Verres, Y. | Search bioRxiv

bioRxiv2025

Mapping the temporal and functional landscape of Sonic Hedgehog signaling reveals new insights into early human forebrain development

The early patterning of the anterior neuroectoderm constitutes a fundamental blueprint for human brain development, orchestrated by multiple signaling pathways. Among them, Sonic Hedgehog (SHH) plays a key influence. However, the transcriptional programs it engages remain poorly defined due to the limited accessibility of human brain tissue. To address this, we established a human induced pluripotent stem cells-derived model of early forebrain differentiation, enabling a precise dissection of SHH-driven transcriptional programs over time. RNA sequencing revealed dynamic transcriptomic landscapes governing forebrain neuroectoderm specification and dorsoventral patterning. In addition, pharmacological perturbation of SHH signaling allowed to identify an extended collection of novel forebrain regionalization markers, including several previously unrecognized dorsal and ventral determinants. By combining in vivo human datasets with functional mouse studies, we enhanced the biological relevance of this extended network of putative SHH-regulated genes and long non-coding RNAs in shaping early forebrain architecture. This work advances our understanding of the temporal dynamics of SHH signaling in human neurodevelopment and provide critical molecular insights into midline brain malformations. It offers a promising foundation for advancing molecular diagnosis of complex rare genetic disorders. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=166 SRC="FIGDIR/small/654466v1_ufig1.gif" ALT="Figure 1"> View larger version (52K): org.highwire.dtl.DTLVardef@dac307org.highwire.dtl.DTLVardef@3a051borg.highwire.dtl.DTLVardef@12559c9org.highwire.dtl.DTLVardef@129cbec_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2023

Low concentrations of ethylene bisdithiocarbamate pesticides maneb and mancozeb impair manganese and zinc homeostasis to induce oxidative stress and caspase-dependent apoptosis in human hepatocytes

The worldwide and intensive use of phytosanitary compounds results in environmental and food contamination by chemical residues. Human exposure to multiple pesticide residues is a major health issue. Considering that the liver is not only the main organ for metabolizing pesticides but also a major target of toxicities induced by xenobiotics, we studied the effects of a mixture of 7 pesticides (chlorpyrifos-ethyl, dimethoate, diazinon, iprodione, imazalil, maneb, mancozeb) often detected in food samples. Effects of the mixture was investigated using metabolically competent HepaRG cells and human hepatocytes in primary culture. We report the strong cytotoxicity of the pesticide mixture towards hepatocytes-like HepaRG cells and human hepatocytes upon acute and chronic exposures at low concentrations extrapolated from the Acceptable Daily Intake (ADI) of each compound. Unexpectedly, we demonstrated that the manganese (Mn)-containing dithiocarbamates (DTCs) maneb and mancozeb were solely responsible for the cytotoxicity induced by the mixture. The mechanism of cell death involved the induction of oxidative stress, which led to cell death by intrinsic apoptosis involving caspases 3 and 9. Importantly, this cytotoxic effect was found only in cells metabolizing these pesticides. Herein, we unveil a novel mechanism of toxicity of the Mn-containing DTCs maneb and mancozeb through their metabolization in hepatocytes generating the main metabolite ethylene thiourea (ETU) and the release of Mn leading to intracellular Mn overload and depletion in zinc (Zn). Alteration of the Mn and Zn homeostasis provokes the oxidative stress and the induction of apoptosis, which can be prevented by Zn supplementation. Our data demonstrate the hepatotoxicity of Mn-containing fungicides at very low doses and unveil their adverse effect in disrupting Mn and Zn homeostasis and triggering oxidative stress in human hepatocytes.

pharmacology and toxicology↗