Direct mapping of meiotic DSBs in human individuals: novel aspects of recombination initiation.

Monday, September 22, 2014 — Poster Session II
4:00 p.m. – 6:00 p.m.	FAES Academic Center	NIDDK	GEN-13

* FARE Award Winner

Authors

• F. Pratto
• K. Brick
• P. Khil
• F. Smagulova
• G. Petukhova
• R.D. Camerini-Otero

Abstract

Meiotic recombination contributes to genetic diversity and ensures the correct segregation of chromosomes. It is initiated by the introduction of double-strand breaks (DSBs) and occurs in narrow regions of the genome called hotspots. We have generated genome-wide high-resolution DSBs maps from 4 different individuals. The individual maps revealed that PRDM9, a protein identified as the major determinant of the location of DSBs in mammals, defines most of the sites where recombination happens in humans. Nonetheless, in individuals with the same PRDM9 allele, ~5% of the hotspots are polymorphic. Most differences cannot be attributed to genomic sequence variation, suggesting that other factors have a role on determining the efficiency of break formation. Interestingly, on a broad scale, we found that DSBs in all the individuals are more frequently found at subtelomeric regions. We examined the distribution of DSBs at different meiotic stages by immunofluorescence and found DSBs are formed earlier and with higher frequency at subtelomeric regions. We used the H3K4me3 signal as a proxy for PRDM9 binding and surprisingly, found that the correlation between hotspot strength and H3K4me3 signal decreased in the distal regions of chromosomes. This suggests that factors other than PRDM9 modulate hotspot strength in the subtelomeric regions.

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