[Methylation epigenetic analysis of a pedigree affected with Fragile X syndrome based on Nanopore long-read sequencing].

Objective: To explore the genetic basis for a Chinese pedigree affected with Fragile X syndrome (FXS) through Nanopore long-read sequencing.

Methods: A FXS pedigree who had undergone genetic counseling at the First Affiliated Hospital of Zhengzhou University in April 2023 was selected as the study subject. Nanopore long-read sequencing, triplet-repeat primed PCR (TP-PCR), methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) and trinucleotide polymorphism genotyping of androgen receptor (AR) gene were used to analyze the FMR1 CGG repeat number, methylation, and X chromosome inactivation of the pedigree members. This study has been approved by the Medical Ethics Committee of the First Affiliated Hospital of Zhengzhou University (No. KS-2018-KY-36).

Results: Full mutation and CpG island hypermethylation were detected in the proband. The elder sister of the proband had full mutation of the FMR1 gene on one X chromosome and hypermethylation of CpG island, while the FMR1 gene on the other X chromosome was normal. FMR1 premutation was detected in the proband's mother.

Conclusion: Nanopore long-read sequencing can simultaneously detect the dynamic mutation and methylation status of the FMR1 gene on the two X chromosomes of females, which has important value for the diagnosis of FXS in different genders.