Biology subjects

Abe, S.

Publications and source records attributed to Abe, S..

17 recordsLinked to original sources

bioRxiv2026

In-Cell Protein Crystallization via a Locally Flexible 24-mer Assembly Precursor

In-cell protein crystallization (ICPC) produces ordered protein crystals within living cells, but the mechanisms used by proteins to acquire long-range crystalline order in the cellular environment remains poorly understood. Here, we define the assembly pathway of CipB, a crystalline inclusion protein from Photorhabdus luminescens. CipB crystals formed in cells dissolve under mild acidic conditions into a predominant 24-mer species, supporting a model in which an in-cell crystal is built from a discrete 24-mer assembly precursor rather than through direct packing of smaller oligomeric states. Structural analysis of recrystallized CipB shows that the same 24-mer architecture packs into a body-centered cubic lattice, consistent with the lattice observed for the in-cell crystals. Cryo-EM and molecular dynamics analyses indicate that the 24-mer assembly precursor preserves its overall architecture while retaining local conformational flexibility at the N-terminal and surface-loop regions. Mutation analyses further link the N-terminal region to the formation of the 24-mer precursor and surface residues to lattice assembly. These observations support a stepwise crystallization model in which N-terminal flexibility facilitates the formation of an assembly-competent 24-mer precursor, whereas defined hydrophobic surface contacts subsequently organize these precursors into a long-range-ordered lattice.

biophysics↗

bioRxiv2026

From introduction to eradication: reconstructing population size and removal history of an invasive species

O_LIUnderstanding the processes underlying successful eradication of invasive species is essential for achieving global island conservation goals. Despite the widespread availability of capture records from eradication programs, modeling frameworks that utilize these datasets to elucidate spatio-temporal population dynamics remain underdeveloped. C_LIO_LIIn this study, we reconstructed the spatio-temporal population dynamics of the small Indian mongoose on Amami-Oshima Island (712 km{superscript 2}), Japan, where the species was introduced in 1979 and officially declared eradicated in 2024 after more than 30 years of systematic removal. We integrated introduction records, capture data, and monitoring data using a hierarchical harvest-based model (HBM). To evaluate the models capacity to support management decisions and assess eradication success, we conducted retrospective analyses and compared estimated eradication probabilities with those obtained from a rapid eradication assessment (REA; Samaniego-Herrera et al., 2013). C_LIO_LIThe estimated population size (before reproduction) peaked at 5,449 individuals (95% CI: 4,703, 6,175) in 2000 and subsequently declined almost monotonically. The maximum invaded area was 547.78 km{superscript 2} (posterior median, 95% CI: 496.47, 566.04) in 2009, indicating that the removal program successfully prevented island-wide expansion. Retrospective analyses showed that population estimates remained within the 95% credible intervals of the full dataset estimates, demonstrating temporal consistency. Eradication probabilities estimated by the HBM were substantially higher than those from the REA, highlighting the sensitivity of estimates to fine-scale heterogeneity in detection processes. C_LIO_LISynthesis and applications: Hierarchical HBMs provide a powerful framework for reconstructing, predicting, and evaluating invasive species eradication dynamics. Being aware of the limitations for application to eradication evaluations, HBMs can support adaptive management in long-term eradication programs and improve our understanding of the mechanisms underlying successful eradication. C_LI

ecology↗

bioRxiv2026

Hormone signaling and immune programs define differential endocrine responsiveness in high-risk breast tissue

