The construction of organic electrochemical transistors (OECTs) using poly(3,4‐ethylenedioxythiophene):tosylate and polyallylamine hydrochloride composites as conducting channel material is presented. The regulation of the polyelectrolyte‐to‐conducting polymer proportion allows one to easily tune both electronic and ionic characteristics of the transistors, yielding devices with low threshold voltages while preserving high transconductance, which is an essential requisite for the effective integration of OECTs with biological systems. Also, the incorporation of the polyelectrolyte enhances the transient response of the OECTs during the ON/OFF switching, probably due to improved ion transport. Furthermore, the integration of pH‐sensitive amino moieties not only improves the pH response of the transistors but also allows for the non‐denaturing electrostatic anchoring of functional enzymes. As a proof‐of‐concept, acetylcholinesterase is electrostatically immobilized by taking advantage of the NH2 moieties, and the OECTs‐based sensors are able to successfully monitor the neurotransmitter acetylcholine in the range 5–125 µm.

Chromatin modifications are critical for the establishment and maintenance of differentiation programs. G9a, the enzyme responsible for histone H3 lysine 9 dimethylation in mammalian euchromatin, exists as two isoforms with differential inclusion of exon 10 (E10) through alternative splicing. We find that the G9a methyltransferase is required for differentiation of the mouse neuronal cell line N2a and that E10 inclusion increases during neuronal differentiation of cultured cells, as well as in the developing mouse brain. Although E10 inclusion greatly stimulates overall H3K9me2 levels, it does not affect G9a catalytic activity. Instead, E10 increases G9a nuclear localization. We show that the G9a E10(+) isoform is necessary for neuron differentiation and regulates the alternative splicing pattern of its own pre-mRNA, enhancing E10 inclusion. Overall, our findings indicate that by regulating its own alternative splicing, G9a promotes neuron differentiation and creates a positive feedback loop that reinforces cellular commitment to differentiation.