Scientists have produced the first complete, end-to-end genome sequence of the common marmoset, creating a high-resolution genetic reference for one of the world’s most important emerging primate models of human disease. The work, led by researchers at the University of California, Santa Cruz Genomics Institute as part of the international Telomere-to-Telomere Consortium, reveals previously inaccessible regions of the marmoset genome and identifies genetic variation relevant to Alzheimer’s disease, immune disorders, and primate evolution. The study was published in Cell on August 6, 2026.
Common marmosets are small New World monkeys native to South America. Their relatively close evolutionary relationship to humans, compact size, and susceptibility to age-related memory decline have made them increasingly valuable in biomedical research. Unlike mice, marmosets share more aspects of primate biology with humans, including features of brain development, aging, immune function, and social behavior. Yet researchers have been working with an incomplete genetic map. The first marmoset reference genome, released in 2014, contained gaps, inaccuracies, and unresolved repetitive sequences that limited the ability to detect important genetic differences between animals.
A reference genome is a standardized representation of a species’ DNA against which individual genomes can be compared. When the reference is incomplete, genetic variants may be missed or incorrectly classified, particularly in repetitive and structurally complex regions. The new sequence applies the Telomere-to-Telomere approach, which aims to reconstruct chromosomes continuously from one end, or telomere, to the other. Advances in long-read DNA sequencing, highly accurate sequencing technologies, and computational assembly algorithms allowed the researchers to resolve regions that conventional methods had previously left fragmented or ambiguous.
“Routine T2T genomics is making findings easier and more plausible, as we’re able to much more easily access these complex regions,” said Prajna Hebbar, a UC Santa Cruz Biomolecular Engineering and Bioinformatics Ph.D. student who led the effort with Professor Benedict Paten. The new marmoset genome is part of a broader wave of Telomere-to-Telomere studies demonstrating that complete genome assembly is becoming practical across species, rather than remaining a landmark achievement limited to humans. The consortium produced the first complete human genome sequence in 2022.
Using the new reference, the team examined genetic variation across 230 marmosets. The analysis found differences in numerous genes associated with Alzheimer’s disease in humans, as well as genes involved in immune defense. The researchers also focused on a set of genes linked to Alzheimer’s, Parkinson’s disease, and related neurodegenerative conditions. They generated high-quality reference sequences for 76 corresponding marmoset gene copies, giving researchers a more reliable foundation for studying how specific variants influence brain health and disease risk.
The genome also revealed previously undescribed forms of several genes when the researchers combined the reference sequence with transcriptomic data. Transcriptomics measures RNA molecules produced by cells and tissues, offering a snapshot of which genes are active and which are silent. Among the genes showing newly identified forms was PSEN1, a gene whose mutations are the most frequent known cause of early-onset familial Alzheimer’s disease. The discovery does not yet establish whether the newly observed forms alter disease susceptibility or progression, but it opens a path for experiments that would have been difficult or impossible with the older reference genome.
Another major result concerns the Major Histocompatibility Complex, or MHC, a dense group of genes that helps the immune system distinguish the body’s own cells from foreign organisms. Variation within the MHC influences susceptibility to autoimmune diseases such as type 1 diabetes, multiple sclerosis, and rheumatoid arthritis, as well as responses to infection and transplantation. The researchers produced a complete record of the marmoset MHC region and annotated several complex genes that had not previously been catalogued. This information could improve the design and interpretation of studies using marmosets to investigate immune-related disease.
The complete sequence further uncovered unusual patterns in ribosomal DNA, or rDNA. These repeated DNA arrays encode essential components of ribosomes, the molecular machines that build proteins. In marmosets, entire rDNA arrays appear to move between chromosomes more freely than expected, with individual chromosomes gaining or losing copies. The researchers also detected differences between males and females in the distribution of these sequences, a pattern previously reported in orangutans and gibbons. Because ribosomal DNA is central to cellular protein production, these findings may offer new clues about chromosome organization and genome stability.
The study also provides a clearer view of centromeres, specialized chromosome regions required for accurate chromosome separation during cell division. Centromeres are often composed of highly repetitive DNA and have historically been among the most difficult portions of genomes to assemble. Their structure can affect chromosome behavior, fertility, development, and disease. By resolving these regions in the marmoset, the new reference gives researchers an opportunity to investigate how primate chromosomes are maintained and how genomic changes accumulate over evolutionary time.
The researchers say the resource will allow scientists to move beyond technical limitations and examine the biology of complex genomic regions directly. The work was conducted by collaborators from UC Santa Cruz, the Jackson Laboratory, the University of Pittsburgh, the University of Washington, Oregon Health & Science University, the Stowers Institute for Medical Research, and the German Primate Center, with support from the U.S. National Institutes of Health. As complete genome sequencing becomes faster and less expensive, the same methods could eventually support personalized genomics, in which an individual’s fully resolved genome serves as the reference for medical care. For now, the marmoset genome offers researchers a substantially more accurate foundation for studying primate evolution, immune biology, aging, and neurodegenerative disease.
Subject of Research: The complete genome sequence of the common marmoset and its applications in disease research, comparative genomics, and primate biology.
Article Title: A Complete Genome for the Common Marmoset
News Publication Date: 6-Aug-2026
Web References: https://doi.org/10.1016/j.cell.2026.07.017
References: Cell, DOI: 10.1016/j.cell.2026.07.017
Image Credits: Carolyn Lagattuta/UC Santa Cruz
Keywords: common marmoset, complete genome, Telomere-to-Telomere, genomics, Alzheimer’s disease, neurodegeneration, MHC, ribosomal DNA, centromeres, primate research, personalized genomics
