Nuclei migrate through constricted spaces using microtubule motors and actin networks in C. elegans hypodermal cells

Abstract

Cellular migrations through constricted spaces are a crucial aspect of many developmental and disease processes including hematopoiesis, inflammation and metastasis. A limiting factor in these events is nuclear deformation. Here, we establish an in vivo model in which nuclei can be visualized while moving through constrictions and use it to elucidate mechanisms for nuclear migration. C. elegans hypodermal P-cell larval nuclei traverse a narrow space that is about 5% their width. This constriction is blocked by fibrous organelles, structures that pass through P cells to connect the muscles to cuticle. Fibrous organelles are removed just prior to nuclear migration, when nuclei and lamins undergo extreme morphological changes to squeeze through the space. Both actin and microtubule networks are organized to mediate nuclear migration. The LINC complex, consisting of the SUN protein UNC-84 and the KASH protein UNC-83, recruits dynein and kinesin-1 to the nuclear surface. Both motors function in P-cell nuclear migration, but dynein, functioning through UNC-83, plays a more central role as nuclei migrate towards minus ends of polarized microtubule networks. Thus, the nucleoskeleton and cytoskeleton are coordinated to move nuclei through constricted spaces.

Epithelial-Mesenchymal Plasticity is regulated by inflammatory signalling networks coupled to cell morphology

“…Alternatively, the forces may be a consequence of MT-bound motors such a kinesin or dynein 26 . In support of this idea, inhibiting the binding of Kinesin-1 to MTs by RBL rescues nuclear morphology in JAM3 deficient cells, and Kinesin-1 activity is required for nuclear deformation during constricted migration of C. elegans P-cells 71 , and nuclear rotation during neuronal migration 72 . Thus the motor function of Kkinesin-1 may be responsible for force generation on the nucleus.…”

“…Thus MTs which bridge cell-cell adhesions and the nucleus can act to promote nuclear mechanical stability and decrease the effective deformability of the nucleus 6,11,43 .But the cytoskeleton can also itself act to deform the nucleus, and in turn regulate cell behaviour and fate; perhaps the best example of which is the separation of chromatin during cell division by the mitotic spindle 44 . The cytoskeleton has a role in shaping the nucleus as migrating cells pass through confined spaces during development and disease 10,[45][46][47][48] . Finally, the cytoskeleton deforms to nucleus to promote differentiation 49, 50 , and DNA repair 51 .In addition to the cytoskeleton, another key factor in determining nuclear deformability is the composition of the nuclear lamina -which is comprised primarily of LMNA and LMNB proteins.The LMNA:LMBA ratio determines the viscoelasticity of the nucleus.…”

Genetic Analysis of Nuclear Migration and Anchorage to Study LINC Complexes During Development of Caenorhabditis elegans

“…2). It takes 15–25 min for one nucleus to completely move through this constriction [16]. These migrations can be filmed live using protocols described in [16, 36].…”

“…It takes 15–25 min for one nucleus to completely move through this constriction [16]. These migrations can be filmed live using protocols described in [16, 36]. tdTomato-labeled nuclei unable to complete the migration through this constriction remain on the lateral side of the late L1 animal and are classified as failed migration events [16, 19].…”

“…2A). These nuclear migration events are particularly interesting because nuclei must flatten to ~5% of their width to squeeze through a constricted space between muscles and the cuticle [16] (Fig. 2B, C).…”