Novel mutations in TUBB8 and ZP3 cause human oocyte maturation arrest and female infertility

Variations in many genes may lead to the occurrence of oocyte maturation defectsand female infertility. The objective was to describe newly discovered mutations in TUBB8 and ZP3, and to characterise the accompanying spectrum of phenotypes and modes of inheritance. TUBB8 and ZP3 were sequenced from genomic DNA samples extracted from peripheral blood of patients and their family members by the whole-exome sequencing. The TUBB8 and ZP3 sequences are then aligned with cryptographic software to identify rare variations. Sanger sequencing and mass spectrometry were used to validate mutations. ExAC database was used to retrieve the frequency of corresponding mutations. PolyPhen-2 and PROVEAN were analyzed for mutations using silicon. We identified Three novel mutations and two known variant in TUBB8 and ZP3 associated with maturation in five families, and fertilization and developmental arrest are in these patients. These mutations include four heterozygous mutations in TUBB8 (c.730G > A, p.Gly244Ser, c.124C > G, p.Leu42Val, c.1172G > T, p.Arg391Leu and c.178G > A, p.Val60Met), and a heterozygous mutation in ZP3 (c.400G > A, p.Ala134Thr). Among them, these variants of TUBB8 were highly conserved among primates. As far as we know, the TUBB8 mutations detected in our study at four sites have not been reported before, and the variant of ZP3 has been published as pathogenic. Our findings extend the known mutant spectrum of TUBB8 and ZP3, and provide insights into the etiology of infertility in human women. The exact molecular mechanism has not been analyzed and should be further investigated in the future.