOC Mutation Research Articles

Glaucoma in iran and contributions of studies in iran to the understanding of the etiology of glaucoma.

Epidemiologic and genetic/molecular research on glaucoma in Iran started within the past decade. A population-based study on the epidemiology of glaucoma in Yazd, a city in central Iran, revealed that 4.4% of studied individuals were affected with glaucoma: 1.6% with high tension primary open angle glaucoma (POAG), 1.6% with normal tension POAG, and 0.4% each with primary angle closure glaucoma (PACG) and pseudoexfoliation glaucoma (PEXG), and other types of secondary glaucoma. Two notable observations were the relatively high frequency of normal tension glaucoma cases (1.6%) and the large fraction of glaucoma affected individuals (nearly 90%) who were unaware of their condition. The first and most subsequent genetic studies on glaucoma in Iran were focused on primary congenital glaucoma (PCG) showing that cytochrome P450 1B1 (CYP1B1) is the cause of PCG in the majority of Iranian patients, many different CYP1B1 mutations are present among Iranian patients but only four mutations constitute the vast majority, and the origins of most mutations in the Iranians are identical by descent (IBD) with the same mutations in other populations. Furthermore, most of the PCG patients are from the northern and northwestern provinces of Iran. A statistically significant male predominance of PCG was observed only among patients without CYP1B1 mutations. Clinical investigations on family members of PCG patients revealed that CYP1B1 mutations exhibit variable expressivity, but almost complete penetrance. A great number of individuals harboring CYP1B1 mutations become affected with juvenile onset POAG. Screening of JOAG patients showed that an approximately equal fraction of the patients harbor CYP1B1 and (myocilin) MYOC mutations; MYOC is a well-known adult onset glaucoma causing gene. Presence of CYP1B1 mutations in JOAG patients suggests that in some cases, the two conditions may share a common etiology. Further genetic analysis of Iranian PCG patients led to identification of Latent-transforming growth factor beta-binding protein 2 (LTBP2) as a causative gene for both PCG and several diseases which are often accompanied by glaucomatous presentations, such as Weill-Marchesani syndrome 3 (WMS3). The findings on LTBP2 have contributed to recognize the importance of the extracellular matrix in pathways leading to glaucoma.

Analysis of MYOC gene mutation in a primary open angle glaucoma family from China

Background Primary open angle glaucoma (POAG) is one of the frequent glaucomatous types,and genetic factor participates in pathogenesis and development of the disease.Recently,MYOC mutation was found to be associated with POAG.Objective This study was to describe the clinical and genetic findings in a POAG family from Luoyang,China.Methods This study protocol was approved by Ethic Committee of Affiliated First Hospital of Henan University of Science and Technology.The study adhered to Declaration of Helsinki.A POAG family with 29 members of 5 generations was surveyed and followed-up for 5-year duration.The mode of inheritance was determined by the pedigree analysis.The periphery blood sample was collected form 12 families and 100 health controls for the extraction of genomic DNA under the informed consent.The third exon and its flanking introns of MYOC were amplified,and quantitative real time PCR products were sequenced,and the structure and function of mutated gene were examined by restriction fragment length polymorphism analysis.The predicted effects of the detected variants on the secondary structure of MYOC protein were evaluated using Garnier-Osguthorpe-Robson (GOR) method,and homology analysis of protein was carried out by Blast software provided by National Center for Biotechnology Information (NCBI).Results This POAG family included 29 members of 5 generations,and the clinical data were not clear in 11 family members.Three individuals from 3 generations were determined POAG,another one was ocular hypertension,and 2 were carriers.Pedigree analysis appeared an autosomal dominant inheritance.In 12 subjects included 6 members genetically affected and 6 members with normal phenotype,the heterozygous mutation was found in the third exon of MYOC gene in 6 genetically affected members,which revealed a T→C transition at position 1021 (p.S341P),resulting in a switch of serine (Ser) to proline (Pro).It was a missense mutation abolished a CviKI-1 restriction site that segregated with the affected members.Secondary structure prediction of p.S341P suggested that myocilin protein was misfolded.Analysis of protein homology and switched Ser was conservative amine acid at position 1021 (p.S341P).No similar change was found in the 6 normal families and the normal controls.Conclusions Ser341Pro MYOC mutation is disease-causing factor in the POAG family of Luoyang.The clinical and genetic features of this mutation warrant further investigation.The mutation spectrum of MYOC is expanded to offer a better diagnosis and treatment for POAG patients. Key words: Glaucoma, open angle/genetics; Pedigree; MYOC gene; Mutation; Base sequence; Cytoskeletal protein; DNA mutational analysis; China

