【求助】请问PC12 N1代表什么?

看一篇文献摘要里多次提到PC12 N1,N1代表什么,是PC12细胞中的一型么?那一型呢?PC12不是只有分化的和没分化的么?望达人赐教.谢谢摘要如下:
JNKs, also known as SAPKs, are activated in response to a wide variety of factors including growth factors, cytokines, UV radiation, and heat
shock. In the rat pheochromocytoma PC12 cells, the JNK signaling pathway mediates diverse functions such as differentiation and apoptosis. We
have previously shown that activated JNK is required for later stages of neuritogeneis induced by NGF in a variant PC12 cell line (N1). Here, the
functional role of JNK in N1 cells is further investigated. We show that NGF treatment, which induces extensive neurite branching and cell soma
enlargement in the N1 cells, stimulates a biphasic activation of JNK. The first phase of activation is rapid and transient, beginning at 15 min after
NGF exposure and lasting approximately 45 min. The second phase of activation is sustained, beginning at 9–12 h of NGF treatment and lasting
for at least 24 h. Similar biphasic pattern of JNK activation is also observed in the parental PC12 cells. Using the specific JNK inhibitor SP600125,
we show that the biphasic activation is necessary for neurite outgrowth and branching, and that inhibition of either phase suppresses neuritogenesis
in the N1 cells. These results suggest that dynamic JNK activation may play a key role in neurite outgrowth during neuronal development.

PC-12细胞是一个常用的神经细胞株。

来源： Rattus norvegicus (褐家鼠) 肾上腺嗜铬细胞瘤（一种交感神经系统的肿瘤）
形态：多角型细胞 生长特性：贴壁较松，容易成团

注释：PC-12细胞株来源于一种可移植的鼠嗜铬细胞瘤，该细胞对神经生长因子（NGF）有可逆的神经元显形反应，该细胞不合成肾上腺素。

培养液：Ham's F12K （含2 mM L-谷氨酰胺，1.5 g/L NaHCO3）+15%马血清+2.5% 胎牛血清。

传代：吸去培养液。 加入新的培养液，用吸管吹下细胞或用手拍打培养瓶或刮下细胞到培养液中，用移液器把细胞吹散。 加适量的细胞到新的培养器皿中。（以1：4为宜，传代期间2-3天更换培养液）

冻存：95%培养液+5%DMSO冻存于液氮。

呃~~我是想知道N1是什么意思

呵呵..
We have previously shown that activated JNK is required for later stages of neuritogeneis induced by NGF in a variant PC12 cell line (N1).
已经说明N1特性,如果要查清具体细节,你可要查下We have previously shown 对应的文章,第一次发表中记载要清楚哦.