Hypoxia Reprograms a Ciliary Scaffold into a Metabolic-Epigenetic Trafficking Hub via a Succinate-Driven DNMT3L-ASXL2 Axis.

Environmental hypoxia is a major yet mechanistically unresolved driver of male infertility. While the canonical hypoxia-inducible factor (HIF) and reactive oxygen species (ROS) pathways dominate current models, how chronic oxygen deprivation persistently rewires spermatogenic epigenetics and flagellar architecture remains unknown. Here, we identify CEP162-traditionally defined as a static ciliary transition zone scaffold-as a dynamic oxygen-sensitive signaling hub that orchestrates a pathogenic metabolic-epigenetic-trafficking axis. In human asthenozoospermia and murine hypoxia models, CEP162 is aberrantly upregulated and strongly correlates with flagellar malformation and motility loss. Mechanistically, hypoxia inhibits succinate dehydrogenase, driving the accumulation of intracellular succinate, which disrupts the DNA methyltransferase 3-like (DNMT3L)-additional sex combs-like 2 (ASXL2) epigenetic repressor complex in a HIF-independent manner. This triggers CEP162 promoter hypomethylation and transcriptional derepression, establishing a stable epigenetic switch. Functionally, elevated levels of CEP162 act as a dominant negative regulator of ciliary protein delivery: biolayer interferometry and nucleotide exchange assays revealed that CEP162 spatially sequesters Rab1a and noncompetitively inhibits TRAPPC9-mediated GTP loading, thereby uncoupling vesicular trafficking from axonemal cargo delivery. Consequently, TEKT2 is not incorporated into the growing flagellum, leading to microtubule doublet destabilization and structural collapse. Genetic silencing of CEP162 or restoration of DNMT3L/ASXL2 activity fully rescues Rab1a activation, vesicular targeting, and sperm motility. Clinically, sperm CEP162 levels showed promising diagnostic potential in our initial cohort (area under the curve [AUC] >0.9) and were inversely correlated with progressive motility. This study redefines CEP162 from a passive structural component to an active metabolic-epigenetic sensor, reveals a noncanonical mechanism of Rab guanosine triphosphatase (GTPase) regulation and establishes a reversible succinate-driven epigenetic trajectory in environmentally induced infertility. These findings provide a mechanistic framework for metabolic-epigenetic coupling in polarized cells, identify actionable targets for environmentally induced male infertility and highlight a pathogenic axis that may warrant further investigation in the context of broader ciliopathies.