The scaling features of the 3D organization of chromosomes are highlighted by a transformation à la Kadanoff of Hi-C data

¹ Dipartimento di Fisica, Università degli Studi di Napoli Federico II, and INFN Napoli, Complesso Universitario di Monte Sant'Angelo - 80126 Naples, Italy
² Berlin Institute for Medical Systems Biology at the Max Delbruck Center for Molecular Medicine in the Helmholtz Association - Berlin, Germany
³ Berlin Institute of Health (BIH), MDC-Berlin - 13125 Berlin, Germany

^(b) mario.nicodemi@na.infn.it (corresponding author)

Received: 13 October 2017
Accepted: 19 January 2018

Abstract

Technologies such as Hi-C and GAM have revealed that chromosomes are not randomly folded into the nucleus of cells, but are composed by a sequence of contact domains (TADs), each typically 0.5 Mb long. However, the larger scale organization of the genome remains still not well understood. To investigate the scaling behaviour of chromosome folding, here we apply an approach à la Kadanoff, inspired by the Renormalization Group theory, to Hi-C interaction data, across different cell types and chromosomes. We find that the genome is characterized by complex scaling features, where the average size of contact domains exhibits a power-law behaviour with the rescaling level. That is compatible with the existence of contact domains extending across length scales up to chromosomal sizes. The scaling exponent is statistically indistinguishable among the different murine cell types analysed. These results point toward a scenario of a universal higher-order spatial architecture of the genome, which could reflect fundamental, organizational principles.