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Sonia Guha, Alejandra Young, Debora Farber; Identification of genes critical for normal pigmentation of RPE and crossing of the optic nerves in mouse embryos. Invest. Ophthalmol. Vis. Sci. 2013;54(15):2017. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular albinism type 1 (OA1) is characterized by the presence of macromelanosomes in the retinal pigment epithelium (RPE) and abnormal crossing of the retinal ganglion cells (RGCs) axons. It is caused by mutations in the OA1 gene. How the reduced melanosomal pigmentation of OA1 RPE exerts its effects upon the RGCs to influence the misrouting of their axons at the optic chiasm remains unsolved. In mouse, by embryonic day 15, the RPE is already melanized, the ipsilateral and contralateral RGCs have been generated and the majority of their axons pass through the optic chiasm. Our aim is to identify candidate genes critical for normal pigmentation of the RPE and crossing of the optic nerves using microarrays hybridized with mRNAs from 15 days post coito (dpc) ocular albino (Oa1-/-) and control (B6/NCrl) embryonic mice eyes.
15.5 dpc mouse embryos (6-10/litter) were collected from pregnant Oa1-/- and the corresponding control B6/NCrl females. Total RNA was isolated from the eyes of each litter and stored as one biological sample at -80°C. Samples were hybridized to 430.2 whole mouse Affymetrix gene arrays at the UCLA Microarray core facility. Microarray data analysis was performed using Ingenuity Systems software and genes were identified as differentially expressed if they showed a fold-change of at least 2 and a p-value < 0.05. RT-PCR with the appropriate primers and the same RNAs used for microarray hybridization was performed to confirm the differential expression of the identified genes in Oa1-/- and control B6/Ncrl mice.
Analysis of the microarrays from Oa1-/- vs. control NCrl mice gave 11 significant, differentially expressed genes. One gene was up-regulated and 10 down-regulated. Some of these genes are associated with neurogenesis, others with neuroprotection and axon guidance. All identified genes were confirmed to be differentially expressed in Oa1-/- and B6/Ncrl mice by RT-PCR.
Microarray analysis of the RNA from 15.5 dpc embryonic eyes of oculoalbino (Oa1-/-) and control (B6/NCrl) mice has provided a comprehensive list of genes potentially involved in optic axon guidance, neurogenesis and neuroprotection in normal mice. The up- or down-regulated expression of these genes may also be associated to the abnormal pigmentation observed in the RPE of the Oa1-/- mouse model of ocular albinism.
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