Left-right asymmetric expression of the Nodal-Lefty-Pitx2 module in developing turtle forebrain

Area of Science:

• Developmental Biology
• Neuroscience
• Evolutionary Biology

Background:

• Zebrafish epithalamus exhibits left-right (L-R) asymmetry, unlike tetrapods.
• Understanding brain L-R asymmetry evolution requires examining diverse vertebrate groups.

Purpose of the Study:

• To investigate the expression patterns of Nodal, Lefty, and Pitx2 in developing reptile brains.
• To explore the evolutionary diversity of brain L-R asymmetry in vertebrates.

Main Methods:

• Examined gene expression of Nodal, Lefty, and Pitx2 in turtle and gecko embryos.
• Assessed Nodal activity via phosphorylated Smad2/3 detection.
• Analyzed habenula asymmetry and Kctd12 expression in Chinese softshell turtles.

Main Results:

• Left-sided expression of Nodal, Lefty, and Pitx2 observed in developing turtle forebrains.
• Nodal activity detected on the left side of the neural epithelium in turtles.
• No L-R asymmetric gene expression found in the developing brains of Madagascar ground geckos.
• Conserved transcriptional enhancer (ASE) for Nodal, Lefty, and Pitx2 across reptiles.

Conclusions:

• Nodal, Lefty, and Pitx2 show potential for asymmetric expression in vertebrate developing brains.
• Brain L-R asymmetry expression varies significantly, even within reptiles.