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Loss of neurogenesis in Hydra leads to compensatory regulation of neurogenic and neurotransmission genes in epithelial cells.

Hydra continuously differentiates a sophisticated nervous system made of mechanosensory cells (nematocytes) and sensory-motor and ganglionic neurons from interstitial stem cells. However, this dynamic adult neurogenesis is dispensable for morphogenesis. Indeed animals depleted of their interstitial stem cells and interstitial progenitors lose their active behaviours but maintain their developmental fitness, and regenerate and bud when force-fed. To characterize the impact of the loss of neurogenesis in Hydra, we first performed transcriptomic profiling at five positions along the body axis. We found neurogenic genes predominantly expressed along the central body column, which contains stem cells and progenitors, and neurotransmission genes predominantly expressed at the extremities, where the nervous system is dense. Next, we performed transcriptomics on animals depleted of their interstitial cells by hydroxyurea, colchicine or heat-shock treatment. By crossing these results with cell-type-specific transcriptomics, we identified epithelial genes up-regulated upon loss of neurogenesis: transcription factors (Dlx, Dlx1, DMBX1/Manacle, Ets1, Gli3, KLF11, LMX1A, ZNF436, Shox1), epitheliopeptides (Arminins, PW peptide), neurosignalling components (CAMK1D, DDCl2, Inx1), ligand-ion channel receptors (CHRNA1, NaC7), G-Protein Coupled Receptors and FMRFRL. Hence epitheliomuscular cells seemingly enhance their sensing ability when neurogenesis is compromised. This unsuspected plasticity might reflect the extended multifunctionality of epithelial-like cells in early eumetazoan evolution.

Animals

Lentiviral-mediated gene complementation rescues pathogenic ABCA3 variants.

The ATP-binding cassette subfamily A member 3 (ABCA3) protein on the limiting membrane of lamellar bodies in alveolar type 2 (AT2) cells transports phospholipids required for pulmonary surfactant assembly. ABCA3 deficiency results from biallelic pathogenic variants in ABCA3 and causes progressive neonatal respiratory failure or childhood interstitial lung disease (chILD). Supportive/compassionate care or lung transplantation are the only current definitive treatments for ABCA3 deficiency and progressive respiratory failure. Complementing dysfunctional ABCA3 by gene addition has therapeutic potential. Previous studies show that repairing or complementing ABCA3 in induced pluripotent stem cell (iPSC)-derived AT2 cells rescues lamellar body morphology and surfactant phospholipid composition. Pathogenic variants disrupt ABCA3 function through altered protein trafficking (type 1) or by impaired phospholipid transport (type 2) into lamellar bodies. Here we tested ABCA3 gene complementation using a human pulmonary epithelial cell line (A549) with a genomically silenced ABCA3 locus (ABCA3 KO). From this line, additional cell lines that stably express individual ABCA3 variant cDNA constructs from a single genomic locus were tested: L101P (type 1), E292V (type 2), E690K (type 2), or wild-type ABCA3. Lentiviral-mediated ABCA3 delivery to each cell line partially rescued localization to LAMP3+ vesicles, lamellar body-like structure morphology, and cell proliferation. A functional assay measuring NF-κB signaling suggested that ABCA3 complementation ameliorated aberrant inflammatory signaling in E292V or E690K (type 2) mutant lines, but not in L101P (type 1) or knockout lines. These studies highlight the therapeutic potential of gene addition as well as differences between ABCA3 pathogenic variants that may influence genetic therapy outcomes.

ABCA3 deficiency

X-linked hyper-IgM syndrome presenting as severe Pneumocystis pneumonia in a 6-month-old infant: a case report.

BACKGROUND: X-linked hyper-immunoglobulin M (XHIGM) syndrome is a rare primary immunodeficiency caused by mutations in the CD40 ligand gene (CD40LG), characterized by defective T-cell-dependent B-cell class-switch recombination. Patients typically present with recurrent infections in early childhood, but diagnosis is often delayed due to heterogeneous clinical manifestations and the fact that serum IgM levels may remain within the normal range in a significant proportion of patients. Here we report a case of XHIGM in an infant whose diagnostic journey began with recurrent lymphadenitis and culminated in life-threatening Pneumocystis jirovecii pneumonia (PJP). CASE PRESENTATION: A 6-month-old male infant was admitted with severe respiratory distress and hypoxemia. He had recurrent axillary lymphadenitis at 1 and 2 months of age and significant failure to thrive. Chest CT showed bilateral consolidative and interstitial opacities. Immunological evaluation revealed markedly decreased IgA, normal IgM and IgG, and profound T-cell lymphopenia. Sputum metagenomic sequencing identified Pneumocystis jirovecii. Whole-genome sequencing identified a hemizygous likely pathogenic CD40LG mutation (NM_000074.3:c.520C>T, p.Q174*); his mother was a carrier. He was treated with mechanical ventilation, trimethoprim-sulfamethoxazole (TMP-SMX), micafungin, corticosteroids, and intravenous immunoglobulin (IVIG), and was discharged after 36 days. CONCLUSIONS: In infants with recurrent or opportunistic infections, persistently low IgA and declining T-cell counts-even when initial screening appears normal-should raise suspicion for underlying immunodeficiency and prompt genetic evaluation. Early aggressive management and evaluation for hematopoietic stem cell transplantation are essential to improve outcomes.Serial immunological evaluation is essential in infants with recurrent or opportunistic infections, as persistently low IgA and declining T-cell counts-even when initial screening appears normal-should prompt genetic evaluation for underlying immunodeficiency. Early aggressive management and evaluation for hematopoietic stem cell transplantation are essential to improve outcomes.

Humans

BET inhibition blunts antibody production and macrophage-mediated fibrosis to restore lung function in murine cGVHD.

Chronic graft-versus-host disease (cGVHD) significantly contributes to late mortality after allogeneic stem cell transplantation, with bronchiolitis obliterans syndrome (BOS) being a particularly lethal and treatment-resistant complication despite available therapies. Bromodomain and extraterminal (BET) proteins are epigenetic readers driving inflammatory transcriptional programs across multiple cell types. We hypothesized that BET inhibition would suppress inflammatory T and B cells and decrease macrophage polarization to a profibrotic phenotype, alleviating disease. In an established BOS cGVHD model, BET inhibition reduced germinal center (GC) formation and responses through a reduction of the CXCL13:CXCR5 axis and inflammatory T follicular helper/GC B cells in the spleen, along with a reduction in plasma cell infiltration within the lung. Mice with cGVHD had elevated pathogenic immunoglobulin G1 (IgG1) and IgM levels, both in circulation and deposited on lung tissue, which were attenuated under BET inhibition. Single-cell RNA-sequencing analysis revealed distinct cell states in the BOS lung vs control. In cGVHD mice, gene set enrichment analysis revealed the upregulation of profibrotic Arginase1 and Tgfb1 expression in alveolar macrophages (AM) and interstitial macrophages (IM), which was significantly reduced with BET inhibition. Furthermore, BET inhibition targeted lung-infiltrating M2 macrophages through the selective depletion of CD206+FcγR+ IM and AM, ultimately resulting in reduced collagen deposition and improved lung function. Our findings reveal a previously unrecognized mechanistic axis of BET regulation during cGVHD fibrosis and highlight BET inhibition as a promising therapeutic strategy.

Animals