Mutation analysis of seven known glaucoma-associated genes in Chinese patients with glaucoma.

To evaluate mutations in the MYOC, WDR36, OPTN, OPA1, NTF4, CYP1B1, and LTBP2 genes in a cohort of Chinese patients with primary glaucoma. Genomic DNA was prepared from 683 unrelated patients, including 50 with primary congenital glaucoma, 104 with juvenile open-angle glaucoma (JOAG), 186 with primary open-angle glaucoma (POAG), and 343 with primary angle-closure glaucoma (PACG). Mutations in the seven genes in 257 patients (36 with JOAG, 89 with POAG, and 132 with PACG) were initially analyzed by exome sequencing and then confirmed by Sanger sequencing. In addition, Sanger sequencing was used to detect MYOC mutations in the remaining 426 patients. Exome sequencing identified 19 mutations (6 in MYOC, 9 in WDR36, 3 in OPA1, and 1 in OPTN) in 20 of 257 patients, including 4 patients with JOAG, 8 patients with POAG, and 8 patients with PACG. No mutation was detected in the other three genes. In addition, Sanger sequencing detected additional MYOC mutations in 5 of the remaining 426 patients, including 3 patients with JOAG and 2 patients with POAG. Twenty-two mutations in MYOC, WDR36, OPA1, and OPTN were detected in 25 of the 683 patients with primary glaucoma, including nine MYOC mutations in 11 patients, nine WDR36 mutations in 11 patients, three OPA1 mutations in 3 patients, and one OPTN mutation in a patient who also carried a MYOC mutation. Eight mutations in MYOC, WDR36, and OPA1 in 8 of the 343 PACG patients are of uncertain significance and need to be analyzed further.

Identification of a novel MYOC mutation, p.(Trp373*), in a family with open angle glaucoma

MYOC gene variants are associated with autosomal dominant primary open angle glaucoma (POAG). In this study, we describe a previously unreported MYOC variant segregating with a POAG phenotype in an Australian family. Two individuals affected with POAG and three unaffected individuals from the same family were recruited through the Australian and New Zealand Registry of Advanced Glaucoma (ANZRAG). Direct sequencing of all MYOC coding exons identified the novel heterozygous single nucleotide transition MYOC:c.1119G>A, p.(Trp373), predicted to encode an aberrant truncated MYOC protein in two affected siblings. Two unaffected siblings and an unaffected niece were negative for the MYOC sequence variant.

New mutation in the myocilin gene segregates with juvenile-onset open-angle glaucoma in a Brazilian family

Mutations in the myocilin gene (MYOC) account for most cases of autosomal dominant juvenile-onset open-angle glaucoma (JOAG), an earlier and more severe form of POAG. We accessed seven members of a Brazilian JOAG family by clinical and molecular investigation. Four out of seven family members were diagnosed with JOAG. All of these patients presented high intraocular pressure and two of them were bilaterally blind. The disease onset varied from 20 to 30years old. There was a nine-year-old family member who had not yet manifested the disease, although he was also a carrier of the mutation. Ophthalmologic examination included: evaluation of the visual field and optic disc, intraocular pressure measurement, and gonioscopy. The three exons and intron/exon junctions of the MYOC gene were screened for mutations through direct sequencing of PCR-amplified DNA fragments. Mutation screening revealed an in-frame mutation in the third exon of the MYOC gene: an insertion of six nucleotides between the cDNA positions 1187 and 1188 (c.1187_1188insCCCAGA, p.D395_E396insDP). This mutation presented an autosomal dominant pattern of inheritance, segregating with the disease in four family members for three generations, and it was absent in 60 normal controls. We also performed a computational structure modeling of olfactomedin-like domain of myocilin protein and conducted in silico analysis to predict the structural changes in the myocilin protein due to the presence of the mutation. These findings may be important for future diagnosis of other presymptomatic family members, as well as for the increase of the panel of MYOC mutations and their effects on phenotype.

