Potentials and pitfalls of epigenetic editing in the gene specific re-expression of epigenetically silenced genes

PhD ceremony: Ms. M.L. de Groote, 14.30 uur, Academiegebouw, Broerstraat 5, Groningen

Dissertation: Potentials and pitfalls of epigenetic editing in the gene specific re-expression of epigenetically silenced genes

Promotor(s): prof. M.G. Rots

Faculty: Medical Sciences

During the research described in this thesis, a start was made with permanently altering gene expression through addition or removal of epigenetic modifications (Epigenetic Editing) to ultimately induce expression of epigenetically silenced genes such as tumor suppressor genes. To reach this goal, fusion proteins were used: gene-specific DNA binding domains fused to proteins that can add or remove epigenetic marks (epigenetic enzymes). A growing number of diseases, in addition to cancer, is associated with epigenetic changes. Epigenetic marks are inheritable modifications to the DNA or the histones that determine gene expression levels and because they are reversible, aberrant mistakes can be repaired. Moreover, as epigenetic marks are heritable, Epigenetic Editing is an interesting new therapeutic approach. Also, this way of gene expression regulation could lead to new fundamental insights. In this thesis, two tumor suppressor genes are described that are epigenetically silenced in cancer cells and to which epigenetic editing could be applied. Also, it is shown that specifically the expression of these genes can be regulated in the endogenous situation using zinc fingers fused to transcription regulating proteins. As a consequence, even a reduction in tumor cell growth was observed. Furthermore, upon targeting certain epigenetic enzymes to a predetermined site, an increased accessibility of the DNA was observed. Further research is needed to study which epigenetic enzyme(s) can be used for expression regulation of specific endogenous genes to achieve a lasting effect.