During tissues development multipotent progenitor cells establish tissue-specific
gene expression programmes, leading to differentiation into specialized cell types. It
has been previously shown that the transcription factor p63, a master regulator of skin
development, controls the expression of adhesion molecules and essential
cytoskeleton components. It has also been shown that p63 plays an important role in
establishing distinct three-dimensional conformations in the Epidermal Differentiation
Complex (EDC) locus (Fessing et al., 2011). Here we show that in p63-null mice about
32% of keratinocytes showed altered nuclear morphology. Alterations in the nuclear
shape were accompanied by decreased expression of nuclear lamins (Lamin A/C and
Lamin B1), proteins of the LINC complex (Sun-1, nesprin-2/3) and Plectin. Plectin links
components of the nuclear envelope (nesprin-3) with cytoskeleton and ChIP-qPCR
assay with adult epidermal keratinocytes showed p63 binding to the consensus binding
sequences on Plectin 1c, Sun-1 and Nesprin-3 promoters.
As a possible consequence of the altered expression of nuclear lamins and
nuclear envelope-associated proteins, changes in heterochromatin distribution as well
as decrease of the expression of several polycomb proteins (Ezh2, Ring1B, Cbx4) has
been observed in p63-null keratinocytes. Moreover, recent data in our lab have showed
that p63 directly regulates Cbx4, a component of the polycomb PRC1 complex.
Here we show that mice lacking Cbx4 displayed a skin phenotype, which partially
resembles the one observed in p63-null mice with reduced epidermal thickness and
keratinocyte proliferation.
All together these data demonstrate that p63-regulated gene expression program
in epidermal keratinocytes includes not only genes encoding adhesion molecules,
cytoskeleton proteins (cytokeratins) and chromatin remodelling factors (Satb1, Brg1),
but also polycomb proteins and components of the nuclear envelope, suggesting the
existence of a functional link between cytoskeleton, nuclear architecture and three
dimensional nuclear organization.
Other proteins important for proper epidermal development and stratification, are
cytokeratins. Here, we show that keratin genes play an essential role in spatial
organization of other lineage-specific genes in keratinocytes during epidermal
development. In fact, ablation of keratin type II locus from chromosome 15 in epidermal
keratinocytes led to changes in the genomic organization with increased distance
between the Loricrin gene located on chromosome 3 as well as between Satb1 gene
located on chromosome 17 and keratin type II locus, resulting in a more peripheral
localization of these genes in the nucleus. As a possible consequence of their
peripheral localization, reduced expression of Loricrin and Satb1 has also been
observed in keratins type II-deficient mice. These findings together with recent
circularized chromosome conformation capture (4C) data, strongly suggest that keratin
5, Loricrin and Satb1 are part of the same interactome, which is required for the proper
expression of these genes and proper epidermal development and epidermal barrier
formation.
Taken together these data suggest that higher order chromatin remodelling and
spatial organization of genes in the nucleus are important for the establishment of
lineage-specific differentiation programs in epidermal progenitor cells. These data
provide an important background for further analyses of nuclear architecture in the
alterations of epidermal differentiation, seen in pathological conditions, such as
psoriasis and epithelial skin cancers.
| Identifer | oai:union.ndltd.org:BRADFORD/oai:bradscholars.brad.ac.uk:10454/7164 |
| Date | January 2014 |
| Creators | Rapisarda, Valentina |
| Contributors | Botchkarev, Vladimir A., Fessing, Michael Y. |
| Publisher | University of Bradford, University of Bradford, Centre for Skin Sciences, Division of Biomedical Sciences, School of Life Sciences |
| Source Sets | Bradford Scholars |
| Language | English |
| Detected Language | English |
| Type | Thesis, doctoral, PhD |
| Rights | <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-nc-nd/3.0/88x31.png" /></a><br />The University of Bradford theses are licenced under a <a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative Commons Licence</a>. |
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