Biology subjects

Posern, G.

Publications and source records attributed to Posern, G..

3 recordsLinked to original sources

bioRxiv2021

miRNA mediated downregulation of non-muscle Cyclase associated protein 1 is required for myogenic differentiation

Myoblast fusion is crucial for the formation, growth and regeneration of healthy skeletal muscle, but the molecular mechanisms that govern fusion and myofiber formation remain poorly understood. Here we report that Cyclase-associated protein 1 (Cap1), a regulator of actin dynamics, plays a critical role in cytoskeletal remodeling during myoblast fusion and formation of myotubes. Cap1 mRNA and protein are expressed in murine C2C12 and human LHCN-M2 myoblasts, but its abundance decreases during myogenic differentiation. Perturbing the temporally controlled expression of Cap1 by overexpression or Crispr-Cas9 mediated knockout impaired actin rearrangement, myoblast alignment, expression of profusion molecules, differentiation into multinucleated myotubes and myosin heavy chain expression. Endogenous Cap1 expression is posttranscriptionally downregulated during differentiation by canonical myomiRs miR-1, miR-133 and miR-206, which have conserved binding sites in the 3 UTR of the Cap1 mRNA. Deletion of the endogenous 3 UTR in C2C12 cells phenocopies overexpression of Cap1 by inhibiting myotube formation. Our findings implicate Cap1 and its myomiR-mediated downregulation in the myoblast fusion process and the generation of skeletal muscle.

cell biology↗

bioRxiv2021

Lamina-associated polypeptide 2α is required for intranuclear MRTF-A activity

Myocardin-related transcription factor A (MRTF-A), a coactivator of serum response factor (SRF), regulates the expression of many cytoskeletal genes in response to cytoplasmic and nuclear actin dynamics. Here we describe a novel mechanism to regulate MRTF-A activity within the nucleus by showing that lamina-associated polypeptide 2 (Lap2), the nucleoplasmic isoform of Lap2, is a direct binding partner of MRTF-A, and required for the efficient expression of MRTF-A/SRF target genes. Mechanistically, Lap2 is not required for MRTF-A nuclear localization, unlike most other MRTF-A regulators, but is required for binding of MRTF-A to its target genes. This regulatory step takes place prior to MRTF-A chromatin binding, because Lap2 neither interacts with, nor specifically influences active histone marks on MRTF-A/SRF target genes. Phenotypically, Lap2 is required for serum-induced cell migration, and deregulated MRTF-A activity may also contribute to muscle and proliferation phenotypes associated with loss of Lap2. Our studies therefore add another regulatory layer to the control of MRTF-A-SRF-mediated gene expression, and broaden the role of Lap2 in transcriptional regulation.

cell biology↗

bioRxiv2017

Dual Phenotype Of MDA-MB-468 Cancer Cells Reveals Mutual Regulation Of Tensin3 And Adhesion Plasticity

Plasticity between adhesive and less-adhesive states is important for mammalian cell behaviour. To investigate adhesion plasticity, we have selected a stable isogenic subpopulation of MDA-MB-468 breast carcinoma cells which grows in suspension. These suspension cells are unable to re-adhere to various matrices or to contract three-dimensional collagen lattices. By transcriptome analysis, we identified the focal adhesion protein tensin3 (Tns3) as a determinant of adhesion plasticity. Tns3 is strongly reduced on mRNA and protein level in suspension cells. Furthermore, challenging breast cancer cells transiently with non-adherent conditions markedly reduces Tns3 expression, which is regained upon re-adhesion. Stable knockdown of Tns3 in parental cells results in defective adhesion, spreading and migration. Tns3 knockdown cells display impaired structure and dynamics of focal adhesion complexes as determined by immunostaining. Restoration of Tns3 expression in suspension cells partially rescues adhesion and focal contact composition. Our work identifies Tns3 as a critical focal adhesion component regulated by, and functionally contributing to, the switch between adhesive and non-adhesive states in MDA-MB-468 cancer cells.\n\nSummary statementWe identify the cell-matrix adapter protein tensin3 as a determinant of adhesion plasticity, using cancer cells selected for non-adherent growth. Tensin3 expression constitutes a feedback loop controlling adhesion and motility.

cell biology↗