Lee HJ, Colby KA. A review of the clinical and genetic aspects of aniridia. Semin Ophthalmol 2013;28(5-6):306-12.Abstract
Aniridia classically presents with a bilateral congenital absence or malformation of the irides, foveal hypoplasia, and nystagmus, and patients tend to develop visually significant pre-senile cataracts and keratopathy. Additionally, they are at high risk for developing glaucoma. Classic aniridia can be genetically defined as the presence of a PAX6 gene deletion or loss-of-function mutation that results in haploinsufficiency. Variants of aniridia, which include a condition previously referred to as autosomal dominant keratitis, are likely due to PAX6 mutations that lead to partial loss of PAX6 function. Aniridia-associated keratopathy (AAK) is a progressive and potentially debilitating problem affecting aniridic patients. The current treatments for AAK are to replace the limbal stem cells through keratolimbal allograft (KLAL) with or without subsequent keratoplasty for visual rehabilitation, or to implant a Boston type 1 keratoprosthesis. Future therapies for AAK may be aimed at the genetic modification of corneal limbal stem cells.
Kruger JM, Mansouri B, Cestari DM. An update on the genetics of comitant strabismus. Semin Ophthalmol 2013;28(5-6):438-41.Abstract
Genetics play a significant role in the development of comitant strabismus and elucidating the relevant mechanisms that cause it may lead to the development of new therapeutic options. The genetics of strabismus are complex and involve the interactions of multiple genes. This article reviews the progress that has been made in the understanding of the genetic causes of comitant strabismus including linkage studies that have identified a variety of candidate sites, RNA and protein studies that have identified genes with altered regulation, and a study that establishes a role for genetic imprinting in comitant strabismus.
Kang MH, Oh D-J, Kang J-heon, Rhee DJ. Regulation of SPARC by transforming growth factor β2 in human trabecular meshwork. Invest Ophthalmol Vis Sci 2013;54(4):2523-32.Abstract
PURPOSE: An increased aqueous level of TGF-β2 has been found in many primary open-angle glaucoma patients. Secreted Protein, Acidic, and Rich in Cysteine (SPARC)-null mice have a lower intraocular pressure. The mechanistic relationship between SPARC and TGF-β2 in trabecular meshwork (TM) is unknown. We hypothesized that TGF-β2 upregulates SPARC expression in TM. METHODS: Cultured TM cells were incubated with selective inhibitors for p38 MAP kinase (p38), Smad3, p42, JNK, RhoA, PI3K, or TGF-β2 receptor for 2 hours, and then TGF-β2 was added for 24 hours in serum-free media. Quantitative polymerase chain reaction (qPCR) and immunoblot analysis were performed. Immunofluorescent microscopy was used to determine nuclear translocation of signaling proteins. Ad5.hSPARC and Lentiviral shRNA for p38 and Smad3 were constructed, and infected human TM cells. RESULTS: SPARC was upregulated by TGF-β2 in the human TM cells (3.8 ± 1.7-fold, n = 6, P = 0.01 for protein and 7.1 ± 3.7-fold, n = 6, P = 0.01 for mRNA), while upregulation of SPARC had no effect on TGF-β2. TGF-β2-induced SPARC expression was suppressed by inhibitors against p38 (-40.3 ± 20.9%, n = 10, P = 0.0001), Smad3 (-56.2 ± 18.9%, n = 10, P = 0.0001), JNK (-49.1 ± 24.6%, n = 10, P = 0.0001), and TGF-β2 receptor (-83.6 ± 14.4%, n = 6, P = 0.003). Phosphorylation and translocation of Smad3, p38, and MAPKAPK2 were detected at 30 minutes and 1 hour, respectively, following TGF-β2 treatment. Phosphorylation of JNK and c-jun was detected before TGF-β2 treatment. SPARC was suppressed 31 ± 13% (n = 5, P < 0.0001) by shRNA-p38 and 41 ± 3% (n = 5, P < 0.0001) by shRNA-Smad3. CONCLUSIONS: TGF-β2 upregulates SPARC expression in human TM through Smad-dependent (Smad2/3) or -independent (p38) signaling pathways. SPARC may be a downstream regulatory node of TGF-β2-mediated IOP elevation.
