Novel PSEN1 transcript variants

By combining the complete reference with transcriptomic data, the team identified novel transcript variants of PSEN1—the most common genetic cause of early-onset familial Alzheimer’s disease—that had been invisible in earlier, gapped assemblies . These new isoforms open a path to studying alternative splicing in neurodegeneration, though their functional significance requires further investigation .

PSEN1 is well-established as the most common causative gene for early-onset Alzheimer’s disease, with more than 300 mutations reported to date . Previous work had already generated genetically engineered marmosets carrying knock-in PSEN1 point mutations (C410Y or A426P) that recapitulate early emergence of Alzheimer’s-related biomarkers . The new T2T reference now provides the genomic foundation to study these and other variants with unprecedented accuracy.

Ribosomal DNA (rDNA) rearrangements

The complete genome revealed that marmosets freely exchange ribosomal DNA arrays between non-homologous chromosomes, a dynamic rearrangement pattern that was previously unobserved . The assembly also uncovered sex-specific rDNA distribution patterns that were impossible to detect without a gapless reference .

Scaling T2T sequencing toward individualized genomes

The marmoset genome is part of a package of studies showing that T2T assembly methods have advanced to the point where they are routinely applicable not only to human genomes but also to other species . The T2T Consortium has continued to drive down costs by refining wet-lab protocols and assembly algorithms, making complete genomes far cheaper to produce than during the original human T2T effort .

As lead author Prajna Hebbar noted, “Routine T2T genomics is making findings easier and more plausible,” and the automated pipeline could set the stage for an era in which each person’s complete genome sequence serves as their own unique medical reference at a fraction of today’s cost . This scalability is already evident in other work: the same consortium has produced haplotype-resolved reference genomes for six ape species, completely sequencing 215 gapless chromosomes telomere-to-telomere .

Broader implications for neurodegenerative disease research

The common marmoset has long been an important model organism for Alzheimer’s and Parkinson’s disease research, in part because many of the same genes involved in human cognitive decline are also present in marmosets . Past attempts to sequence the marmoset genome left many gaps, but the new gapless assembly now makes it possible to study these genes with high accuracy and detail, revealing unseen features that could lead to new insights into disease mechanisms and potential therapies .

Novel PSEN1 transcript variants

By combining the complete reference with transcriptomic data, the team identified novel transcript variants of PSEN1—the most common genetic cause of early-onset familial Alzheimer’s disease—that had been invisible in earlier, gapped assemblies . These new isoforms open a path to studying alternative splicing in neurodegeneration, though their functional significance requires further investigation .

PSEN1 is well-established as the most common causative gene for early-onset Alzheimer’s disease, with more than 300 mutations reported to date . Previous work had already generated genetically engineered marmosets carrying knock-in PSEN1 point mutations (C410Y or A426P) that recapitulate early emergence of Alzheimer’s-related biomarkers . The new T2T reference now provides the genomic foundation to study these and other variants with unprecedented accuracy.

Ribosomal DNA (rDNA) rearrangements

The complete genome revealed that marmosets freely exchange ribosomal DNA arrays between non-homologous chromosomes, a dynamic rearrangement pattern that was previously unobserved . The assembly also uncovered sex-specific rDNA distribution patterns that were impossible to detect without a gapless reference .

Scaling T2T sequencing toward individualized genomes

The marmoset genome is part of a package of studies showing that T2T assembly methods have advanced to the point where they are routinely applicable not only to human genomes but also to other species . The T2T Consortium has continued to drive down costs by refining wet-lab protocols and assembly algorithms, making complete genomes far cheaper to produce than during the original human T2T effort .

As lead author Prajna Hebbar noted, “Routine T2T genomics is making findings easier and more plausible,” and the automated pipeline could set the stage for an era in which each person’s complete genome sequence serves as their own unique medical reference at a fraction of today’s cost . This scalability is already evident in other work: the same consortium has produced haplotype-resolved reference genomes for six ape species, completely sequencing 215 gapless chromosomes telomere-to-telomere .

Broader implications for neurodegenerative disease research

The common marmoset has long been an important model organism for Alzheimer’s and Parkinson’s disease research, in part because many of the same genes involved in human cognitive decline are also present in marmosets . Past attempts to sequence the marmoset genome left many gaps, but the new gapless assembly now makes it possible to study these genes with high accuracy and detail, revealing unseen features that could lead to new insights into disease mechanisms and potential therapies .