Abstract
Abstract: :
Purpose: WNTs are secreted glycoproteins that play important roles in cell growth, motility and differentiation during embryogenesis. Very little is known about the role of Wnt signaling in eye development, especially with the respect to the development of an anterior part of the eye. However, the available data, based on the analysis of a few mouse mutants and human genetic disorders, has provided important evidence about the involvement of the Wnt signaling pathway in eye development. As a first step toward understanding the role of Wnt signaling in the development of the anterior segment of the eye, we have analyzed the expression patterns for all chicken Wnt genes during embryonic development. Methods: To date, 19 Wnt ligands were identified in the human and mouse genome (http://www.stanford.edu/∼rnusse/wntwindow.html). However, only 10 chicken Wnts were known at the time we started this project. In order to identify additional chicken Wnts, we performed BLAST analysis against a Chicken Genome Trace Archive using nucleotide sequences of known human, mouse or Xenopus Wnt genes. Assembled sequences were used to design primers for RT–PCR. The PCR fragments were cloned into pGEM3z(f+). Consensus sequences were determined and compared to available sequences in a Trace Archive. 5’RACE was performed to obtain the full coding sequence of cWnt3a, cWnt5b, Wnt7b, Wnt9b and cWnt16. Altogether, we cloned full–length or partial sequences for cWnt1, cWnt2, cWnt3, cWnt5b, cWnt6, cWnt7b, cWnt8b, cWnt9b, cWnt10a and cWnt16. For known Wnt genes PCR primers were designed based on the sequence information available in a GenBank, and the PCR fragments were cloned into pGEM3z(f+). Digoxigenin–labeled hybridization probes were prepared for all 18 chicken Wnts using standard techniques. Non–radioactive in situ hybridization was performed on the vibratome sections of chicken embryos at different stages starting from st.23 (E3.5) until st.31 (E7). Results: Out of 18 Wnt genes, 13 genes were expressed in different tissues of the anterior eye in distinct spatial and temporal patterns. 6 Wnts were expressed in the lens, 5 Wnts were expressed in the ciliary epithelium, and 7 Wnts were expressed in the cornea. Conclusions: These data suggest that different Wnt signaling pathways, canonical and non–canonical, are involved in the patterning of the anterior segment of the eye.
Keywords: anterior segment • growth factors/growth factor receptors • in situ hybridization