Journal article
Microchromosomes are building blocks of bird, reptile, and mammal chromosomes
National Academy of Sciences. Proceedings, Vol.118(45), pp.1-11
2021
PMCID: PMC8609325
PMID: 34725164
Abstract
Microchromosomes, once considered unimportant shreds of the chicken genome, are gene-rich elements with a high GC content and few transposable elements. Their origin has been debated for decades. We used cytological and whole-genome sequence comparisons, and chromosome conformation capture, to trace their origin and fate in genomes of reptiles, birds, and mammals. We find that microchromosomes as well as macrochromosomes are highly conserved across birds and share synteny with single small chromosomes of the chordate amphioxus, attesting to their origin as elements of an ancient animal genome. Turtles and squamates (snakes and lizards) share different subsets of ancestral microchromosomes, having independently lost microchromosomes by fusion with other microchromosomes or macrochromosomes. Patterns of fusions were quite different in different lineages. Cytological observations show that microchromosomes in all lineages are spatially separated into a central compartment at interphase and during mitosis and meiosis. This reflects higher interaction between microchromosomes than with macrochromosomes, as observed by chromosome conformation capture, and suggests some functional coherence. In highly rearranged genomes fused microchromosomes retain most ancestral characteristics, but these may erode over evolutionary time; surprisingly, de novo microchromosomes have rapidly adopted high interaction. Some chromosomes of early-branching monotreme mammals align to several bird microchromosomes, suggesting multiple microchromosome fusions in a mammalian ancestor. Subsequently, multiple rearrangements fueled the extraordinary karyotypic diversity of therian mammals. Thus, microchromosomes, far from being aberrant genetic elements, represent fundamental building blocks of amniote chromosomes, and it is mammals, rather than reptiles and birds, that are atypical.
Details
- Title
- Microchromosomes are building blocks of bird, reptile, and mammal chromosomes
- Authors
- Paul D Waters (Author) - UNSW AustraliaHardip R Patel (Author) - Australian National UniversityAurora Ruiz-Herrera (Author) - Universitat Autònoma de BarcelonaLucía Álvarez-González (Author) - Universitat Autònoma de BarcelonaNicholas C Lister (Author) - UNSW AustraliaOleg Simakov (Author) - University of ViennaTariq Ezaz (Author) - University of CanberraParwinder Kaur (Author) - The University of Western AustraliaCeline Frere (Author) - University of the Sunshine Coast, Queensland, School of Science, Technology and EngineeringFrank Grützner (Author) - The University of AdelaideArthur Georges (Author) - University of CanberraJennifer A. Marshall Graves (Author) - La Trobe University
- Publication details
- National Academy of Sciences. Proceedings, Vol.118(45), pp.1-11
- Publisher
- National Academy of Sciences
- Date published
- 2021
- DOI
- 10.1073/pnas.2112494118
- ISSN
- 1091-6490
- PMID
- 34725164; PMC8609325
- Organisation Unit
- University of the Sunshine Coast, Queensland; School of Science, Technology and Engineering
- Language
- English
- Record Identifier
- 99584807002621
- Output Type
- Journal article
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- Genetics & Heredity
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