Background
Recurrent 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.Results
Four homozygous variants were identified in the PREA cohort: two of
TUBA1C
(p.Gln358Ter and p.Asp444Metfs*42) and two of
TUBA4A
(p.Arg339Cys and p.Tyr440Ter). These variants cause varying degrees of spindle assembly defects. Additionally, we characterised changes in the human arrested embryo transcriptome carrying
TUBA4A
variants, with a particular focus on spindle organisation, chromosome segregation and mRNA decay.
Conclusion
Our findings identified
TUBA1C
as a novel genetic marker and expanded the genetic and phenotypic spectrum of
TUBA4A
in female infertility and RPEA, which altogether highlighted the importance of α-tubulin isotypes in preimplantation embryonic development.