An ancient Turing-like patterning mechanism regulates skin denticle development in sharks

Area of Science:

• Developmental biology
• Evolutionary biology
• Mathematical modeling

Background:

• Vertebrate epithelial appendages like scales, feathers, and hair exhibit diverse patterns.
• Alan Turing's reaction-diffusion system is a theoretical model for pattern formation.
• The role of reaction-diffusion in early-diverging vertebrate lineages is understudied.

Purpose of the Study:

• To investigate the developmental patterning of shark skin denticles.
• To determine if a Turing-like mechanism explains shark denticle arrangement.
• To explore the evolutionary conservation of appendage patterning mechanisms.

Main Methods:

• Computational simulation models of reaction-diffusion systems.
• Gene expression analysis in developing shark denticles.
• Experimental gene pathway inhibition.

Main Results:

• Simulation models successfully replicated shark denticle patterning using a Turing-like mechanism.
• Gene expression patterns and pathway inhibition supported the involvement of this system.
• The shark denticle patterning mechanism showed strong similarities to avian feather patterning.

Conclusions:

• A conserved Turing-like reaction-diffusion system is proposed to pattern diverse vertebrate appendages.
• This ancient system likely predates tetrapods and is conserved across major vertebrate groups.
• Genetic modifications to this core system explain the variety of appendage forms.