Expanding the Genetic and Phenotypic Spectrum of Female Infertility Caused by TUBB8 Mutations

Tubulin beta eight class VIII (TUBB8) is a subtype of β-tubulin that only exists in primates. TUBB8 mutations have been reported to cause arrest of oocyte maturation and embryonic development. We aim to further investigate the mutational spectrum of TUBB8 and its relevance with female infertility. In our study, infertile patients were recruited, and their basal and clinical characteristics were analyzed. Genomic DNA was extracted from peripheral blood donated by patients. Candidate variants were identified by whole-exome sequencing, selected by relevant criteria, and validated by Sanger sequencing. We found five heterozygous variants: c.C208A(p.P70T), c.T907C(p.C303R), c.G173A(p.R58K), c.G326T(p.G109V), and c.C916T(p.R306C) in TUBB8 among six infertile patients characterized by abnormal phenotypes in oocyte maturation, fertilization, or embryo development. Most of oocytes retrieved from affected individuals were arrested at GV (germinal vesicle) stage and early embryos were arrested at variable stages. In vitro experiments were performed, and the relationship between variant c.G173A(p.R58K), c.C208A(p.P70T), and infertility phenotype was confirmed. We also discussed the possibility about patient II-1 from family 4 is affected by germinal/germline mosaicism. These results expand the kinds of variants and phenotypic spectrum of TUBB8 variants with regard to female infertility.