Rek, an Axl/Tyro3-related receptor-class tyrosine kinase, is expressed in Müller glia and differentiating neural subpopulations in the avian retina.

Rek is a receptor-class tyrosine kinase of the Axl/Tyro3 family that has transforming capability and is expressed in the avian nervous system. To gain insight into its normal cellular function, the spatial and temporal expression of Rek was analyzed in the developing chick retina by immunoperoxidase staining and Western blotting using Rek-specific antibodies. Rek was developmentally regulated in the retina with maximal expression of the 140 kD full-length kinase at embryonic stage 34 (E8), when retinal glia and neurons begin to differentiate. Rek immunoreactivity was most prominent in the processes of developing and mature retinal Müller glia, and appeared transiently in the bodies of differentiating ganglion and amacrine neurons. In the developing optic tract Rek was found in oligodendroglial-type cells but not in ganglion cell axons. Rek antibodies also stained brain ependymal cells and some cerebellar neuronal cell types (Purkinje, basket and stellate cells). This expression pattern suggests that the Rek tyrosine kinase participates in an aspect of Müller glial function, and may also contribute to the development of restricted populations of glia and neurons in the brain and retina.