Biology subjects

Stein, I.

Publications and source records attributed to Stein, I..

6 recordsLinked to original sources

bioRxiv2026

Stage-specific metabolic rewiring coordinates nucleotide supply and demand during spermatogenesis

Male meiotic prophase I features a major transition from leptotene/zygotene to pachytene/diplotene characterized by a massive transcriptomic and proteomic shift, yet how metabolism is coordinated across this transition remains unclear. Here, using stage-resolved purification of spermatogenic cells combined with respirometry, proteomics, metabolomics, and isotope tracing, we define metabolic programs across these stages. Early prophase cells rely on glutamine and fatty acid {beta}-oxidation to sustain mitochondrial respiration while directing glucose into the pentose phosphate pathway and de novo pyrimidine synthesis. In contrast, late prophase cells utilize glucose and lactate as fuels, suppress fatty-acid oxidation, lose pentose phosphate pathway entry, and silence nucleotide biosynthesis despite a surge in nascent RNA synthesis and lower nucleotide pools. Inhibiting nucleoside uptake does not impair meiotic progression, indicating that late prophase transcription depends primarily on nucleotide pools synthesized earlier. These findings reveal a developmentally programmed separation between nucleotide production in early prophase and nucleotide use in later meiotic stages. TEASERMeiotic germ cells rewire central carbon metabolism to match stage-specific nucleotide production and RNA demand during spermatogenesis.

developmental biology↗

bioRxiv2025

Chemokine Signaling Shapes Hepatic Lipid Homeostasis through the CXCL12/CXCR4/CXCR7 Axis

The CXCL12/CXCR4/CXCR7 signaling axis, long recognized for its roles in cancer, fibrosis, and tissue repair, is emerging as a broader regulator of tissue homeostasis. Here, we uncover a previously unappreciated function of this pathway in regulating hepatic metabolism. We show that Cxcl12, Cxcr4, and Ackr3 (encoding CXCR7) are dynamically regulated during the fasting-refeeding transition and become dysregulated under conditions of diet-induced insulin resistance. Hepatocyte-specific depletion of Cxcl12 or overexpression of Ackr3 each led to hepatic triglyceride accumulation, whereas hepatocyte Cxcr4 overexpression did not reproduce this phenotype, supporting a nonredundant role for CXCR7 in hepatocytes. Hepatic SDF-1 measurements across the three in vivo models further supported coordinated regulation of ligand availability within the axis, including a marked reduction in the Ackr3 overexpression model, consistent with enhanced ligand scavenging. In primary hepatocytes, Ackr3 overexpression promoted lipid accumulation and was associated with altered AKT-linked signaling, particularly under lipid-rich conditions. Analysis of human liver transcriptomic datasets revealed reduced CXCL12 and elevated CXCR4 and ACKR3 expression in NAFLD and NASH, supporting the translational relevance of this pathway. Together, our results identify the CXCL12/CXCR4/CXCR7 axis as an integral regulator of hepatic lipid balance and highlight CXCR7 as a potential therapeutic target for metabolic liver disease.

physiology↗

bioRxiv2024

Immune organization in sentinel lymph nodes of melanoma patients is prognostic of distant metastases

Sentinel lymph node (sLN) biopsy is part of melanoma staging, as involved LNs indicate a higher risk of recurrence. However, how the sLN is shaped by the tumor and reciprocally affects metastatic progression is poorly understood. Here, we mapped immune organization in involved and non-involved sLNs of 69 melanoma patients using high-resolution spatial proteomics, spatial transcriptomics and deep learning, leveraging the data for prognostic evaluation. In patients with involved LNs, a robust T cell response correlated with absence of recurrence. In non-involved LNs, protection from metastases was linked to expanded sinuses colocalized with plasmablasts whereas CCR7+ cells and Tregs correlated with future development of distant metastases. We trained a model that predicts development of distant metastases with 79% and 93% AUC for non-metastatic and metastatic LNs, respectively. Our findings reveal conserved immune patterns in sLNs that prospectively identify patients at risk for metastatic disease and may aid in therapeutic decisions.

cancer biology↗

bioRxiv2022

RORc expressing immune cells support pro-tumorigenic functions of tertiary lymphoid structures

