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Distribution of a murine protein tyrosine phosphatase BL‐β‐galactosidase fusion protein suggests a role in neurite outgrowth

We have generated a gene trap insertion into the protein tyrosine phosphatase‐BL (PTP‐BL) locus, which produces a fusion of the N‐terminal half of PTP‐BL with β‐galactosidase. During development, β‐galactosidase activity was seen in all epithelial cells: strong staining was observed in the stomach and kidney epithelium, the ependymal layer of the central nervous system, and the surface ectoderm. Particularly prominent β‐galactosidase activity was seen in the peripheral nervous system, which correlated with neurite outgrowth. In epithelial cells, staining was seen in the apical portion of the cells. In nerves, β‐galactosidase activity was associated with growth cones as well as with Schwann cells. This suggests that the amino‐terminal portion of PTP‐BL contains sequences sufficient to target the fusion protein to specific subcellular compartments. In situ hybridization with a PTP‐BL probe demonstrated that all tissues in which β‐galactosidase activity was seen were genuine sites of expression of the PTP‐BL gene, although differences in the stability of the PTP‐BL protein and the PTP‐BL‐β‐galactosidase fusion protein may exist. The distribution of β‐galactosidase activity in the peripheral nervous system, together with the structure of the wild‐type protein, suggests that this phosphatase may have a role in regulation of the cytoskeleton during the development of the peripheral nervous system. Dev. Dyn. 1998;212:250–257. © 1998 Wiley‐Liss, Inc.