Hormone therapies are frequently used to reduce breast cancer risk in individuals at increased risk for primary or subsequent disease; however, tissue-level responses to these therapies are heterogeneous and incompletely understood. Background parenchymal enhancement (BPE) on breast magnetic resonance imaging (MRI) provides a non-invasive radiologic readout of breast tissue features associated with endocrine responsiveness and cancer risk. Although BPE is associated with hormonal exposure, a subset of patients with BPE do not show a response to preventive endocrine therapy and therefore may remain at increased breast cancer risk. In this study, we integrated single-nucleus RNA sequencing and spatial transcriptomics to define the determinants of endocrine responsiveness in the setting of BPE. We identify hormone-driven epithelial cells with high levels of estrogen signaling and endocrine responsiveness, together with immune-associated epithelial programs characterized by diminished luminal identity and increased expression of immune-modulatory pathways, including major histocompatibility complex (MHC) class II and CD74. Functional organoid assays validate that these epithelial states exhibit differential sensitivity to tamoxifen and demonstrate that inflammatory signals can induce immune-modulatory epithelial programs. Together, our findings identify hormone signaling and immune programs as key determinants of endocrine responsiveness in breast tissue and provide a biological basis for interpreting radiologic markers relevant to cancer prevention.

cancer biology↗

bioRxiv2025

Mechanosensitive Stanniocalcin-1 Attenuates Pulmonary Arterial Hypertension by Suppressing Smooth Muscle Cell Proliferation

BackgroundIdiopathic pulmonary arterial hypertension (IPAH) is driven by progressive pulmonary vascular remodeling, particularly pulmonary arterial smooth muscle cell (PASMC) proliferation. Current combination vasodilator therapies have markedly improved outcomes; however, prognosis remains poor in subgroups such as patients with respiratory comorbidities, highlighting the need for novel therapies. Elevation of intravascular hydrostatic pressure is a hallmark of IPAH, yet its direct role in PASMC pathobiology remains largely unexplored. We developed a cyclic hydrostatic pressurization culture system to model hypertensive hemodynamic stress in vitro and identify pressure-responsive mediators. MethodsPASMCs from 4 patients with IPAH were exposed to high hydrostatic pressure (70/40 mmHg, 60 bpm). Transcriptomic profiling identified differentially expressed genes, validated by qPCR. Functional studies included piezo-type mechanosensitive ion channel component 1 (PIEZO1) modulation, recombinant human stanniocalcin-1 (rhSTC1) treatment, bromodeoxyuridine (BrdU) incorporation, and western blotting for cell-cycle regulators. In vivo, chronic hypoxia-induced pulmonary hypertension was assessed in wild-type and Stc1-/- mice by hemodynamic and histological analyses, with or without intratracheal rhSTC1 administration. ResultsRNA sequencing revealed STC1 as a robustly pressure-induced gene in IPAH PASMCs. PIEZO1 activation upregulated STC1, whereas knockdown blunted this response. Elevated STC1 expression was observed in PASMCs of IPAH lung tissues, and rhSTC1 reduced PASMC proliferation and increased p-p53, p21, and p27 expression. In the chronic hypoxia model, Stc1-/- mice exhibited higher right ventricular systolic pressure (RVSP) (43.7 {+/-} 1.3 vs. 30.6 {+/-} 0.9 mmHg) and greater pulmonary arterial medial thickness (39.1 {+/-} 2.5% vs. 26.5 {+/-} 1.3%) than wild-type mice. CD68-positive macrophages were increased in Stc1-/- mice under normoxia and further elevated with hypoxia. In wild-type and Stc1-/- PAH models, intratracheal administration of rhSTC1 markedly reduced medial thickening, CD68-positive macrophage accumulation, and RVSP in both wild-type and Stc1-/- mice. ConclusionsWe demonstrate that elevated hydrostatic pressure drives STC1 expression via PIEZO1, conferring potent anti-remodeling effects in IPAH. STC1 supplementation represents a potential therapeutic strategy that addresses an urgent medical need not fulfilled by conventional therapies. Clinical PerspectiveO_ST_ABSWhat Is New?C_ST_ABSO_LIWe established a novel hydrostatic pressurization system to recapitulate idiopathic pulmonary arterial hypertension (IPAH) hemodynamic conditions in vitro. C_LIO_LIStanniocalcin-1 (STC1) is a hydrostatic pressure-responsive gene in pulmonary arterial smooth muscle cells (PASMCs) from IPAH patients, induced via the mechanosensitive receptor piezo type mechanosensitive ion channel component 1 (PIEZO1). C_LIO_LIExogenous STC1 suppresses PASMC proliferation and attenuates pulmonary vascular remodeling in chronic hypoxia-induced PAH models. C_LI What Are the Clinical Implications?O_LISTC1 supplementation represents a potential therapeutic strategy for IPAH, acting through a non-vasodilatory mechanism. C_LIO_LISTC1 supplementation may offer benefit in patients with limited response to current vasodilator therapies or with comorbid respiratory disease. C_LIO_LITargeting mechanotransduction pathways could expand treatment options for pulmonary hypertension. C_LI