A de novo MYOC mutation detected in juvenile open angle glaucoma associated with reduced myocilin protein in aqueous humor

MYOC mutations were originally identified in patients with juvenile open angle glaucoma (JOAG). Cell culture and mouse studies suggest that MYOC mutations cause glaucoma through a dominant-negative effect on myocilin protein secretion. We tested this hypothesis with patient samples in this study. Glaucoma and control patients underwent complete ocular examination. DNA samples from glaucoma patients, unaffected relatives and controls were used for DNA sequencing of MYOC. Aqueous humor (AH) samples from glaucoma and control patients were obtained at the time of surgery. Myocilin protein in AH was detected by quantitative Western blot analysis. A de novo Val251Ala mutation of MYOC was found to segregate with disease in a family with autosomal dominant JOAG. Myocilin protein was detected in all control AH samples but was nearly undetectable in AH samples from a patient heterozygous for the Val251Ala mutation. Our results using human patient samples are consistent with a dominant-negative effect of pathogenic MYOC mutations on myocilin secretion.

CYP1B1, MYOC, and LTBP2 Mutations in Primary Congenital Glaucoma Patients in the United States

To screen primary congenital glaucoma patients in the United States for sequence variants within the CYP1B1, LTBP2, and MYOC genes using Sanger and whole exome sequencing. Retrospective case-control study. Fifty-seven primary congenital glaucoma patients (47 families), 71 unaffected family members of the primary congenital glaucoma probands, and 101 healthy unrelated individuals were recruited from a single institution. Sanger sequencing of the primary congenital glaucoma gene, CYP1B1, was performed on 47 proband deoxyribonucleic acid samples. Simultaneously, whole exome sequencing was conducted on 3 families, each including more than 1 affected individual. Concurrently, 33 of 47 primary congenital glaucoma probands with extended family deoxyribonucleic acid samples were screened for LTBP2 and MYOC gene mutations. Exome-sequenced variations were validated by additional Sanger sequencing to confirm segregation of filtered disease-causing single nucleotide variations. Seven primary congenital glaucoma families (14.9%) manifested disease phenotypes attributable to CYP1B1 mutations. One primary congenital glaucoma family possessed homozygous mutant alleles, whereas 6 families carried compound heterozygous mutations. Five novel combinations of compound heterozygous mutations were identified, of which 2 combinations were found with whole exome sequencing. No disease-causing mutations within the LTBP2 and MYOC genes were discovered. This study analyzed CYP1B1, LTBP2, and MYOC mutations in a cohort of primary congenital glaucoma patients from the United States, applying whole exome sequencing as a complementary tool to Sanger sequencing. Whole exome sequencing, coupled with Sanger sequencing, may identify novel genes in primary congenital glaucoma patients who have no mutations in known primary congenital glaucoma genes.

