Biology subjects

Sauter, C.

Publications and source records attributed to Sauter, C..

6 recordsLinked to original sources

bioRxiv2026

A synthetic xeno-free extracellular matrix surrogate supports robust human induced pluripotent stem cell maintenance and multilineage differentiation

Animal-derived surface coatings present the gold standard in stem cell culture. However, they come with major drawbacks such as lot-to-lot inconsistency and an ethically problematic production. Approaches to develop synthetic coating alternatives have largely failed to recapitulate biological functions essential to PSC-self renewal and differentiation. In this study, we have investigated the suitability of a fully synthetic, chemically defined extracellular matrix-mimicking coating named BIOINSTRUCT for hiPSC culture. BIOINSTRUCT was employed during maintenance culture of IMR90-4 cells, as well as directed differentiation of HIHCNi008-A, ACTN2-GFP, and UKKI-011-A cells. BIOINSTRUCT preserved hiPSC characteristics over the experimental period of 10 passages similar to Matrigel. Spontaneous differentiation resulted in the formation of ectodermal, mesodermal and endodermal derivatives, confirming the retention of pluripotency. Directed differentiation on BIOINSTRUCT enabled the generation of neuronal, cardiac and pancreatic endocrine cells. Altogether, our data underscore BIOINSTRUCT as a promising alternative to animal-derived extracellular matrix coatings.

cell biology↗

bioRxiv2026

Engineering autologous ossicles for the personalized modeling of acute myeloid leukemia

Acute Myeloid Leukemia (AML) is the most lethal hematological malignancy in adults and is characterized by significant genetic and cytogenetic heterogeneity. This diversity drives substantial patient-to-patient variability in disease progression and therapeutic response. Increasing evidence indicates that bone marrow mesenchymal stem/stromal cells (MSCs) play a critical role in AML emergence, evolution and treatment resistance. However, progress in the field is challenged by the lack of experimental models supporting sustained AML survival while faithfully recapitulating the human bone marrow niche. Humanized ossicles (hOss) have recently emerged as ectopic human bone/bone marrow microenvironments composed of MSCs and hematopoietic elements, enabling improved AML engraftment in vivo. Nonetheless, those models typically exploit healthy MSCs largely because primary patient-derived cells exhibit diminished ossification potential. Here, we introduce OssiGel, a novel engineered human cartilage extracellular matrix produced by a mesenchymal cell line. We hypothesized that combining OssiGel with primary MSCs would enable the robust formation of hOss in healthy and malignant settings. We report that OssiGel supports fast and reproducible formation of hOss through endochondral ossification using MSCs isolated from both healthy and AML bone marrow samples. Within hOss, AML-MSCs were shown to persist long-term and to generate a human stromal microenvironment supporting the establishment of autologous AML hematopoietic cells, enabling the generation of autologous (autologOss). Single-cell RNA sequencing (scRNA-seq) revealed that autologOss recapitulate the majority of the AML blood populations observed in the corresponding patient bone marrow samples. Moreover, proof-of-concept sequencing of AML-MSCs from autologOss allowed predictive interrogation of interactions with leukemic populations and revealed the acquisition of an inflammatory-like phenotype, characteristic of AML. Taken together, our study establishes OssiGel as a novel platform for the robust engineering of autologous ossicles from AML patient samples. This provides a relevant tool to decipher patient-specific cellular interactions and drug responses, with potential translational value to broad hematological malignancies.

bioengineering↗

bioRxiv2026

Human mascRNA interacts with SUMO E1 and reshapes nuclear SUMOylation

Human mascRNA is a tRNA-like 58-nucleotide non-coding RNA processed from the 3' end of the MALAT1 transcript. Although mascRNA has been implicated in diverse cellular processes, its molecular mechanism has remained unclear. Here, we reveal a direct functional link between mascRNA and the SUMOylation pathway. Structural probing and SEC-SAXS confirm the compact, tRNA-like architecture of mascRNA in solution, while biochemical assays demonstrate its direct interaction with the SUMO E1 activating enzyme in vitro. Proteomic analyses show that mascRNA engages nuclear protein networks enriched for SUMOylated factors, including chromatin remodelers and nucleolar components. Transfection of synthetic mascRNA alters SAE2 and SUMO1 nuclear organization and broadly reduces nuclear SUMOylation, accompanied by decreased ProMyeLocytic (PML) body abundance and SUMO colocalization. SUMO1 immunoprecipitation and mass spectrometry reveal widespread decreases in SUMO conjugation, particularly among proteins involved in RNA metabolism and rRNA biogenesis with nuclear body localization. We further validate reduced SUMOylation of nucleolar factors such as BEND3 and ZNF106. These findings position mascRNA as a structured RNA ligand that modulates SUMO-dependent nuclear architecture and protein homeostasis, uncovering an unexpected intersection between RNA biology and post-translational modification networks. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/700226v1_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@e94a88org.highwire.dtl.DTLVardef@1c62aforg.highwire.dtl.DTLVardef@192cf37org.highwire.dtl.DTLVardef@1624896_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

