P-540 Strategic implementation of PGT-M for multiple genes post qhole exome sequencing in couples with familial history: a comprehensive study
Authors: Ogur C , Kaya B , Ayar B , Taç H  A , Sarı E , Usaç G , Bakhshaliyeva N , Karadayı H , Berkil H 
Published: July 2024

Abstract

Study question
What advantages does Whole Exome Sequencing offer to couples with a familial history of hereditary disorders?

Summary answer
WES offers a comprehensive risk assessment, facilitating the development of an effective PGT-M for Multiple Genes in the prevention of severe diseases in their offspring

What is known already
PGT-M enables the transfer of unaffected embryos to couples at risk of transmitting monogenic disorders. With the advancements in technologies like Whole Exome Sequencing (WES) and Whole Genome Sequencing (WGS) identifying causal mutations, there is a growing demand for PGT-M applications that concurrently assess multiple genetic disorders. This is particularly crucial, as families initially referred for one condition may later be discovered to be at risk for additional monogenic disorders due to the common carriership status of the couples.

Study design, size, duration
This is a retrospective study including couples with previous familial history of genetic disorders referred to a single genetic unit between years 2020-2024. Either WES-DUO or WES-TRIO analysis were performed in the absence or presence of an affected child, respectively.

Participants/materials, setting, methods
WES-DUO or WES-Trio analyses were performed on 94 couples with a familial history of genetic diseases encompassing diverse medical domains. Around 50% of the couples exhibited consanguinity. Utilizing the Novaseq 6000 next-generation sequencing platform, exonic regions were sequenced with an average coverage of 100X. Bioinformatic analysis followed the manufacturer’s recommended workflow, and variant analysis adhered to ACMG criteria, ClinVar, and HGMD. Segregation analysis was conducted through Sanger sequencing using region-specific primers.

Main results and the role of chance
WES, followed by segregation analysis, pinpointed reportable pathogenic or likely pathogenic variants in 46 out of 94 families as the root cause of the referral condition. Interestingly, 42 of these families exhibited at least one additional common gene mutation in both partners. Notably, among the 27 families with confirmed diagnoses, in vitro fertilization (IVF) and preimplantation genetic testing for monogenic disorders (PGT-M) were undertaken. Within this cohort, PGT-M for multiple genes was successfully conducted in 22 families, 96 embryos were found to be transferable resulting in the birth of healthy infants.

Limitations, reasons for caution
The overall diagnostic confirmation rate of WES analysis reached 48.9%. A quite high diagnostic yield achieved in this study is notably influenced by the substantial prevalence of consanguineous cases.

Wider implications of the findings
This study highlights the need for implementing PGT-M for multiple genes. Failure to undergo such testing would potentially lead to the birth of children affected by other conditions.This study also underscores the efficiency of encompassing WES, mutation confirmation, segregation analysis, bioinformatic processing and PGT applications in a single genetic unit.

Trial registration number
none