Biology subjects

Sakagami, N.

Publications and source records attributed to Sakagami, N..

3 recordsLinked to original sources

bioRxiv2025

Plasmid-mediated macrolide resistance among rapidly growing mycobacteria in Japan

ObjectivesThe spread of a transmissible plasmid carrying the 23S rRNA methylase gene erm(55), which confers inducible macrolide resistance in rapidly growing mycobacteria (RGM), has raised significant clinical concerns. The aim of this study was to investigate the prevalence of erm(55)-carrying plasmids in clinically isolated RGM strains in Japan. MethodsIn total, 607 RGM clinical isolates, representing 32 species or complexes, collected between 2019 and 2023 in Japan were examined. To detect the presence of erm(55)-carrying plasmids, we conducted PCR screening, minimum inhibitory concentration testing for clarithromycin, and whole-plasmid genome sequencing. Comparative genomic analyses were performed to characterise the plasmids. ResultsAmong the 607 RGM isolates, 0.8% (5/607) possessed the plasmid with the erm(55) gene and exhibited inducible macrolide resistance, with ratios of 100% (1/1) in Mycobacterium murale, 50% (3/6) in M. obuense, and 0.8% (1/125) in M. chelonae. The erm(55)-carrying plasmids ranged from 126,187 to 170,220 bp in size. Pairwise BLASTn comparisons of the erm(55)-carrying plasmids showed weighted percent identity values ranging from 99.5% to 99.9%, with query and subject coverage values ranging from 74.2% to 100%. All erm(55) sequences (813 bp) were identical and located within a horizontal gene transfer region. ConclusionsThis study confirmed the presence of macrolide-resistant RGMs related to the erm(55)-carrying plasmid in Japan, although the overall prevalence remains low. These findings emphasise the need to consider plasmid-mediated resistance when treating infections caused by the RGM species.

microbiology↗

bioRxiv2023

Growth plate resting zone chondrocytes acquire transient clonal competency upon Hedgehog activation and efficiently transform into trabecular bone osteoblasts

The resting zone of the postnatal growth plate is organized by slow-cycling chondrocytes expressing parathyroid hormone-related protein (PTHrP), which include a subgroup of skeletal stem cells that contribute to the formation of columnar chondrocytes. The PTHrP-indian hedgehog (Ihh) feedback regulation is essential for sustaining growth plate activities; however, molecular mechanisms regulating cell fates of PTHrP+ resting chondrocytes and their eventual transformation into osteoblasts remain largely undefined. Here, in a mouse model, we utilized a tamoxifen-inducible PTHrP-creER line with Patched-1 (Ptch1) floxed and tdTomato reporter alleles to specifically activate Hedgehog signaling in PTHrP+ resting chondrocytes and trace the fate of their descendants. Hedgehog-activated PTHrP+ chondrocytes formed large concentric clonally expanded cell populations within the resting zone ( patched roses) and generated significantly wider columns of chondrocytes, resulting in hyperplasia of the growth plate. Interestingly, Hedgehog-activated PTHrP+ cell-descendants migrated away from the growth plate and eventually transformed into trabecular osteoblasts in the diaphyseal marrow space in the long term. Therefore, Hedgehog activation drives resting zone chondrocytes into transit-amplifying states as proliferating chondrocytes and eventually converts these cells into osteoblasts, unraveling a novel Hedgehog-mediated mechanism that facilitates osteogenic cell fates of PTHrP+ skeletal stem cells.

developmental biology↗

bioRxiv2020

Chondrocytes in the resting zone of the growth plate are maintained in a Wnt-inhibitory environment

Chondrocytes in the resting zone of the postnatal growth plate are characterized by slow cell cycle progression, and encompass a population of parathyroid hormone-related protein (PTHrP)-expressing skeletal stem cells that contribute to the formation of columnar chondrocytes. However, how these chondrocytes are maintained in the resting zone remains undefined. We undertook a genetic pulse-chase approach to isolate slow cycling, label-retaining chondrocytes (LRCs) from the growth plate using a chondrocyte-specific doxycycline-controllable Tet-Off system regulating expression of histone 2B-linked GFP. Comparative RNA-seq analysis identified significant enrichment of inhibitors and activators for Wnt/{beta}-catenin signaling in LRCs and non-LRCs, respectively. Activation of Wnt/{beta}-catenin signaling in PTHrP+ resting chondrocytes using Pthrp-creER and Apc-floxed allele impaired their ability to form columnar chondrocytes. Therefore, slow-cycling chondrocytes are maintained in a canonical Wnt-inhibitory environment within the resting zone, unraveling a novel mechanism regulating maintenance and differentiation of PTHrP+ skeletal stem cells of the postnatal growth plate.

developmental biology↗