Evolutionary dynamics of germline-restricted chromosomes in songbirds

All cells within a multicellular organism are expected to contain the same genome because they originate from a single cell.

However, programmed DNA elimination can remove DNA during germline–soma differentiation, leading to dramatic germline–soma genome differences. Why this evolved remains mysterious due to lack of an evolutionary framework. However, a role in minimizing germline–soma genetic conflict has been suggested.

This conflict arises when gene expression is beneficial for the germline but deleterious for the soma.

This project will test whether programmed DNA elimination allows germline-specific expression of developmental genes to minimize germline–soma conflict.

Using the germline-restricted chromosome (GRC) of the zebra finch as a model, we recently pioneered high-throughput genomics of programmed DNA elimination.

Combining this with transcriptomics, proteomics, and cytogenetics will provide unprecedented insights into the evolution of germline–soma genome differences. First, we will generate a zebra finch GRC reference assembly with RNA and protein expression evidence. Second, we will test how the GRC is inherited and maintained in zebra finch populations.

Third, we will elucidate the long-term evolutionary history of GRCs across songbirds to reveal genes that are candidates for GRC function.

This evolutionary framework will significantly advance our understanding of germline–soma genome differences, a phenomenon likely widespread across the Tree of Life.