Differential developmental strategies by Sonic hedgehog in thalamus and hypothalamus

Publication date: Available online 12 December 2015 Source:Journal of Chemical Neuroanatomy Author(s): Yuanfeng Zhang, Gonzalo Alvarez-Bolado The traditional concept of diencephalon (thalamus plus hypothalamus) and with it the entire traditional subdivision of the developing neural tube are being challenged by novel insights obtained by mapping the expression of key developmental genes. A model in which the hypothalamus is placed in the most rostral portion of the neural tube, followed caudally by a diencephalon formed by prethalamus, thalamus and pretectum has been proposed. The adult thalamus and hypothalamus are quite unlike each other in connectivity and functions. Here we review work on the role of the secreted morphogen protein Sonic hedgehog (Shh) in the developing diencephalon and hypothalamic region to show how different these two regions are also from this point of view. Shh from the prechordal plate (PCP) induces and patterns the hypothalamus but there is no evidence that this role is fulfilled by a morphogen gradient. Later, the hypothalamic primordium itself expresses Shh and a large part of the hypothalamus belongs to the Shh lineage, including the ventral domains. Neural Shh is necessary to complete the specification (lateral hypothalamus), differentiation and growth of the hypothalamus. Although Gli2A is the major effector of Shh in this region, hypothalamic specification also depends on the suppression of Gli3R by Shh secreted by the PCP as well as th...
Source: Journal of Chemical Neuroanatomy - Category: Neuroscience Source Type: research