molecular biology↗

bioRxiv2025

Fine needle aspiration biopsy of breast specimens effectively harvests cells for patient-derived organoids modeling breast ductal carcinoma in situ

BackgroundPatient-derived organoids (PDOs) generated from benign breast tissue and breast carcinomas have successfully recapitulated their respective in vivo counterparts. PDOs model tumorigenesis and allow for screening of novel therapeutics personalized to individual patients. However, acquiring cells to generate PDOs is cumbersome. We demonstrate the feasibility of fine needle aspiration biopsy (FNAB) for harvesting cells for PDOs modeling ductal carcinoma in situ (DCIS). MethodsSurgical specimens from patients with biopsy-proven DCIS were used for this study. Core needle biopsy (CNB) was performed on fresh specimens in the operating room, and tissue was mechanically dissociated before culture in basement membrane extract (BME) and organoid medium to generate PDOs. FNAB was performed in the gross room on fresh specimens, and the remaining aspirate was similarly submitted for PDO culture. ResultsPDOs were successfully generated in 15/18 specimens obtained by CNB and 7/11 specimens obtained by FNAB. The average time to initial organoid growth was 4 days for FNAB specimens compared to 19.3 days for CNB specimens. Tumor cells were seen on 7/11 FNAB smears and 16/18 CNB touch preps. Immunofluorescence staining confirmed the presence of both luminal and myoepithelial cells in derived PDOs. ConclusionsFNAB effectively obtains cells for PDOs modeling DCIS. CNB after mincing yielded PDOs with a high success rate, but they were slow to establish. Notably, the time to organoid growth was significantly shorter for FNAB specimens. Thus, FNAB offers an efficient alternative for breast PDO culture and can reduce the time and resources spent on generating PDO cultures.

cell biology↗

bioRxiv2025

Cell-Free Protein Crystallization Enables Rapid Structure Determination of Disaccharides and Trisaccharides Using Galectin-10 Crystals

It is critical to understand the conformational selection and dynamics of flexible saccharides via protein-ligand interactions in efforts to elucidate their biofunctional roles. Protein crystals can serve as scaffolds to immobilize small molecules, enabling structural and dynamic analysis of saccharides that are difficult to study by conventional approaches. However, constructing versatile scaffold crystals for high-throughput structural analysis remains challenging because this work involves laborious protein production and crystallization workflows. Here, we report rapid crystallization and structural analysis of saccharide-bound scaffolds by applying cell-free protein crystallization (CFPC) to galectin-10 (Gal-10), a lectin known to crystallize spontaneously in vivo. Using CFPC-generated Gal-10 crystals, we obtained the first atomic-resolution structures of melezitose, one of the trisaccharide, bound to the protein scaffold, revealing binding modes inaccessible by conventional approaches. Normalized B-factor analysis combined with molecular dynamics simulations reveals how the binding-site architecture modulates saccharide flexibility and immobilization. This platform can be extended to other flexible ligands and fragment-based screening.

biophysics↗

bioRxiv2025

Muc6-expressing gastric isthmus progenitors contribute to regeneration and metaplasia supported by myeloid-mesenchymal interactions

