Expression of the mRNA for two isoforms of neural plakophilin-related arm-repeat protein/delta-catenin in rodent neurons and glial cells.

Neural plakophilin-related arm-repeat protein (NPRAP) is a mammalian brain protein of the armadillo family. Here, in an attempt to elucidate its function, we determined the mouse brain regions and cell types expressing the mRNAs for two NPRAP isoforms (the longer and the shorter isoforms), and examined the regulation of expression of the NPRAP mRNAs during the differentiation of P19 cells into neurons. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that both variants were expressed in various mouse brain regions, but the mRNA for the short isoform was predominant in most regions. Primary cultures of both neurons and glial cells exhibited high expression levels of both the mRNAs, indicating that NPRAP mRNA expression is not neuron-specific. The expression of the two NPRAP mRNA variants was dramatically induced even prior to the terminal neuronal and glial differentiation of P19 cells after retinoic acid treatment. These data suggest that the two NPRAP isoforms function not only in neurons and glial cells in the brain, but also play a role in the differentiation of precursor cells into neurons and glial cells.