Abstract
The typical vertebrate centromeres contain long stretches of highly repeated DNA sequences (satellite DNA). We previously demonstrated that the karyotypes of the species belonging to the genus Equus are characterized by the presence of satellite-free and satellite-based centromeres and represent a unique biological model for the study of centromere organization and behavior. Using horse primary fibroblasts cultured in vitro, we compared the segregation fidelity of chromosome 11, whose centromere is satellite-free, with that of chromosome 13, which has similar size and a centromere containing long stretches of satellite DNA. The mitotic stability of the two chromosomes was compared under normal conditions and under mitotic stress induced by the spindle inhibitor, nocodazole. Two independent molecular-cytogenetic approaches were used—the interphase aneuploidy analysis and the cytokinesis-block micronucleus assay. Both assays were coupled to fluorescence in situ hybridization with chromosome specific probes in order to identify chromosome 11 and chromosome 13, respectively. In addition, we tested if the lack of centromeric satellite DNA affected chromatid cohesion under normal and stress conditions. We demonstrated that, in our system, the segregation fidelity of a chromosome is not influenced by the presence of long stretches of tandem repeats at its centromere. To our knowledge, the present study is the first analysis of the mitotic behavior of a natural satellite-free centromere.
Highlights
IntroductionThe centromere is a locus essential for chromosome segregation and genome integrity; this function is carried out by supporting kinetochore assembly and attachment to spindle microtubules
The centromere is a locus essential for chromosome segregation and genome integrity; this function is carried out by supporting kinetochore assembly and attachment to spindle microtubules.Most vertebrate centromeres are composed of long stretches of highly repeated DNA sequences named satellite DNA [1,2]
The species belonging to the genus Equus are characterized by karyotypes where chromosomes with canonical satellite-based centromeres are present together with chromosomes with satellite-free centromeres [6,14,29,30,31,32,33,34]
Summary
The centromere is a locus essential for chromosome segregation and genome integrity; this function is carried out by supporting kinetochore assembly and attachment to spindle microtubules. Most vertebrate centromeres are composed of long stretches of highly repeated DNA sequences named satellite DNA [1,2]. DNA sequence, and the centromeres are epigenetically determined, the modified H3 histone CENP-A (CENtromere Protein A) being the marker of centromere function. DNA at centromeres plays any functional role. Centromeric repetitive DNA is typically devoid of active genes, it may aid the formation of a heterochromatic environment, which would favor the stability of the chromosome during mitosis and meiosis [1,2,5].
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