GSE111307
Neuronal Development And The Onset Of Electrical Activity In The Human Enteric Nervous System
Objective: To assess the development of neuronal subtypes and the emergence of evoked electrical activity within the developing human ENS. Methods: Human foetal gut samples were obtaining via the MRC-Wellcome Trust Human Developmental Biology Resource (UK). Characterisation of the developing ENS was performed by immunohistochemistry, calcium imaging, RNAseq and qRT-PCR Results: Human foetal colon samples displayed robust Tuj1 immunohistochemistry by embryonic week (EW) 12 with a dense neuronal network at the level of the myenteric plexus. At EW12 expression of excitatory neurotransmitter markers (VAChT and Sub P) was observed. By contrast, inhibitory neurotransmitter markers (nNOS and VIP) were not observed until EW14. Co-labeling with synaptic markers (SYN1/SNAP-25) demonstrated the development of synaptic contacts by EW12. However, electrical train stimulation (40V,2s,20Hz of 300?s electrical pulses) did not evoke activity within the myenteric plexus of EW12 foetal gut (n=0/3). Similarly, the majority of EW14 gut tissues assessed (80%), demonstrated no response to electrical stimulation (n=4/5). Interestingly, at EW16 Tuj1+ expression, in the myenteric plexus, was observed within discrete ganglia and was combined with the emergence of calcium transients (F/F0=1.273±0.024;n=3), upon electrical stimulation (n=3/3), which were abolished after the addition of 1uM TTX (n=3/3). RNAseq and qRT-PCR analysis between EW12-16 revealed increases in expression in genes involved in neurotransmission and action potential generation including SCN9A and KCNQ3. Conclusion: Here we demonstrate the temporal development of human enteric neuronal subtypes from EW12-14 and the subsequent emergence of coordinated electrical activity within the human foetal ENS at approximately EW16. Overall design: total RNA was isolated from three human embryonic colon samples. Three technical replicates/timepoint were sequenced.