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© 2014 by the authors. The last fifteen years have seen the identification of some of the mechanisms involved in anterior neural plate specification, patterning, and morphogenesis, which constitute the first stages in the formation of the forebrain. These studies have provided us with a glimpse into the molecular mechanisms that drive the development of an embryonic structure, and have resulted in the realization that cell segregation in the anterior neural plate is essential for the accurate progression of forebrain morphogenesis. This review summarizes the latest advances in our understanding of mechanisms of cell segregation during forebrain development, with and emphasis on the impact of this process on the morphogenesis of one of the anterior neural plate derivatives, the eyes. ; My research is funded by a National Project Grant of the Spanish Government (BFU2011-24701) and the EU (PCIG11-GA-2012-321788), and by an Institutional Grant from the Fundación Ramón Areces to the Centro de Biología Molecular Severo Ochoa ; We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI) ; Peer Reviewed

As animals develop, tissue bending contributes to shape the organs into complex three-dimensional structures. However, the architecture and packing of curved epithelia remains largely unknown. Here we show by means of mathematical modelling that cells in bent epithelia can undergo intercalations along the apico-basal axis. This phenomenon forces cells to have different neighbours in their basal and apical surfaces. As a consequence, epithelial cells adopt a novel shape that we term ¿scutoid¿. The detailed analysis of diverse tissues confirms that generation of apico-basal intercalations between cells is a common feature during morphogenesis. Using biophysical arguments, we propose that scutoids make possible the minimization of the tissue energy and stabilize three-dimensional packing. Hence, we conclude that scutoids are one of nature's solutions to achieve epithelial bending. Our findings pave the way to understand the three-dimensional organization of epithelial organs. ; Ministerio Español de Ciencia y Tecnología (grants numbers BFU2013-48988-C2-1-P and BFU2016-80797 to M.D.M.-B.). A.V.-E. is supported by a FPI studentship (BES-2014-068850) from the Ministerio de Economía y Competitividad. S.S. is supported by grant of the MICINN/FEDER to J.C.-G. Hombría (BFU2016-76528-P). F.C. work is funded by Spanish Government Grant BFU2014-55918 and BBVA Foundation Personal Grant IN[16]_BBM_BAS_0078. J.B. acknowledges core funding by Lehigh University. L.M.E. and P.G.-G. are supported by the Ramón y Cajal program (PI13/01347); L.M.E., A.M., and C.G. work is funded by the Ministry of Economy, Industry, and Competitiveness grant BFU2016-74975-P co-funded by FEDER funds. P.V.-M. is supported by a contract co-funded by the Asociación Fundación Española contra el Cáncer and the Seville University. A.M.C. is supported by Fundación Pública Andaluza Progreso y Salud (Consejería de Salud), ref. PI-0033-2014. C.F. and A.T. is supported by a contract from Sistema Nacional de Garantía Juvenil and Programa Operativo de Empleo Juvenil 2014–2020 ; Peer Reviewed

The earliest known determinants of retinal nasotemporal identity are the transcriptional regulators Foxg1, which is expressed in the prospective nasal optic vesicle, and Foxd1, which is expressed in the prospective temporal optic vesicle. Previous work has shown that, in zebrafish, Fgf signals from the dorsal forebrain and olfactory primordia are required to specify nasal identity in the dorsal, prospective nasal, optic vesicle. Here, we show that Hh signalling from the ventral forebrain is required for specification of temporal identity in the ventral optic vesicle and is sufficient to induce temporal character when activated in the prospective nasal retina. Consequently, the evaginating optic vesicles become partitioned into prospective nasal and temporal domains by the opposing actions of Fgfs and Shh emanating from dorsal and ventral domains of the forebrain primordium. In absence of Fgf activity, foxd1 expression is established irrespective of levels of Hh signalling, indicating that the role of Shh in promoting foxd1 expression is only required in the presence of Fgf activity. Once the spatially complementary expression of foxd1 and foxg1 is established, the boundary between expression domains is maintained by mutual repression between Foxd1 and Foxg1 ; the European Commission [CIG321788 to F.C.]; the Comunidad Autonoma de Madrid (CAM) [S2010/BMD-2315 to P.B.]; the Deutsche Forschungsgemeinschaft [SFB655-A3 to P.B.]; and the European Union (Zf-Health) [HEALTH-F4-2010-242048 to M.B and S.W.W.]. An institutional grant from the Fundación Ramón Areces ; Peer Reviewed