Monocytes differentiate along two alternative pathways during sterile inflammationVillar, Javiera; Ouaknin, Léa; Cros, Adeline; Segura, Elodie
doi: 10.15252/embr.202256308pmid: 37191947
During inflammation, monocytes differentiate within tissues into macrophages (mo‐Mac) or dendritic cells (mo‐DC). Whether these two populations derive from alternative differentiation pathways or represent different stages along a continuum remains unclear. Here, we address this question using temporal single‐cell RNA sequencing in an in vitro model, allowing the simultaneous differentiation of human mo‐Mac and mo‐DC. We find divergent differentiation paths, with a fate decision occurring within the first 24 h and confirm this result in vivo using a mouse model of sterile peritonitis. Using a computational approach, we identify candidate transcription factors potentially involved in monocyte fate commitment. We demonstrate that IRF1 is necessary for mo‐Mac differentiation, independently of its role in regulating transcription of interferon‐stimulated genes. In addition, we describe the transcription factors ZNF366 and MAFF as regulators of mo‐DC development. Our results indicate that mo‐Macs and mo‐DCs represent two alternative cell fates requiring distinct transcription factors for their differentiation.
Old and newly synthesized histones are asymmetrically distributed in Drosophila intestinal stem cell divisionsZion, Emily H; Ringwalt, Daniel; Rinaldi, Kristina; Kahney, Elizabeth W; Li, Yingying; Chen, Xin
doi: 10.15252/embr.202256404pmid: 37255015
We report that preexisting (old) and newly synthesized (new) histones H3 and H4 are asymmetrically partitioned during the division of Drosophila intestinal stem cells (ISCs). Furthermore, the inheritance patterns of old and new H3 and H4 in postmitotic cell pairs correlate with distinct expression patterns of Delta, an important cell fate gene. To understand the biological significance of this phenomenon, we expressed a mutant H3T3A to compromise asymmetric histone inheritance. Under this condition, we observe an increase in Delta‐symmetric cell pairs and overpopulated ISC‐like, Delta‐positive cells. Single‐cell RNA‐seq assays further indicate that H3T3A expression compromises ISC differentiation. Together, our results indicate that asymmetric histone inheritance potentially contributes to establishing distinct cell identities in a somatic stem cell lineage, consistent with previous findings in Drosophila male germline stem cells.
O‐GlcNAcylation promotes topoisomerase IIα catalytic activity in breast cancer chemoresistanceLiu, Yangzhi; Yu, Kairan; Zhang, Keren; Niu, Mingshan; Chen, Qiushi; Liu, Yajie; Wang, Lingyan; Zhang, Nana; Li, Wenli; Zhong, Xiaomin; Li, Guohui; Wu, Sijin; Zhang, Jianing; Liu, Yubo
doi: 10.15252/embr.202256458pmid: 37249035
DNA topoisomerase IIα (TOP2A) plays a vital role in replication and cell division by catalytically altering DNA topology. It is a prominent target for anticancer drugs, but clinical efficacy is often compromised due to chemoresistance. In this study, we investigate the role of TOP2A O‐GlcNAcylation in breast cancer cells and patient tumor tissues. Our results demonstrate that elevated TOP2A, especially its O‐GlcNAcylation, promotes breast cancer malignant progression and resistance to adriamycin (Adm). O‐GlcNAcylation at Ser1469 enhances TOP2A chromatin DNA binding and catalytic activity, leading to resistance to Adm in breast cancer cells and xenograft models. Mechanistically, O‐GlcNAcylation‐modulated interactions between TOP2A and cell cycle regulators influence downstream gene expression and contribute to breast cancer drug resistance. These results reveal a previously unrecognized mechanistic role for TOP2A O‐GlcNAcylation in breast cancer chemotherapy resistance and provide support for targeting TOP2A O‐GlcNAcylation in cancer therapy.
A CcdB toxin‐derived peptide acts as a broad‐spectrum antibacterial therapeutic in infected miceBhowmick, Jayantika; Nag, Manish; Ghosh, Pritha; Rajmani, Raju S; Chatterjee, Ritika; Karmakar, Kapudeep; Chandra, Kasturi; Chatterjee, Jayanta; Chakravortty, Dipshikha; Varadarajan, Raghavan
doi: 10.15252/embr.202255338pmid: 37166011
The bacterial toxin CcdB (Controller of Cell death or division B) targets DNA Gyrase, an essential bacterial topoisomerase, which is also the molecular target for fluoroquinolones. Here, we present a short cell‐penetrating 24‐mer peptide, CP1‐WT, derived from the Gyrase‐binding region of CcdB and examine its effect on growth of Escherichia coli, Salmonella Typhimurium, Staphylococcus aureus and a carbapenem‐ and tigecycline‐resistant strain of Acinetobacter baumannii in both axenic cultures and mouse models of infection. The CP1‐WT peptide shows significant improvement over ciprofloxacin in terms of its in vivo therapeutic efficacy in treating established infections of S. Typhimurium, S. aureus and A. baumannii. The molecular mechanism likely involves inhibition of Gyrase or Topoisomerase IV, depending on the strain used. The study validates the CcdB binding site on bacterial DNA Gyrase as a viable and alternative target to the fluoroquinolone binding site.
