Biology subjects

Pfanzelter, J.

Publications and source records attributed to Pfanzelter, J..

3 recordsLinked to original sources

bioRxiv2026

Actomyosin active torques determine body plan handedness in C. elegans

Left-right (LR) asymmetries are a defining feature of bilaterian body plans, but the mechanisms that convert molecular chirality into a conserved body-axis handedness remain unclear. In C. elegans, LR axis specification proceeds via a chiral spindle skew that establishes a handed cell-cell contact pattern (CCP) at the 6-cell stage; an arrangement that, when reversed, leads to situs inversus nematodes [1]. Chiral acto-myosin flows that arise from active chiral torques have been previously identified as the driver of this LR asymmetric spindle skew [2]. Here, we show that high amounts of Lifeact::mKate2, widely used to visualize F-actin, reverse the handedness of active torques in the cortex. We find that this results in reversed chiral acto-myosin flows during LR symmetry breaking, leading to mirrored 6-cell embryos and situs inversus nematodes. Our findings demonstrate that reversing the handedness of active torques changes the LR handedness at the organismal level and establish active chiral torques as instructive for LR axis specification in worms.

biophysics↗

bioRxiv2025

An active torque dipole across tissue layers drives avian left-right symmetry breaking

Unlike in mice, frogs, and fish, left-right (L/R) body axis formation in avian embryos does not arise from the chiral beat of cilia. Instead, a counter-clockwise tissue rotation around Hensens node, the organizer of amniote development, repositions cells expressing L/R sidedness genes. Yet, the physical origin of this rotation remains elusive. Here, we provide evidence that in quail embryos, the node tissue generates an active chiral torque of [~]6{micro}N{micro}m to drive the chiral tissue flow. Microsurgery experiments reveal that this torque depends on actomyosin molecular activity, is generated within the dorsal node tissue, and requires the underlying ventral meso-/endoderm to act as a mechanical substrate sustaining the counter-torque. We conclude that a dorsoventrally oriented tissue-scale active torque dipole at the node translates cell-scale chirality to organismal L/R asymmetry, adding a mechanical dimension to the canonical function of embryonic organizers as signaling hubs.

biophysics↗

bioRxiv2020

A hydraulic instability drives the cell death decision in the nematode germline

Oocytes are large and resourceful. During oogenesis some germ cells grow, typically at the expense of others that undergo apoptosis. How germ cells are selected to live or die out of a homogeneous population remains unclear. Here we show that this cell fate decision in C. elegans is mechanical and related to tissue hydraulics. Germ cells become inflated when the pressure inside them is lower than in the common cytoplasmic pool. This condition triggers a hydraulic instability which amplifies volume differences and causes some germ cells to grow and others to shrink. Shrinking germ cells are extruded and die, as we demonstrate by reducing germ cell volumes via thermoviscous pumping. Together, this reveals a robust mechanism of mechanochemical cell fate decision making in the germline.

developmental biology↗