Chromosome synapsis and recombination in simple and complex chromosome heterozygotes of tuco-tuco (Ctenomys talarum: Rodentia: Ctenomyidae)

BASHEVA EKATERINA; TORGASHEVA ANNA; GÓMEZ FERNÁNDEZ JIMENA; BOSTON EMMA; MIROL PATRICIA; BORODIN PAVEL

CHROMOSOME RESEARCH

SPRINGER

Lugar: Berlin; Año: 2014 vol. 22 p. 351 - 363

0967-3849

Abstract The chromosomal speciation hypothesissuggests that irregularities in synapsis, recombination,and segregation in heterozygotes for chromosomerearrangements may restrict gene flow betweenkaryotypically distinct populations and promote speciation.Ctenomys talarum is a South American subterraneanrodent inhabiting the coastal regions ofArgentina, whose populations polymorphic forRobertsonian and tandem translocations seem to havea very restricted gene flow. To test if chromosomaldifferences are involved in isolation among its populations,we examined chromosome pairing, recombination,and meiotic silencing of unsynapsed chromatinin male meiosis of simple and complex translocationheterozygotes using immunolocalization of theMLH1 marking mature recombination nodules andphosphorylated histone γH2A.X marking unrepaireddouble-strand breaks. We observed small asynapticareas labeled by γH2A.X in pericentromeric regionsof the chromosomes involved in the trivalents andquadrivalents. We also observed a decrease of recombinationfrequency and a distalization of the crossoverdistribution in the heterozygotes and metacentrichomozygotes compared to acrocentric homozygotes.We suggest that the asynapsis of thepericentromeric regions are unlikely to induce germcell death and decrease fertility of the heterozygotes;h o w e v e r, s up p r e s s e d r e c o m b i n a t i o n i npericentromeric areas of the multivalents may reducegene flow between chromosomally different populationsof the Talas tuco-tuco.