Scuola Normale Superiore, Piazza dei Cavalieri 7, Pisa - Italy -

Laboratory of Biology BIO@SNS

teaching: Developmental Neurobiology 

Our research focuses on the molecular mechanisms spcifying distinct types of neurons during retinal and cortical development:

Cell cycle and cell fate in retinal development

A main task of nervous system development is the generation of the right cells in the right places at the right time. Cell cycle of neural progenitor plays a crucial role in establishing such a cell diversity (1). We have identified homeobox genes that maintain early retinal progenitors in a stem cell state (2), or address them toward specific differentiation types (3,4). Recently, we found that cell cycle progression and cell cycle lengthening of Xenopus retinal progenitors plays a crucial role in the translational control of three key homeobox genes, Xotx5b/crx, Xvsx1 and Xotx2, which specify the latest types of retinal neurons, photoreceptors bipolar and neurons (5). We found that the translation of the three genes is inhibited at early developmental stages and orderly released at later stages, due to the presence of specific cis-acting signals in their 3’ UTRs. Currently, we are functionally assaying a number of miRNAs that are good candidates to link cell cycle progression and the translational activation of the three genes during retinal development. By combining in vivo functional approaches and cell culture assays, large scale miRNAs screening and assays for their functional validation, we recently discovered a set of miRNAs that links the molecular machineries of cell cycle and neural cell fate (6-8).

A Xenopus retina section showing cells and optic nerve fibers labeled by RFP in vivo lipofection.

Mouse embryonic stem cells (mESCs) as tool to investigate cortical and retinal development in vitro

We recently established a method of in vitro mESC neuralization in minimal culture medium that allows to investigate the effects of growth factors and morphogens endogenously produced by ESCs on the types of neurons produced. We found that endogenous BMPs produced by mESC-derived neural progenitors inhibit an intrinsic program of forebrain differentiation (9). Interfeering with BMP, Wnt and Activin/nodal signaling allows to steer the identity of mESC-generated neural progenitor cells toward cortical or retinal cell identity. By manipulating morphogens and miRNAs of retinal and cortical development, ongoing projects in the lab aim to :
- obtain progenitor cell populations with retinal or cortical identity from either mouse or human pluripotent cell cultures;
- specify the identity of retinal or cortical progenitors toward distinct cell types.

mESC-derived neural progenitors (Musashi-positive red cells) and neurons (Beta-III-Tubulin-positive green cells) in a 14 days old cell culture.

Selected publications
  1. Cremisi, F., Philpott, A. & Ohnuma, S. Cell cycle and cell fate interactions in neural development. Curr Opin Neurobiol 13, 26-33 (2003).
  2. Casarosa, S. et al. Xrx1 controls proliferation and multipotency of retinal progenitors. Mol Cell Neurosci 22, 25-36. (2003).
  3. D'Autilia, S. et al. Cloning and developmental expression of the Xenopus homeobox gene Xvsx1. Dev Genes Evol 216, 829-834 (2006).
  4. Onorati, M. et al. A specific box switches the cell fate determining activity of XOTX2 and XOTX5b in the Xenopus retina. Neural Develop 2, 12 (2007).
  5. Decembrini, S., Andreazzoli, M., Vignali, R., Barsacchi, G. & Cremisi, F. Timing the generation of distinct retinal cells by homeobox proteins. PLoS Biol 4, e272 (2006).
  6. Decembrini S, Bressan D, Vignali R, Pitto L, Mariotti S, Rainaldi G, Wang X, Evangelista M, Barsacchi G, Cremisi F. MicroRNAs couple cell fate and developmental timing in retina. Proc Natl Acad Sci U SA. 106(50): 21179-84 (2009)
  7. Pitto L, Cremisi F. Timing neurogenesis by cell cycle? Cell Cycle 9(3): 434-5 (2010)
  8. Cremisi F. MicroRNAs and cell fate in cortical and retinal development. Front Cell Neurosci. 2013 Sep 3;7:141. eCollection 2013. Review
  9. Bertacchi M, Pandolfini L, Murenu E, Viegi A, Capsoni S, Cellerino A, Messina A, Casarosa S, Cremisi F. The positional identity of mouse ES cell-generated neurons is affected by BMP signaling. Cell Mol Life Sci. 2013 Mar;70(6):1095-111