Minowa, R. | bioRxiv Science

bioRxiv2025

Dolutegravir Developmental Toxicity is Mitigated by Magnesium and Folate in Zebrafish Embryos

Integrase-strand-transfer inhibitors have transformed HIV therapy, yet the widely prescribed drug dolutegravir (DTG) has been linked to developmental toxicity and its teratogenic mechanism remains uncertain. Here we use zebrafish to dissect DTG toxicity during early vertebrate development. DTG exposure from 2-4 h post-fertilization (hpf) to 24 hpf produced high mortality and abnormal morphology; co-treatment with folic acid or 5-methyltetrahydrofolate partially restored normal morphology, whereas calcium had no effect. Strikingly, supplementation with magnesium (Mg) rescued DTG-exposed embryos almost as effectively as folate, implicating magnesium availability in protection. In competitive binding assays, Mg increased binding of folate to purified folate receptor (FOLR1) by 30% in the presence of DTG. Maternal-zygotic zebrafish folr1 mutant embryos contained significantly less endogenous folate than wild-type embryos yet displayed marked hypersensitivity to DTG that could not be mitigated by folate supplementation. Critically, magnesium supplementation partially rescued DTG toxicity in folr1 mutants, indicating a Folr1-independent component and placing the free DTG vs Mg-bound DTG balance upstream of folate transport. These results support a model in which free DTG antagonizes FOLR1, and Mg modifies DTG developmental toxicity by both FOLR1 dependent and independent processes. Our work identifies magnesium status as a modifiable determinant of DTG teratogenicity and provides a proof-of-concept zebrafish model that could be adapted for rapid in vivo screening of integrase inhibitors for developmental phenotypes.

developmental biology↗

bioRxiv2019

The Reissner Fiber is Highly Dynamic in vivo and Controls Morphogenesis of the Spine

Spine morphogenesis requires the integration of multiple musculoskeletal tissues with the nervous system. Cerebrospinal fluid (CSF) physiology is important for development and homeostasis of the central nervous system and its disruption has been linked to scoliosis in zebrafish [1, 2]. Suspended in the CSF is an enigmatic glycoprotein thread called the Reissner fiber, which is secreted from the subcomissural organ (SCO) in the brain and extends caudally through the central canal to where it terminates at the base of the spinal cord. In zebrafish, scospondin null mutants are unable to assemble the Reissner fiber and fail to extend a straight body axis during embryonic development [3]. Here, we describe zebrafish hypomorphic missense alleles, which assemble the Reissner fiber and straighten the body axis during early embryonic development, yet progressively lose the fiber, concomitant with the emergence of body curvature, alterations in neuronal gene expression, and scoliosis in adults. Using an endogenously tagged scospondin-GFP zebrafish knock-in line, we directly visualized Reissner fiber dynamics during the normal development and during the progression of scoliosis, and demonstrate that the Reissner fiber is critical for the morphogenesis of the spine. Our study establishes a framework for future investigations of mechanistic roles of the Reissner fiber including its dynamic properties, molecular interactions, and how these processes are involved in the regulation of spine morphogenesis and scoliosis. HighlightsO_LIHypomorphic mutations in zebrafish scospondin result in progressive scoliosis C_LIO_LIThe disassembly of the Reissner fiber in scospondin hypomorphic mutants results in the strong upregulation of neuronal receptors and synaptic transport components C_LIO_LIAn endogenous fluorescent knock-in allele of scospondin reveals dynamic properties of the Reissner fiber during zebrafish development C_LIO_LILoss of the Reissner fiber during larval development is a common feature of zebrafish scoliosis models C_LI

genetics↗