PROTEIN-TYROSINE PHOSPHATASES EXPRESSED IN DEVELOPING BRAIN AND RETINAL MULLER GLIA

Regulation of protein function through tyrosine phosphorylation is cri tical to many developmental processes involving cell-cell communicatio n. A number of protein tyrosine phosphatases (PTPs) have been identifi ed in the early postnatal and mature central nervous system (CNS), but the PTPs expressed during its development have not been well characte rized. Using a polymerase chain reaction with degenerate primers, we a nalyzed PTPs expressed in fetal (E18) rat brain and Muller glia cultur es from embryonic chick retina, two systems in which cell-to-cell cont acts 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. Muller glia exhibited a distinct but overlapping pa ttern of expression: four known receptor PTPs (PTP alpha, PTP gamma, P TP delta, PTP zeta) and PTP1B. In addition, two novel PTPs, termed MG- PTP1 and 2 (Muller glia PTP 1 and 2) were identified in Muller glia cD NA. MG-PTP1 was related to, but distinct from PTP delta, while MG-PTP2 was related to, but distinct from the cytosolic T-cell phosphatase. T hese results demonstrate that a distinct but overlapping set of PTPs i s expressed in the developing brain and retinal Muller glia, including two novel PTPs that may participate in neural cell communication.