Ocular Development (ocular + development)

Distribution by Scientific Domains

Selected Abstracts

Coordinated regulation of dorsal bone morphogenetic protein 4 and ventral Sonic hedgehog signaling specifies the dorso-ventral polarity in the optic vesicle and governs ocular morphogenesis through fibroblast growth factor 8 upregulation

Takuma Kobayashi
Dorsal and ventral specification in the early optic vesicle plays a crucial role in vertebrate ocular morphogenesis, and proper dorsal-ventral polarity in the optic vesicle ensures that distinct structures develop in separate domains within the eye primordium. The polarity is determined progressively during development by coordinated regulation of extraocular dorsal and ventral factors. In the present study, we cultured discrete portions of embryonic chick brains by preparing anterior cephalon, anterior dorsal cephalon and anterior ventral cephalon, and clearly demonstrate that bone morphogenetic protein 4 (BMP4) and Sonic hedgehog (Shh) constitute a dorsal-ventral signaling system together with fibroblast growth factor 8 (FGF8). BMP4 and Shh upregulate Tbx5 and Pax2, as reported previously, and at the same time Shh downregulates Tbx5, while BMP4 affects Pax2 expression to downregulate similarly. Shh induces Fgf8 expression in the ventral optic vesicle. This, in turn, determines the distinct boundary of the retinal pigmented epithelium and the neural retina by suppressing Mitf expression. The lens develops only when signals from both the dorsal and ventral regions come across together. Inverted deposition of Shh and BMP4 signals in organ-cultured optic vesicle completely re-organized ocular structures to be inverted. Based on these observations we propose a novel model in which the two signals govern the whole of ocular development when they encounter each other in the ocular morphogenic domain. [source]

A novel genetic variant of BMP2K contributes to high myopia

Hsin-Ping Liu
Abstract Loss of eye growth regulation may cause myopia, because modulation of optic globe size is essential for the generation of normal optic power. Evidence has implied variations of BMP2 gene expression mediate ocular development and retinal tissue remodeling. Given BMP2 as a potential regulator involved in myopia development, we investigate whether gene BMP2-inducible kinase (BMP2K, BIKe), whose expression is up-regulated during BMP2-induced osteoblast differentiation, contributes to susceptibility of high myopia. Participants grouped into high myopia had a spherical equivalent greater than ,6.00 D, compared with a control group of spherical equivalent less than ,0.5 D. Genotyping of polymorphisms 1379 G/A (rs2288255) and 3171 C/G (rs12507099), corresponding with 405 Gly/Ser and 1002 Thr/Ser variation in the BMP2K gene were determined by PCR-restriction fragment length polymorphism and associative study performed by comparing high myopic subjects and healthy controls. The frequency of A allele in the BMP2K gene 1379 G/A polymorphism showed a significant difference between cases and controls (P<0.001, OR=2.99, 95% CI=1.62,5.54) and subjects with either AA or AG genotype show higher risk than GG genotype (P<0.001, OR=3.07, 95% CI=1.59,5.92), while 3171 C/G polymorphism was not significant from this survey. These data suggest that BMP2K gene 1379 G/A variant is strongly correlated with high myopia and may contribute to a genetic risk factor for high degrees of myopic pathogenesis. J. Clin. Lab. Anal. 23:362,367, 2009. 2009 Wiley-Liss, Inc. [source]

Effects of hyperglycaemia on ocular development in rabbit: refraction and biometric changes

Peter Herse
Abstract Aim:, To determine the effect of acute and chronic hyperglycaemia on the refraction and development of the rabbit eye. Methods:, Ocular dimensions of five alloxan-induced hyperglycaemic and six control rabbits were measured over 9 weeks using A scan biometry. Refraction was measured using retinoscopy. The animals were 10 weeks of age at the start of the experiment. Results:, The acute onset of hyperglycaemia was associated with a fast and stable 2 D hyperopic shift in refraction. Lens thickness increased during the first 2 weeks of hyperglycaemia, returned to near normal thickness after 3,5 weeks of hyperglycaemia and then decreased in thickness in the last 4 weeks of the study. The hyperopic refraction remained unchanged during changes in lens thickness. Nine weeks of hyperglycaemia was associated with a 25% reduction in the growth of both the globe and the lens and a 17% decrease in body mass compared with the controls. Conclusion:, The hyperopic refraction change of acute hyperglycaemia is likely to be because of a change in the refractive index of the cortical fibres of the lens and is the probable source of the fluctuating refraction seen in diabetic patients. Chronic hyperglycaemia reduced the axial development of the eye and is the probable source of the chronic hyperopic refraction seen in children with Type I diabetes. [source]

