FoxC1 activates limbal epithelial stem cells following corneal epithelial debridement.

Limbal epithelial stem cells are not only critical for corneal epithelial homeostasis but also have the capacity to change from a relatively quiescent mitotic phenotype to a rapidly proliferating cell in response to population depletion following corneal epithelial wounding. Pax6 mice display many abnormalities including corneal vascularization and these aberrations are consistent with a limbal stem cell deficiency (LSCD) phenotype. FoxC1 has an inhibitory effect on corneal avascularity and a positive role in stem cell maintenance in many tissues.

BMP3 is a novel locus involved in the causality of ocular coloboma.

Coloboma, a congenital disorder characterized by gaps in ocular tissues, is caused when the choroid fissure fails to close during embryonic development. Several loci have been associated with coloboma, but these represent less than 40% of those that are involved with this disease. Here, we describe a novel coloboma-causing locus, BMP3.

Genetics and therapy for pediatric eye diseases.

Ocular morphogenesis in vertebrates is a highly organized process, orchestrated largely by intrinsic genetic programs that exhibit stringent spatiotemporal control. Alternations in these genetic instructions can lead to hereditary or nonhereditary congenital disorders, a major cause of childhood visual impairment, and contribute to common late-onset blinding diseases. Currently, limited treatment options exist for clinical phenotypes involving eye development.

The Axenfeld-Rieger Syndrome Gene Contributes to Left-Right Patterning.

Precise spatiotemporal expression of the -- cascade in the lateral plate mesoderm establishes the left-right axis, which provides vital cues for correct organ formation and function. Mutations of one cascade constituent and, separately, the Forkhead transcription factor independently cause a multi-system disorder known as Axenfeld-Rieger syndrome (ARS). Since cardiac involvement is an established ARS phenotype and because disrupted left-right patterning can cause congenital heart defects, we investigated in zebrafish whether contributes to organ laterality or situs.

Ocular coloboma: Genetic variants reveal a dynamic model of eye development.

Ocular coloboma is a congenital disorder of the eye where a gap exists in the inferior retina, lens, iris, or optic nerve tissue. With a prevalence of 2-19 per 100,000 live births, coloboma, and microphthalmia, an associated ocular disorder, represent up to 10% of childhood blindness. It manifests due to the failure of choroid fissure closure during eye development, and it is a part of a spectrum of ocular disorders that include microphthalmia and anophthalmia.

foxc1 is required for embryonic head vascular smooth muscle differentiation in zebrafish.

Vascular smooth muscle of the head derives from neural crest, but developmental mechanisms and early transcriptional drivers of the vSMC lineage are not well characterized. We find that in early development, the transcription factor foxc1b is expressed in mesenchymal cells that associate with the vascular endothelium. Using timelapse imaging, we observe that foxc1b expressing mesenchymal cells differentiate into acta2 expressing vascular mural cells.

Non-Synonymous variants in premelanosome protein (PMEL) cause ocular pigment dispersion and pigmentary glaucoma.

Pigmentary glaucoma (PG) is a common glaucoma subtype that results from release of pigment from the iris, called pigment dispersion syndrome (PDS), and its deposition throughout the anterior chamber of the eye. Although PG has a substantial heritable component, no causative genes have yet been identified. We used whole exome sequencing of two independent pedigrees to identify two premelanosome protein (PMEL) variants associated with heritable PDS/PG.

Morphogenetic defects underlie Superior Coloboma, a newly identified closure disorder of the dorsal eye.

The eye primordium arises as a lateral outgrowth of the forebrain, with a transient fissure on the inferior side of the optic cup providing an entry point for developing blood vessels. Incomplete closure of the inferior ocular fissure results in coloboma, a disease characterized by gaps in the inferior eye and recognized as a significant cause of pediatric blindness. Here, we identify eight patients with defects in tissues of the superior eye, a congenital disorder that we term superior coloboma.

A targeted approach to genome-wide studies reveals new genetic associations with central corneal thickness.

Purpose: To evaluate the ability of a targeted genome-wide association study (GWAS) to identify genes associated with central corneal thickness (CCT).

Methods: A targeted GWAS was used to investigate whether ten candidate genes with known roles in corneal development were associated with CCT in two Singaporean populations. The single nucleotide polymorphisms (SNPs) within a 500 kb interval encompassing each candidate were analyzed, and in light of the resulting data, members of the Wnt pathway were subsequently screened using similar methodology.

Genetic background-dependent role of for eyelid development.

EGR1 is an early growth response zinc finger transcription factor with broad actions, including in differentiation, mitogenesis, tumor suppression, and neuronal plasticity. Here we demonstrate that mice on the C57BL/6 background have normal eyelid development, but back-crossing to BALB/c background for four or five generations resulted in defective eyelid development by day E15.5, at which time EGR1 was expressed in eyelids of WT mice.

A secreted WNT-ligand-binding domain of FZD5 generated by a frameshift mutation causes autosomal dominant coloboma.

Ocular coloboma is a common eye malformation resulting from incomplete fusion of the optic fissure during development. Coloboma is often associated with microphthalmia and/or contralateral anophthalmia. Coloboma shows extensive locus heterogeneity associated with causative mutations identified in genes encoding developmental transcription factors or components of signaling pathways.

Mutation of FOXC1 and PITX2 induces cerebral small-vessel disease.

Patients with cerebral small-vessel disease (CSVD) exhibit perturbed end-artery function and have an increased risk for stroke and age-related cognitive decline. Here, we used targeted genome-wide association (GWA) analysis and defined a CSVD locus adjacent to the forkhead transcription factor FOXC1. Moreover, we determined that the linked SNPs influence FOXC1 transcript levels and demonstrated that patients as young as 1 year of age with altered FOXC1 function exhibit CSVD.

