Functional analysis of Prdm14 during Xenopus embryogenesis
by Rolf Patrick Berndt
Date of Examination:2015-06-29
Date of issue:2016-06-23
Advisor:Dr. Kristine Henningfeld
Referee:Prof. Dr. Gregor Bucher
Referee:Prof. Dr. Andreas Wodarz
Persistent Address:
http://dx.doi.org/10.53846/goediss-5704
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Abstract
English
Prdm14 is a member of the conserved family of Prdm proteins, which are emerging as crucial regulators of multiple early developmental processes and diseases. Members of the Prdm family are characterized by the presence of a single PR domain and a variable number of DNA-binding zinc fingers. Most members of the Prdm proteins directly influence transcription through intrinsic histone methyltransferase activity or recruitment of cofactors. In this thesis, a functional analysis of Prdm14 was undertaken to elucidate its role during early vertebrate development using the X. laevis model system. Prdm14 is expressed during gastrulation in the prospective neuroectoderm. At late neural plate stages, the expression is restricted to the territories of primary neurogenesis. In tailbud stage embryos, expression of prdm14 is detected in postmitotic neurons of the central nervous system and a subset of the cranial ganglia. Prdm14 is regulated positively by the proneural bHLH gene neurog2 and negatively by the Notch signaling pathway, which is strongly suggestive for a role during primary neurogenesis. Overexpression of prdm14 in X. laevis embryos promotes the proliferation of neural progenitor cells, which results in the expansion of the neural plate and in a transient inhibition of neuronal differentiation. In tailbud stage embryos, prdm14 overexpression induces the formation of ectopic neurons in the non-neural ectoderm that express markers indicative of a sensory glutamatergic neuronal cell fate. In pluripotent animal cap cells, prdm14 overexpression is sufficient to induce a glutamatergic neuronal cell fate supporting the studies in embryos. The downstream transcriptional network induced by prdm14 was studied through RNA-sequencing analysis of prdm14-injected animal caps at the equivalent of neural plate and tailbud stage. Predominant among the prdm14- upregulated genes were ligands and signaling components of the Wnt pathway and Wnt-regulated genes. Consistent with the RNA-sequencing analysis, prdm14 overexpression in the embryo activated a canonical Wnt-signaling reporter. In addition, many of the upregulated genes have previously been shown to be involved in neural crest and sensory neuron specification, including the key neural plate border specifiers pax3 and zic1. The activation of these genes may in part be attributed to the ability of prdm14 to activate canonical Wnt-signaling. Taken together, the results of this thesis provide evidence for multiple roles of Prdm14 during the development of the nervous system. During gastrulation Prdm14 promotes maintenance of the neural ectoderm and the specification of the neural plate border, which will give rise to neural crest and Rohon-Beard sensory neurons. Also suggested by the expression and regulation of prdm14, is a role during neuronal differentiation and maturation.
Keywords: Xenopus; Prdm14
