Three Novel Mutations in TUBB8 Cause Female Infertility Due to Multiple Morphological Abnormalities of the Oocyte and Early Embryo

Abstract

Recent years have seen a global increase in infertility, affecting up to 17.5% of the population. For successful human reproduction, the proper development process of the oocyte, fertilization, and early embryo is required. Assisted reproductive technology (ART), which is the primary treatment for infertility, uses the morphology of oocytes and zygotes as parameters to predict ART outcomes. However, factors such as large perivitelline space (PVS), centrally located granular cytoplasm (CLGC), multi-pronuclei (MPN) formation, and final early embryonic development arrest often lead to repeated failure of ART treatment. Genetic analysis has identified various pathogenic genetic factors contributing to infertility, suggesting that genetic variation plays a significant role in recurrent ART treatment failure. However, maternal genes responsible for large PVS, CLGC, and MPN formation are rarely reported. In this study involving Whole Exome Sequencing (WES) and Sanger sequencing validation, three novel heterozygous missense mutations (p.M403V, p.R306H, p.H190Y) in TUBB8 were identified as being associated with large PVS, CLGC, MPN formation, and early embryonic development arrest. These mutant sites are evolutionarily conserved in different species. Additionally, in silico and in vitro experiments demonstrate that these variants disrupt the conformation, expression, and microtubule structures of the TUBB8 protein. Therefore, these findings contribute significantly to understanding TUBB8-related large PVS, CLGC, and MPN formation in the context of ARTs. This broadens our insight into the genetic connection in human reproduction and emphasizes the importance of comprehensive genetic screening and personalized intervention strategies for PVS, CLGC, and MPN formation.

Keywords: Assisted reproductive technology; Early embryonic development; Female infertility; Oocyte morphology; TUBB8.