Sox11 is required to maintain proper levels of Hedgehog signaling during vertebrate ocular morphogenesis.

Ocular coloboma is a sight-threatening malformation caused by failure of the choroid fissure to close during morphogenesis of the eye, and is frequently associated with additional anomalies, including microphthalmia and cataracts. Although Hedgehog signaling is known to play a critical role in choroid fissure closure, genetic regulation of this pathway remains poorly understood. Here, we show that the transcription factor Sox11 is required to maintain specific levels of Hedgehog signaling during ocular development.

Mutation of SALL2 causes recessive ocular coloboma in humans and mice.

Ocular coloboma is a congenital defect resulting from failure of normal closure of the optic fissure during embryonic eye development. This birth defect causes childhood blindness worldwide, yet the genetic etiology is poorly understood. Here, we identified a novel homozygous mutation in the SALL2 gene in members of a consanguineous family affected with non-syndromic ocular coloboma variably affecting the iris and retina.

Molecular mechanisms regulating ocular apoptosis in zebrafish gdf6a mutants.

Purpose: To characterize the molecular mechanisms underlying retinal apoptosis induced by loss of Gdf6, a TGFβ ligand.

Methods: The role of Gdf6 in regulating apoptosis was studied using a zebrafish gdf6a(-/-) mutant, which encodes a truncated, nonfunctional protein. To investigate whether intrinsic or extrinsic apoptotic mechanisms were involved, morpholino antisense oligonucleotides targeting baxa, baxb, and p53 were employed.

Mutations in PIK3R1 cause SHORT syndrome.

SHORT syndrome is a rare, multisystem disease characterized by short stature, anterior-chamber eye anomalies, characteristic facial features, lipodystrophy, hernias, hyperextensibility, and delayed dentition. As part of the FORGE (Finding of Rare Disease Genes) Canada Consortium, we studied individuals with clinical features of SHORT syndrome to identify the genetic etiology of this rare disease. Whole-exome sequencing in a family trio of an affected child and unaffected parents identified a de novo frameshift insertion, c.

Apoptotic and proliferative defects characterize ocular development in a microphthalmic BMP model.

Purpose: Vision is critically dependent on ocular size, which is regulated by environmental and genetic factors. Mutation of human Growth and Differentiation Factor 6 (GDF6) or zebrafish gdf6a results in a spectrum of small eye phenotypes (microphthalmia, anophthalmia, and coloboma). However, current models do not explain their etiology fully.

Longitudinal fluorescent observation of retinal degeneration and regeneration in zebrafish using fundus lens imaging.

Purpose: Longitudinal observation of retinal degeneration and regeneration in animal models is time-consuming and expensive. To address this challenge, we used a custom fundus lens and zebrafish transgenic lines with cell-specific fluorescent reporters to document the state of individual retinal neurons in vivo.

Methods: We empirically tested several versions of a custom fundus lens and assessed its capabilities under a stereomicroscope to image retinal neurons in transgenic zebrafish lines expressing fluorescent reporters.

Contribution of growth differentiation factor 6-dependent cell survival to early-onset retinal dystrophies.

Retinal dystrophies are predominantly caused by mutations affecting the visual phototransduction system and cilia, with few genes identified that function to maintain photoreceptor survival. We reasoned that growth factors involved with early embryonic retinal development would represent excellent candidates for such diseases. Here we show that mutations in the transforming growth factor-β (TGF-β) ligand Growth Differentiation Factor 6, which specifies the dorso-ventral retinal axis, contribute to Leber congenital amaurosis.

Disparities in healthcare utilisation rates for Aboriginal and non-Aboriginal Albertan residents, 1997-2006: a population database study.

Background: It is widely recognised that significant discrepancies exist between the health of indigenous and non-indigenous populations. Whilst the reasons are incompletely defined, one potential cause is that indigenous communities do not access healthcare to the same extent. We investigated healthcare utilisation rates in the Canadian Aboriginal population to elucidate the contribution of this fundamental social determinant for health to such disparities.

Evidence of genetic heterogeneity in Alberta Hutterites with Usher syndrome type I.

Purpose: To identify the genetic defect in a Hutterite population from northern Alberta with Usher syndrome type I.

Methods: Complete ophthalmic examinations were conducted on two boys and two girls from two related Hutterite families diagnosed with Usher syndrome type I. DNA from patients and their parents was first evaluated for a mutation in exon 10 of the protocadherin-related 15 (PCDH15) gene (c.

Evidence for additional FREM1 heterogeneity in Manitoba oculotrichoanal syndrome.

Purpose: Manitoba Oculotrichoanal (MOTA) syndrome is an autosomal recessive disorder present in First Nations families that is characterized by ocular (cryptophthalmos), facial, and genital anomalies. At the commencement of this study, its genetic basis was undefined.

Methods: Homozygosity analysis was employed to map the causative locus using DNA samples from four probands of Cree ancestry.

Homozygosity mapping in an anophthalmic pedigree provides evidence of additional genetic heterogeneity.

Purpose: Anophthalmia is a heterogeneous developmental disorder characterized by absent eyes whose diverse etiology encompasses chromosomal and monogenic aberrations, as well as environmental causes. Since the molecular basis has been defined in only a small proportion of cases and extending this offers potential to enhance understanding of key steps in ocular development, a consanguineous anophthalmic pedigree was investigated using homozygosity mapping.

Methods: DNA samples from six individuals, two anophthalmic, were genotyped with an array featuring approximately 620,000 single nucleotide polymorphisms (SNPs) in order to identify homozygous or copy number variant (CNV) regions.