A pathway for mitotic chromosome formation.

   October 30th, 2018 at 2:35pm



Mitotic chromosomes fold as compact arrays of chromatin loops. To identify the pathway of mitotic chromosome formation, we combined imaging and Hi-C analysis of synchronous DT40 cell cultures with polymer simulations. Here we show that in prophase, the interphase organization is rapidly lost in a condensin-dependent manner, and arrays of consecutive 60-kilobase (kb) loops are formed. During prometaphase, ~80-kb inner loops are nested within ~400-kb outer loops. The loop array acquires a helical arrangement with consecutive loops emanating from a central "spiral staircase" condensin scaffold. The size of helical turns progressively increases to ~12 megabases during prometaphase. Acute depletion of condensin I or II shows that nested loops form by differential action of the two condensins, whereas condensin II is required for helical winding.


Gibcus JH  •  Samejima K  •  Goloborodko A  •  Samejima I  •  Naumova N  •  Nuebler J  •  Kanemaki MT  •  Xie L  •  Paulson JR  •  Earnshaw WC  •  Mirny LA  •  Dekker J



Science (New York, N.Y.)



February 9th, 2018

About this Study

This study takes advantage of the chicken cell line DT40 with a Cdk1as (analog-sensitive) mutant, in which Cdk1 can be inactivated with 1NM-PP1 in order to synchronize the cells. This allows the authors to perform Hi-C on cells at different stages of mitosis, and they compare control cells to cells with condensin I or II depleted to look at chromosome condensation and the relative contribution of the condensins.

HiGlass Displays

Hi-C on Synchronized DT40 (chicken) cells  

Cells were arrested in G2 to synchronize, then released from arrest and fixed at several time points. Later timepoints were treated with nocodazole to prevent metaphase to anaphase transition. From left to right, top then bottom: G2 (0m); early prophase (5m); late prophase (10m); early prometaphase (15m); prometaphase (30m, blocked with nocodazole); prometaphase (60m, blocked with nocodazole). Note the large-scale changes in contact frequencies as mitosis begins.

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Hi-C on Synchronized SMC2-mAID DT40 cells  

Hi-C of Synchronized CAPH2-mAID cells  

Hi-C of Synchronized CAPH-mAID DT40 cells