Sonic Hedgehog Signaling and Development of the Dentition

Abstract

Sonic hedgehog (Shh) is an essential signaling peptide required for normal embryonic development. It represents a highly-conserved marker of odontogenesis amongst the toothed vertebrates. Signal transduction is involved in early specification of the tooth-forming epithelium in the oral cavity, and, ultimately, in defining tooth number within the established dentition. Shh also promotes the morphogenetic movement of epithelial cells in the early tooth bud, and influences cell cycle regulation, morphogenesis, and differentiation in the tooth germ. More recently, Shh has been identified as a stem cell regulator in the continuously erupting incisors of mice. Here, we review contemporary data relating to the role of Shh in odontogenesis, focusing on tooth development in mammals and cartilaginous fishes. We also describe the multiple actions of this signaling protein at the cellular level.

Post-Turing tissue pattern formation: Advent of mechanochemistry

“…Results appeared to be numerically stationary after t ≈ 20 days (referring to the model-time; corresponding to about 85000 numerical time steps), which is a typical order of magnitude for developmental processes. Indeed, co-localisation of high morphogen levels and local tissue curvatures have been described in many organisms and developmental steps, from head formation events in the freshwater polyp Hydra [ 69 ] through tooth outgrowth in vertebrates [ 70 ] and shoot-meristem growth in the plant Arabidopsis [ 71 ]. Interestingly, for all three processes mentioned above, there are experimental evidences that mechanochemical interactions play an indispensable role during pattern formation [ 40 , 71 – 74 ].…”

The transition betweenCarcharocles chubutensisandCarcharocles megalodon(Otodontidae, Chondrichthyes): lateral cusplet loss through time

“…There is significant research indicating that tooth development in all vertebrates over the past 450 million years is linked to the sonic hedgehog (SHH) pathway (Smith et al, 2009;Maisey et al, 2013;Rasch et al, 2016). During the embryonic development of the catshark (Scyliorhinus), a superficial layer of epithelial cells makes up an odontogenic band from which teeth form (Smith et al, 2009;Rasch et al, 2016;Seppala et al, 2017). The SHH pathway and enamel knot dictate the position and shape of a tooth within this odontogenic band.…”

Hedgehog Signaling in Cancer: A Prospective Therapeutic Target for Eradicating Cancer Stem Cells

“…Of all the Hh ligands, SHH is the most studied ligand and acts as a cell–cell signaling factor, modulating cell fates through an autocrine or paracrine mechanism. During embryogenesis, SHH has been shown to be expressed in embryonic structures and involved in pattern formation in the embryo, including the development of the limb at the zone of polarizing activity (ZPA), notochord, or the floor plate of the neural tube [ 38 , 39 ] In addition, SHH is also expressed in the development of the lung [ 40 , 41 ], teeth [ 42 , 43 ], brain [ 44 ], hair follicle [ 45 ], pancreas [ 46 ], and intestine [ 47 ]. IHH is involved in the differentiation and cell fate decision of several specific tissues, including the differentiation of colonic epithelial cells [ 48 , 49 ] and the decision of neuroectodermal cell fate by activating the development of the earliest hemato-vascular system [ 50 ].…”