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Published on: July 27, 2010
Clonal propagation and the fast generation of karyotype diversity: An in vitro Leishmania model
J-C Dujardin1, S De Doncker, D Jacquet
1Unit of Molecular Parasitology, Instituut voor Tropische Geneeskunde, 155 Nationalestraat, B-2000 Antwerpen, Belgium. jcdujard@itg.be
Abstract:
In the present work we studied the karyotype stability during long-term in vitro maintenance in 3 cloned strains of Leishmania (Viannia) peruviana, Leishmania (Viannia) braziliensis and a hybrid between both species. Only the L. (V.) peruviana strain showed an unstable karyotype, even after subcloning. Four chromosomes were studied in detail, each of them characterized by homologous chromosomes of different size (heteromorphy). Variations in chromosome patterns during in vitro maintenance were rapid and discrete, involving loss of heteromorphy or appearance of additional chromosome size variants. The resulting pattern was not the same according to experimental conditions (subinoculation rate or incubation temperature), and interestingly, this was associated with differences in growth behaviour of the respective parasites. No change in total ploidy of the cells was observed by flow cytometry. We discuss several mechanisms that might account for this variation of chromosome patterns, but we favour the occurrence of aneuploidy, caused by aberrant chromosome segregation during mitosis. Our results provide insight into the generation of karyotype diversity in natural conditions and highlight the relativity of the clone concept in parasitology.
Insights
Karyotype instability was observed in Leishmania (Viannia) peruviana during long-term in vitro culture, leading to variations in chromosome patterns and growth behavior. This suggests aneuploidy as a likely cause for karyotype diversity in parasites.
Area of Science:
- Parasitology
- Molecular Biology
- Genetics
Background:
- Karyotype stability is crucial for understanding parasite genetics.
- Long-term in vitro maintenance can induce genetic variations in protozoan parasites.
- Leishmania species are significant human pathogens with complex genomes.
Purpose of the Study:
- To investigate karyotype stability in cloned strains of Leishmania (Viannia) peruviana and a hybrid during extended in vitro cultivation.
- To identify specific chromosomal changes and their correlation with experimental conditions and parasite behavior.
- To elucidate the mechanisms underlying karyotype variations in Leishmania.
Main Methods:
- Long-term in vitro maintenance of three cloned Leishmania strains (L. (V.) peruviana, L. (V.) braziliensis, and a hybrid).
- Karyotype analysis to detect chromosomal variations and heteromorphy.
- Flow cytometry to assess total ploidy changes.
- Monitoring of experimental conditions including subinoculation rate and incubation temperature.
Main Results:
- Only the Leishmania (Viannia) peruviana strain exhibited karyotype instability, even after subcloning.
- Observed variations included loss of chromosome heteromorphy and appearance of new size variants.
- Karyotype pattern changes were dependent on experimental conditions and linked to altered parasite growth.
- No overall change in cell ploidy was detected via flow cytometry.
Conclusions:
- The study highlights significant karyotype instability in Leishmania (Viannia) peruviana under in vitro conditions.
- Aneuploidy resulting from aberrant mitotic segregation is proposed as the primary mechanism for observed chromosome variations.
- Findings provide insights into karyotype diversity generation in natural parasite populations and challenge the strict definition of clones in parasitology.
