RT Journal Article SR Electronic T1 Modeling of DNA methylation in cis reveals principles of chromatin folding in vivo in the absence of crosslinking and ligation JF bioRxiv FD Cold Spring Harbor Laboratory SP 407031 DO 10.1101/407031 A1 Josef Redolfi A1 Yinxiu Zhan A1 Christian Valdes A1 Mariya Kryzhanovska A1 Isabel Misteli Guerreiro A1 Vytautas Iesmantavicius A1 Guido Tiana A1 Tim Pollex A1 Jop Kind A1 Sebastien Smallwood A1 Wouter de Laat A1 Luca Giorgetti YR 2018 UL http://biorxiv.org/content/early/2018/09/03/407031.abstract AB Mammalian chromosomes are folded into an intricate hierarchy of structural domains, within which topologically associating domains (TADs) and CTCF-associated loops partition the physical interactions between regulatory sequences. Current understanding of chromosome folding largely relies on chromosome conformation capture (3C)-based experiments, where chromosomal interactions are detected as ligation products after crosslinking of chromatin. To measure chromosome structure in vivo, quantitatively and without relying on crosslinking and ligation, we have implemented a new method named damC. DamC combines DNA-methylation based detection of chromosomal interactions with next-generation sequencing and a biophysical model of methylation kinetics. DamC performed in mouse embryonic stem cells provides the first in vivo validation of the existence of TADs and CTCF loops, confirms 3C-based measurements of the scaling of contact probabilities within TADs, and provides evidence that mammalian chromatin in vivo is essentially rigid below 5 kilobases. Combining damC with transposon-mediated genomic engineering shows that new loops can be formed between ectopically introduced and endogenous CTCF sites, which alters the partitioning of physical interactions within TADs. This establishes damC as a crosslinking-and ligation-free framework to measure and modify chromosome interactions combined with a solid theoretical background for rigorous data interpretation. This orthogonal approach to 3C validates the existence of key structural features of mammalian chromosomes and provides novel insights into how chromosome structure within TADs can be manipulated.