Novel mutations in transducin-like enhancer of split 6 cause infertility in women with embryonic arrest.

Purpose: Embryonic arrest is a major cause of failure in assisted reproductive technologies. This study investigates the genetic basis of embryonic arrest in three unrelated patients and explores associated mechanisms.

Methods: Whole exome sequencing (WES) was used to identify mutations in the transducin-like enhancer of split 6 (TLE6) gene. Embryonic development was monitored using time-lapse monitoring, and immunofluorescence quantified TLE6 expression. WES and whole genome sequencing (WGS) further analyzed mutation sites. Mini-gene assays were utilized to assess the impact of these mutations on gene expression.

Results: TLE6 mutations were found 3.19% of infertile individuals with embryonic arrest, with arrest consistently occurring before the third cleavage division. Immunofluorescence analysis revealed reduced TLE6 protein expression in embryos. Four novel TLE6 mutation sites were identified: a homozygous splicing mutation (c.1386 + 1G > A), a compound heterozygous mutation consisting of a frameshift (c.859 dup), a splicing (c.51G > A), and a frameshift mutation (c.1589dup). Mini-gene assays revealed an exon 14 deletion due to c.1386 + 1G > A mutation and an exon 2 deletion due to c.51G > A mutation. In one proband, WES identified only a heterozygous variant (c.1589dup), whereas WGS additionally detected a heterozygous variant (NC_000019.9:g.2976171A > C) in the 2 kb upstream region of TLE6, suggesting potential regulatory roles.

Conclusion: This study identifies 4 novel TLE6 mutations associated with early embryonic arrest, thereby expanding the mutation spectrum in patients with TLE6 mutations and providing insights for genetic counseling. Additionally, this study highlights the limitations of WES and suggests that WGS could be used to complement and extend the findings of WES.