FIGURE 1.

A model of heterochromatin roles in migrating cells. Schematic representation of cells migrating through small pores while (A) increasing their heterochromatin levels or (B) leaving their heterochromatin levels low as before receiving the migration signals. Higher heterochromatin levels support better the migration process by the following mechanisms: (i) Heterochromatin-dependent stiffness of the nucleus leads to faster nuclear movement out of the restraining pore. (ii) Increased nuclear stiffness may help the actomyosin network to increase the intracellular pressure in the anterior of the cytoplasm to induce formation of lobopodial protrusions. (iii) Increased nuclear stiffness may protect the nucleus of mechanical insults, preventing nuclear envelope rupture and DNA damage such as double strand breaks (DSBs). (iv) Heterochromatin inhibits transcription of migration inhibitory factors (marked in gray) and of repressors of transcription (TF, marked in red) thus preventing transcriptional inhibition of migration promoting factors (marked in green). (v) Heterochromatin also prevents unnecessary transcriptional alterations.