EXPRESSION OF LAR-PTP2 IN RAT LUNG IS CONFINED TO PROLIFERATING EPITHELIA LINING THE AIRWAYS AND AIR SACS

The LAR family tyrosine phosphatase LAR-PTP2B (RPTP sigma) was previou sly shown to be expressed in the central and peripheral nervous system . Here we show that LAR-PTP2, the larger alternatively spliced form of the gene, is expressed in proliferating undifferentiated lung epithel ia in a developmentally regulated manner. Using in situ hybridization and parallel immunostaining with proliferating cell nuclear antigen to detect proliferating cells, we demonstrate that LAR-PTP2 is expressed exclusively in the undifferentiated epithelial cell layer lining the bronchi, bronchioles, and air sacs in late fetal development and in th e neonatal lung. These cells correspond to Clara and fetal alveolar ty pe II cells, as determined by parallel immunostaining with antibodies to surfactant proteins A and B. LAR-PTP2 expression declined progressi vely with postnatal development, and by adult stage there was no detec table expression in the airways or in the distal (type I and II) matur e nonproliferating alveolar epithelial cells. These results suggest th at LAR-PTP2 may be involved in the regulation of epithelial cell proli feration/differentiation during lung development.