A novel zebrafish model unveils folate deficiency disrupts embryonic development via p53-driven cell cycle arrest

Introduction: Folate (vitamin B9) is a fundamental cofactor in one-carbon metabolism, essential for embryonic development. While maternal folate deficiency is a well-established risk factor for neural tube and congenital heart defects, its specific impact on early embryogenesis, particularly during early post-blastula stages, and the underlying molecular mechanisms remain insufficiently characterized. Objectives: This study aimed to establish a vertebrate model to facilitate real-time visualization and mechanistic dissection of how folate deficiency drives diverse developmental defects. Methods and results: We used CRISPR/Cas9 to generate a folrΔ1 zebrafish line harboring a one-nucleotide deletion in the folate receptor gene (folr), resulting in maternal folate deficiency. Embryos derived from folrΔ1 homozygote females exhibited embryonic lethality and defective dorsoventral patterning. Untargeted metabolomics analysis revealed that folate deficiency disrupts nucleotide biosynthesis and mitochondrial homeostasis. Specifically, maternal folate deficiency impaired embryonic DNA synthesis, exacerbated DNA damage, and induced G1/S phase cell cycle arrest. It also compromised mitochondrial integrity, triggering compensatory mitophagy. Notably, suppression of p53 activation in folr mutants improved dorsoventral patterning and alleviated cell cycle arrest. However, it did not mitigate the extent of DNA damage or mitophagy, suggesting p53 acts downstream of these metabolic stresses. Conclusion: We have established a robust zebrafish model of maternal folate deficiency that recapitulates key metabolic and developmental features of the human condition. Our findings demonstrated that folate deficiency disrupts metabolism, leading to DNA damage and mitochondrial dysfunction. Crucially, this pathology activates p53, which drives G1/S cell cycle arrest and severe embryonic defects, including impaired body axis formation. This model provides a powerful platform for further delineating the precise roles of folate in vertebrate development and in the pathogenesis of congenital anomalies.