Biology subjects

Tran, M. P.

Publications and source records attributed to Tran, M. P..

8 recordsLinked to original sources

bioRxiv2026

Programmable Edge-to-Edge Assembly of RNA Nanostructures

Constructing complex three-dimensional RNA nanostructures requires precise molecular connectors for controlled self-assembly. Existing RNA-RNA connectors, such as kissing loops, are restricted to coaxial, end-to-end joining, limiting the range of accessible geometries. Here, we introduce the alpha kissing loop (alphaKL), a compact, sequence-programmable RNA connector that enables edge-to-edge helix association. The alphaKL combines a four-nucleotide kissing loop with minor- and major-groove triplex interactions that pre-organize an -shaped conformation compatible with co-transcriptional folding. Embedded into RNA origami tiles, alphaKLs drive multivalent assembly into filaments and lattices, visualized at nanoscale resolution by atomic force microscopy. All-atom molecular dynamics simulations reveal that triplex occupancy at each sequence position controls the preferred inter-helical angle. Cooperative backbone contacts progressively rigidify the multi-alphaKL interface beyond what individual motifs achieve alone. By linking helices along their edges rather than their ends, the alphaKL expands the structural design space of programmable RNA nanostructures, unlocking previously inaccessible architectures and applications.

biophysics↗

bioRxiv2024

Genetic encoding and expression of RNA origami cytoskeletons in synthetic cells

The central dogma at the core of molecular biology states that information flows from DNA to RNA and then to protein. Our research seeks to introduce a conceptually novel approach towards synthetic life by leveraging RNA origami, as an alternative to proteins, requiring only a single copying step between genetic information and function. Here, we report the genetic encoding and expression of an RNA origami cytoskeleton-mimic within giant unilamellar lipid vesicles (GUVs). We design the first RNA origami tiles which fold co-transcriptionally from a DNA template and self-assemble into higher-order 3D RNA origami nanotubes at constant 37{whitebullet} C in GUVs, where they reach several micrometers in length. Unlike pre-formed and encapsulated DNA cytoskeletons, these GUVs produce their own molecular hardware in an out-of-equilibrium process fuelled by nucleotide feeding. To establish genotype-phenotype correlations, we investigate how sequence mutations govern the contour and persistence length of the RNA origami nanotubes with experiments and coarse-grained molecular-dynamics simulations, realizing a phenotypic transition to closed rings. Finally, we achieve RNA origami cortex formation and GUV deformation without chemical functionalization by introducing RNA aptamers into the tile design.Altogether, this work pioneers the expression of RNA origami-based hardware in vesicles as a new approach towards active, evolvable and RNA-based synthetic cells.

synthetic biology↗

bioRxiv2024

Gene expression differences associated with intrinsic hindfoot muscle loss in the jerboa, Jaculus jaculus

Vertebrate animals that run or jump across sparsely vegetated habitats, such as horses and jerboas, have reduced the number of distal limb bones, and many have lost most or all distal limb muscle. We previously showed that nascent muscles are present in the jerboa hindfoot at birth and that these myofibers are rapidly and completely lost soon after by a process that shares features with pathological skeletal muscle atrophy. Here, we apply an intra- and inter-species approach, comparing jerboa and mouse muscles, to identify gene expression differences associated with the initiation and progression of jerboa hindfoot muscle loss. We show evidence for reduced Hepatocyte Growth Factor (HGF) and Fibroblast Growth Factor (FGF) signaling and an imbalance in nitric oxide signaling; all are pathways that are necessary for skeletal muscle development and regeneration. We also find evidence for phagosome formation, which hints at how myofibers may be removed by autophagy or by non-professional phagocytes without evidence for cell death or immune cell activation. Last, we show significant overlap between genes associated with jerboa hindfoot muscle loss and genes that are differentially expressed in a variety of human muscle pathologies and rodent models of muscle loss disorders. All together, these data provide molecular insight into the mechanism of evolutionary and developmental muscle loss in jerboa hindfeet.

developmental biology↗

bioRxiv2023

Amphiphiles formed from synthetic DNA-nanomotifs mimic the dispersal of transcriptional clusters in the cell nucleus

Stem cells exhibit prominent clusters controlling the transcription of genes into RNA. These clusters form by a phase-separation mechanism, and their size and shape are controlled via an amphiphilic effect of transcribed genes. Here, we construct amphiphile-nanomotifs purely from DNA, and achieve similar size and shape control for phase-separated droplets formed from fully synthetic, self-interacting DNA-nanomotifs. Low amphiphile concentrations induce rounding of droplets, followed by splitting and, ultimately, full dispersal at higher concentrations. Super-resolution microscopy data obtained from zebrafish embryo stem cells reveal a comparable transition for transcriptional clusters with increasing transcription levels. Brownian dynamics and lattice simulations further confirm that addition of amphiphilic particles is sufficient to explain the observed changes in shape and size. Our work reproduces key aspects of the complex organization of transcription in biological cells using relatively simple, DNA sequence-programmable nanostructures, opening novel ways to control mesoscopic organization of synthetic nanomaterials. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=151 SRC="FIGDIR/small/525851v2_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@1a8cc4borg.highwire.dtl.DTLVardef@fc6651org.highwire.dtl.DTLVardef@a17c74org.highwire.dtl.DTLVardef@1f1cf14_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2022

