Endogenous retrovirus K111 traces structural diversification of human acrocentric chromosomes across great-ape evolution

A preprint posted to bioRxiv reports the use of K111 — an endogenous retrovirus embedded within the short arms of human acrocentric chromosomes — as a sequence marker to track how nucleolar organiser regions (NORs) have evolved across great-ape lineages and within human populations.

The five pairs of human acrocentric chromosomes (13, 14, 15, 21, and 22) carry NOR-associated repeat domains on their short arms. These regions are notoriously difficult to sequence and assemble, and their evolutionary history has remained poorly resolved. The authors leveraged comparative and haplotype-resolved genome assemblies to show that K111-derived sequences have expanded specifically across human acrocentrics, with predominantly full-length ancestral forms giving way to extensive structural diversification — including recurrent sequence mosaicism — that varies across human populations and between parent and offspring.

The study addresses a long-standing gap in understanding how these structurally complex chromosome regions are transmitted and how they contribute to genome diversity. NORs are essential for ribosome biogenesis, and structural variation in these regions has been linked to human disease in other contexts, though the preprint does not report direct clinical associations.

The work draws on parent-offspring trio data to examine transmission patterns. It has not yet undergone peer review and is a preprint.