During meiotic cell division, proper chromosome synapsis and accurate repair of 
DNA double strand breaks (DSBs) are required to maintain genomic integrity, loss 
of which leads to apoptosis or meiotic defects. The mechanisms underlying 
meiotic chromosome synapsis, DSB repair and apoptosis are not fully understood. 
Here, we report that the chromodomain-containing protein MRG-1 is an important 
factor for genomic integrity in meiosis in Caenorhabditis elegans. Loss of mrg-1 
function resulted in a significant increase in germ cell apoptosis that was 
partially inhibited by mutations affecting DNA damage checkpoint genes. 
Consistently, mrg-1 mutant germ lines exhibited SPO-11-generated DSBs and 
elevated exogenous DNA damage-induced chromosome fragmentation at diakinesis. In 
addition, the excessive apoptosis in mrg-1 mutants was partially suppressed by 
loss of the synapsis checkpoint gene pch-2, and a significant number of meiotic 
nuclei accumulated at the leptotene/zygotene stages with an elevated level of 
H3K9me2 on the chromatin, which was similarly observed in mutants deficient in 
the synaptonemal complex, suggesting that the proper progression of chromosome 
synapsis is likely impaired in the absence of mrg-1. Altogether, these findings 
suggest that MRG-1 is critical for genomic integrity by promoting meiotic DSB 
repair and synapsis progression in meiosis.