Centromere inactivation on a neo-Y fusion chromosome in threespine stickleback fish
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Having one and only one centromere per chromosome is essential for proper chromosome segregation during both mitosis and meiosis. Chromosomes containing two centromeres are known as dicentric and often mis-segregate during cell division, resulting in aneuploidy or chromosome breakage. Dicentric chromosome can be stabilized by centromere inactivation, a process which reestablishes monocentric chromosomes. However, little is known about this process in naturally occurring dicentric chromosomes. Using a combination of fluorescence in situ hybridization (FISH) and immunofluorescence combined with FISH (IF-FISH) on metaphase chromosome spreads, we demonstrate that centromere inactivation has evolved on a neo-Y chromosome fusion in the Japan Sea threespine stickleback fish (Gasterosteus nipponicus). We found that the centromere derived from the ancestral Y chromosome has been inactivated. Our data further suggest that there have been genetic changes to this centromere in the two million years since the formation of the neo-Y chromosome, but it remains unclear whether these genetic changes are a cause or consequence of centromere inactivation.
KeywordsDicentric chromosome fusion Centromere inactivation CENP-A ChIP-seq Gasterosteus aculeatus Gasterosteus nipponicus
Bacterial artificial chromosome
Centromere protein A
Chromatin immunoprecipitation sequencing
Fluorescence in situ hybridization
Threespine stickleback (Gasterosteus aculeatus) centromeric repeat sequence
Immunofluorescence combined with FISH
Phosphate-buffered saline Tween-20
We thank Kohta Yoshida for his initial observations, and the Peichel Lab, Sue Biggins, and Steve Henikoff for helpful discussions on this project and manuscript. We thank the Fred Hutchinson Cancer Research Center Genomics Shared Resource for the help with the ChIP-seq experiment and Ryan Basom for the help with data analysis. This research was supported by a National Science Foundation Graduate Research Fellowship (DGE-1256082), the National Institutes of Health Chromosome Metabolism and Cancer Training Grant (T32 CA009657), a National Institutes of Health grant (R01 GM116853), and the Fred Hutchinson Cancer Research Center.
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