A Mutant Receptor Tyrosine Phosphatase, CD148, Causes Defects in Vascular Development

Abstract

Vascularization defects in genetic recombinant mice have defined critical roles for a number of specific receptor tyrosine kinases. Here we evaluated whether an endothelium-expressed receptor tyrosine phosphatase, CD148 (DEP-1/PTPη), participates in developmental vascularization. A mutant allele, CD148^ΔCyGFP, was constructed to eliminate CD148 phosphatase activity by in-frame replacement of cytoplasmic sequences with enhanced green fluorescent protein sequences. Homozygous mutant mice died at midgestation, before embryonic day 11.5 (E11.5), with vascularization failure marked by growth retardation and disorganized vascular structures. Structural abnormalities were observed as early as E8.25 in the yolk sac, prior to the appearance of intraembryonic defects. Homozygous mutant mice displayed enlarged vessels comprised of endothelial cells expressing markers of early differentiation, including VEGFR2 (Flk1), Tal1/SCL, CD31, ephrin-B2, and Tie2, with notable lack of endoglin expression. Increased endothelial cell numbers and mitotic activity indices were demonstrated. At E9.5, homozygous mutant embryos showed homogeneously enlarged primitive vessels defective in vascular remodeling and branching, with impaired pericyte investment adjacent to endothelial structures, in similarity to endoglin-deficient embryos. Developing cardiac tissues showed expanded endocardial projections accompanied by defective endocardial cushion formation. These findings implicate a member of the receptor tyrosine phosphatase family, CD148, in developmental vascular organization and provide evidence that it regulates endothelial proliferation and endothelium-pericyte interactions.

ACKNOWLEDGMENTS

We thank Brigid Hogan for valuable discussions and invaluable experimental method instruction, Stephen J. Brandt for providing anti-Tal1/SCL antibody, and Cathy Pettepher, Tsutom Kume, Keita Hirano, and Cornelia Crooke for technical assistance. We also thank the Francis Willams Preston Transgenic Mouse/ES Cell Shared Resource, supported by Cancer Center Support Grant P30 CA 68485 and Diabetes Center Support Grant P60 DK 20593, for screening and microinjection of ES cells. Analysis was performed in part through use of the VICC Cell Imaging Resource supported by CA68485 and DK20593.

This work was supported by grants from the National Institutes of Health (DK38517 to T.O.D. and DK52483 to D.R.A.) and the Juvenile Diabetes Foundation (2-2000-147 to T. Takahashi).