A novel compound heterozygous mutation in TUBB8 causing early embryonic developmental arrest

Purpose: Mutations in the beta-tubulin isotype, TUBB8, can cause female infertility. Although several mutations of TUBB8 have been reported, the full spectrum for guiding genetics counseling still needs to be further explored. Here, we sought to identify novel variants in TUBB8 and their phenotypic effects on microtubule network structure in vitro. Methods: Whole-exome sequence analysis was performed in two families with infertility to detect pathogenic variants, with validation by Sanger sequencing. All gene variants and protein structures were predicted in silico. Cells were transfected with wild-type and mutants, and immunofluorescence analysis was performed to visualize microtubule network changes. Results: We detected a novel compound heterozygous mutation, c.915_916delCC (p.Arg306Serfs*21) and c.82C > T (p.His28Tyr), and a benign heterozygous variant c.1286C > T (p.Thr429Met) in TUBB8 in the two families. Female patients with p.Arg306Serfs*21 and p.His28Tyr were infertile with early embryonic developmental arrest. The female patient with p.Thr429Met gave birth to a healthy baby in the second in vitro fertilization frozen embryo transfer cycle. The p.Arg306Serfs*21 mutation was predicted to cause large structural alteration in the TUBB8 protein and was confirmed to produce a truncated and trace protein by western blot analysis. Immunofluorescence analysis of transfected HeLa cells showed that p.Arg306Serfs*21 significantly disrupted microtubule structure. Conclusions: Our findings expand the known mutational spectrum of TUBB8 associated with early embryonic developmental arrest and female infertility.

Automated summary

This study aimed to identify novel variants in the TUBB8 gene and examine their phenotypic effects on microtubule network structure in vitro. Whole-exome sequencing analysis was performed in two families with infertility, and a compound heterozygous mutation and a benign heterozygous variant in TUBB8 were detected. Immunofluorescence analysis showed that the compound heterozygous mutation significantly disrupted microtubule structure.