OBJECTIVETo investigate the expression of Junctophilin 1 (JP1) in cardiogenesis of mammalian.

METHODSCardiac differentiation of embryonic stem cells (ESCs) was generated by hanging drop method. Fetal heart was obtained from the rats aged d 14-20 of gestation. The expression of JP1 and JP2 during cardiogenesis of ESCs and rat embryos was analyzed by RT-PCR or Western blotting. Immunofluorescence staining was employed to reveal the distribution of JP1 and JP2 in embryoid body (EB), probing for merging of JP1 and JP2 and cardiac sarcomeric α-Actinin or Troponin-T. Percentage of JP1 and JP2-positive staining cells was analyzed quantitatively by FCS on d17.

RESULTSJP1 mRNA was up-regulated at the early stage (d 5-11) and then decreased. The expression of JP1 protein was up-regulated at the early stage (d 7-9), then decreased gradually and disappeared after d 15. While JP2 gene and protein expression increased in a time-dependent manner during cardiogenesis of rat embryos. The results of immunofluorescence staining showed that there was a parallel co-localization of JP2 with Troponin-T or α-Actinin on d17, while JP1 failed to express in the sarcomeric positive area at the same time point. Furthermore, FCS analysis showed that about 16.59% of cells were JP2-positive, while no cells were stained positively for JP1 in d17 EBs.

CONCLUSIONJP1 gene is expressed during the whole process of cardiogenesis, while JP1 protein only appears on the early stage. The expression of JP1 in cardiogenesis of ESCs is consistent with that of rat embryos.