# Frequency-Dependent Premature Differentiation of Pheochromocytoma Cells Exhibits Band-Pass Filter Behavior Correlation with Intracellular Enzyme Activation Kinetics

## TL;DR

This study shows how pheochromocytoma cells differentiate in response to periodic growth factor inputs, with enzyme activation patterns influencing the outcome.

## Contribution

The novel contribution is linking input frequency to enzyme activation kinetics using a model that predicts differentiation outcomes.

## Key findings

- Differentiation peaks at specific input frequencies for EGF and NGF.
- A model combining enzyme activation transfer functions qualitatively matches experimental results.
- The system exhibits band-pass filter behavior in response to input frequency.

## Abstract

Advances in microfluidics, optogenetics and electronics have enabled the study of dynamically controlled inputs on cellular fate. Here, we applied a microfluidic system to deliver periodic inputs of growth factors to pheochromocytoma cells and measured the extent of premature differentiation as a function of input frequency. Epidermal growth factor-triggered differentiation peaked at two cycles/hour, while nerve growth factor-triggered differentiation peaked at one cycle/hour. To interpret the results, we analyzed a published model that attributed pheochromocytoma cell differentiation to the linear combination of activated enzymes extracellular signal-regulated kinase (ERK), cAMP response element binding protein (CREB), protein kinase B (AKT) and c-Jun N-terminal kinase (JNK) at specific times after step input stimulation. Transfer functions for enzyme activation were derived from the published time-domain activation kinetics and these transfer functions were combined in a parallel architecture as a predictor of neurite outgrowth, as a function of input frequency. Qualitative agreement was observed between the model and the experiments.