The Role of Dystroglycan in Nuclear Mechanics

It has recently been suggested that b-dystroglycan localises to the nucleus in a range of cell types. At the nucleus it is thought that b-dystroglycan plays a role in maintaining nuclear morphology and regulating structural nuclear proteins lamin B1 and emerin in mouse C2C12 myoblasts. It is hypothesised that b-dystroglycan is involved in regulating the mechanical properties of nuclei through interactions with lamin B1 and emerin or by adding additional support to the Linker of Nucleoskeleton and Cytoskeleton complex. This hypothesis was investigated using CRISPR/Cas9 disruption of the dystroglycan gene (DAG1) in human myoblast cells. In this DAG1 disrupted cell line, the previous reports of abnormal nuclear shape were not observed, however, it was found that both nuclear and cell size was greater in DAG1 disrupted cells. This increase in size was also rescued by the addition of exogenous dystroglycan. The increase in size was not due to a senescence phenotype as previously suggested, however, the reason for an increase in size has yet to be fully understood.
As with nuclear shape, the previously reported abnormal levels and localisation of lamin B1 and emerin in DAG1 disrupted C2C12 cells were not observed in the human myoblasts. Further, following analysis of nuclear mechanical properties of DAG1 disrupted and control cells using atomic force microscopy it was found that there was no difference in nuclear mechanics at a whole cell level. However, when nuclei were isolated from the whole cell environment, the DAG1 disrupted nuclei were less stiff than control nuclei.
The results described here suggest that disruption of the DAG1 gene has little effect on nuclear shape, regulation of nuclear proteins or nuclear mechanics. This suggests previously published results from C2C12 mouse myoblasts are not universal across cell lines and species and may require broader investigation.