Genetics of primary glaucoma

To provide an overview of the genetics of the primary open-angle glaucomas with particular attention to congenital, infantile, and juvenile forms. Mutations in CYP1B1, in addition to being the most common identifiable cause of autosomal recessive primary congenital/infantile glaucoma, can infrequently underlie juvenile and even primary adult-onset open-angle glaucoma, particularly in certain consanguineous populations. In 2009, patients diagnosed with congenital/infantile glaucoma were found to have recessive mutations in a second gene, LTBP2, with a phenotypic spectrum that includes primary megalocornea, spherophakia with ectopia lentis, and lens-related glaucoma. The most common identifiable cause of primary juvenile open-angle glaucoma across most populations remains heterozygous (autosomal dominant) MYOC mutation, underlying up to one-third of cases and possibly sometimes involved in earlier and later onset glaucomas Although primary adult-onset open-angle glaucoma usually does not follow simple Mendelian genetics and is etiologically complex, genome-wide association studies are uncovering genetic susceptibility factors. In some cases, primary adult-onset open-angle glaucoma can be caused by heterozygous mutation in MYOC, OPTN, or WDR36. In addition, in 2009, heterozygous NTF4 mutation was associated with the phenotype in a small percentage of patients from a German cohort. Seemingly unaffected siblings of children with CYP1B1-related primary congenital/infantile glaucoma should undergo genetic testing because of variable expressivity for the phenotype; such testing should also be considered for other asymptomatic relatives, especially in consanguineous families. In western populations, dominant MYOC mutation remains a common cause of primary open-angle juvenile glaucoma and infrequently can be implicated in congenital/infantile or adult-onset forms; identified families should undergo genetic counseling. Primary adult-onset open-angle glaucoma rarely follows simple Mendelian genetics, but genomic studies in different populations are revealing potential genetic risk factors for the phenotype.

Familial juvenile glaucoma with underlying homozygous p.G61E CYP1B1 mutations

We describe siblings with familial primary juvenile glaucoma from a consanguineous Saudi Arabian family. The phenotype segregated with homozygous p.G61E CYP1B1 mutations while MYOC mutation was not detected, illustrating that mutations in CYP1B1 rather than mutation in MYOC can underlie familial primary juvenile glaucoma in certain populations.

Study on MYOC/TIGR gene mutations in primary open-angle glaucoma

To study the mutations in the trabecular meshwork induced-glucocorticoid response protein gene (TIGR/MYOC) in Chinese POAG patients. It was a case-control study. One hundred and eighteen Chinese patients with POAG and 150 control subjects without POAG were screened for coding sequence of the MYOC gene by polymerase chain reaction, single-strand conformation polymorphism (SSCP) and DNA sequence. Restriction endonuclease analysis was used to detect the SSCP in 150 gender- and aged-matched controls. Statistical significance of the difference in frequencies of MYOC mutations between POAG patients and the controls was determined by the chi-squared test. Three coding sequence variants that lead to amino acid changes were identified in MYOC gene. One mutation of MYOC gene was novel, I288M, which was present in one patient with POAG and 3 control subjects. G12R and Y353I have been reported previously. I288M and Y353I were found in both the subjects with and without POAG, the difference of the frequency of these two mutations between POAG and the controls was χ(2) = 0.07, P = 0.791 and χ(2) = 0.56, P = 0.453, respectively. Coding sequence mutations of MYOC were found in 4.23% POAG patients. Frequency of G12R mutation in POAG patients was significantly greater than that in the controls (χ(2) = 4.37, P = 0.037). One novel variant locus in the MYOC/TIGR (I288M) was found in the present study, but this mutation is not associated with POAG. G12R is the most common mutation in MYOC locus in Chinese subjects with POAG. Approximately 4.23% sporadic POAG patients have mutation in the exon 1 in MYOC/TIGR.

Genotype/Phenotype Correlation in Primary Congenital Glaucoma Patients From Different Ethnic Groups of the Israeli Population

To investigate the roles of CYP1B1 and MYOC mutations and characterize the phenotype of primary congenital glaucoma in Israeli patients from 3 different ethnic backgrounds. Interventional case series. This institutional study included 34 Israeli primary congenital glaucoma patients (26 families) comprising 9 Jews (9 families), 17 non-Bedouin Muslim Arabs (10 families), and 8 Druze (7 families). The patients and their relatives (n = 99) were screened for CYP1B1 and MYOC mutations. Mutations in the CYP1B1 gene were detected in 12 of 26 families (46%) with primary congenital glaucoma (5 Muslim Arab, 5 Druze, and 2 Jewish). The Jewish families had compound heterozygous mutations and digenic mutations (ie, an Ashkenazi family had mutations in the CYP1B1 gene [Arg368His, R48G, A119S, and L432V haplotypes] and an Ashkenazi-Sephardic family had a mutation on the CYP1B1 gene [1908delA, Sephardic] with a second missense mutation on the MYOC gene [R76K, Ashkenazi]). The Muslim Arabs and Druze tended to have a more severe phenotype than that of the Jews. The phenotype and spectrum of the CYP1B1 and MYOC mutation roles in the clinical characteristics of primary congenital glaucoma varied according to ethnicity. The rarity of mutations in the CYP1B1 gene among Ashkenazi primary congenital glaucoma patients indicates that a different locus may be involved in the phenotype.

