CFH, VEGF and HTRA1 promoter genotype may influence the response to intravitreal ranibizumab therapy for neovascular age-related macular degeneration.

AIMS: To investigate an association between genotype for three single nucleotide polymorphisms strongly associated with the development of age-related macular degeneration (AMD) and the early response to treatment with intravitreal ranibizumab for neovascular AMD. METHODS: Best corrected visual acuity letter score was recorded at baseline and each subsequent visit. Age, sex, smoking history, lesion type and the number of injections were also recorded. Genotypes were obtained for rs11200638 in HTRA1, rs1061170 in CFH and rs1413711 in VEGF. Data were analysed with treatment response at month 6 as both a binary (>5 letter improvement vs ≤5 letter gain) and a linear trait. RESULTS: This initial study cohort consisted of 104 Caucasian neovascular AMD patients treated with intravitreal ranibizumab. Trends towards a more favourable outcome were seen with the higher AMD risk genotypes in CFH and VEGF in both the linear and binary models and in HTRA1 in the linear model alone. For CFH, mean letter score change after 6 months was +1.6, +5.9 and +7.2 letters for the TT, TC and CC genotypes and a >5 letter gain was seen in 34.6%, 56.6% and 56%, respectively. For VEGF, mean letter score change after 6 months was +1.3, +5.8 and +7.4 letters for the TT, TC and CC genotypes and a >5 letter gain was seen in 40%, 55.8% and 51.9%, respectively. For HTRA1, mean letter score change was +2.2, +7.5 and +2.9 letters for the GG, GA and AA genotypes. CONCLUSIONS: This study reports preliminary evidence suggesting that the higher AMD risk genotypes in CFH, VEGF and HTRA1 may influence the short-term response to treatment with ranibizumab for neovascular AMD.

Homozygous FOXE3 mutations cause non-syndromic, bilateral, total sclerocornea, aphakia, microphthalmia and optic disc coloboma.

PURPOSE: To investigate the genetic basis of recessively-inherited congenital, non syndromic, bilateral, total sclerocornea in two consanguineous pedigrees, one from the Punjab province of Pakistan and the other from the Tlaxcala province of Mexico. METHODS: Ophthalmic examinations were conducted on each family member to confirm their diagnosis and magnetic resonance imaging (MRI) or ultrasonography of the eyes was performed on some family members. Genomic DNA was analyzed by homozygosity mapping using the Affymetrix 6.0 SNP array and linkage was confirmed with polymorphic microsatellite markers. Candidate genes were sequenced. RESULTS: A diagnosis of autosomal recessive sclerocornea was established for 7 members of the Pakistani and 8 members of the Mexican pedigrees. In the Pakistani family we established linkage to a region on chromosome 1p that contained Forkhead Box E3 (FOXE3), a strong candidate gene since FOXE3 mutations had previously been associated with various anterior segment abnormalities. Sequencing FOXE3 identified the previously reported nonsense mutation, c.720C>A, p.C240X, in the Pakistani pedigree and a novel missense mutation which disrupts an evolutionarily conserved residue in the forkhead domain, c.292T>C, p.Y98H, in the Mexican pedigree. Individuals with heterozygous mutations had no ocular abnormalities. MRI or ultrasonography confirmed that the patients with sclerocornea were also aphakic, had microphthalmia and some had optic disc coloboma. CONCLUSIONS: This is the fourth report detailing homozygous FOXE3 mutations causing anterior segment abnormalities in human patients. Previous papers have emphasized aphakia and microphthalmia as the primary phenotype, but we find that the initial diagnosis - and perhaps the only one possible in a rural setting - is one of non-syndromic, bilateral, total sclerocornea. Dominantly inherited anterior segment defects have also been noted in association with heterozygous FOXE3 mutations. However the absence of any abnormalities in the FOXE3 heterozygotes described suggests that genetic background and environmental factors plays a role in the penetrance of the mutant allele.

Macular dystrophy associated with the Arg172Trp substitution in peripherin/RDS: genotype-phenotype correlation.

PURPOSE: To document the evolution of geographic atrophy in the peripherin/RDS Arg172Trp substitution, provide age-related estimates of visual acuity, and compare with other missense mutations with a similar phenotype (Arg142Trp, Arg172Gln, and Arg195Leu). METHODS: Total area of geographic atrophy in 18 affected individuals with the peripherin/RDS Arg172Trp substitution was measured from retinal photographs and plotted as a function of age. Visual acuity data from these individuals were collated with previously published cases of Arg172Trp substitution to obtain age-related estimates of visual acuity. These were compared with published series with the Arg142Trp, Arg172Gln, and Arg195Leu substitutions, using linear regression. RESULTS: In patients with the Arg172Trp substitution, the increase in total area of chorioretinal atrophy and decline in visual acuity showed significant association with age (R2 = 0.619, P < 0.001; R2 = 0.761, P < 0.001). A trend was observed toward earlier age at onset and worse visual acuity with the Arg172Trp substitution as compared with the Arg142Trp and Arg172Gln substitutions. Linear regression analysis showed that until the age of 60 years, at any given age, visual acuity with the Arg172Trp substitution was significantly worse than the Arg142Trp (P < 0.001) and the Arg172Gln substitutions (P = 0.04). Patients above the age of 60 years were excluded as a floor effect on visual acuity was observed with visual acuity being worse than 6/60 for most patients. CONCLUSION: This paper demonstrates that visual prognosis in macular dystrophies associated with peripherin/RDS may be mutation specific and, for the Arg172Trp substitution, worse than the Arg142Trp and Arg172Gln substitutions.

