Biology subjects

Wallrath, L. L.

Publications and source records attributed to Wallrath, L. L..

3 recordsLinked to original sources

bioRxiv2024

The 4T1 breast carcinoma model possesses hybrid epithelial/mesenchymal traits linked to a highly metastatic phenotype

Epithelial-mesenchymal transitions (EMTs) have emerged as a mechanism for carcinomas to gain metastatic capabilities. As classically defined, EMTs entail downregulation of E-cadherin, viewed as a master enforcer of an epithelial phenotype, and upregulation of mesenchymal markers such as N-cadherin and vimentin. Contrary to this, E-cadherin appears to be retained in many invasive carcinomas and promote collective cell invasion. Therefore, major questions remain concerning the role of E-cadherin in metastasis. To investigate how E-cadherin regulates metastasis, we selected murine 4T1 breast carcinoma cells, a widely utilized model of stage IV metastatic breast cancer that retains E-cadherin expression. Using RNA interference and constitutive expression, we demonstrate that the expression level of E-cadherin does not determine 4T1 metastatic capacity in mice. Despite high levels of expression, E-cadherin is unable to confer an epithelial phenotype with stable organized cell-cell junctions. Moreover, orthotopic 4T1 tumors in mice display co-expression of E-cadherin and vimentin and contain subregions of EMT-like loss of E-cadherin. In addition, we find that 4T1 cells co-express epithelial and mesenchymal isoforms of p120-catenin. These findings support 4T1 cells as a model for carcinomas that possess hybrid traits of epithelial and mesenchymal states that promote invasion and metastasis. As such, the 4T1 model provides a platform for investigating strategies to reinstate E-cadherins ability to promote stable cell-cell junctions in E-cadherin-positive cancers, and for identifying which aspects of an epithelial phenotype may serve to facilitate the macroscopic growth of metastatic colonies.

cancer biology↗

bioRxiv2021

Impaired lamin localization to the nuclear envelope is responsible for nuclear damage in LMNA mutant iPSC-derived cardiomyocytes

The LMNA gene encodes the nuclear envelope proteins Lamins A and C, which comprise a major part of the nuclear lamina, provide mechanical support to the nucleus, and participate in diverse intracellular signaling. LMNA mutations give rise to a collection of diseases called laminopathies, including dilated cardiomyopathy (LMNA-DCM) and muscular dystrophies. Although nuclear deformities are a hallmark of LMNA-DCM, the role of nuclear abnormalities in the pathogenesis of LMNA-DCM remains incompletely understood. Using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) from LMNA mutant patients and healthy controls, we show that LMNA mutant iPSC-CM nuclei have altered shape or increased size compared to healthy control iPSC-CM nuclei. The LMNA mutation exhibiting the most severe nuclear deformities, R249Q, additionally caused reduced nuclear stiffness and increased nuclear fragility. Importantly, for all cell lines, the degree of nuclear abnormalities corresponded to the degree of Lamin A/C and Lamin B1 mislocalization from the nuclear envelope. The mislocalization was likely due to altered assembly of Lamin A/C. Collectively, these results point to the importance of correct lamin assembly at the nuclear envelope in providing mechanical stability to the nucleus and suggest that defects in nuclear lamina organization may contribute to the nuclear and cellular dysfunction in LMNA-DCM.

cell biology↗

bioRxiv2018

Mutant lamins cause mechanically-induced nuclear envelope rupture, DNA damage, and DNA-PK activation in muscle

Mutations in the human LMNA gene, which encodes the nuclear envelope (NE) proteins lamins A and C, cause autosomal dominant Emery-Dreifuss muscular dystrophy, congenital muscular dystrophy, limb-girdle muscular dystrophy, and other diseases collectively known as laminopathies. The molecular mechanisms responsible for these diseases remain incompletely understood, but the muscle-specific defects suggest that mutations may render nuclei more susceptible to mechanical stress. Using three mouse models of muscle laminopathies, we found that Lmna mutations caused extensive NE abnormalities, consisting of chromatin protrusions into the cytoplasm and transient rupture of the NE in skeletal muscle cells. NE damage was associated with DNA damage, activation of DNA damage response pathways, and reduced viability. Intriguingly, NE damage resulted from nuclear migration in maturing skeletal muscle cells, rather than actomyosin contractility. NE damage and DNA damage was reduced by either depletion of kinesin-1 or disruption of the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. LINC complex disruption rescued myofiber function and viability in Lmna mutant myofibers, indicating that the myofiber dysfunction is the result of mechanically induced NE damage. The extent of NE damage and DNA damage in Lmna mouse models correlated with the disease onset and severity in vivo. Moreover, inducing DNA damage in wild-type muscle cells was sufficient to phenocopy the reduced cell viability of lamin A/C-deficient muscle cells, suggesting a causative role of DNA damage in disease pathogenesis. Corroborating the mouse model data, muscle biopsies from patients with LMNA muscular dystrophy revealed significant DNA damage compared to age-matched controls, particularly in severe cases of the disease. Taken together, these findings point to a new and important role of DNA damage as a pathogenic contributor for LMNA skeletal muscle diseases.

cell biology↗