VPS4B mutation disrupts oocyte meiosis and is associated with pregnancy loss

Abstract

Pregnancy loss represents one of the most common adverse outcomes in human reproduction, yet its genetic etiology remains incompletely understood. Our study aimed to identify novel genetic causes in patients presenting with pregnancy loss and hydatidiform mole. We recruited 80 patients with a history of adverse pregnancy outcomes. Among them, 74 patients had experienced at least one hydatidiform mole. After excluding six patients carrying pathogenic NLRP7 variants, we performed whole-exome sequencing (WES) on the remaining 74 patients. Pathological analysis was used to confirm the diagnosis of hydatidiform mole. Mechanistic studies included in vitro overexpression assays in Chinese hamster ovary cells and siRNA-mediated knockdown in mouse oocytes. We identified a rare homozygous missense variant in VPS4B (c.965C>T, p.Thr322Met) in a consanguineous family. In vitro overexpression assays revealed that the mutation markedly reduced VPS4B protein expression. Knockdown of Vps4b in mouse oocytes induced profound defects in meiotic spindle architecture and chromosome alignment, with the proportion of bipolar spindles decreasing from 86.5% in controls to 18.6% in knockdown oocytes, whereas the proportion of multipolar spindles increased from 13.5% to 81.4% ( P < 0.001). The polar body extrusion rate decreased from 80.8% to 3.3% ( P < 0.001). Although fertilization rates were unaffected (65.5% vs. 70.0%; P = 0.785, not significant), VPS4B-depleted embryos exhibited spindle multipolarity (36.8% vs. 9.5%) and micronucleation (47.4% vs. 0%), indicating severe post-fertilization mitotic failure. The VPS4B c.965C>T variant is associated with pregnancy loss and hydatidiform mole. VPS4B dysfunction in oocytes causes meiotic defects and abnormal early embryonic development, positioning VPS4B as a candidate gene for reproductive failure. These findings extend the known functions of VPS4B to female meiosis and early embryogenesis, with potential implications for genetic counseling in affected families.