Recombination study by MLH1 immunostaining of mouse spermatocytes after dietary treatments

Meiotic recombination is a critical process for sexually reproducing
organisms. This exchange of genetic information between homologous
chromosomes during meiosis is important not only because it generates
genetic diversity, but also because it is often required for proper
chromosome segregation. Consequently, the frequency and distribution of
crossovers are tightly controlled to ensure fertility and offspring
viability. However, in many systems it has been shown that environmental
factors can alter the frequency of crossover events. We have explored for
the first time the effect of dietary changes on crossover frequency per
nucleus. Our study was performed in spermatocytes of 3 mouse
inbred strains by analyzing the number and position of crossovers along
the synaptonemal complexes, as well as the length of such synaptonemal
complexes, by immunostaining with antibodies against MLH1 (which allows
the identification of the crossover sites) and SYCP3 (a component of the
synaptonemal complex). Our results show that male
recombination rate is sensitive to dietary changes, and this sensitivity
depends on the genetic background in mice. This is first to
report a nutrition effect on genome-wide levels of recombination.