Polarized expression of the receptor protein tyrosine kinase Cek5 in the developing avian visual system
Abstract
Receptor protein tyrosine kinases of the Eph subfamily have been proposed to play roles in pattern formation based on their distribution during embryonic development. Cek5 (chicken embryo kinase 5) and Cek8 (chicken embryo kinase 8) are Eph-related kinases highly expressed in the chicken embryonic retina. To assess their potential roles in the development of the visual pathway, we examined their distribution by immunoperoxidase labeling. Cek8 is expressed throughout the pathway of the retinal ganglion cell axons, including the nerve fiber layer of the retina, optic nerve, optic chiasm, and stratum opticum of the tectum. Cek5 immunoreactivity is highly concentrated in only a portion of the optic nerve and optic chiasm, and in retinal cultures, Cek5 is detected in neurons. This prompted us to examine the regional distribution of Cek5 in the developing retina and led to the observation that Cek5 is most concentrated in the ventral aspect. RT-PCR established that the differential regulation of Cek5 expression in different portions of the retina occurs at the transcriptional level. Immunoblotting analysis revealed that this unusual expression pattern is distinctive for Cek5, as three other members of the Eph subfamily, Cek4, Cek8, a...Continue Reading
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