Enhancer redundancy provides phenotypic robustness in mammalian development.

Area of Science:

• Genomics
• Developmental Biology
• Molecular Biology

Background:

• Mammalian genomes contain numerous tissue-specific enhancers that regulate gene expression.
• The functional significance of this complex regulatory network, particularly enhancer redundancy, is not well understood.

Purpose of the Study:

• To investigate the functional importance of multiple enhancers with similar activities near the same gene.
• To determine if enhancer redundancy confers phenotypic robustness to loss-of-function mutations.

Main Methods:

• Utilized genome editing to create 23 mouse deletion lines targeting limb development enhancers.
• Performed single and combinatorial enhancer deletions.
• Integrated epigenomic and transcriptomic data from 29 mouse developmental tissues.

Main Results:

• Deletions of individual limb enhancers did not cause noticeable morphological changes.
• Removal of pairs of limb enhancers resulted in discernible limb phenotypes, indicating functional redundancy.
• Genes are commonly associated with multiple enhancers exhibiting similar spatiotemporal activity, providing a regulatory buffer.

Conclusions:

• Enhancer redundancy is a widespread feature in mammalian genomes.
• This redundancy provides phenotypic robustness by buffering against the loss of individual enhancers.
• Enhancer redundancy ensures normal gene expression and prevents deleterious phenotypic consequences during development.