Identification of compound heterozygous deletion of the WWOX gene in WOREE syndrome

Background: Biallelic loss-of-function variants in WWOX cause WWOX-related epileptic encephalopathy (WOREE syndrome), which has been reported in 60 affected individuals to date. In this study, we report on an affected individual with WOREE syndrome who presented with early-onset refractory seizures and global neurodevelopmental delay and died at the age of two and a half years.

Methods: We present clinical and molecular findings in the affected individual, including biallelic pathogenic variants in the WWOX gene. We employed different molecular approaches, such as whole exome sequencing, quantitative real-time polymerase chain reaction (qPCR), and whole-genome sequencing, to identify the genetic variants. The breakpoints were determined through gap PCR and Sanger sequencing.

Result: Whole exome sequencing revealed homozygous exon 6 deletion in the WWOX gene in the proband. Quantitative real-time PCR confirmed that the parents were heterozygous carriers of exon 6 deletion. However, using whole-genome sequencing, we identified three larger deletions (maternal allele with exon 6-8 deletion and paternal allele with two deletions in proximity one in intron 5 and the other in exon 6) involving the WWOX gene in the proband, with deletion sizes of 13,261 bp, 53,904 bp, and 177,200 bp. The exact breakpoints were confirmed through gap PCR and Sanger sequencing. We found that the proband inherited the discontinuous deletion of intron 5 and exon 6 from the father, and the exons 6-8 deletion from the mother using gap PCR.

Conclusion: Our findings extend the variant spectrum of WOREE syndrome and support the critical role of the WWOX gene in neural development.