Biology subjects

Suman, S. K.

Publications and source records attributed to Suman, S. K..

5 recordsLinked to original sources

bioRxiv2026

Persistent and recyclable myosin II minifilaments drive cortical contractility in the early C. elegans embryo

Non-muscle myosin II is a key regulator of cell and tissue morphogenesis, yet the cortical dynamics of myosin minifilaments in vivo remain poorly understood. Here, we combine SIM-TIRF and single-molecule TIRF microscopy to characterize the structure and dynamics of myosin minifilaments in an early developing embryo. High-temporal-resolution SIM-TIRF imaging revealed diverse minifilament behaviors, including partition-like events, long-range alignment of multiple minifilaments into collective structures we called proto-stress fibers, partial unbinding, and sequential unbinding and rebinding to the cortex. Photoconversion experiments showed that minifilaments persist as intact units after cortical unbinding, diffuse through the cytoplasm, and can be recycled over long distances rather than disassembling upon detachment. Despite these dynamic behaviors, minifilaments are predominantly stationary when bound to actin. Numerical simulations demonstrated that this static behavior is essential to sustain cortical stress within a continuously remodeling actin network. Using myosin motor-domain mutants, we further investigated the contribution of motor activity to these behaviors. Together, our results reveal that myosin minifilaments can persist as stable units while cycling between the cortex and cytoplasm, and that their predominantly static behavior when bound to actin enables sustained force generation in a continuously renewing cortical network. These findings provide new insights into myosin organization, recycling, and force generation during early embryonic development.

cell biology↗

bioRxiv2026

The SynMuvA lin-15A licenses natural transdifferentiation by antagonizing identity safeguarding mechanisms

The mechanisms that restrict or enable latent cellular plasticity have attracted growing interest over the past decade, with important implications for cancer and regenerative therapies. However, the diversity of both pro- and anti-plasticity mechanisms remains incompletely understood. Here, we identify the THAP domain gene lin-15A as a novel factor involved in the natural rectal-to-neuronal Y-to-PDA transdifferentiation in Caenorhabditis elegans. We found that, unlike previously described essential factors, lin-15A is not a Driver of transdifferentiation. Instead, it antagonizes several chromatin-modifying complexes known to safeguard differentiated cell identities. We also show that lin-15A is not a core plasticity factor per se but acts as one specifically in the Y cell context. Together, our findings support a model in which diverse molecular players coordinate controlled cell identity conversions: plasticity factors function as Drivers, while others like lin-15A which we propose to term Licensers attenuate identity safeguarding mechanisms, thereby facilitating transdifferentiation.

developmental biology↗

bioRxiv2024

Conditional nmy-1 and nmy-2 alleles establish that non-muscle myosins are required for late C. elegans embryonic elongation

The elongation of C. elegans embryos allows examination of mechanical interactions between adjacent tissues. Muscle contractions during late elongation induce the remodelling of epidermal circumferential actin filaments through mechanotransduction. We investigated the possible role of the non-muscle myosins NMY-1 and NMY-2 in this process using nmy-1 and nmy-2 thermosensitive alleles. Our findings suggest these myosins act redundantly in late elongation, and that they are involved in the multi-step process of epidermal remodeling. When inactivated, NMY-1 was seen to form protein aggregates.

developmental biology↗

bioRxiv2020

Rapid assembly of a polar network architecture by formins downstream of RhoA pulses drives efficient cortical actomyosin contractility

SO_SCPLOWUMMARYC_SCPLOWActin network architecture and dynamics play a central role in cell contractility and tissue morphogenesis. Pulsed contractions driven by RhoA represent a generic mode of actomyosin contractility, but the mechanisms underlying (1) how their specific architecture emerges, and (2) how this architecture supports the contractile function of the network, remain unclear. Here, we combine quantitative microscopy, single-molecule imaging, numerical simulations and simple mathematical modelling, to explore the dynamic network architecture underlying pulsed contraction. We show that during pulsed contractions, two subpopulations of formins are recruited by RhoA from the cytoplasm and bind to the cell surface in the early C. elegans embryo: recruited formins, a functionally inactive population, and elongating formins, which actively participate in actin filaments elongation. Focusing on formin dynamics during pulses, we show that minority elongating formins precede recruited formins, a kinetic dynamics compatible with formins capturing and rapidly saturating barbed ends available for filament elongation. We then show that these elongating formins assemble a polar network of actin, with barbed ends pointing out of the pulse, pointing to a kinetic rather than mechanical control of network architecture. Finally, our numerical simulations demonstrate that this geometry favors rapid network contraction. Our results thus show that formins saturate available actin filaments barbed ends and convert a local, biochemical gradient of RhoA activity into a polar network architecture, thereby driving rapid and efficient network contractility, an important evolutionary feature in a metazoan with a rapid embryonic cell cycles. HO_SCPLOWIGHLIGHTSC_SCPLOWO_LIThe formin CYK-1 drives actin network assembly during RhoA-driven pulses C_LIO_LIThe process is extremely rapid, with a formin-based actin elongation rate higher than 1.3 m{middle dot}s-1 C_LIO_LIA barbed-end saturation mechanism allows for responsive F-actin assembly C_LIO_LIRapid and responsive F-actin elongation results in the assembly of aster-like polar actin networks C_LIO_LINumerical simulations show network polarity drives very efficient network contractility C_LI

cell biology↗

bioRxiv2019

The C. elegans plectin homologue VAB-10 acts as a hemidesmosome mechanosensor

Mechanical forces control many cellular processes by eliciting a mechanotransduction response in target cells. The initial steps of mechanotransduction at hemidesmosomes remain undefined in contrast to focal adhesions and adherens junctions. Here, we focus on the C. elegans plectin homolog VAB-10A, the only evolutionary conserved hemidesmosome component. In C. elegans, muscle contractions induce a mechanotransduction pathway in the epidermis through hemidesmosomes. We used CRISPR to precisely remove spectrin repeats (SR) or a partially hidden Src-homology-3 (SH3) domain within the VAB-10 plakin domain. Deleting the SH3 or SR8 domains in combination with mutations affecting mechanotransduction, or just part of SR5 shielding the SH3 domain induced embryonic elongation arrest because hemidesmosomes collapse. Notably, recruitment of GIT-1, the first mechanotransduction player, requires the SR5 domain and the hemidesmosome transmembrane receptor LET-805. Furthermore, Molecular Dynamics simulations confirmed that forces acting on VAB-10 can render the central SH3 domain, otherwise in contact with SR4, available for interaction. Collectively, our data strongly argue that the plakin domain plays a central role in mechanotransduction and raise the possibility that VAB-10/plectin might act as a mechanosensor.\n\nSummary statementCRISPR-derived deletions reveal the roles of three spectrin repeats and an atypical SH3 domain from the plakin domain of the VAB-10 hemidesmosome component in mechanotransduction during C. elegans morphogenesis

developmental biology↗