Replication of the recessive STBMS1 locus but with dominant inheritance.

PURPOSE: Strabismus is a common eye disorder with a prevalence of 1% to 4%. Comitant strabismus accounts for approximately 75% of all strabismus, yet more is known about the less common incomitant disorders. Comitant strabismus is at least partly inherited, but only one recessive genetic susceptibility locus, on chromosome 7p, has been identified in one family. The purpose of this study was to determine the frequency of STBMS1 as a cause of primary nonsyndromic comitant esotropia (PNCE). METHODS: Twelve families were recruited within the UK Hospital Eye Service as children attended for treatment of PNCE. All consenting persons were clinically assessed, and DNA was sampled. Chromosome 7 microsatellite markers were genotyped in all 12 families, and LOD scores were calculated under recessive and dominant models. RESULTS: One family was linked to STBMS1; in three, linkage was significantly excluded; and the remainder were uninformative. Twenty-six members from three generations of the linked family were analyzed further. Five family members were defined as affected; two had esotropia with an accommodative element; and three underwent strabismus surgery and appeared to have had an infantile/early-onset esotropia. A maximum LOD score of 3.21 was obtained under a dominant mode of inheritance; a recessive model gave an LOD score of 1.2. CONCLUSIONS: This study confirms that PNCE can result from sequence variants in an unknown gene at the STBMS1 locus. However, this locus accounts for only a proportion of cases, and other genetic loci remain to be identified. In contrast with the previously reported family, the pedigree described in this study is consistent with dominant rather than recessive inheritance at the STBMS1 locus.

Identification of a novel splice-site mutation in the Lebercilin (LCA5) gene causing Leber congenital amaurosis.

PURPOSE: Leber congenital amaurosis (LCA) is one of the most common causes of hereditary blindness in infants. To date, mutations in 13 known genes and at two other loci have been implicated in LCA causation. An examination of the known genes highlights several processes which, when defective, cause LCA, including photoreceptor development and maintenance, phototransduction, vitamin A metabolism, and protein trafficking. In addition, it has been known for some time that defects in sensory cilia can cause syndromes involving hereditary blindness. More recently evidence has come to light that non-syndromic LCA can also be a "ciliopathy." METHODS: Here we present a homozygosity mapping analysis in a consanguineous sibship that led to the identification of a mutation in the recently discovered LCA5 gene. Homozygosity mapping was done using Affymetrix 10K Xba I Gene Chip and a 24.5cM region on chromosome 6 (6q12- q16.3) was identified to be significantly homozygous. The LCA5 gene on this region was sequenced and cDNA sequencing also done to characterize the mutation. RESULTS: A c.955G>A missense mutation in the last base of exon 6 causing disruption of the splice donor site was identified in both the affected sibs. Since there is a second consensus splice donor sequence 5 bp into the adjacent intron, this mutation results in a transcript with a 5 bp insertion of intronic sequence, leading to a frameshift and premature truncation. CONCLUSIONS: We report a missense mutation functionally altering the splice donor site and leading to a truncated protein. This is the second report of LCA5 mutations causing LCA. It may also be significant that one affected child died at eleven months of age due to asphyxia during sleep. To date the only phenotype unambiguously associated with mutations in this gene is LCA. However the LCA5 gene is known to be expressed in nasopharynx, trachea and lungs and was originally identified in the proteome of bronchial epithelium ciliary axonemes. The cause of death in this child may therefore imply that LCA5 mutations can in fact cause a wider spectrum of phenotypes including respiratory disease.

Mutations in LCA5, encoding the ciliary protein lebercilin, cause Leber congenital amaurosis.

Leber congenital amaurosis (LCA) causes blindness or severe visual impairment at or within a few months of birth. Here we show, using homozygosity mapping, that the LCA5 gene on chromosome 6q14, which encodes the previously unknown ciliary protein lebercilin, is associated with this disease. We detected homozygous nonsense and frameshift mutations in LCA5 in five families affected with LCA. In a sixth family, the LCA5 transcript was completely absent. LCA5 is expressed widely throughout development, although the phenotype in affected individuals is limited to the eye. Lebercilin localizes to the connecting cilia of photoreceptors and to the microtubules, centrioles and primary cilia of cultured mammalian cells. Using tandem affinity purification, we identified 24 proteins that link lebercilin to centrosomal and ciliary functions. Members of this interactome represent candidate genes for LCA and other ciliopathies. Our findings emphasize the emerging role of disrupted ciliary processes in the molecular pathogenesis of LCA.