General pattern of meiotic recombination in male dogs estimated by MLH1 and RAD51 immunolocalization.

The aim of this study was to estimate a general pattern of meiotic recombination in the domestic dog (Canis familiaris) using immunolocalization of MLH1, a mismatch repair protein of mature recombination nodules. We prepared synaptonemal complex (SC) spreads from 124 spermatocytes of three male dogs and mapped 4959 MLH1 foci along 4712 autosomes. The mean number of MLH1 foci for all autosomes was 40.0 foci per cell. Total recombination length of the male dog autosomal genome map was estimated as 2000 cM. A global pattern of MLH1 foci distribution along the autosomal bivalents was rather similar to that found in the mammals studied: a high frequency near the telomeres and a low frequency near the centromeres. An obligate MLH1 focus in the X-Y pairing region was usually located very close to Xp-Yq telomeres. The distances between MLH1 foci at autosomal bivalents were consistent with crossover interference. A comparison of the interference estimates coming from the distribution of MLH1 interfocus distances and RAD51/MLH1 focus ratio indicated a substantial variation between species in the strength of interference.