Jacobo SMP, Deangelis MM, Kim IK, Kazlauskas A. Age-related macular degeneration-associated silent polymorphisms in HtrA1 impair its ability to antagonize insulin-like growth factor 1. Mol Cell Biol 2013;33(10):1976-90.Abstract
Synonymous single nucleotide polymorphisms (SNPs) within a transcript's coding region produce no change in the amino acid sequence of the protein product and are therefore intuitively assumed to have a neutral effect on protein function. We report that two common variants of high-temperature requirement A1 (HTRA1) that increase the inherited risk of neovascular age-related macular degeneration (NvAMD) harbor synonymous SNPs within exon 1 of HTRA1 that convert common codons for Ala34 and Gly36 to less frequently used codons. The frequent-to-rare codon conversion reduced the mRNA translation rate and appeared to compromise HtrA1's conformation and function. The protein product generated from the SNP-containing cDNA displayed enhanced susceptibility to proteolysis and a reduced affinity for an anti-HtrA1 antibody. The NvAMD-associated synonymous polymorphisms lie within HtrA1's putative insulin-like growth factor 1 (IGF-1) binding domain. They reduced HtrA1's abilities to associate with IGF-1 and to ameliorate IGF-1-stimulated signaling events and cellular responses. These observations highlight the relevance of synonymous codon usage to protein function and implicate homeostatic protein quality control mechanisms that may go awry in NvAMD.
Hamrah P, Cruzat A, Dastjerdi MH, Prüss H, Zheng L, Shahatit BM, Bayhan HA, Dana R, Pavan-Langston D. Unilateral herpes zoster ophthalmicus results in bilateral corneal nerve alteration: an in vivo confocal microscopy study. Ophthalmology 2013;120(1):40-7.Abstract
PURPOSE: Herpes zoster ophthalmicus (HZO), thought to be a unilateral disease, results in loss of corneal sensation, leading to neurotrophic keratopathy. This study aimed to analyze bilateral corneal nerve changes in patients with HZO by in vivo confocal microscopy (IVCM) and their correlation with corneal sensation as a measure of nerve function. DESIGN: Prospective, cross-sectional, controlled, single-center study. PARTICIPANTS: Twenty-seven eyes with the diagnosis of HZO and their contralateral clinically unaffected eyes were studied and compared with normal controls (n = 15). METHODS: In vivo confocal microscopy (Confoscan 4; Nidek Technologies, Gamagori, Japan) and corneal esthesiometry (Cochet-Bonnet; Luneau Ophthalmologie, Chartres, France) of the central cornea were performed bilaterally in all patients and controls. Patients were grouped into normal (>5.5 cm), mild (>2.5-5.5 cm), and severe (<2.5 cm) loss of sensation. MAIN OUTCOME MEASURES: Changes in corneal nerve density, total nerve number, main nerve trunks, branching, and tortuosity were evaluated after IVCM and were correlated to corneal sensation, disease duration, and number of recurrences. RESULTS: Eyes with herpes zoster ophthalmicus had a significant (P<0.001) decrease in total nerve length (595.8±358.1 vs. 2258.4±989.0 μm/frame), total number of nerves (5.4±2.8 vs. 13.1±3.8), number of main nerve trunks (2.3±1.1 vs. 4.7±1.2), and number of nerve branches (3.2±2.3 vs. 8.4±3.7) as compared with controls. In the contralateral clinically unaffected eyes, total nerve length (1053.1±441.4 μm/frame), total number of nerves (8.3±2.9), and main nerve trunks (3.1±1.0) also were decreased significantly as compared with controls (P<0.01). Reduced nerve density, total nerve count, main trunks, and tortuosity was correlated significantly with corneal sensation across all subgroups (P<0.001). CONCLUSIONS: Patients with unilateral HZO demonstrated a profound and significant bilateral loss of the corneal nerve plexus as compared with controls, demonstrating bilateral changes in a clinically unilateral disease. Loss of corneal sensation strongly correlated with subbasal nerve plexus alterations as shown by IVCM. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.
