Heterologous Synapsis and Crossover Suppression in Heterozygotes for a Pericentric Inversion in the Zebra Finch

DEL PRIORE LUCIA; PIGOZZI M.I.

CYTOGENETIC AND GENOME RESEARCH

KARGER

Lugar: Basel; Año: 2015 vol. 147 p. 154 - 160

1424-8581

In the zebra finch, 2 alternative morphs regarding centromereposition were described for chromosome 6. This polymorphismwas interpreted to be the result of a pericentricinversion, but other causes of the centromere repositioningwere not ruled out. We used immunofluorescence localizationto examine the distribution of MLH1 foci on synaptonemalcomplexes to test the prediction that pericentric inversionscause synaptic irregularities and/or crossover suppressionin heterozygotes. We found complete suppression ofcrossing over in the region involved in the rearrangement inmale and female heterozygotes. In contrast, the same regionshows high levels of crossing over in homozygotes for theacrocentric form of this chromosome. No inversion loops orsynaptic irregularities were detected along bivalent 6 in heterozygotessuggesting that heterologous pairing is achievedduring zygotene or early pachytene. Altogether these findingsstrongly indicate that the polymorphic chromosome 6originated by a pericentric inversion. Since inversions arecommon rearrangements in karyotypic evolution in birds, itseems likely that early heterologous pairing could help to fixthese rearrangements, preventing crossing overs in heterozygotesand their deleterious effects on fertility.