The nucleating agent crystallophore induces instant protein crystallization

The rapid preparation of homogeneous suspensions of micro- or nano-crystals is a crucial step in serial crystallography. We show how additives, such as the crystallophore (TbXo4) that acts as a molecular glue by promoting protein-protein interactions, can facilitate sample preparation for both serial synchrotron crystallography (SSX) and micro electron diffraction (3D ED). This lanthanide complex was used here for its nucleating properties to crystallize hen egg white lysozyme. SAXS monitoring indicates that crystals formed in a few minutes in low salt conditions that would not lead to spontaneous nucleation. Resulting micro- and nano-crystals were successfully used to determine the structure of the lysozyme-TbXo4 complex by SSX and 3D ED, illustrating the diffraction quality of the produced crystals and the usefulness of such compounds in the sample preparation pipeline for serial crystallography.

biophysics↗

bioRxiv2020

Monitoring the production of high diffraction-quality crystals of two enzymes in real time using in situ dynamic light scattering

The reproducible preparation of well diffracting crystals is a prerequisite for every structural study based on crystallography. An instrument called the XtalController has recently been designed that allows the monitoring of crystallization assays using dynamic light scattering and microscopy, and integrates piezo pumps to alter the composition of the mother liquor during the experiment. We have applied this technology to study the crystallization of two enzymes, the CCA-adding enzyme of the psychrophilic bacterium Planococcus halocryophilus and the hen egg white lysozyme in the presence of a synthetic chemical nucleant. We were able to i) detect early nucleation events and ii) drive the crystallization system (through cycles of dissolution/crystallization) towards growth conditions yielding crystals with excellent diffraction properties. This technology opens a way to the rational production of samples for crystallography, ranging from nanocrystals for electron diffraction, microcrystals for serial or conventional X-ray diffraction, to larger crystals for neutron diffraction.

biochemistry↗

bioRxiv2019

Structural basis of nanobody-recognition of grapevine fanleaf virus and of virus resistance loss

Grapevine fanleaf virus (GFLV) is a picorna-like plant virus transmitted by nematodes that affects vineyards worldwide. Nanobody (Nb)-mediated resistance against GFLV has been created recently and shown to be highly effective in plants including grapevine, but the underlying mechanism is unknown. Here we present the high-resolution cryo-EM structure of the GFLV-Nb23 complex which provides the basis for the molecular recognition by the nanobody. The structure reveals a composite binding site bridging over 3 domains of the capsid protein (CP) monomer. The structure provides a precise mapping of the Nb23 epitope on the GFLV capsid in which the antigen loop is accommodated through an induced fit mechanism. Moreover, we uncover and characterize several resistance-breaking GFLV isolates with amino acids mapping within this epitope, including C-terminal extensions of the CP, which would sterically interfere with Nb binding. Escape variants with such extended CP fail to be transmitted by nematodes linking Nb-mediated resistance to vector transmission. Together, these data provide insights into the molecular mechanism of Nb23-mediated recognition of GFLV and of virus resistance loss.\n\nSignificanceGrapevine fanleaf virus (GFLV) is a picorna-like plant virus that severely impacts vineyards worldwide. While Nanobodies (Nb) confer resistance to GFLV in plants the underlying molecular mechanism of action is unknown. Here we present the high-resolution cryo-EM structure of the GFLV-Nb complex. It uncovers the conformational epitope on the capsid surface which is a composite binding site into which the antigen loop is accommodated through an induced fit mechanism. Furthermore, we describe several resistance-breaking isolates of GFLV with reduced Nb binding capacity. Those that carry a C-terminal extension also fail to be transmitted by nematodes. Together, these data provide structure-function insights into the Nb-GFLV recognition and the molecular mechanism leading to loss of resistance.

biochemistry↗