Primary open angle glaucoma due to T377M MYOC: Population mapping of a Greek founder mutation in Northwestern Greece

Mutations in the MYOC gene have been shown to explain 5% of unrelated primary open angle glaucoma (POAG) in different populations. In particular, the T377M MYOC mutation has arisen at least three separate times in history, in Great Britain, India, and Greece. The purpose of this study is to investigate the distribution of the mutation among different population groups in the northwestern region of Greece. We explored the distribution of the "Greek" T377M founder mutation in the Epirus region in Northwestern Greece, which could be its origin. Genotyping was performed in POAG cases and controls by PCR amplification of the MYOC gene, followed by digestion with restriction enzyme. Statistical analyses were performed by an exact test, the Kaplan-Meier method and the t-test. In the isolated Chrysovitsa village in the Pindus Mountains, a large POAG family demonstrated the T377M mutation in 20 of 66 family members while no controls from the Epirus region (n = 124) carried this mutation (P < 0.001). Among other POAG cases from Epirus, 2 out of 14 familial cases and 1 out of 80 sporadic cases showed the mutation (P = 0.057). The probability of POAG diagnosis with advancing age among mutation carriers was 23% at age 40, and reached 100% at age 75. POAG patients with the T377M mutation were diagnosed at a mean age of 51 years (SD +/- 13.9), which is younger than the sporadic or familial POAG cases: 63.1 (SD +/- 11) and 66.8 (SD +/- 9.8) years, respectively. The T377M mutation was found in high proportion in members of the Chrysovitsa family (30.3%), in lower proportion in familial POAG cases (14.2%) and seems rare in sporadic POAG cases (1.2%), while no controls (0%) from the Epirus region carried the mutation. Historical and geographical data may explain the distribution of this mutation within Greece and worldwide.

Association of POAG Risk Factors and the Thr377MetMYOCMutation in an Isolated Greek Population

To characterize the MYOC genotype correlation with phenotypes in an isolated Greek population with a high incidence of glaucoma. Five hundred thirty-one villagers were enrolled in the study. Participants underwent a comprehensive ophthalmic examination. All three exons of myocilin were bidirectionally sequenced. Power calculations and measured genotype analysis was conducted using the genetic variance analysis program, SOLAR version 4.2, to account for the relatedness between individuals. The participants, 376 of whom were linked in a single 11-generation pedigree, ranged in age from 10 to 95 years with a mean age of 49. Sixty-five individuals had POAG, and 27 of those carried the Thr377Met MYOC mutation. Both peak intraocular pressure and vertical cup-to dis- ratio were significantly associated with the MYOC Thr377Met variant (P = 9 x 10(-14) and P = 9 x 10(-8), respectively), whereas central corneal thickness showed no significant association (P < 0.7). This village had a high frequency of glaucoma, with 12% of the participants aged 10 to 95 years having the disease. In this cohort, the Thr377Met MYOC mutation was significantly associated with both high intraocular pressures and high vertical cup-to-disc ratios. No association was found with central corneal thickness.