Gastric mucosal homeostasis is maintained by tissue-resident stem and progenitor cells residing in the isthmus region. Following mucosal injury, surviving cells contribute to regeneration, coinciding with characteristic pathological changes such as atrophic gastritis and metaplasia. To comprehensively understand the cellular dynamics involved in this process, we performed single-cell and spatial transcriptomics using newly generated transgenic mice. In human samples and mouse models, loss of gastric chief cells precedes, and even induces, loss of parietal cells during the progression of atrophy and metaplasia, validating the causal relationship underlying the decrease of these two lineages. Single-cell analysis confirmed robust stemness and metaplastic changes in the Muc6-expressing neck lineage following either chief or parietal cell ablation, and lineage-tracing experiments revealed that Muc6-expressing isthmus progenitors serve as a source of metaplasia and regeneration. Mechanistically, mucosal injury recruits IL-1-expressing myeloid cells, which stimulates NRG1 production in stromal fibroblasts, leading to mucosal proliferation and regeneration mediated by Myc activation in isthmus progenitors. These findings highlight the injury-responsible stem cell-like function of Muc6-expressing isthmal progenitors, which play a critical role in mucosal homeostasis and disease progression. Visual abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/648856v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@10fc2eaorg.highwire.dtl.DTLVardef@1c5b82corg.highwire.dtl.DTLVardef@1be747dorg.highwire.dtl.DTLVardef@d1d722_HPS_FORMAT_FIGEXP M_FIG C_FIG

cell biology↗

bioRxiv2024

Temporal Parameters Determine the Efficacy of Vagus Nerve Stimulation Directed Neural Plasticity

Combining vagus nerve stimulation (VNS) with rehabilitation represents an emerging treatment for a range of neurological disorders, and identifying stimulation parameters that maximize the effects of VNS may provide a means to optimize this therapy. A number of prior studies show that varying the intensity of stimulation, which influences the amount of neuromodulatory activation in response to VNS, determines the strength of VNS-dependent enhancement of synaptic plasticity in cortical circuits. The impact of the temporal parameters of stimulation, such as the frequency and distribution of pulses within a stimulation train, remains underexplored. In this study, we evaluated how varying these temporal parameters impacts the magnitude of VNS-directed plasticity. In the first experiment, rats received trains of VNS at one of three moderate pulse frequencies (20, 30, or 45Hz) timed to occur with movement during training on a simple motor task. After five days of training, we evaluated the cortical movement representations using intracortical microstimulation. All three moderate pulse frequencies produced equivalent increases in the cortical representation of the paired movement compared to sham stimulation. In a second experiment, we used a similar paradigm to explore whether burst stimulation would enhance VNS-dependent plasticity. Unexpectedly, we found that both burst stimulation or a matched number of pulses distributed evenly in time failed to produce significant enhancement of plasticity compared to sham stimulation, whereas moderate pulse frequency stimulation did. These findings illustrate the importance of the temporal dynamics of stimulation in determining the effects of VNS and provide guidelines for designing novel VNS sequences.

bioengineering↗

bioRxiv2024

Comparative analysis of trans-chromosomic rodent models reveals improved somatic hypermutation and class-switch recombination in rats

Humanized rodent models, especially humanization of genetic/genomic components involved in immunity have significantly advanced our understanding of human immune system. Here, we utilized trans-chromosomic (Tc) technology to generate a TC-mAb rat model that stably harbors a mouse artificial chromosome carrying full-length human immunoglobulin (Ig) heavy and kappa light chain genes (IGHK-NAC) in a rat Ig knockout background. In contrast with TC-mAb mice, serum human IgG concentration was found higher than IgM. Number of lymphocytes was recovered, and B cell population in the spleen was normal. Remarkably, repertoire analysis revealed similarities between the model and human PBMCs; somatic hypermutation and class-switch recombination also more closely resembled humans. Furthermore, immunization resulted in generation of antigen-specific human antibodies. Collectively, our strategy to generate both rat and mouse models through introduction of the identical IGHK-NAC offers unprecedented opportunities to comprehensively evaluate genomic regulation and its outcomes associated with genomic sequences and host-derived protein factors.

bioengineering↗

bioRxiv2023

High-throughput structure determination of an intrinsically disordered protein using cell-free protein crystallization

