miRNAs and their role in neural crest development

Ward, Nicole J. (2017) miRNAs and their role in neural crest development. Doctoral thesis, University of East Anglia.

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Abstract

The neural crest (NC) is a multipotent, migratory cell population that is unique to
vertebrate embryos and gives rise to many derivatives, such as the craniofacial
skeleton, sensory neurons and pigment cells. A complex gene regulatory network
underlies the process of NC formation, which involves the early induction of the
neural plate border (NPB), specification of the NC, migration of the NC away from
the neural tube along distinct pathways and differentiation into diverse cell types.
microRNAs (miRNAs) are a class of non-coding regulatory genes, which act posttranscriptionally
to regulate gene expression. They are of widespread
significance and have been implicated in many biological processes. Many
miRNAs have now been identified, however, as of yet, they have not been shown
to have any direct roles in early NC development. Using various molecular
techniques this study has placed specific miRNAs within the complex NC gene
network. These miRNAs are miR-196a and miR-219. SRNA sequencing of
induced Xenopus NC tissue generated a miRNA expression profile which in
combination with whole mount in situ hybridisation (WISH) revealed multiple
candidate miRNAs expressed in NC. Using knockdown (KD) experiments, the
depletion of miR-196a and miR-219 resulted in aberrant NC development
including abnormal craniofacial cartilage development. Using luciferase assays,
this study shows for the first time that miR-219 directly targets the transcription
factor Eya1 in vitro. This gene lies directly upstream of the NPB marker Pax3.
When miR-219 is knocked down, Pax3 expression is expanded across the
surface ectoderm of the embryo suggesting the miR-219 serves to inhibit the
Pax3 domain. To begin to understand the molecular mechanisms behind both
this phenotype and why the NC is lost, RNA sequencing on dissected NC tissue
was employed. Results from this sequencing data demonstrated that following
miR-219 KD the NPB and the placodes form whilst the NC is lost. This indicates
that miR-219 is playing a role in ensuring the correct specification of NC. In
comparison, following miR-196a KD the NPB development is impaired and
derivatives are lost (placode and NC). This implies miR-196a has an earlier role
in ensuring the correct induction of the NPB possibly through fine-tuning early
inducing signals such as BMP and Notch. Using the data presented in this study,
the first models of how specific miRNAs could function in NC development have
been formulated.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Katie Miller
Date Deposited: 12 Oct 2017 10:31
Last Modified: 12 Oct 2017 10:31
URI: https://ueaeprints.uea.ac.uk/id/eprint/65119
DOI:

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