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M.T. Escano, R.K. Ladher; Tissue Interactions in Chicken Eye Development . Invest. Ophthalmol. Vis. Sci. 2005;46(13):3143.
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© ARVO (1962-2015); The Authors (2016-present)
Background: Normal eye growth in the embryo is dependent on numerous factors. Certain eye diseases stem from abnormalities in eye growth. The head mesoderm plays an important role in the formation of the three coats of the eye. However, during development of the eye, the mesoderm, as a layer, is conspicuously absent in the area where the paired optic vesicles initially evaginate from the primitive forebrain. Purpose: To understand early mechanisms of eye growth, we evaluated tissue interactions involved in embryonic chick eye development, particularly the mesoderm, using transplantation and explantation methods. Methods: A layer of donor anterior lateral mesoderm from Hamburger–Hamilton (HH) Stages 7 to 8 quail embryos were isolated and transplanted between the ectoderm and endoderm of the head region of same stage recipient chick embryos (transplant embryo group). A sham experiment (dissection but without mesoderm transplantation) was done to serve as controls (sham experiment group). The embryos were incubated for 24 hours and observed under light microscopy for morphological abnormalities. Similarly, tissues from the presumptive optic vesicle in the anterior head region of HH Stages 7 to 8 chick embryos were cultured in collagen drops as explants with addition of quail mesoderm (explant experimental group) and without extra mesoderm (explant control group). Explants were incubated for 24 hours. Expression levels of the eye field transcription factors Pax6, Rax, Six3 and Otx2 in the explants were evaluated by in–situ hybridization. In addition, RNA isolated from the experimental and control explant groups were used to evaluate the expression differences of the same transcription factors by real–time PCR assay. Results: Morphologically abnormal eyes were observed in 15% of the transplant embryo group compared to 0% in the sham experiment group. Abnormalities in heart development and poor midline trunk fusion were observed in both groups. In the real–time PCR quantitative assay, Pax6, Rax, Six 3 and Otx2 expression levels were decreased compared to the explant control group. However only Pax6 and Rax showed significant difference in expression (p < 0.05). In–situ hybridization showed a similar trend. The staining patterns of Pax6 and Rax in the explant experimental group were lesser when compared with the explant control group. Conclusions: Moving the mesoderm caudally would interfere with normal expression of some eye field transcription factors. The position of the mesoderm is important for ensuring normal development of the embryonic chicken eye.
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