Epigenetic origin of evolutionary novel centromeres

Area of Science:

• Genetics
• Epigenetics
• Evolutionary Biology

Background:

• Evolutionary new centromeres (ENCs) are typically complex structures with satellite DNA and segmental duplications.
• A prevailing hypothesis suggests ENCs originate epigenetically in anonymous DNA before acquiring centromeric features over time.
• Evidence to support this hypothesis has been limited.

Purpose of the Study:

• To investigate the initial formation and characteristics of an evolutionary new centromere (ENC).
• To test the hypothesis that ENCs are seeded epigenetically in non-complex DNA regions.

Main Methods:

• Genome sequencing of an orangutan homozygous for an identified ENC on chromosome 12.
• Comparative analysis of the ENC domain and its wild-type counterpart.
• Assessment of DNA sequence variation and chromatin compaction.

Main Results:

• No significant DNA sequence variations were found between the ENC and wild-type regions.
• The ENC domain exhibited significantly higher chromatin compaction compared to the wild-type region.
• The sole gene within the ENC region showed significantly repressed expression.

Conclusions:

• This study provides the first clear evidence that evolutionary new centromere (ENC) seeding is epigenetic in nature.
• ENCs can arise without underlying DNA sequence changes, initiating in anonymous DNA.
• Epigenetic modifications, such as increased compaction and gene repression, characterize early ENC formation.