FUNCTIONAL ELUCIDATION OF PRDM15 IN DEVELOPMENT AND DISEASE

PRDM15 is a member of the PRDM (PRD-BF1 and RIZ homology domain containing) family that originated in metazoans and consists of 16 proteins in mouse and 17 in humans. These proteins have a very similar structure as they all present a N-terminal PR-domain with putative histone methyl transferase activity and a set of classical C2H2 DNA-binding zinc fingers spanning towards the C-terminus of the protein. The functional elucidation of PRDM15 is still limited to mESCs where it has been shown that PRDM15 controls naïve pluripotency by directly regulating key components of the WNT/-catenin and MAPK/ERK signaling pathways as Rspo1 and Spry1 expression. In my thesis project I have expanded the current knowledge of Prdm15 function in mouse by modeling PRDM15 mouse-C842Y/human-C844Y point mutation causative of a syndromic form of Holoprosencephaly known as Galloway Mowat Syndrome by generating a CRISPR-Cas9 mediated knock-in mESCs and demonstrating that this mutation is a Loss of Function mutation. Moreover, PRDM15 has been studied in a Prdm15F/F;CreER;EµMyc Mouse Model, which is a tamoxifen inducible Prdm15 KO in the genetic background of the Eµ-Myc mouse model. This study has shown that PRDM15 promotes transcription of key regulators of cancer metabolism such as Igf1R and InsR, upstream activators of the PI3K/AKT/mTOR pathway. Hence, protein level analyses in the steady state, under stimulation with IGF1 and Insulin, after treatment with linsitinib and everolimus, and in InsR Binding Site CRISPR/Cas9 mutants have shown that Prdm15 regulates a transcriptional program that sustains the activity of the PI3K/AKT/mTOR pathway and glycolysis in B-cell lymphomas. All these experiments clearly provide a small, but significative advancement in the understanding of PRDM15 in development and disease.