Candidate Genes Screen And Gene Mapping In Infantile Glaucoma Patients And Juvenile Glaucoma Pedigrees

Glaucoma is a genetic heterogeneous eye disease, which is also an important causeof blindness. The disease produces characteristic progressing visual field changes,usually in association with elevated intraocular pressure (IOP). We investigated thecause of the disease from the genetic point of view by candidate genes screen andlinkage analysis.Partâ… : Candidate genes screen in sporadic infantile glaucoma patientsPurpose: To determine the role of CYP1B1 and MYOC in causing infantileglaucoma in Chinese population and to report the spectrum of the CYP1B1 and MYOCmutations.Methods: The study included 116 unrelated cases of primary infantile glaucomaand 120 unrelated healthy controls in China. Peripheral blood was collected andgenomic DNA was extracted. The coding sequence and the promoter region of CYP1B1and the coding sequence of MYOC were amplified by polymerase chain reaction (PCR)from genomic DNA, followed by direct DNA sequencing to identify disease-causingvariants.Results: Twenty mutations were identified in the coding regions of CYP1B1 intwenty patients, among which six were previously published. They were g.4449G>T(p.S2151) , g.4397G>A (p.V1981) , g.7927G>A (p.V364M), g.8006G>A (p.R390H),g.8168G>A (p.R444Q), g.8242C>T (p.R469W). Another fourteen mutations were novel.These variants included g.3972delC (p.A56GGX), g.3985C>G (p.160M), g.4089T>C(p.V95A), g.4124C>G (p.L107V), g.4157C>T (p.P118S), g.4168₄169insGACCGGCCGGCCTTCGCC (p.A121_S122insDRPAFA), g.4206T>C (p.F134S),g.4413A>G (p.N203S), g.4664G>A (p.A287S), g.4677A>G (p.D291G), g.4761A>G(p.N319S), T7925>A (p.V363D), g.7940G>T (p.R368L), and g.8209₈213 delAGCAG ins TTGTTGAAAAA (p.S458_R459delinsLLKK). There was no mutationdetected in the promoter region of CYP1B1．Overall, CYP1B1 was involved in 20 (17．2%) cases out of 116 cases and homozygosity of mutant alleles was seen in 5 cases,heterozyosity in 11 cases and compound heterozygosity in 4 cases respectively. Inaddition, eight single nucleotide polymorphisms (SNPs) g.2805C>T, g.3130C>T,g.3793T>C, g.3947C>G, g.4160G>T, g.8131C>G, g.8184C>T, g.8195A>G showed noobvious frequency difference between patients and controls. Three mutations c.688G>A(p.E230K), c.814C>T (p.R272X), and c.938C>T (p.S313F) of MYOC were observed inthree cases without CYP1B1 mutations. Seven previously reported polymorphismsc.34G>C (p.G12R), c.57G>T (p.Q19H), c.136C>T (p.R46X), c.227G>A (p.R76K),c.369C>T (p.T123T), c.864C>T (p.I288I) and c.1058C>T (p.T353I) were detected inboth patients and controls. Thus, MYOC was involved in 2．6% (3 in 116) of infantileglaucoma patients.Conclusions: This study provides a mutation spectrum of CYP1B1 and MYOCcausing primary infantile glaucoma in Chinese populations. CYP1B1 may beresponsible for part of infantile glaucoma affected patients, while MYOC contributesless to the disease.Partâ…¡: Candidate genes screen and gene mapping in juvenile glaucomapedigreesPurpose: To determine the role of MYOC in juvenile glaucoma pedigrees inChinese population. To search for new candidate loci by gene mapping with wholegenome scan on large juvenile open angle glaucoma (JOAG) pedigrees.Methods: The study included 12 juvenile open angle glaucoma pedigrees.Peripheral blood was collected from each member of these pedigrees and genome DNAwas extracted. Three exons of MYOC were amplified by polymerase chain reaction(PCR) followed by direct DNA sequencing to identify disease-causing variants. MYOC,OPTN, WDR36 were excluded by linkage analysis with short tandem repeats (STRs)near the three genes. Whole genome scan was performed to map the loci for two largepedigrees.Results: All the 12 juvenile open angle glaucoma pedigrees showed autosomaldominant inheritance. The median onset age was 26years (19-32years), median IOPbefore therapy was 39mmHg (32．5-46．5mmHg). There was two families with P370L(c.1109C>T) mutation, one family with D380Y (c.1138G>T), and another family withT438I (c.1313C>T) mutation. P370L (c.1109C>T) and T438I (c.1313C>T) were reported previously, while D380Y (c.1138G>T) was first reported. It didn't appear inthe 120 unrelated healthy controls. No mutation in MYOC was found in else pedigrees.So altogether the frequency of mutations in MYOC was 33% (4 in 12) . The wholegenome scan was performed using micro satellite markers for 2 large JOAG pedigrees.Two point linkage analyses showed significant linkage on chromosome 3 in J4 family.The maximum LOD score was 3．87 (θ=0．00) with the marker D3S1292．Haplotypeanalysis further refined the region to an 88cM (102Mb) interval betweenD3S1566-D3S1565 at 3p14-q26, which covered the GLC1C locus. In J8 family, twopoint linkage analyses showed significant linkage on chromosome 2．The maximumLOD score was 5．06 (θ=0．00) with the marker D2S337．Haplotype analysis furtherrefined the region to a 16cM (21Mb) interval between D2S391-D2S2368 at 2p14-21,which covered the GLC1H locus.Conclusions: Nearly one thirds of juvenile open angle glaucoma (JOAG) pedigreeshave MYOC mutations. Gene test in such pedigrees would be helpful to early diagnosis.GLC1C and GLC1H are two promising loci of JOAG Fine mapping and candidategenes screen should be carried out in order to discover the disease causing genes.