Centromere Destiny in Dicentric Chromosomes: New Insights from the Evolution of Human Chromosome 2 Ancestral Centromeric Region.
Dicentric chromosomes are products of genomic rearrangements that place two centromeres on the same chromosome. Due to the presence of two primary constrictions, they are inherently unstable and overcome their instability by epigenetically inactivating and/or deleting one of the two centromeres, thus resulting in functionally monocentric chromosomes that segregate normally during cell division. Our understanding to date of dicentric chromosome formation, behavior and fate has been largely inferred from observational studies in plants and humans as well as artificially produced de novo dicentrics in yeast and in human cells. We investigate the most recent product of a chromosome fusion event fixed in the human lineage, human chromosome 2, whose stability was acquired by the suppression of one centromere, resulting in a unique difference in chromosome number between humans (46 chromosomes) and our most closely related ape relatives (48 chromosomes). Using molecular cytogenetics, sequencing, and comparative sequence data, we deeply characterize the relicts of the chromosome 2q ancestral centromere and its flanking regions, gaining insight into the ancestral organization that can be easily broadened to all acrocentric chromosome centromeres. Moreover, our analyses offered the opportunity to trace the evolutionary history of rDNA and satellite III sequences among great apes, thus suggesting a new hypothesis for the preferential inactivation of some human centromeres, including IIq. Our results suggest two possible centromere inactivation models to explain the evolutionarily stabilization of human chromosome 2 over the last 5-6 million years. Our results strongly favor centromere excision through a one-step process.
Department of Biology, University of Bari "Aldo Moro", Bari, Italy.|Department of Biology, Anthropology Laboratories University of Florence, Florence, Italy.
Giorgia
G
Chiatante
Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
Giuliana
G
Giannuzzi
Department of Biology, University of Bari "Aldo Moro", Bari, Italy.
Francesco Maria
FM
Calabrese
Department of Genome Sciences, University of Washington School of Medicine, Seattle, WA.|Howard Hughes Medical Institute, University of Washington, Seattle, WA.
Evan E
EE
Eichler
Department of Biology, University of Bari "Aldo Moro", Bari, Italy.
Mario
M
Ventura
D002503:Centromere / Q000235:genetics* / Q000502:physiology; D002889:Chromosomes, Human, Pair 2; D000072441:DNA, Ancient; D019143:Evolution, Molecular; D006801:Humans; D014178:Translocation, Genetic
D000072441:DNA, Ancient
centromere evolution and inactivation; dicentric chromosomal stability; satellite III and rDNA evolution