Marko CK, Menon BB, Chen G, Whitsett JA, Clevers H, Gipson IK. Spdef null mice lack conjunctival goblet cells and provide a model of dry eye. Am J Pathol 2013;183(1):35-48.Abstract
Goblet cell numbers decrease within the conjunctival epithelium in drying and cicatrizing ocular surface diseases. Factors regulating goblet cell differentiation in conjunctival epithelium are unknown. Recent data indicate that the transcription factor SAM-pointed domain epithelial-specific transcription factor (Spdef) is essential for goblet cell differentiation in tracheobronchial and gastrointestinal epithelium of mice. Using Spdef(-/-) mice, we determined that Spdef is required for conjunctival goblet cell differentiation and that Spdef(-/-) mice, which lack conjunctival goblet cells, have significantly increased corneal surface fluorescein staining and tear volume, a phenotype consistent with dry eye. Microarray analysis of conjunctival epithelium in Spdef(-/-) mice revealed down-regulation of goblet cell-specific genes (Muc5ac, Tff1, Gcnt3). Up-regulated genes included epithelial cell differentiation/keratinization genes (Sprr2h, Tgm1) and proinflammatory genes (Il1-α, Il-1β, Tnf-α), all of which are up-regulated in dry eye. Interestingly, four Wnt pathway genes were down-regulated. SPDEF expression was significantly decreased in the conjunctival epithelium of Sjögren syndrome patients with dry eye and decreased goblet cell mucin expression. These data demonstrate that Spdef is required for conjunctival goblet cell differentiation and down-regulation of SPDEF may play a role in human dry eye with goblet cell loss. Spdef(-/-) mice have an ocular surface phenotype similar to that in moderate dry eye, providing a new, more convenient model for the disease.
Gipson IK. Age-related changes and diseases of the ocular surface and cornea. Invest Ophthalmol Vis Sci 2013;54(14):ORSF48-53.Abstract
Aging of the ocular surface and corneal tissues, major components of the visual system, causes major eye disease and results in substantial cost in medical and social terms. These diseases include the highly prevalent dry eye disease that affects the ocular surface and its glands, leading to tear film alterations, discomfort, and decreased vision. Studies show that 14.4% of the population in the United States older than 50 years have dry eye disease and demonstrate that it is particularly prevalent among women. Annual medical costs per patient with dry eye in the United States are estimated at $783 per year, with an overall medical cost adjusted to prevalence of $3.84 billion per year. Societal costs, which include loss of productivity, are estimated per patient at $11,302 per year, with overall costs adjusted to prevalence of $55.4 billion per year. Because there are few effective treatments for the disease, more research on its etiology and mechanisms is warranted and needed. Increased public education about risk factors for the disease is also required. Another major age-related eye disease of the cornea that leads to vision impairment and potentially blindness if left untreated is Fuchs' endothelial corneal dystrophy. This disease leads to loss of the endothelial cells on the internal side of the cornea that are responsible for keeping the cornea in the proper hydration state to ensure its transparency to light. The mechanism of cell loss is unknown, and the only treatment available to date is surgical transplantation of the cornea or inner part of the cornea. These medically costly procedures require donor corneas, eye banking, and medical follow-up, with accrued costs. Fuchs' endothelial corneal dystrophy is a major cause of corneal transplantation in the United States; therefore, research support is needed to determine the mechanism of this age-related disease, to develop medical, nonsurgical methods for treatment.
Lee NG, Kim LA, Freitag SK. The role of genetics in the pathogenesis of periocular cutaneous neoplasms: implications for targeted therapy. Semin Ophthalmol 2013;28(5-6):267-74.Abstract
In the past, cutaneous malignancies of the periocular region were primarily treated surgically with few other options. As the genetic bases of these tumors have become elucidated, targeted therapies aimed specifically at pathways that are felt to be responsible for cellular proliferation and uncontrolled growth have emerged with new promise. This review contains a summary of the various genetic implications of cutaneous neoplasms as well as their corresponding targeted systemic therapies.
Kwon MY, Nandy AS, Tjan BS. Rapid and persistent adaptability of human oculomotor control in response to simulated central vision loss. Curr Biol 2013;23(17):1663-9.Abstract
The central region of the human retina, the fovea, provides high-acuity vision. The oculomotor system continually brings targets of interest into the fovea via ballistic eye movements (saccades). Thus, the fovea serves both as the locus for fixations and as the oculomotor reference for saccades. This highly automated process of foveation is functionally critical to vision and is observed from infancy. How would the oculomotor system adjust to a loss of foveal vision (central scotoma)? Clinical observations of patients with central vision loss suggest a lengthy adjustment period, but the nature and dynamics of this adjustment remain unclear. Here, we demonstrate that the oculomotor system can spontaneously and rapidly adopt a peripheral locus for fixation and can rereference saccades to this locus in normally sighted individuals whose central vision is blocked by an artificial scotoma. Once developed, the fixation locus is retained over weeks in the absence of the simulated scotoma. Our data reveal a basic guiding principle of the oculomotor system that prefers control simplicity over optimality. We demonstrate the importance of a visible scotoma on the speed of the adjustment and suggest a possible rehabilitation regimen for patients with central vision loss.
