DOI: 10.5061/dryad.cfxpnvx6d
title: Recombination study by MLH1 immunostaining of mouse spermatocytes after dietary treatments

description: 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.
description: We performed two
 studies: in the initial one, adult males from the three strains were
 analyzed for the effect of two diets on recombination (undernourishment
 (reduction to 50% daily intake) and breeding diets (Teklad Global 18%
 Protein Rodent Diet)) provided during 24 days relative to a control group
 kept <i>ad libitum</i> with maintenance diet (Teklad Global
 14% Protein Rodent Maintenance Diet). After the 24-day diet
 period, adult male mice were euthanized by cervical dislocation and
 weighed. After removing and weighing the testes, chromosome spreads for
 immunostaining as previously
 described (Anderson et al. 1999; de Boer et al. 2009; Milano et al. 2019).
 MLH1 immunostaining allows for identification of about 90% of mammalian
 crossover sites (Anderson et al. 1999; Cole et al. 2012). All slides were
 imaged on a Zeiss LSM 710 confocal microscope and analyzed using Zeiss Zen
 lite software. Only mid and mid-late pachytene stage spermatocytes were
 scored. For each spermatocyte, we counted the number of foci localizing to
 the SC of the 19 autosomes (Anderson et al. 1999); total SC length and
 interfocus distances were also measured in autosomes only.
description: The dataset is an Excel file with five sheets that contain the
 following information: Sheet 1 ("1st experiment, 3
 strains"): MLH1 foci count per spermatocyte per mice, strain and
 diet Sheet 2 ("2nd experiment, B6
 males"): MLH1 foci count per spermatocyte per C57BL/6 mice treated
 with two diets (2nd experiment). Columns indicate the mouse ID and number
 of spermatocytes analyzed in parenthesis.  Sheet 3
 ("intercrossover distances"): Interfocus distances in control
 mice (maintenance diet) of 3 strains. Values are shown as percentage of
 synaptonemal complex length. Sheet 4
 ("synaptonemal c. length, 1st"): Total autosomal length of
 synaptonemal complexes per strain, control groups (maintenance
 diets)  Sheet 5 ("synaptonemal c. length,
 2nd"): Total autosomal length of synaptonemal complexes per diet in
 C57BL/6 mice (2nd experiment)