Genomic instability in Schistosoma mansoni.
In schistosomes, the W chromosome characterizes the heterogametic female-sex (ZW) whereas males are homogametic (ZZ). In the heterochromatic region of the W chromosome, the repetitive elements W1 and W2 are located which had originally been found as female-specific sequences in Puerto Rican isolates of Schistosoma mansoni. An analysis of the strain- and sex-specific occurrence of these elements revealed that both elements can occur gender-independently in other Puerto Rican isolates and in a variety of other strains of S. mansoni. This result contradicted earlier findings and indicated the existence of polymorphic Z chromosomes. A genetic analysis of the occurrence of W1 and W2 in a series of clonal populations of Schistsoma mansoni is presented. Although clones of this parasite are regarded as genetically identical, striking inter- and even intra-clonal variations have been found by PCR and Southern-blot experiments with the DNA of individual clones and of the progeny of crossing experiments. The results do not support the hypothesis of polymorphic Z chromosomes. Instead, they strongly suggest genomic instability probably originating from unusual DNA recombination events at the meiotic and mitotic level. These findings suggest a further method of generating variability within schistosomes. rights reserved.
Institute for Genetics, Genetic Parasitology and Center for Biological and Medical Research, Heinrich-Heine-University, Düsseldorf, Germany. greveld@uni-duesseldorf.de
C G
CG
Grevelding
D000818:Animals; D015139:Blotting, Southern; D003433:Crosses, Genetic; D005260:Female; D017238:Genes, Helminth; D014644:Genetic Variation; D008297:Male; D016133:Polymerase Chain Reaction; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*; D012550:Schistosoma mansoni / Q000235:genetics* / Q000254:growth & development