Electrophysiological determination of P19CL6-derived cardiomyocytes and their modification by the transcription factor Csx/Nkx2-5

同源盒基因Csx/Nkx 2 -5是心脏富集的转录因子之一，在早期心脏发生中起着重要作用。我们研究了Csx/Nkx 2 -5对P19 CL 6衍生的心肌细胞的心脏离子通道表达的影响。P19 CL 6细胞和Csx/Nkx 2 -5过表达的P19 CL 6细胞（P19 CL 6-Csx细胞）通过用二甲基亚砜处理有效地分化为心肌细胞。采用全细胞膜片钳技术，分别在细胞分化早期（搏动后1- 5d）和晚期（搏动后10-15 d）测定细胞动作电位和膜电流。P19 CL 6和P19 CL 6-Csx细胞系的自发搏动率随着分化的进展而增加。P19 CL 6-Csx细胞的最大舒张电位随着分化而变得更加去极化。两<50>种细胞系的APD均随分化程度的增加而缩短。P19 CL 6细胞体积增大。在P19 CL 6细胞中，I_<to>，I_，I<Kr>_，I<Ks>_<K1>，I_&lt;K，ACh&gt;，其中I_&lt;K，ATP&gt;在早期就已表达，且I_<to>在所有K^+电流中占主导地位。Csx/Nkx 2 -5过表达可抑制I_2的发育性降低<to>。含同源异型盒基因Csx/Nkx 2 -5在分化过程中调节心肌离子通道的表达，主要在I_2期<to>。

The homeobox-containing gene Csx/Nkx2-5 is one of cardiac-enriched transcription factors and it plays a critical role for early cardiogenesis. We investigated the effect of Csx/Nkx2-5 on the expression of cardiac ion channels with P19CL6-derived cardiomyocytes. P19CL6 cells and P19CL6 cells with Csx/Nkx2-5 overexpression(P19CL6-Csx cells) were efficiently differentiated into cardiomyocytes by a treatment with dimethyl sulfoxide. Action potentials and membrane currents were measured by whole cell patch clamp at distinct differentiation stage : the early stage(1-5 days after beating) and the late stage(10-15 days after beating). Spontaneous beating rate increased as differentiation advanced both in P19CL6 and P19CL6-Csx cell lines. Maximal diastolic potential of P19CL6-Csx cells was changed to more depolarized as differentiated. APD_<50> was shortened as differentiated in both cell lines. Cell size increased in P19CL6 cells. In P19CL6 cells, I_<to>,I_<Kr>,I_<Ks>,I_<K1>,I_<K,ACh>, where I_<K,ATP> were expressed from the early stage, and I_<to> was predominant in the all K^+ currents. By overexpression of Csx/Nkx2-5, developmental decrease of I_<to> was suppressed invariantly. Homeobox-containing gene Csx/Nkx2-5 modified the expression of cardiac ionic channels during differentiation period, dominantly in I_<to>.