Biallelic variants in α-tubulin isotypes cause female infertility characterised as recurrent preimplantation embryo arrest

Abstract

BackgroundRecurrent preimplantation embryo developmental arrest (RPEA) is the most common phenotype in assisted reproductive technology treatment failure associated with identified genetic abnormalities. Currently known maternal genetic variants explain only a limited number of cases. Variants of the β-tubulin subunit gene,TUBB8, cause oocyte meiotic arrest and RPEA through a broad spectrum of spindle defects. In contrast, α-tubulin subunit genes are poorly studied in the context of preimplantation embryonic development.MethodsWhole exome sequencing was performed on the PREA cohort. Functional characterisations of the identified candidate disease-causing variants were validated using Sanger sequencing, bioinformatics, in vitro functional analyses and single-cell RNA-sequencing of arrested embryos.ResultsFour homozygous variants were identified in the PREA cohort: two ofTUBA1C(p.Gln358Ter and p.Asp444Metfs*42) and two ofTUBA4A(p.Arg339Cys and p.Tyr440Ter). These variants cause varying degrees of spindle assembly defects. Additionally, we characterised changes in the human arrested embryo transcriptome carryingTUBA4Avariants, with a particular focus on spindle organisation, chromosome segregation and mRNA decay.ConclusionOur findings identifiedTUBA1Cas a novel genetic marker and expanded the genetic and phenotypic spectrum ofTUBA4Ain female infertility and RPEA, which altogether highlighted the importance of α-tubulin isotypes in preimplantation embryonic development.