[Prenatal diagnosis of families with de novo monogenic diseases and origin analysis of recurrent de novo mutations].

Objective: To analyze the prenatal diagnostic results in families with de novo monogenic diseases and the mutation origins in affected children from families with reproductive history of children with recurrent de novo mutations (DNMs). Methods: This study was a cross-sectional study. A total of 41 cases with adverse pregnancy history of de novo monogenic diseases who underwent genetic counseling and prenatal diagnosis from January 2021 to December 2023 at the Obstetrics and Gynecology Hospital of Fudan University were included. Prenatal diagnosis and other clinical data were reviewed, and peripheral blood of the parents, peripheral blood or tissue of the probands, and amniotic fluid or chorionic villus were collected. For families with reproductive history of children with recurrent DNMs, additional saliva and semen were collected from all the parents. Targeted high-throughput sequencing was performed to assess parental somatic mosaicism and male germline mosaicism. As for the cases in which the mutation was undetected in the semen, Sanger sequencing was utilized to search for single nucleotide polymorphism (SNP) sites upstream and downstream of the mutation site and clarify the mutation origins in combination with TA cloning. Results: A total of 41 families were included, with male age of (34.1±3.9) years (41 cases) and female age of (33.0±3.9) years (41 cases). Moreover, 32 causative genes were involved, with neurodevelopmental disorders, hereditary myopathies, hereditary bone diseases, hereditary ophthalmopathies, hereditary cardiovascular diseases and other multisystem diseases accounting for 53.7% (22/41), 12.2% (5/41), 7.3% (3/41), 4.9% (2/41), 2.4% (1/41), and 19.5% (8/41), respectively. One DNMs was detected in 37 families who underwent prenatal diagnosis during the second trimester. Four families with reproductive history of children with recurrent DNMs were analyzed for the mutation origins, of which two families had a low proportion of mosaicism detected in paternal semen, with variant allele fraction (VAF) of 3.7% and 12.8%, respectively, and the origins were from the parents detected by Sanger sequencing in combination with TA cloning in another two families. Conclusions: DNMs are at risk of recurrence. The"targeted high-throughput sequencing+Sanger sequencing+TA cloning"process is conducive to identifying the parental origin of the mutation.