Karamichos D, Rich CB, Zareian R, Hutcheon AEK, Ruberti JW, Trinkaus-Randall V, Zieske JD. TGF-β3 stimulates stromal matrix assembly by human corneal keratocyte-like cells. Invest Ophthalmol Vis Sci 2013;54(10):6612-9.Abstract
PURPOSE: We have previously shown that TGF-β3 (T3) stimulates extracellular matrix (ECM) assembly while maintaining antifibrotic characteristics in a model using human corneal fibroblasts (HCFs). This model, however, requires non-physiological levels of serum. In the current study, we tested whether T3 could stimulate human corneal keratocytes (HCKs) in vitro to assemble a functional ECM, while maintaining their characteristics. METHODS: Human corneal keratocytes and HCFs were isolated and cultured using 1% or 10% serum, respectively ±T3. The constructs were processed for indirect immunofluorescence (IF), transmission electron microscopy (TEM), and qRT-PCR, analyzing for keratocyte marker, keratocan, and ECM components, collagen (col) types I, III, and V. RESULTS: Quantitative reverse transcriptase PCR data showed that keratocan, col I, and V were all upregulated in HCKs compared with HCFs, whereas col III was expressed at low levels in HCKs. Transforming growth factor beta 3 stimulation further enhanced the level of change. Without T3, HCK constructs were very thin, approximately 5 μm; however, as with HCFs, upon stimulation with T3, HCK constructs increased in thickness by approximately 5-fold. Cell counts and ECM production revealed that HCKs assembled more ECM per unit area compared with HCFs, and IF revealed downregulation of fibrotic markers, col III, and thrombospondin-1, with T3 stimulation. Transmission electron microscopy data revealed aligned ECM with long fibrils for all conditions except HCK Controls. Human corneal keratocytes+T3 also showed denser collagen fibrils with more consistent fibril diameter. CONCLUSIONS: Overall, the data suggests that it is possible to stimulate matrix secretion and assembly by HCKs in vitro by using a single growth factor, T3.
Jakobiec FA, Zakka FR, Yoon MK. Complex orbital angiomyoma with features of a lymphangiohemangioma. Ophthalmic Plast Reconstr Surg 2013;29(2):e61-5.Abstract
A 31-year-old woman developed left frontal headache and retrobulbar pain with exotropia and mild limitation of upgaze without proptosis. Imaging studies disclosed a circumscribed mass measuring 1.5 cm in the greatest diameter. At surgery, the lesion was adherent to the surrounding normal orbital tissues, making for a difficult and dangerous resection. Histopathologically and immunohistochemically, the lesion was a mixed cavernous angiomatous (CD31-positive) and lymphangiomatous (D2-40-positive) tumor with abundant interstitial smooth muscle. Such lesions can present significant surgical challenges due to incomplete pseudoencapsulation.
Matsumoto H, Miller JW, Vavvas DG. Retinal detachment model in rodents by subretinal injection of sodium hyaluronate. J Vis Exp 2013;(79)Abstract
Subretinal injection of sodium hyaluronate is a widely accepted method of inducing retinal detachment (RD). However, the height and duration of RD or the occurrence of subretinal hemorrhage can affect photoreceptor cell death in the detached retina. Hence, it is advantageous to create reproducible RDs without subretinal hemorrhage for evaluating photoreceptor cell death. We modified a previously reported method to create bullous and persistent RDs in a reproducible location with rare occurrence of subretinal hemorrhage. The critical step of this modified method is the creation of a self-sealing scleral incision, which can prevent leakage of sodium hyaluronate after injection into the subretinal space. To make the self-sealing scleral incision, a scleral tunnel is created, followed by scleral penetration into the choroid with a 30 G needle. Although choroidal hemorrhage may occur during this step, astriction with a surgical spear reduces the rate of choroidal hemorrhage. This method allows a more reproducible and reliable model of photoreceptor death in diseases that involve RD such as rhegmatogenous RD, retinopathy of prematurity, diabetic retinopathy, central serous chorioretinopathy, and age-related macular degeneration (AMD). [corrected].