Variable Clinical Spectrum of the Myocilin Gln368X Mutation in a Dutch Family with Primary Open Angle Glaucoma

Purpose: To describe the clinical phenotype in a family with primary open angle glaucoma harboring a p.Gln368X mutation in MYOC.Materials and Methods: We identified a proband with primary open angle glaucoma and the p.Gln368X MYOC mutation. She and her six siblings were examined clinically, including Heidelberg Retina Tomography II, and venous blood samples were screened for other variants in MYOC, WDR36, OPTN, and CYP1B1.Results: Four individuals showed the p.Gln368X MYOC mutation, no other genetic variations were assessed. Two of these four siblings had glaucomatous optic disc changes with corresponding visual field losses and abnormal Heidelberg Retina Tomography results by the Moorfields regression analysis, one had abnormal results by the Moorfields regression analysis but no visual field loss, and one showed no glaucomatous signs or symptoms at all. These findings did not correlate with the age of the affected individuals.Conclusion: In the primary open angle glaucoma family described here, we documented a wide range in clinical symptoms, demonstrating a highly variable penetrance of the MYOC p.Gln368X mutation.

CYP1B1 and MYOC Mutations in 116 Chinese Patients With Primary Congenital Glaucoma

To clinically characterize 116 Chinese patients with primary congenital glaucoma and to determine the role of CYP1B1 and MYOC mutations in this cohort. This study included 116 unrelated patients with primary congenital glaucoma and 120 ethnically matched, unrelated, healthy controls in China. CYP1B1 and MYOC were amplified from genomic DNA, followed by direct DNA sequencing to identify disease-causing variants. Twenty patients (17.2%) had CYP1B1 mutations. Five of these patients had homozygous mutant alleles and 4 had compound heterozygous mutations. Fourteen of the mutations were novel. Three patients (2.6%) had MYOC mutations, all of which were novel. This study describes the spectrum of CYP1B1 and MYOC mutations in a large cohort of Chinese patients with primary congenital glaucoma. The role of mutations in CYP1B1 and MYOC varies, depending on the ethnic origin of the patients. Clinical Relevance Patients with primary congenital glaucoma and CYP1B1 mutations tend to have a more severe phenotype than those without mutations. Genetic testing of CYP1B1 mutations may help predict new cases and their prognoses.

Recurrent Myocilin Asn480Lys Glaucoma Causative Mutation Arises De Novo in a Family of Andean Descent

To search for MYOC mutations in Peruvian primary open angle glaucoma (POAG) families. Two patients from each of the 11 POAG Peruvian families were screened for sequence variants in MYOC coding exons by conformational sensitive gel electrophoresis and sequencing was performed on the samples indicating probable sequence changes. We detected 2 families bearing distortions of conformational sensitive gel electrophoresis indicating mutations. Sequencing of these samples revealed coding sequence changes. A native Andean descent family presented with a MYOC mutation, Asn480Lys (C-->G at nucleotide 1440). This is different from the previously reported C-->A change at nucleotide 1440 that causes Asn480Lys in 2 unrelated French and Dutch families with glaucoma of variable expressivity, and indicates a third independent event. A second family of admixed origin showed the presence of the known Arg76Lys polymorphism. In the study of MYOC variants in 11 POAG Peruvian families, we have found a family of ethnically admixed origin with polymorphism Arg76Lys and a family of Andean descent bearing a third event of the Asn480Lys, the MYOC mutation that has been reported in the highest number of POAG patients (>80 cases). Analysis of this family could contribute with information about disease manifestation, progression, and treatment response in the context of a distinct genetic background and also climatic, altitude, and socioeconomical conditions.

Clinical and Genetic Characteristics of Primary Juvenile-Onset Open-Angle Glaucoma (JOAG)

Juvenile-onset open-angle glaucoma (JOAG) is an autosomal dominant disease characterized by an early age of onset and severely elevated intraocular pressures. Large JOAG pedigrees have been pivotal in genetic linkage analyses that have helped establish the association between JOAG and the myocilin gene (MYOC). Numerous disease-causing MYOC mutations have now been identified, and additional loci on other chromosomes have been linked to JOAG. Ongoing molecular genetic studies on myocilin andthe search for new gene defects associated with JOAG may offer new directions in our scientific understanding and clinical management of open-angle glaucoma.

