Sonic hedgehog in vertebrate neural tube development

Abstract

The formation and wiring of the vertebrate nervous system involves the spatially and temporally ordered production of diverse neuronal and glial subtypes that are molecularly and functionally distinct. The chick embryo has been the experimental model of choice for many of the studies that have led to our current understanding of this process, and has presaged and informed a wide range of complementary genetic studies, in particular in the mouse. The versatility and tractability of chick embryos means that it remains an important model system for many investigators in the field. Here we will focus on the role of Sonic hedgehog (Shh) signaling in coordinating the diversification, patterning, growth and differentiation of the vertebrate nervous system. We highlight how studies in chick led to the identification of the role Shh plays in the developing neural tube and how subsequent work, including studies in the chick and the mouse revealed details of the cell intrinsic programs controlling cell fate determination. We compare these mechanisms at different rostral-caudal positions along the neuraxis and discuss the particular experimental attributes of the chick that facilitated this work.

Myosin 10 and a Cytoneme-Localized Ligand Complex Promote Morphogen Transport

“…Induction of these genes is exquisitely sensitive to alteration of SHH signaling, so monitoring their expression allows for robust analysis of gradient function (32,33). Examination of wild type and Myo10 m1J/m1J neural tubes revealed normal floorplate specification in Myo10 mutants, as evidenced by similar FoxA2 expression domains between the two genotypes ( Figure 3G, G').…”

ARL13B regulates Sonic Hedgehog signaling from outside primary cilia

“…Initially discovered in Drosophila where there is a single Hh ligand, (Ci in Drosophila) that act as both activators (GliA) and repressors (GliR) to control 18 target gene transcription (Briscoe et al 2013). There are three Hh ligands in 19 vertebrates, Sonic (Shh), Indian (Ihh) and Desert (Dhh), that regulate a multitude of 20 developmental processes including formation of the limbs and digits, the bones of the 21 skull and face, and the patterning of the neural tube (Placzek et al 2018). Diminished 22…”

Positional Information—A concept underpinning our understanding of developmental biology

“…Subsequently gradients of secreted extracellular morphogens were found to pattern the embryonic dorsoventral axis, the anteroposterior axis of the segments and the imaginal discs in Drosophila . In vertebrates, gradients of secreted morphogens pattern not only the digits of the limb but also, for example, the germ layers and the dorsoventral axis of the neural tube (reviewed in References and ). Furthermore, as predicted by the concept of positional information, the same morphogen molecule can be used repeatedly in development and in different animals without dictating a specific cell fate.…”