mTORC1 activity negatively regulates human hair follicle growth and pigmentationSuzuki, Takahiro; Chéret, Jérémy; Scala, Fernanda Dinelli; Akhundlu, Aysun; Gherardini, Jennifer; Demetrius, Dana‐Lee; O'Sullivan, James D B; Kuka Epstein, Gorana; Bauman, Alan J; Demetriades, Constantinos; Paus, Ralf
doi: 10.15252/embr.202256574pmid: 37212043
Dysregulation of the activity of the mechanistic target of rapamycin complex 1 (mTORC1) is commonly linked to aging, cancer, and genetic disorders such as tuberous sclerosis (TS), a rare neurodevelopmental multisystemic disease characterized by benign tumors, seizures, and intellectual disability. Although patches of white hair on the scalp (poliosis) are considered as early signs of TS, the underlying molecular mechanisms and potential involvement of mTORC1 in hair depigmentation remain unclear. Here, we have used healthy, organ‐cultured human scalp hair follicles (HFs) to interrogate the role of mTORC1 in a prototypic human (mini‐)organ. Gray/white HFs exhibit high mTORC1 activity, while mTORC1 inhibition by rapamycin stimulated HF growth and pigmentation, even in gray/white HFs that still contained some surviving melanocytes. Mechanistically, this occurred via increased intrafollicular production of the melanotropic hormone, α‐MSH. In contrast, knockdown of intrafollicular TSC2, a negative regulator of mTORC1, significantly reduced HF pigmentation. Our findings introduce mTORC1 activity as an important negative regulator of human HF growth and pigmentation and suggest that pharmacological mTORC1 inhibition could become a novel strategy in the management of hair loss and depigmentation disorders.
Dicer structure and function: conserved and evolving featuresZapletal, David; Kubicek, Karel; Svoboda, Petr; Stefl, Richard
doi: 10.15252/embr.202357215pmid: 37310138
RNase III Dicer produces small RNAs guiding sequence‐specific regulations, with important biological roles in eukaryotes. Major Dicer‐dependent mechanisms are RNA interference (RNAi) and microRNA (miRNA) pathways, which employ distinct types of small RNAs. Small interfering RNAs (siRNAs) for RNAi are produced by Dicer from long double‐stranded RNA (dsRNA) as a pool of different small RNAs. In contrast, miRNAs have specific sequences because they are precisely cleaved out from small hairpin precursors. Some Dicer homologs efficiently generate both, siRNAs and miRNAs, while others are adapted for biogenesis of one small RNA type. Here, we review the wealth of recent structural analyses of animal and plant Dicers, which have revealed how different domains and their adaptations contribute to substrate recognition and cleavage in different organisms and pathways. These data imply that siRNA generation was Dicer's ancestral role and that miRNA biogenesis relies on derived features. While the key element of functional divergence is a RIG‐I‐like helicase domain, Dicer‐mediated small RNA biogenesis also documents the impressive functional versatility of the dsRNA‐binding domain.
LTK and ALK promote neuronal polarity and cortical migration by inhibiting IGF1R activityChristova, Tania; Ho, Stephanie KY; Liu, Ying; Gill, Mandeep; Attisano, Liliana
doi: 10.15252/embr.202356937pmid: 37291945
The establishment of axon‐dendrite polarity is fundamental for radial migration of neurons, cortical patterning, and formation of neuronal circuits. Here, we show that the receptor tyrosine kinases, Ltk and Alk, are required for proper neuronal polarization. In isolated primary mouse embryonic neurons, the loss of Ltk and/or Alk causes a multiple axon phenotype. In mouse embryos and newborn pups, the absence of Ltk and Alk delays neuronal migration and subsequent cortical patterning. In adult cortices, neurons with aberrant neuronal projections are evident and axon tracts in the corpus callosum are disrupted. Mechanistically, we show that the loss of Alk and Ltk increases the cell‐surface expression and activity of the insulin‐like growth factor 1 receptor (Igf‐1r), which activates downstream PI3 kinase signaling to drive the excess axon phenotype. Our data reveal Ltk and Alk as new regulators of neuronal polarity and migration whose disruption results in behavioral abnormalities.