Intrinsically disordered proteins (IDPs) play a crucial role in various biological phenomena, dynamically changing their conformations in response to external environmental cues. To gain a deeper understanding of these proteins, it is essential to identify the determinants that fix their structures at the atomic level. Here, we developed a pipeline for rapid crystal structure analysis of IDP using a cell-free protein crystallization (CFPC) method. Through this approach, we successfully demonstrated the determination of the structure of an IDP to uncover the key determinants that stabilize its conformation. Specifically, we focused on the 11-residue fragment of c-Myc, which forms an -helix through dimerization with a binding partner protein. This fragment was strategically fused with an in-cell crystallizing protein and was expressed in a cell-free system. The resulting crystal structures of the c-Myc fragment were successfully determined at a resolution of 1.92 [A] and we confirmed that they are identical to the structures of the complex with the native binding partner protein. This indicates that the environment of the scaffold crystal can fix the structure of c-Myc. Significantly, these crystals were obtained directly from a small reaction mixture (30 L) incubated for only 72 hours. Analysis of 8 crystal structures derived from 22 mutants revealed two hydrophobic residues as the key determinants responsible for stabilizing the -helical structure. These findings underscore the power of our CFPC screening method as a valuable tool for determining the structures of challenging target proteins and elucidating the essential molecular interactions that govern their stability.

biophysics↗

bioRxiv2023

Structural insights into a single semi-clathrate hydrate formed in a confined environment of porous protein crystal.

Water behavior on protein surfaces influences protein structure and function. Antifreeze Proteins (AFPs) have been intensively studied in context of biological cytotechnology. AFPs inhibit growth of ice microcrystals by forming unique water-cluster networks which are influenced by protein surface morphology and hydrophobicity. Such unique water-cluster networks have been identified as semi-clathrate structures in crystals and are believed to be stabilized by intermolecular interactions within the confined environment. However, there is little atomic-level information about the process of formation of semi-clathrates and the structural units of water-clathrate networks. We identified a single semi-clathrate formed on the pore surface of ferritin crystal which has a structure similar to that of a natural AFP. Comparison of ferritin mutants and determination of temperature-dependent structures revealed that semi-clathrate water molecules on an -helix undergo structural alterations with increasing temperature. Lowering the temperature regenerates the semi-clathrate structure. Water molecules hydrogen-bonded to main chain carbonyl groups are stably immobilized at room temperature and serve as starting points for clathrate formation. These findings provide a mechanistic understanding of water networks in AFPs and guidelines for designing new cryomaterials.

biophysics↗

bioRxiv2022

Liver type 1 innate lymphoid cells lacking IL-7 receptor are a native killer cell subset fostered by parenchymal niches

Group 1 innate lymphoid cells (G1-ILCs), including circulating natural killer (NK) cells and tissue-resident type 1 ILCs (ILC1s), are innate immune sentinels critical for responses against infection and cancer. In contrast to relatively uniform NK cells through the body, diverse ILC1 subsets have been characterized across and within tissues in mice, but their developmental and functional heterogeneity remain unsolved. Here, using multimodal in vivo approaches including fate-mapping and targeting of the interleukin 15 (IL-15)-producing microenvironment, we demonstrate that liver parenchymal niches support the development of a cytotoxic ILC1 subset lacking IL-7 receptor (7R- ILC1s). During ontogeny, fetal liver (FL) G1-ILCs arise perivascularly and then differentiate into 7R- ILC1s within sinusoids. Hepatocyte-derived IL-15 supports parenchymal development of FL G1-ILCs to maintain adult pool of 7R- ILC1s. IL-7R+ (7R+) ILC1s in the liver, candidate precursors for 7R- ILC1s, are not essential for 7R- ILC1 development in physiological conditions. Functionally, 7R- ILC1s exhibit killing activity at steady state through granzyme B expression, which is underpinned by constitutive mTOR activity, unlike NK cells with exogenous stimulation-dependent cytotoxicity. Our study reveals the unique ontogeny and functions of liver-specific ILC1s, providing a detailed interpretation of ILC1 heterogeneity.

