In a new study, MIT researchers have measured chromatin movement at timescales ranging from hundreds of microseconds to hours, allowing them to rigorously quantify those dynamics for the first time.

Their analysis revealed that chromatin can exist in two different categories: In one, chromatin moves in a constrained way that allows it to primarily contact only neighboring regions of the genome; in the other, chromatin moves more freely and contacts regions that are farther away, but only over longer timescales.

The findings offer insight into how gene expression is regulated, as well as how chromatin segments come together for other processes such as DNA repair, the researchers say.

Head and neck microvascular free flap reconstruction is frequently challenged by compromised vessel conditions due to tumor extension, radiation therapy, and surgical scarring. Microvascular couplers effectively promote intima-to-intima contact, reducing thrombosis risk, but have limitations in vessel size compatibility and cost. We developed the Evert Style Vessel Anastomosis (ESVA) technique to achieve similar intimal apposition benefits without couplers and evaluated its efficacy and safety.

We retrospectively analyzed 32 patients who underwent head and neck microvascular free flap reconstruction between 2020 and 2024. Vessel conditions were classified as Type 1 (easily evertible), Type 2 (evertible with atherosclerosis/inflammation), Type 3 (technically difficult eversion), or Type 4 (non-evertible). Anastomoses were performed using either nylon or ACRI+Asflex sutures. The ESVA technique involved 90-degree needle insertion with external vessel wall eversion. Outcome measures included anastomosis time, vascular complications, and flap survival rates. Only end-to-end arterial and venous anastomoses were included in the present analyses.

A total of 30 arterial and 31 venous anastomoses were performed using the ESVA technique. Three anastomoses involving Type 4 (non-evertible) vessels required conventional anastomosis without eversion. Among vessels suitable for ESVA, Type 2 vessels were most common, followed by Type 3 and Type 1. The mean arterial anastomosis time was significantly shorter with ACRI+Asflex sutures (20.8 ± 2.4 min) compared with nylon (23.4 ± 2.8 min; p = 0.007). Similarly, venous anastomosis time was reduced from 21.4 ± 2.7 min with nylon to 19.2 ± 1.2 min with ACRI+Asflex sutures (p = 0.007). In ESVA cases involving Type 1 and/or Type 2 vessels, ACRI+Asflex sutures significantly reduced arterial (20.8 vs. 23.4 min; p = 0.014) and venous (18.7 vs. 20.2 min; p = 0.04) anastomosis times. Even in anastomoses involving Type 3 vessels (either donor, recipient, or both), significant time reduction was observed for both arteries (23.0 vs. 25.6 min; p = 0.008) and veins (19.5 vs. 24.8 min; p = 0.00014).

As tissues age, mutant clones carrying driver mutations expand, yet the abundance of these variants in normal tissues suggests that fitness-based selection is often uncoupled from malignancy. Cheek et al. introduce a framework that disentangles clonal success from true carcinogenic potential, showing that fitness and fate are not synonymous.

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¹ Holman Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, New York University Grossman School of Medicine, New York, New York, USA.

²Keenan Centre for Biomedical Research, St. Michael’s Hospital, and Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada.

³Department of Foundations of Medicine, Diabetes and Obesity Research Center, New York University Grossman Long Island School of Medicine, Mineola, New York, USA.