Zebrafish zic2a patterns the forebrain through modulation of Hedgehog-activated gene expression

Area of Science:

• Developmental Biology
• Genetics
• Neuroscience

Background:

• Holoprosencephaly (HPE) is a common congenital forebrain malformation.
• Mutations in genes like Sonic hedgehog (Shh), Six3, and Zic2 cause HPE.
• The interaction between Zic2 and the Shh/Six3 pathway in forebrain development is not fully understood.

Purpose of the Study:

• To investigate the role of Zic2a in regulating Shh signaling during zebrafish forebrain development.
• To determine if Zic2a interacts with Six3b and Shh signaling in the developing eye structures.
• To elucidate the function of Zic2a in the gene regulatory network underlying HPE.

Main Methods:

• Utilized zebrafish as a model organism.
• Analyzed gene expression patterns using in situ hybridization.
• Performed gene knockdown and rescue experiments to assess functional roles.
• Investigated the effects of manipulating Shh signaling pathways.

Main Results:

• Confirmed that Hh signaling activates six3b and zic2a transcription in the zebrafish forebrain.
• Demonstrated that Zic2a non-cell-autonomously represses six3b, essential for prethalamus formation.
• Showed that Zic2a limits Hh targets (pax2a, fgf8a) in the optic stalk and retina.
• Rescue experiments indicated Zic2a acts by attenuating Hh signaling.

Conclusions:

• Zic2a acts as a novel modulator of Hh-activated gene expression in the developing forebrain.
• Zic2a plays a critical role in patterning the prethalamus, optic stalk, and retina.
• These findings advance the understanding of the gene regulatory network disrupted in HPE.