Birthdating of myenteric neuron subtypes in the small intestine of the mouse

Abstract

There are many different types of enteric neurons. Previous studies have identified the time at which some enteric neuron subtypes are born (exit the cell cycle) in the mouse, but the birthdates of some major enteric neuron subtypes are still incompletely characterized or unknown. We combined 5-ethynynl-2’-deoxyuridine (EdU) labeling with antibody markers that identify myenteric neuron subtypes to determine when neuron subtypes are born in the mouse small intestine. We found that different neurochemical classes of enteric neuron differed in their birthdates; serotonin neurons were born first with peak cell cycle exit at E11.5, followed by neurofilament-M neurons, calcitonin gene-related peptide neurons (peak cell cycle exit for both at E12.5-E13.5), tyrosine hydroxylase neurons (E15.5), nitric oxide synthase 1 (NOS1) neurons (E15.5) and calretinin neurons (P0). The vast majority of myenteric neurons had exited the cell cycle by P10. We did not observe any EdU+/NOS1+ myenteric neurons in the small intestine of adult mice following EdU injection at E10.5 or E11.5, which was unexpected as previous studies have shown that NOS1 neurons are present in E11.5 mice. Studies using the proliferation marker, Ki67, revealed that very few NOS1 neurons in the E11.5 and E12.5 gut were proliferating. However, Cre-lox-based genetic fate-mapping revealed a small sub-population of myenteric neurons that appears to express NOS1 only transiently. Together, our results confirm a relationship between enteric neuron subtype and birthdate, and suggest that some enteric neurons exhibit neurochemical phenotypes during development that are different from their mature phenotype.

Myenteric expression of nerve growth factor and the p75 neurotrophin receptor regulate axonal remodeling as a consequence of colonic inflammation in mice

“…Qualitatively, the densities of EGFP + and NOS1 + neurons (i.e., EGFP -) in the colons of NGF -/-pups were comparable to those seen in age-matched NGF +/+ and NGF +/-siblings (data not shown). No calretinin + myenteric neurons were seen in pups at this age, likely due to the fact that calretinin expression by murine myenteric neurons commences on the day of birth (Bergner et al, 2013). RT-PCR revealed comparable trkA mRNA levels in the colons of postnatal day 1-2 NGF +/+ , NGF +/-, and NGF -/-siblings (data not shown); these data show that trkA expression persists in the colon of postnatal mice in spite of a loss of A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT 11 NGF.…”

Appearance of cholinergic myenteric neurons during enteric nervous system development: comparison of different ChAT fluorescent mouse reporter lines

“…A recent study demonstrated that the birthdate of Hu+ neurons extends from E10.5 to P0 in the mouse SI (28). Subsequent to their birthdate it is thought that neurons acquire their neurotransmitter identity.…”

Emerging roles of gut microbiota and the immune system in the development of the enteric nervous system

“…Interestingly, this phenotype was reproduced in mice with ENSspecific deletion of the common TLR signal transducer MyD88 (111), suggesting that TLR4 signaling is a cell-autonomous requirement within ENS lineages. Since the vast majority of nNOS + enteric neurons are born during embryogenesis (18,19), these experiments indicate that TLR4 is either required for the late expression of the molecular profile of specific subsets of enteric neurons or for their survival within the microenvironment of the postnatal gut. In support of the latter idea, Anitha and colleagues showed that LPS promoted the survival of cultured enteric neurons in an NF-κB-dependent manner (111).…”

“…Nucleotide analog (such as BrdU) incorporation during embryogenesis in conjunction with marker analysis in adult mice has demonstrated that enteric neuron subtypes are generated during specific but overlapping periods of development. Thus, 5-HT + enteric neurons are among the first to be born during embryogenesis, while CGRP + neurons are generated mostly postnatally (18,19). Unlike many parts of the CNS, the period of enteric gliogenesis overlaps extensively with neurogenesis: it commences at around midgestation (when neurogenesis is at its peak) and starts to decline postnatally (17).…”