Myocilin Variants in Indian Patients With Open-angle Glaucoma

To identify and evaluate MYOC variant alleles among patients with primary open-angle glaucoma (POAG) and age-matched control subjects in an Indian population. Three hundred fifteen patients with POAG and 100 unrelated control subjects from the same ethnic background were enrolled in the study. The coding sequence of MYOC was amplified by polymerase chain reaction using genomic DNA, followed by sequencing of the polymerase chain reaction products. Four single nucleotide polymorphisms were genotyped in different Indian subpopulations comprising 1466 individuals using SEQUENOM's homogeneous MassEXTEND assay. One novel mutation (Gly399Asp), 6 reported mutations (Gln48His, Thr256Met, Thr353Ile, Gln368Stop, Pro370Leu, and Ala427Thr), and 6 single nucleotide polymorphisms were identified in MYOC. Ala427Thr was identified in a patient with POAG and Parkinson disease. Four single nucleotide polymorphisms genotyped in control subjects were highly heterozygous and displayed a similar pattern of linkage disequilibrium among all linguistic groups. MYOC mutations account for 2.2% of POAG cases. The Gln368Stop mutation (common among persons of the white race) found in 2 families does not seem to be of white race origin. Identification of a MYOC mutation (Ala427Thr) in a patient with POAG and Parkinson disease is interesting with respect to reported interaction of myocilin with synucleins. Studying the genetics of POAG is helpful for preclinical identification and for better disease management.

Mutated Mouse and Human Myocilins Have Similar Properties and Do Not Block General Secretory Pathway

The present study compared properties of wild-type and mutated mouse and human myocilin (Myoc) proteins as a prerequisite for development of a mouse model of glaucoma. cDNA encoding full-length mouse Myoc was cloned into the p3XFLAG-CMV-14 vector. Tyr423His and Ile463Ser mutations were introduced into the mouse Myoc protein by in vitro mutagenesis. Intracellular localization and secretion of wild-type and mutated mouse Myoc proteins were studied in immunostaining and Western blotting experiments, respectively, after transfection into COS-7 cells. Similar to human MYOC, wild-type and mutated mouse Myoc demonstrated vesicular staining in transfected cells. However, while wild-type human and mouse Myoc were preferentially located in both the endoplasmic reticulum and Golgi, mutated human and mouse Myoc were located mainly in the endoplasmic reticulum and were excluded from Golgi. Similar to mutations in human MYOC, mutations in mouse Myoc dramatically reduced its secretion from transfected cells. Secretion of mutated Myoc was partially restored by culturing cells at 30 degrees C instead of 37 degrees C. The presence of mutated human MYOC prevented secretion of wild-type mouse Myoc but did not dramatically affect secretion of alkaline phosphatase, thrombospondin, Timp3 or olfactomedin-1. Properties of the mouse Myoc protein are similar to those of the human MYOC. The presence of mutated mouse or human Myoc does not block a general secretory pathway. Expression of mutated Myoc in the eye in mice may mimic human glaucoma and lead to development of a genetic mouse model of glaucoma.

Identification of flotillin-1 as a protein interacting with myocilin: Implications for the pathogenesis of primary open-angle glaucoma

Mutations in MYOC gene encoding myocilin are responsible for primary open-angle glaucoma (POAG). In order to search for protein(s) that can interact with myocilin, we screened a human skeletal muscle cDNA library using yeast two-hybrid system and identified flotillin-1, a structural protein of lipid raft that is detergent-resistant and a liquid ordered microdomain, as a protein interacting with myocilin. The interaction was confirmed by in vitro glutathione S-transferase pulldown and in vivo co-immunoprecipitation studies. In yeast two-hybrid assay, the C-terminus of myocilin, an olfactomedin-like domain in which most mutations related to POAG are scattered, was found to be necessary and sufficient for the interaction. However, myocilins with mutations such as G364V, K423E, and Y437H on the domain failed to interact with flotillin-1. Although the physiological significance of the interaction has yet to be elucidated, our results showed that the alteration of the interaction by mutations in MYOC might be a key factor of the pathogenesis of POAG.