A DNA segregation module for synthetic cells

The bottom-up construction of an artificial cell requires the realization of synthetic cell division. Significant progress has been made towards reliable compartment division, yet mechanisms to segregate the DNA-encoded informational content are still in their infancy. Herein, droplets of DNA Y-motifs are formed by liquid-liquid phase separation (LLPS). Entropy-driven DNA droplet segregation is obtained by cleaving the linking component between two populations of DNA Y-motifs. In addition to enzymatic cleavage, photolabile sites are introduced for spatio-temporally controlled DNA segregation in bulk as well as in cell-sized water-in-oil droplets and giant unilamellar lipid vesicles (GUVs). Notably, the segregation process is slower in confinement than in bulk. The ionic strength of the solution and the nucleobase sequences are employed to regulate the segregation dynamics. The experimental results are corroborated in a lattice-based theoretical model which mimics the interactions between the DNA Y-motif populations. Altogether, engineered DNA droplets, reconstituted in GUVs, could represent a strategy towards an entropy-driven DNA segregation module within bottom-up assembled synthetic cells. Table of Contents O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY An entropy-driven DNA segregation module for bottom-up assembled synthetic cells is realized. It is based on DNA droplets that are engineered to segregate upon enzymatic or photocleavage inside giant unilamellar lipid vesicles (GUVs). The segregation kinetics is altered by the confinement, as confirmed by lattice-based numerical simulations. DNA segregation is further controlled by temperature, ionic strengths and nucleobase sequence. C_FIG_DISPLAY

biophysics↗

bioRxiv2022

Mechanochemical signal transduction in synthetic cells

Mechanotransduction determines the adaptive response of natural cells via transmem-brane proteins1. The incorporation of membrane-spanning structures to guide cellular function and to enable transmembrane signalling is therefore a critical aim for bottom-up synthetic biology2,3,4. Here, we design membrane-spanning DNA origami signalling units (DOSUs) and mechanically couple them to DNA cytoskeletons5 encapsulated within giant unilamellar vesicles (GUVs). We verify the assembly and incorporation of the DOSUs into the GUV membranes and achieve their clustering upon external stimulation. The transmembrane-spanning DOSUs act as a pore to allow for the transport of single-stranded DNA into the GUVs. We employ this to externally trigger the reconfiguration of DNA cytoskeletons within GUVs using strand displacement reactions. In addition to chemical signalling, we achieve the mechanical coupling of the externally added DOSUs and the internal DNA cytoskeletons. We induce clustering of the DOSUs, which triggers a symmetry break in the organization of the DNA cytoskeleton which is mechanically coupled to the DOSU.Our work thus provides a mechanical and chemical transmembrane signaling module towards the assembly of stimuli-responsive and adaptive synthetic cells.

biophysics↗

bioRxiv2019

Interspecies transcriptome analyses identify genes that control the development and evolution of limb skeletal proportion

Despite the great diversity of vertebrate limb proportion and our deep understanding of the genetic mechanisms that drive skeletal elongation, little is known about how individual bones reach different lengths in any species. Here, we directly compare the transcriptomes of homologous growth cartilages of the mouse (Mus musculus) and bipedal jerboa (Jaculus jaculus), which has extremely long metatarsals of the feet and mouse-like arms. When we intersected gene expression differences in metatarsals of the two species with expression differences in forearms, we found that about 10% of all orthologous genes are associated with disproportionate elongation of jerboa feet. Among these, Shox2, has gained expression in jerboa metatarsals where it is not expressed in other vertebrates that have been assessed. This transcription factor is necessary for proximal limb elongation, and we show that it is sufficient to increase mouse distal limb length. Unexpectedly, we also found evidence that jerboa foot elongation occurs in part by releasing latent growth potential that is repressed in mouse feet. In jerboa metatarsals, we observed higher expression of Crabp1, an antagonist of growth inhibitory retinoic acid, lower expression of Gdf10, an inhibitory TGF{beta} ligand, and lower expression of Mab21L2, a BMP signaling inhibitor that we show is sufficient to reduce limb bone elongation. By intersecting our data with prior expression analyses in other systems, we identify mechanisms that may both establish limb proportion during development and diversify proportion during evolution. The genes we identified here therefore provide a framework to understand the modular genetic control of skeletal growth and the remarkable malleability of vertebrate limb proportion.

developmental biology↗

bioRxiv2019

Evolutionary loss of foot muscle during development with characteristics of atrophy and no evidence of cell death

Many species that run or leap across sparsely vegetated habitats, including horses and deer, evolved the severe reduction or complete loss of foot muscles as skeletal elements elongated and digits were lost, and yet the developmental mechanisms remain unknown. Here, we report the natural loss of foot muscles in the bipedal jerboa, Jaculus jaculus. Although adults have no muscles in their feet, newborn animals have muscles that rapidly disappear soon after birth. We were surprised to find no evidence of apoptotic or necrotic cell death during stages of peak myofiber loss, countering well-supported assumptions of developmental tissue remodeling. We instead see hallmarks of muscle atrophy, including an ordered disassembly of the sarcomere associated with upregulation of the E3 ubiquitin ligases, MuRF1 and Atrogin-1. We propose that the natural loss of muscle, which remodeled foot anatomy during evolution and development, involves cellular mechanisms that are typically associated with disease or injury.

developmental biology↗