The expression of NPPA splice variants during mouse cardiac development.

Natriuretic peptide precursor-A (NPPA) is an early and specific marker for functional myocardium of the embryonic heart. NPPA gene encodes for a precursor of atrial natriuretic peptide (ANP). So far, three alternatively spliced variants have been reported for NPPA in human. In mouse, no alternatively spliced transcript of NPPA has been reported. In the current study, we investigated the expression of NPPA gene during cardiac differentiation of mouse adipose-tissue-derived stem cells (ADSCs) and embryonic stem (ES) cells. As revealed by reverse-transcription polymerase chain reaction analysis, 2-week-differentiated cells expressed some cardiac-specific makers, including ANP. Three additional intron-retained splice variants of NPPA were also detected during cardiac differentiation of the ADSCs and ES cells. In addition, we detected three intron-retained splice variants of NPPA in 8.5-day mouse embryonic heart. In the mature cardiomyocytes of 1-week-old mice, only the correctly spliced isoform of NPPA gene was expressed. Freshly isolated stromal vascular fraction also expressed one intron-retained isoform of NPPA gene. In conclusion, our findings have provided evidence for the expression of intron-retained splices of NPPA mRNA during the early stages of mouse cardiogenesis as well as in the mouse adipose tissue.