Relative Axial Myopia Induced by Prolonged Light Exposure in C57BL/6 Mice

Xiangtian Zhou
Ambient lighting is essential for ocular development in many species, however, disruption in diurnal lighting cycle can affect the development in refraction and axial growth of the eye. This study investigated the effects of prolonged daily lighting on refraction and various optical components of the eye by raising C57BL/6 mice under three different light/dark cycles (18/6, 12/12 and 6/18). Egr-1 mRNA expression, apoptosis and histology of the retina and size of the scleral fibrils were evaluated in these three lighting cycles. Results showed that there was a trend of myopic development, increasing vitreous chamber depth and thinning of the retina in eyes from 6/18 to 18/6 groups. Retinal Egr-1 mRNA expression and diameter of scleral fibrils were reduced with the prolongation of daily lighting from 6/18 to 18/6. However, retinal apoptosis was not detected in all the groups. These results suggest that prolonged lighting can induce axial myopia in inbred mice. This model, which uses mice with similar genetic backgrounds, provides an alternative to the currently available models and therefore is useful for evaluation of refractive errors caused by changes in environmental illumination. [source]

2243: Update on inherited ocular developmental disease

Purpose To provide an overview of progress in understanding of the genetics of developmental ocular disease. Methods A systematic review, including case presentations, to illustrate insights into genes underlying developmental ocular disorders: Results Studies suggest that, in developed countries, between a third and a half of the diagnoses underlying childhood blind or partial-sighted registration are genetic while a number of other ,non-genetic' conditions also have a substantial genetic contribution. Such a figure is likely to be an underestimate. Although most of these conditions are rare, many of the issues regarding diagnosis and counselling apply to the group as a whole and it is therefore possible to consider a common approach to many aspects of their clinical management. An important challenge, for example, is to improve genetic counselling for patients affected by, and at risk of, disorders that may be caused by a genetic change in one of many possible genes, which typifies many inherited conditions associated with blindness (developmental ocular disorders, early-onset retinal dystrophies, congenital cataract). Most diagnostic genetic testing currently being undertaken focuses on single genes; this will be illustrated for ocular conditions such as retinoblastoma, Norrie disease and microphthalmia. However future prospects will focus upon use of new higher throughput technologies (e.g Microarray technologies). Conclusion The recent identification of genes underlying, for example, anophthalmia/microphthalmia spectrum (e.g. VSX2, SOX2, BCOR), anterior segment dysgenesis (e.g. PITX2, FOXC1, FOXE3) and early,onset retinal disorders (e.g. ADVIRC, RPE65) has shed light on the pathways and processes underlying a range of the biological processes underlying ocular development. [source]

New blood for hemoglobin in the lens: roles in stem cell differentiation and fibre cell organelle loss?

Purpose Evidence is emerging for haemoglobin (Hb) expression outside the vascular system. We previously demonstrated Hb expression in the mouse lens during post-natal development and cataract progression. Here, we extended this work by carrying out a comprehensive spatio-temporal analysis of Hb subunit expression during mouse lens development and maturation. Methods We used RT-PCR, Western blotting and immunofluorescence to analyze Hb expression in mouse eyes (E16.5 to 9 wks). We also used a sensitive heme assay to test for the presence of heme in the lens by colourimetric assay and histological staining of paraffin-embedded sections. Results Hb subunits were expressed in lens epithelial cells and cortical lens fibre cells. However, the heme assay revealed negligible levels of this prosthetic group in the lens. Hb immunofluorescence was also observed in other regions of the developing eye including the cornea, the retinal ganglion cell layer and the retinal pigment epithelium. Finally, we also observed Hb expression in early embryos by microarray and during differentiation of embryonic stem (ES) cells into embryoid bodies (EBs) in vitro. Conclusion These results suggest a paradigm shift: Hb subunits are expressed in the eye during development and in the adult and, therefore, may have novel roles in ocular development, physiology and pathophysiology. The absence of heme from the lens indicates that at least some of these functions may be independent of oxygen metabolism. The pattern of expression of Hb in lens epithelial cells and cortical lens fibre cells may indicate an involvement for Hb subunits in lens epithelial cell differentiation into lens fibre cells and/or lens fibre cell organelle loss. [source]