engleski

Epigenomics of holocentromere

Centromeres are chromosomal regions essential for kinetochore attachment to mitotic spindle and proper chromosome segregation during cell divisions. They are determined epigenetically with centromere-specific variant of histone H3 (CenH3). While centromere function is conserved, CenH3 and underlying DNA evolve rapidly. Most research has been done on sexual species with monocentric chromosomes characterized by a single CenH3-containing region. In contrast, holocentromeres have their function dispersed throughout the entire length of chromosome. In this study, we used holocentric nematodes of the genus Meloidogyne as a model organism for the centromere study [1]. CenH3 characterization is done for three closely related, polyploid mitotic parthenogenetic species together with distantly related meiotic parthenogen species. We found that ancestral duplication of CenH3 gene resulted in one conserved CenH3 (αCenH3) and other gene that evolved rapidly into four different CenH3 variants. Immunofluorescence performed on mitotic M. incognita revealed a dominant role of αCenH3 histone on its centromere (Figure 1) while the other CenH3s have lost their function. In addition, ChIP-Seq analysis showed that αCenH3-associated DNA is comprised of tandem repeats with divergent monomers but completely conserved 19-bp long box. Preservation of αCenH3 and DNA constituents is also proven for other investigated species. These results elucidate unique characteristics where CenH3 and associated DNA are maintained over long period of time in holocentromeres of exclusively mitotic species. Our findings of centromere evolution in asexual, holocentric organisms thus help building an integrated view on the centromere (epi)genomics.

holocentromere ; epigenomics ; Meloidogyne

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