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xNgn2 induces expression of predominantly sensory neuron markers in Xenopus whole embryo ectoderm but induces mixed subtype expression in isolated ectoderm explants

Published version
Peer-reviewed

Type

Article

Change log

Authors

Hardwick, Laura 

Abstract

Proneural basic-helix-loop-helix (bHLH) proteins, such as Neurogenin2 (Ngn2) and Ascl1, are critical regulators at the onset of neuronal differentiation. Endogenously they have largely complementary expression patterns, and have conserved roles in the specification of distinct neuronal subtypes. In Xenopus embryos, xNgn2 is the master regulator of primary neurogenesis forming sensory, inter- and motor neurons within the neural plate, while xAscl1 is the master regulator of autonomic neurogenesis, forming noradrenergic neurons in the antero-ventral region of the embryo. Here we characterise neuronal subtype identity of neurons induced by xNgn2 in the ectoderm of whole Xenopus embryos in comparison with xAscl1, and in ectodermal “animal cap” explants. We find that the transcriptional cascades mediating primary and autonomic neuron formation are distinct, and while xNgn2 and xAscl1 can upregulate genes associated with a non-endogenous cascade, this expression is spatially restricted within the embryo. xNgn2 is more potent than xAscl1 at inducing primary neurogenesis as assayed by neural-β-tubulin. In ectoderm of the intact embryo, these induced primary neurons have sensory characteristics with no upregulation of motor neuron markers. In contrast, xNgn2 is able to up-regulate both sensory and motor neuron markers in naïve ectoderm of animal cap explants, suggesting a non-permissive environment for motor identity in the patterned ectoderm of the whole embryo.

Description

Keywords

StemCellInstitute, Neurogenin2, neurogenesis, Xenopus, bHLH, proneural, sensory, motor

Journal Title

Wellcome Open Research

Conference Name

Journal ISSN

2398-502X
2398-502X

Volume Title

3

Publisher

Wellcome Open Research
Sponsorship
Wellcome Trust (203151/Z/16/Z)
Medical Research Council (MC_PC_12009)
This work is supported by the Wellcome Trust [203151] (AP). LH has been supported by an MRC Doctoral Training Award and Peterhouse Research Fellowship.