Ttc21b is required to restrict sonic hedgehog activity in the developing mouse forebrain.

Area of Science:

• Developmental biology
• Neuroscience
• Cell biology

Background:

• Developing brains rely on organizing centers for patterning cues, such as Sonic hedgehog (Shh).
• Cilia play crucial roles in cellular signaling and development.
• Intraflagellar transport is essential for ciliary function.

Purpose of the Study:

• To characterize the forebrain phenotype resulting from Ttc21b gene loss.
• To investigate the role of Ttc21b in ciliary function and Shh signaling during brain development.
• To determine the impact of Ttc21b mutations on embryonic patterning.

Main Methods:

• Utilized ENU mutagenesis to identify novel ciliary genes.
• Generated and analyzed Ttc21b mutant embryos.
• Assessed Shh signaling levels using molecular markers.
• Examined Wnt signaling pathways.

Main Results:

• Ttc21b loss causes significant defects in limb, eye, and brain development.
• Elevated Shh signaling was observed in the rostral embryonic brain of Ttc21b mutants.
• Ciliary defects in Ttc21b mutants extend to the embryonic brain.
• Reducing Shh levels ameliorated the Ttc21b brain phenotype.
• Wnt signaling did not appear to contribute to the observed neurodevelopmental defects.

Conclusions:

• Ttc21b is a novel ciliary gene essential for proper forebrain patterning.
• Aberrant Shh signaling due to ciliary dysfunction is a key mechanism underlying the Ttc21b brain phenotype.
• Ciliary physiology is critical for embryonic brain development and Shh pathway regulation.