A novel homozygous C-terminal deletion in BTG4 causes zygotic cleavage failure and female infertility

Abstract

Purpose: We aimed to identify pathogenic variants in a female patient with primary infertility and recurrent failure of in vitro fertilization with zygotic cleavage failure.

Methods: The genomic DNA from the affected individual was subjected to whole-exome sequencing and the variant was confirmed by Sanger sequencing. The functional effect of the identified variant was further investigated in 293 T cells.

Results: We identified a novel homozygous deletion in BTG4 (c.580_616del) in the affected individual. The deletion results in frameshift and replacement of the last 29 residues (aa195-223) with 66 random amino acids. The mutated amino acid residues are highly conserved among mammalian species. Co-immunoprecipitation in 293 T cells showed that the mutation abolished the interaction between BTG4 and PABPN1L.

Conclusion: This study conforms previous studies and expands the mutational spectrum of BTG4. Our findings prove the functional importance of the C-terminal of BTG4. BTG4 is a potential diagnostic and therapeutic target for patients suffering from zygotic cleavage failure.

Keywords: BTG4; Deletion; Female infertility; Zygotic cleavage failure.

Fig. 1

The morphology of a control zygote and the affected individual’s zygotes on day 0 and day 3. The white arrowheads indicate the pronuclei

Fig. 2

Pedigree-based identification of the pathogenic variant in BTG4. a The pedigree of the patient affected by female infertility and ZCF in Family 1. b The variant was confirmed by Sanger sequencing. The variants c.580_616del in BTG4 were inherited from the parents of the affected individual

Fig. 3

Location of variants and amino acid conservation across species of mutated residues in BTG4. a The location of the variants previously reported and in this study in the gene and protein structure. b The conservation analysis of the mutated residues in the C-terminal (aa195-223) of BTG4 among species

Fig. 4

Effect of the variant on the BTG4-PABPN1L interaction. Co-IP experiment showing the loss-of-the BTG4 and PABPN1L interaction by the replacement of the BTG4 C-terminal (MUT) or just deletion of last 29 amino acids (DEL) in 293 T cells. Cell lysates were immunoprecipitated with anti-FLAG beads, and the resulting protein samples were analyzed via Western blotting using antibodies against the HA tag (n = 3)