Chick receptor protein tyrosine phosphatase λ/ψ (cRPTPλ/cRPTPψ) is dynamically expressed at the midbrain-hindbrain boundary and in the embryonic neural retina

The isthmic organizer, located near the boundary between the developing midbrain and hindbrain, controls the patterning of adjacent brain regions. Here we describe the spatial and temporal expression of chick receptor-like protein tyrosine phosphatase lambda (cRPTPλ, also known as cRPTPψ) during the development of this structure. After an initial widespread expression throughout the caudal forebrain and midbrain region, expression of cRPTPλ is confined to the ventral midline of the neural tube, the future neural retina and lens, and a sharp ring at the isthmic constriction, overlying the molecular mid-hindbrain boundary (MHB). MHB expression of cRPTPλ borders at the caudal limit of the expression domain of the transcription factor Otx2, appears to partially overlap with that of the secreted protein Wnt1 and is similar to that of the Ig-CAM CEPU-1. In the neural retina, expression is restricted to the ventricular zone, where the cell bodies of retinal progenitor cells reside.