Naturally occurring, rostrally conjoining chicken twins attempt to make a forebrain

Area of Science:

• Developmental Biology
• Embryology
• Genetics

Background:

• Conjoined twinning is a rare complication of monozygotic, monoamniotic twinning with low survival rates.
• Chicken embryos provide a model to study conjoined twinning, often exhibiting fused heads and abnormal brains.
• The developmental timing of brain formation relative to fusion in conjoined twins remains unclear.

Purpose of the Study:

• To investigate the early brain development and gene expression in spontaneously occurring conjoined chicken twins.
• To determine if abnormal brain anatomy results from fusion or a failure of initial development.
• To establish a temporal framework for studying conjoined twin interactions and fusion mechanisms.

Main Methods:

• Collection and staging of conjoined and normal chicken embryos (HH4-HH13).
• Analysis of brain anatomy in twinned embryos.
• Gene expression analysis using markers for rostral epiblast (Otx2) and ventral forebrain (Six3).

Main Results:

• Normal brain anatomy and marker gene expression (Otx2, Six3) were observed up to embryonic stage HH9.
• By stages HH12-13, brain anatomy deteriorated, but marker gene expression persisted.
• This indicates an attempt at forebrain development in conjoined twins.

Conclusions:

• Chicken embryos with conjoined twins attempt to form a brain, including the forebrain, despite fusion.
• The study provides a timeline for investigating the mechanisms of conjoined twin fusion.
• Findings may contribute to understanding and managing risk factors for conjoined twinning in humans.