Complex relationship between meiotic recombination frequency and autosomal synaptonemal complex length per cell in...

Although the relationship between meiotic recombination frequency and synaptonemal complex (SC) length has been of interest for a long time, how recombination frequency is related to SC length has not been carefully explored. To address this question, we have measured the meiotic recombination frequency as represented by MLH1 foci in 889 pachytene spermatocytes and measured the length of 19,558 autosomal SCs from 10 human males. A complex relationship between the number of MLH1 foci and total autosomal SC length per cell was observed. A positive correlation with significant correlation coefficients between the two variables was found in eight of the ten donors examined, with three donors showing weak correlation, and five showing moderate correlation. Two donors who did not show any correlation between the two variables were identified for the first time. Moreover, most cells with similar total autosomal SC length showed very different numbers of MLH1 foci both between individuals and even within an individual, and vice versa. Our data provide the first evidence for a complex relationship between the recombination frequency and total length of autosomal SCs per cell in human males.