B chromosomes: from cytogenetics to systems biology

Area of Science:

• Genetics
• Molecular Biology
• Cytogenetics

Background:

• B chromosomes are accessory chromosomes found in various eukaryotes, historically considered genetically inert and parasitic.
• Their distribution is widespread, but a unified theory explaining their biological role remains elusive.

Purpose of the Study:

• To re-evaluate the biological role and characteristics of B chromosomes using modern high-throughput analyses.
• To investigate the gene content and regulatory functions of B chromosomes.

Main Methods:

• High-throughput DNA and RNA sequencing (omics analyses).
• Advanced molecular cytogenetic techniques.
• Analysis of gene transcription and modulation of autosomal gene activity.

Main Results:

• B chromosomes possess transcriptionally active sequences, including functional genes.
• B chromosomes can actively modulate the expression of autosomal genes.
• Omics data suggest B chromosomes influence cellular processes to ensure their own perpetuation.

Conclusions:

• The classical view of B chromosomes as non-functional repetitive DNA is outdated.
• B chromosomes play active roles in cell biology, potentially influencing host genome regulation.
• Their complex interactions may be key to their maintenance and evolutionary persistence.