Protein tyrosine phosphatases expressed in developing brain and retinal Müller glia

Regulation of protein function through tyrosine phosphorylation is critical to many developmental processes involving cell-cell communication. A number of protein tyrosine phosphatases (PTPs) have been identified in the early postnatal and mature central nervous system (CNS), but the PTPs expressed during its development have not been well characterized. Using a polymerase chain reaction with degenerate primers, we analyzed PTPs expressed in fetal (E18) rat brain and Müller glia cultures from embryonic chick retina, two systems in which cell-to-cell contacts are numerous. Fetal rat brain expressed four known receptor-like PTPs (PTP delta, LAR, LAR-PTP2, LRP (PTP alpha)) and the non-receptor phosphatase PTP1B. Müller glia exhibited a distinct but overlapping pattern of expression: four known receptor PTPs (PTP alpha, PTP gamma, PTP delta, PTP zeta) and PTP1B. In addition, two novel PTPs, termed MG-PTP1 and 2 (Müller glia PTP 1 and 2) were identified in Müller glia cDNA. MG-PTP1 was related to, but distinct from PTP delta, while MG-PTP2 was related to, but distinct from the cytosolic T-cell phosphatase. These results demonstrate that a distinct but overlapping set of PTPs is expressed in the developing brain and retinal Müller glia, including two novel PTPs that may participate in neural cell communication.