Francesco Blasi
Francesco Blasi
affiliation: IFOM-FIRC Institute of Molecular Oncology
research area(s): Cancer Biology, Cell Biology
Course: Molecular Medicine: Molecular Oncology and Computational Biology
University/Istitution: Università di Milano, UNIMI-SEMM
Prep1 is an homeodomain transcription factor, essential in various steps of embryonic development and adult life. Prep1 acts by dimerizing with Pbx proteins, which allows its nuclear localization and DNA binding. Prep1 hypomorphic mice (Prep1i) develop spontaneous tumors and Prep1 haploinsufficiency accelerates the insurgence of tumors, i.e. Prep1 acts as a tumor suppressor. For this reason we are analyzing cohorts of breast cancer patients to determine the level of Prep1 expression and the mechanisms inducing its down regulation in human tumors. Prep1 hypomorphic embryos have a major deficiency in Hematopoietic Stem Cells (HSC). We have identified genes that are differentially expressed in HSCs of the Prep1i mice, and on this basis are analyzing signaling pathways affecting HSC asymmetric cell division.

A minority of the Prep1i mice are born and live a normal length life. In addition to developing tumors, we have found a phenotype also in the mammary gland which may be due to deficiencies in mammary stem cells. Unlike Prep1-hypomorphic, Prep1-null embryos die before gastrulation because the epiblast cells go into p53-dependent apoptosis. Therefore we are interested in determining the molecular basis for the apoptosis phenotype, whether it is possibly caused by accumulation of DNA damage due to aberrant chromatin modifications, and to determine the molecular basis. This interest is being pursued in both mice (crosses with mice Ko for important signaling pathways) as well as in cells, HSC, embryonic fibroblasts and Embryonic Stem cells (ES).

Meis1 is a Prep1 family member that, like Prep1, binds Pbx forming a DNA-binding complex and sharing with Prep1 three homologous domain, including the DNA-binding and the Pbx-interacting domains. Importantly, Meis1 is an oncogene, i.e. has a function opposite to Prep1. Interestingly, both Meis1-null and Prep1 hypomorphic embryos have a very similar phenotype, in particular hematopoietic stem cells (HSC) deficiency. However, double heterozygous Prep1-Meis1 mice are perfectly normal, indicating that despite, their phenotype similarity, Prep1 and Meis1 affect different, but essential, pathways in HSCs.

We are also interested in identifying the genes that are regulated by Prep1 on a global basis. We have already obtained data by chromatin immunoprecipitation using a mouse promoters array and are now completing the study by ChIP-Seq. In parallel, we are doing the same experiment with Meis1, the Prep1 homologue. This will lead to an analysis of why two proteins, having homologous DNA binding and identical Pbx-interacting domains, can affect transcription of different genes.
1)Penkov D, Palazzolo M, Mondino A, Blasi F.
Cytosolic sequestration of Prep1 influences early stages of T cell development.
PLoS ONE. 2008, Jun 18;3(6); e2424.

2)Cortese K, Sahores M, Madsen CD, Tacchetti C, Blasi F.
Clathrin and LRP-1-independent constitutive endocytosis and recycling of uPAR.
PLoS ONE. 2008, 3(11); e3730. NO IF

3)D’Alessio, S., Gerasi, L. and Blasi, F.
The urokinase receptor (uPAR) Ko mice keratinocytes fail to produce EGF-receptor-dependent Laminin-5 affecting migration in vitro and in vivo.
2008. J Cell Sci 121, 3922-3932.

4)F. Oriente, L.C. Fernandez Diaz, C. Miele, S. Iovino, S. Mori, V. E. Diaz, G. Troncone, A. Cassese, P. Formisano, F. Blasi, F. Beguinot.
Prep1 deficiency induces protection from diabetes and increased insulin sensitivity through a p160a-mediated mechanism.
2008. Mol Cell Biol 28, 5634–5645.

5)Matafora, V, D’Amato, A, Mori, S, Blasi, F & Bachi, A.
Proteomic analysis of nucleolar SUMO-1 target proteins upon proteasome inhibition.
In press, Mol.Cell. Proteomics (2009), 8.10, 2243-2255.

6)Blasi, F, Sidenius, N.
Efferocytosis: another function of uPAR.
Blood. 14(4):752-7533 (2009)

7)Ferrai, C., Naum-Ongania, G., Palazzolo, M., Longobardi, E., Disanza, A., Diaz, V.M., Crippa, M.P., Scita, G. and Blasi, F.
Induction of HoxB transcription by retinoic acid requires actin polymerization.
Mol Biol Cell, 20, 3525-3533m, 2009.

8)Villaescusa, JC, Buratti, C, Penkov, D, Mathiasen, L, Planagumà, J, Ferretti, E and Blasi, F.
Cytoplasmic Prep1 interacts with 4EHP inhibiting HoxB4 translation.
PLOS One (2009). 4:e5213. Epub 2009 Apr 13

9)Tjwa, M, Sidenius, N, Moura, R, Jansen, S, Theunissen, K, Moons, L, Andolfo, A, De Mol, M, Dewerchin, M, Blasi, F, Verfaillie, C & Carmeliet, P.
Membrane-anchored uPAR regulates the proliferation, marrow pool size, engraftment and mobilization of hematopoietic stem/progenitor cells.
J. Clin. Invest. 2009. 119, 1008-1018.

10)Micali, N. Ferrai, C., Fernandez Diaz, L.C., Blasi, F and Crippa, M.P.
Prep1 regulates the intrinsic apoptotic pathway by directly controlling Bcl-XL expression. MCB. 29, 1143-1151. (2009)

11)Iotti G, Longobardi E, Masella S, Dardaei L, De Santis F, Micali N, Blasi F.
Homeodomain transcription factor and tumor suppressor Prep1 is required to maintain genomic stability. Proc Natl Acad Sci U S A. 2011 Jun 29.

12)Blasi F
The Urokinase Receptor in Hematopoietic Stem Cells Mobilization.Curr Pharm Des. 2011 Jun 27.

13)Fernandez-Diaz LC, Laurent A, Girasoli S, Turco M, Longobardi E, Iotti G, Jenkins NA, Fiorenza MT, Copeland NG, Blasi F.
The absence of Prep1 causes p53-dependent apoptosis of mouse pluripotent epiblast cells
Development. 2010 Oct;137(20):3393-403.

14)Blasi F, Sidenius N.
The urokinase receptor: focused cell surface proteolysis, cell adhesion and signaling. FEBS Lett. 2010 May 3;584(9):1923-30.
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