Biology subjects

Bontempo, A.

Publications and source records attributed to Bontempo, A..

3 recordsLinked to original sources

bioRxiv2026

Low Transcriptional Complexity Cells Represent a Conserved, Aging-Relevant Maintenance State Overlooked by Single-Cell Transcriptomics

Whether mature tissues harbor transcriptionally quiet yet biologically functional cellular reservoirs remains largely unexplored. Here, using publicly available single-cell and single-nucleus transcriptomic datasets, we identify a previously unrecognized cellular state within fully differentiated human cell lineages characterized by low transcriptomic complexity (<1000 genes per cell) but preserved lineage identity and coherent functional gene expression. These "low-transcriptional" (low-T) states, often excluded by standard single-cell quality control thresholds or subsumed within major populations, are widespread across major organs including heart, brain, lung, and immune system, comprising substantial fractions of nearly all mature cell types. Despite reduced transcript abundance, low-T cells exhibit organized molecular programs distinct from high-T counterparts enriched in pathways related to cellular maintenance, metabolic resilience, survival, and aging, while lacking stress, apoptosis, senescence, or inflammation signatures. Low-T programs are conserved across mature cell lineages within organs but remain tissue-specific, revealing a hidden axis of cellular organization orthogonal to cell identity. Their abundance declines with age in brain and immune tissues, linking this state to organismal aging. Together, our findings uncover a transcriptionally quiescent yet functionally mature cellular state conserved across tissues. This previously overlooked population represents a biologically meaningful reservoir with implications for tissue maintenance, longevity, regenerative biology, and potential pharmacological aging interventions, and challenges conventional interpretations of transcriptional sparsity in single-cell genomics.

molecular biology↗

bioRxiv2024

Mechanosensing by Piezo1 regulates osteoclast differentiation via PP2A-Akt axis in periodontitis

Mechanical stimulus to the multicellular bone unit (MBU) plays a key role in normal bone remodeling, whereas disuse osteoporosis, for example, represents loss of bone owing to lack of mechanical stresses. The analogy can be applied to a variety of pathogenic bone lytic complications, including periodontitis, in which local mechanical stress appears to be diminished. The activation of mechanosensitive Piezo1 Ca2+ channel expressed by osteoblasts and osteocytes in the MBU elicits the osteogenic signals in those cells. However, since osteoclast (OC)-specific Piezo1-gene knockout mice showed no skeletal phenotype, it has been assumed that Piezo1 might not play any role in OC-mediated bone remodeling. Here, however, we showed that mechanical stimulation of Piezo1 expressed on preosteoclasts (pre-OCs) downmodulates OC formation and, hence, bone resorptive activity in periodontitis, accompanied by significantly reduced expression of NFATc1, a master transcription factor for RANKL-induced OC-genesis. We know that the Ca2+/calcineurin/NFAT axis upregulates NFATc1 activation in pre-OCs. Interestingly, Piezo1-elicited Ca2+ influx did not affect NFATc1 expression. Instead, PP2A-mediated dephosphorylation of Akt downregulated NFATc1 in Piezo1-activated pre-OCs. However, systemic administration with Yoda1, a Piezo1 chemical agonist, or local injection of PP2A agonist, significantly downregulated the bone resorption induced in a mouse model of periodontitis, together with reduced numbers of TRAP+/phospho-Akt+ pre-OCs in local bone. These results suggest that mechanosensing by Piezo1 expressed on pre-OCs can downmodulate the RANKL-induced OC-genesis via the PP2A/Akt-dephosphorylation pathway, but that such Piezo1-mediated downregulation of bone resorption is attenuated in periodontitis. Significance StatementThe mechanosensitive Ca2+ channel Piezo1 plays important regulatory roles in a variety of cellular activities. RANKL-mediated OC-genesis requires permissive co-stimulatory signal from ITAM receptors, such as OSCAR and TREM2, to trigger the calcineurin/calmodulin signaling axis via Ca2+ oscillation, thereby upregulating NFATc1 expression. Activation of Piezo1 remarkably suppressed RANKL-induced NFATc1 activation which, in turn, reduced OC-genesis. Such mechanical activation of Piezo1 expressed on pre-OCs induced intracellular Ca2+ influx. Nonetheless, PP2A-mediated dephosphorylation of Akt, not the calcineurin/calmodulin pathway, suppressed NFATc1 in RANKL-elicited OC-genesis and resultant bone resorption, both in vitro and in vivo. These results indicate that mechanostress applied to pre-OCs can downregulate pathogenic OC-genesis and that Piezo1, as the mediator, is a novel molecular target for the development of anti-osteolytic therapies.

cell biology↗

bioRxiv2024

Inhibition of SARS-CoV-2 infection by Porphyromonas gingivalis and the oral microbiome

The COVID-19 pandemic persists despite the availability of vaccines, and it is therefore crucial to develop new therapeutic and preventive approaches. In this study, we investigated the potential role of the oral microbiome in SARS-CoV-2 infection. Using an in vitro SARS-CoV-2 pseudovirus infection assay, we found a potent inhibitory effect exerted by Porphyromonas gingivalis on SARS-CoV-2 infection mediated by known P. gingivalis compounds such as phosphoglycerol dihydroceramide (PGDHC) and gingipains as well as by unknown bacterial factors. We found that the gingipain-mediated inhibition of infection is likely due to cytotoxicity, while PGDHC inhibited virus infection by an unknown mechanism. Unidentified factors present in P. gingivalis supernatant inhibited SARS-CoV-2 likely via the fusion step of the virus life cycle. We addressed the role of other oral bacteria and found certain periodontal pathogens capable of inhibiting SARS-CoV-2 pseudovirus infection by inducing cytotoxicity on target cells. In the human oral cavity, we observed the modulatory activity of oral microbial communities varied among individuals in that some saliva-based cultures were capable of inhibiting while others were enhancing infection. These findings contribute to our understanding of the complex relationship between the oral microbiome and viral infections, offering potential avenues for innovative therapeutic strategies in combating COVID-19.

microbiology↗