immunology↗

bioRxiv2022

Cell-free Protein Crystallization for Nanocrystal Structure Determination

In-cell protein crystallization (ICPC) has attracted attention as a next-generation structural biology tool because it does not require multistep purification processes and large-scale crystallization screenings. However, significant issues remain to be solved in context of obtaining various protein crystals in sufficient amounts and quality for structure determination by ICPC. Here, we report the development of cell-free protein crystallization (CFPC), a direct protein crystallization technique which uses cell-free protein synthesis. The most crucial advantages of CFPC are that the reaction scale and time can be minimized and that various reagents can be added during the reaction. We obtained high-quality nano-sized polyhedra crystals, which are produced in insect cells by infection with cytoplasmic polyhedrosis virus, at a 200 L reaction scale within 6 h. We applied this technology to structure determination of crystalline inclusion protein A (CipA) by suppressing twin crystal formation with addition of an inhibitor to the reaction solution. We succeeded in determining a 2.11 [A] resolution structure from the nanocrystals of CipA. This technology, which integrates in-cell and in vitro crystallizations significantly expands the tools available for high throughput protein structure determination, particularly in context of unstable, low-yield, or substrate-binding proteins, which are difficult to analyze by conventional methods.

biophysics↗

bioRxiv2021

Transcriptional regulation of neonatal neural stem cells is a determinant of social behavior

Rare gene variants confer a high level of penetrance to neurodevelopmental disorders, but their developmental origin and cellular substrates remain poorly understood. To address this limitation, we explored the role of TBX1, a gene encoded in a rare copy number variant, in cell and mouse models. Here, we report that neonatal Tbx1 deficiency contributes to defective peripubertal social behavior and impairs the proliferation of neonatal neural stem/progenitor cells. Moreover, TBX1 transcriptionally regulates genes linked to post-embryonic neurogenesis and neurodevelopmental disorders associated with other rare gene variants. Our data indicate a precise time window and cell type through which the social dimension is altered by a gene encoded in a rare CNV and provide a potential common mechanistic basis for a group of neurodevelopmental disorders. One-Sentence SummaryTbx1, a gene affecting neonatal stem cell proliferation, influences peripubertal social behavior.

neuroscience↗

bioRxiv2021

The first transchromosomic rat model with human chromosome 21 shows robust Down syndrome features

Progress in earlier detection and symptom management has increased life expectancy and quality of life in people with Down syndrome (DS). However, no drug has been approved to help individuals with DS live independently and fully. Although rat models could support more robust physiological, behavioral, and toxicology analysis than mouse models during preclinical validation, no DS rat model is available due to technical challenges. We developed the first transchromosomic rat model of DS, TcHSA21rat, which contains a freely segregating, EGFP-inserted, human chromosome 21 (HSA21) with >93% of its protein coding genes. RNA-Seq of neonatal forebrains demonstrates that TcHSA21rat not only expresses HSA21 genes but also has an imbalance in global gene expression. Using EGFP as a marker for trisomic cells, flow cytometry analyses of peripheral blood cells from 361 adult TcHSA21rat animals show that 81% of animals retain HSA21 in >80% of cells, the criterion for a "Down syndrome karyotype" in people. TcHSA21rat exhibits learning and memory deficits and shows increased anxiety and hyperactivity. TcHSA21rat recapitulates well-characterized DS brain morphology, including smaller brain volume and reduced cerebellar size. In addition, the rat model shows reduced cerebellar foliation, a prominent feature of DS that is not observed in DS mouse models. Moreover, TcHSA21rat exhibits anomalies in craniofacial morphology, heart development, husbandry, and stature. TcHSA21rat is a robust DS animal model that can facilitate DS basic research and provide a unique tool for preclinical validation to accelerate DS drug development.

genetics↗

bioRxiv2019

A non-mosaic humanized mouse model of Down syndrome, trisomy of the long arm of human chromosome 21 in mouse chromosome background

