Developmental Expression and Localization of Protein Phosphatase 2A in the Kidney † 1649

Abstract

Although a number of growth and transcription factors are known to regulate kidney growth and development, the signal transduction molecules necessary to mediate developmental signals in the kidney remain largely unknown. Therefore activity, mRNA and protein expression of the signal transduction molecule protein phosphatase 2A (PP2A) were examined in kidneys from embryonic day 17 to 90 day old adults. Northern analysis of total kidney RNA or western analysis of kidney protein homogenates demonstrated developmental regulation of both the catalytic and major 55 kDa regulatory subunits of PP2A with the highest levels in the embryonic and newborn kidneys. Similarly PP2A enzyme activity was highest in the embryonic and newborn kidney. In situ hybridization with a digoxigenin labeled catalytic subunit cRNA probe mapped to mRNA expressing cells predominately in the nephrogenic cortex, particularly to developing glomeruli and not to developing tubular elements in the embryonic day 20 and newborn kidney. Similarly immunocytochemistry with a specific PP2A catalytic subunit polyclonal peptide antibody demonstrated localized catalytic subunit expression particularly to podocytes of developing glomeruli. Therefore the developmental regulation of PP2A during kidney development and its mapping predominately to developing glomeruli suggests a role for PP2A in the regulation of glomerular development.