Tertiary lymphoid structures (TLSs) are formed in many cancer types and have been correlated with better prognosis and response to immunotherapy. In liver cancer, TLSs have been reported to be pro-tumorigenic as they harbor tumor progenitor cells and nurture their growth. The processes involved in TLS development and the acquisition of a pro- or anti-tumorigenic phenotype in cancer are largely unknown. RORc expressing immune cells have been previously implicated in TLS formation, however we find that they are not necessary for TLS neogenesis in the context of inflammation-associated liver cancer. On the contrary, RORc expressing cells negatively regulate TLS formation, since in their absence TLSs form in excess. CD4 cells are essential for liver TLS formation whereas B cells are required for TLS formation specifically in the absence of RORc expressing cells. Importantly, in chronically inflamed livers lacking RORc expressing cells, TLSs become anti-tumorigenic, resulting in reduced tumor load. Comparing liver pro- and anti-tumorigenic TLSs by transcriptional, proteomic and immunohistochemical analyses, revealed enrichment of exhausted CD8 cells that retained effector functions as well as germinal center B cells and plasma cells in anti-tumorigenic TLSs. Cell depletion experiments revealed a role mainly for B cells in limiting tumor development, possibly via tumor directed antibodies. Thus, RORc expressing cells negatively regulate B cell responses, and facilitate the pro-tumorigenic functions of hepatic TLSs. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=85 SRC="FIGDIR/small/498540v2_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@385067org.highwire.dtl.DTLVardef@126c45corg.highwire.dtl.DTLVardef@25ad06org.highwire.dtl.DTLVardef@1829326_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

2-hydroxyglutarate controls centromere and heterochromatin conformation and function in the male germline

2-hydroxyglutarate (2HG) is recognized as an epigenetic regulator in cancer and some transient biological processes. Of all organs, the testis harbors the highest baseline physiological levels of 2HG, yet its putative functions in germ cell biology are unknown. Here we show that 2HG is generated in specific stages of spermatogenesis by the testis specific lactate dehydrogenase C (LDHC), beginning at the last stages of prophase I. Unexpectedly LDHC enters nuclei and concentrates in centromeres. LDHC-generated L-2HG controls centromere condensation and pericentromeric heterochromatin organization through multiple effects including clustering of chromocenters, centromere and chromocenter condensation and expression of satellite RNAs. These effects are rapid and specific to L but not D-2HG. In vivo depletion of L-2HG causes centromere malfunction and activation of the spindle assembly checkpoint. Our findings reveal that 2HG can directly affect centromere and pericentromeric heterochromatin conformation and function and is necessary for licensing chromosome segregation.

cell biology↗

bioRxiv2018

Long-term acclimation to different stress types: revealing tradeoffs between mesophyll and stomatal conductance

Ziziphus spina-christi, a thermophilic tree, became more abundant in the Mediterranean, presumably due to increased winter temperatures. In order to predict the plant acclimation to future climate changes, we attempted to understand which factors underlie photosynthetic stress acclimation.\n\nStress acclimation to three major long-term abiotic stresses (drought, salinity and temperature) was investigated by measuring growth, gas exchange, chlorophyll fluorescence and leaf structure. We developed a stress index that allowed to precisely define stress level, enabling a comparison between stress types. For each stress, photosynthesis-limiting factors were compared: stomatal conductance (gs), mesophyll conductance (gm) and maximum capacity for Rubisco carboxylation (Vcmax).\n\nPhotosynthesis under all stresses was limited mostly by gs and gm (80-90%); whereas biochemistry (Vcmax) made a minor contribution (10-20%). The relative contribution of gs and gm on photosynthetic limitation was influenced by stress type. During acclimation to drought or salinity, photosynthesis was limited by a decline in gs, while intolerance to low temperatures was driven by decline in gm. Low mesophyll-imposed limitation was the best predictor of abiotic stress tolerance.\n\nThe results demonstrate how warming climate benefits thermophilic species. Moreover, current work gives methodology for stress studies, and defines the main factors underlying the plant response to climate change.\n\nHighlightWe have compared the photosynthesis limitation resulting from long-term acclimation to three major a-biotic stresses (drought, salinity and temperature) to understand which limiting-factor are dominant under each type of stress.

plant biology↗