Down syndrome (DS) is a complex human condition, and animal models trisomic for human chromosome 21 (HSA21) genes or orthologs provide insights into better understanding and treating DS. However, HSA21 orthologs are distributed into three mouse chromosomes, preventing us from generating mouse models trisomy of a complete set of HSA21 orthologs. The only existing humanized mouse DS model, Tc1, carries a HSA21 with over 20% of protein coding genes (PCGs) disrupted. More importantly, due to the human centromere, Tc1 is mosaic (a mix of euploid and trisomic cells), which makes every mouse unique and compromises interpretation of results. Here, we used mouse artificial chromosome (MAC) technology to "clone" the 34 MB long arm of HSA21 (HSA21q). Through multiple steps of microcell-mediated chromosome transfer we created a new humanized DS mouse model, Tc(HSA21q;MAC)1Yakaz ("TcMAC21"). Constitutive EGFP expression from the transchromosome and fluorescent in situ hybridization validate that TcMAC21, containing a hybrid chromosome of HSA21q and mouse centromere, is not mosaic. Whole genome sequencing shows that TcMAC21 contains a nearly complete copy of HSA21q with 93% of intact PCGs, while RNA-seq and additional mRNA/protein expression analyses confirm that PCGs are transcribed and regulated. A battery of tests show that TcMAC21 recapitulates many DS phenotypes including morphological anomalies in heart, craniofacial skeleton and brain, pathologies at molecular and cellular level, and impairments in learning, memory and synaptic plasticity. TcMAC21 is the most complete mouse model of DS extant and has potential for supporting a wide range of basic and preclinical research. Significance StatementIn the last 25 years, mouse models of trisomy 21 have supported research into Down syndrome, from defining the basis for developmental effects up to support for clinical trials. However, existing models have significant shortfalls, especially for preclinical studies. These deficiencies include incomplete or inappropriate representation of trisomic genes, absence of an extra chromosome, and mosaicism. Using cutting edge technologies we produced a mouse artificial chromosome containing the entire 34Mb long arm of human chromosome 21 and, with assisted reproductive technologies, established it in the germ line of mice. This trisomic mouse manifests developmental and functional features of Down syndrome, including hippocampal-based learning and memory deficits. This is the most complete model of Down syndrome produced to date.

genetics↗

bioRxiv2019

Micro- and nanostructural characteristics of rat masseter muscle entheses -Characteristics of masseter muscle entheses-

The entheses of the masticatory muscles differ slightly from those of the trunk and limb muscles. However, the bones of the skull are subject to various functional pressures, including masticatory force, resulting in a complex relationship between bone structure and muscle function that remains to be fully elucidated. The present study aimed to clarify aspects of masseter muscle-tendon-bone morphological characteristics and local load environment through quantitative analysis of biological apatite (BAp) crystallite alignment and collagen fiber orientation together with histological examination of the entheses.\n\nResult of histological observation, the present findings show that, in the entheses of the masseter muscle in the first molar region, tendon attaches to bone via unmineralized fibrocartilage, while some tendon collagen fibers insert directly into the bone, running parallel to the muscle fibers. Furthermore, BAp crystallites in the same region show uniaxial preferential alignment at an angle that matches the insertion angle of the tendon fibers. Conversely, in the entheses of the masseter muscle in the third molar region, the tendon attaches to the bone via a layer of thickened periosteum and chondrocytes. As in the first molar region, the results of bone quality analysis in the third molar region showed BAp crystallite alignment parallel to the orientation of the tendon fibers. This indicates that the local mechanical environment generates differences in enthesis morphology.\n\nThe present study showed a greater degree of uniaxial BAp crystallite alignment in entheses with direct insertion rather than indirect tendon-bone attachment and the direction of alignment was parallel to the orientation of tendon fibers. These findings suggest that functional pressure from the masseter muscle greatly affects bone quality as well as the morphological characteristics of the enthesis, specifically causing micro- and nanostructural anisotropy in the direction of resistance to the applied pressure.

biophysics↗