Topologically associating domain boundaries are required for normal genome function.

Area of Science:

• Genomics
• Developmental Biology
• Epigenetics

Background:

• Topologically associating domains (TADs) are fundamental units of genome organization, partitioning the genome into regulatory territories.
• Disruption of TAD boundaries is anecdotally linked to gene expression changes and disease, but the extent is largely unknown.

Purpose of the Study:

• To investigate the in vivo consequences of targeted TAD boundary deletions on genome function and organismal development.
• To determine the functional importance of TAD boundary sequences in maintaining genome architecture and gene regulation.

Main Methods:

• Utilized CRISPR genome editing in mice to delete eight distinct TAD boundaries (11-80 kb).
• Assessed molecular phenotypes including chromatin interactions and gene expression.
• Evaluated organismal phenotypes such as viability and anatomical development.

Main Results:

• All eight deleted TAD boundaries resulted in detectable molecular or organismal phenotypes.
• Altered 3D chromatin architecture was observed in 88% of cases, including TAD merging.
• Boundary deletions caused developmental defects in 63% of cases, including embryonic lethality and anatomical malformations (e.g., lung defects).

Conclusions:

• TAD boundary sequences are essential for maintaining in vivo genome function and normal development.
• Targeted deletion of TAD boundaries can lead to significant molecular and organismal disruptions.
• Clinical consideration of noncoding deletions affecting TAD boundaries is crucial for genetic screening and understanding disease pathogenicity.