Abstract
The rat adrenal pheochromocytoma PC12 cell line is one of the traditional models for the study of neurite outgrowth and growth cone behavior. To clarify to what extent PC12 neurite terminals can be compared to neuronal growth cones, we have analyzed their morphology and protein distribution in fixed PC12 cells by immunocytochemistry. Our results show that that PC12 cells display a special kind of neurite terminal that includes a varicosity in close association with a growth cone. This hybrid terminal, or “varicone”, is characterized by the expression of specific markers not typically present in neuronal growth cones. For example, we show that calpain-2 is a specific marker of varicones and can be detected even before the neurite develops. Our data also shows that a fraction of PC12 neurites end in regular growth cones, which we have compared to hippocampal neurites as a control. We also report the extraordinary incidence of varicones in the literature referred to as “growth cones”. In summary, we provide evidence of two different kinds of neurite terminals in PC12 cells, including a PC12-specific terminal, which implies that care must be taken when using them as a model for neuronal growth cones or neurite outgrowth.
Highlights
The rat adrenal pheochromocytoma (PC12) cell line was originally derived in 1976 from a tumor arising from adrenal medulla chromaffin cells [1]
Using Differential Interference Contrast (DIC) microscopy, the presence of numerous big and elongated varicosities was very noticeable (Figure 1A–C, ‘‘v’’), as these appeared extraordinarily thick in comparison to the rest of the cell processes (Figure 1A–B, ‘‘gc’’)
Our results show that that PC12 cells display a special kind of neurite terminal that includes a varicosity in close association with a growth cone
Summary
The rat adrenal pheochromocytoma (PC12) cell line was originally derived in 1976 from a tumor arising from adrenal medulla chromaffin cells [1]. PC12 cells have become a very popular model for studying the signaling pathways of cell survival, proliferation and differentiation, resulting in the generation of a large amount of knowledge on these processes [2,3,4,5]. An interesting feature of PC12 cells, previously observed in their first description, is their capacity to grow neurite-like processes in response to nerve growth factor (NGF) [1]. Because PC12 cells can be passaged indefinitely and are much easier to culture and manipulate than their neuronal counterparts, they are a useful model for the study of neurite outgrowth. Differentiated PC12 cells, together with sympathetic and cortical neurons, are currently some of the most extensively used models for the study of neurite growth and growth cone function [8,9,10]. PC12 cells were used to describe the role of vinculin in mediating growth cone attachment to the substrate [8], and helped describe the crucial role of the Rho family of GTPases in neurite formation, outgrowth and retraction [11,12,13,14]
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