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J. M. Skarie, B. A. Link; Loss of Wdr36 Function in the Zebrafish Results in an Ocular Phenotype During Development. Invest. Ophthalmol. Vis. Sci. 2007;48(13):5593.
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WDR36 was recently identified as the causative gene at the primary open angle glaucoma (POAG) locus GLC1G. Subsequent studies in different populations have identified some of the originally reported disease causing mutations in normal patients. Further, these studies have investigated locus GLC1G in other families and have not found mutations in WDR36. Combined, these results have made the role of WDR36 in the pathogenesis of POAG unclear. The purpose of this study was to investigate the function of Wdr36 in the zebrafish model system and begin to determine its role in glaucoma pathogenesis.
Homology of WDR36 was assessed by BLAST analysis and protein sequence alignment. Expression of wdr36 in the developing zebrafish was assessed by whole mount in situ hybridization. A zebrafish line containing a viral insertion within the wdr36 gene was obtained from a forward genetic screen and confirmed by PCR. Antisense morpholinos, which block translation, were designed against wdr36, and used to confirm the genetic mutant and to further assess wdr36 knockdown phenotypes. Both wdr36 genetic mutant and morphant phenotypes were assessed by light microscopy, Northern blot, immuno-based markers, and histology.
A previous study, along with BLAST and sequence alignment analysis, suggests that vertebrate WDR36 may be the functional homolog of the yeast gene Utp21; a protein involved in ribosome biogenesis. Expression analysis in the zebrafish revealed a ubiquitous low level expression of the gene, but also enriched expression within highly proliferative tissues including the eye, tectum and GI tract. The homozygous wdr36 mutant zebrafish dies during embryogenesis, and shows phenotypes that include a small eye, small forebrain, cataract and liver necrosis that appear by 3-4 days post fertilization (dpf). Analysis of wdr36 morphants showed an identical phenotype that develops by 2 dpf. Histological analysis revealed a decrease in the size of the retinal marginal zone and a thickened lens epithelium.
Genetic studies have suggested that WDR36 may play a role in glaucoma pathogenesis, but the exact relationship to the disease and mechanism of pathogenesis are currently unclear. This study has begun to address these questions by investigating loss of Wdr36 in the zebrafish model system and has shown that this loss results in ocular phenotypes during development.
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