Back to Search Start Over

Chromosome fusion and programmed DNA elimination shape karyotypes of parasitic nematodes.

Authors :
Simmons JR
Estrem B
Zagoskin MV
Oldridge R
Zadegan SB
Wang J
Source :
BioRxiv : the preprint server for biology [bioRxiv] 2023 Dec 23. Date of Electronic Publication: 2023 Dec 23.
Publication Year :
2023

Abstract

A growing list of metazoans undergo programmed DNA elimination (PDE), where a significant amount of DNA is selectively lost from the somatic genome during development. In some nematodes, PDE leads to the removal and remodeling of the ends of all germline chromosomes. In several species, PDE also generates internal breaks that lead to sequence loss and an increased number of somatic chromosomes. The biological significance of these karyotype changes associated with PDE and the origin and evolution of nematode PDE remain largely unknown. Here, we assembled the single germline chromosome of the horse parasite Parascaris univalens and compared the karyotypes, chromosomal gene organization, and PDE features among ascarid nematodes. We show that PDE in Parascaris converts an XX/XY sex-determination system in the germline into an XX/XO system in the somatic cells. Comparisons of Ascaris , Parascaris, and Baylisascaris ascarid chromosomes suggest that PDE existed in the ancestor of these parasites, and their current distinct germline karyotypes were derived from fusion events of smaller ancestral chromosomes. The DNA breaks involved in PDE resolve these fused germline chromosomes into their pre-fusion karyotypes, leading to alterations in genome architecture and gene expression in the somatic cells. Cytological and genomic analyses further suggest that satellite DNA and the heterochromatic chromosome arms play a dynamic role in the Parascaris germline chromosome during meiosis. Overall, our results show that chromosome fusion and PDE have been harnessed in these ascarids to sculpt their karyotypes, altering the genome organization and serving specific functions in the germline and somatic cells.<br />Competing Interests: Declaration of interests The authors declare no competing interests.

Details

Language :
English
Database :
MEDLINE
Journal :
BioRxiv : the preprint server for biology
Accession number :
38187595
Full Text :
https://doi.org/10.1101/2023.12.21.572835