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Independent evolution of holocentric chromosomes in an early branching apicomplexan parasite

Abigail Kimball1, Wanyi Huang1, Rui Xu1

  • 1Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO 63110, USA.

Biorxiv : the Preprint Server for Biology
|November 19, 2025
PubMed

Insights

Cryptosporidium parvum has a unique holocentric chromosome structure, unlike related species. This study visualizes centromeres, revealing scattered binding sites across all chromosomes during nuclear division.

Area of Science:

  • Cell Biology
  • Genetics
  • Parasitology

Background:

  • Cryptosporidium parvum undergoes asexual reproduction involving nuclear division.
  • Chromosome organization and segregation during C. parvum mitosis are poorly understood.

Purpose of the Study:

  • To investigate chromosome organization and segregation during Cryptosporidium parvum mitosis.
  • To characterize centromere structure and function in C. parvum.

Main Methods:

  • Visualization of H3-histones (including CENH3), telomeres, and centrosomes during mitosis.
  • Centromere capture and DNA sequencing using CENH3.
  • Microscopy techniques to observe nuclear division and microtubule dynamics.

Main Results:

  • Nuclear division involves centriole duplication and elongated microtubules spanning synchronously dividing nuclei.
  • C. parvum centromeres, detected by CENH3, show diffuse staining and overlap with telomeres.
  • DNA sequencing revealed numerous GA-rich repeat sequences as centromere binding sites across all eight chromosomes.

Conclusions:

  • C. parvum possesses a unique holocentric chromosome structure, distinct from regional centromeres in related apicomplexans.
  • This holocentric structure likely evolved independently.
  • The findings provide novel insights into the genetics and evolution of C. parvum.
Keywords:
Cryptosporidiumapicomplexancentromeresholocentricmitosis

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