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Abstract Background Facioscapulohumeral muscular dystrophy (FSHD) is the second most common form of muscular dystrophy, which is characterized by a reduction in the number of D4Z4 repeats on chromosome 4q35. Prenatal diagnosis of FSHD has been challenging due to the large quantity and high-quality DNA required for Southern blot (SB) analysis. Optical genome mapping (OGM) technology has shown promise in identifying repeat contraction disorders and presents a potential tool for the prenatal diagnosis of FSHD. Methods In this retrospective cohort study, we investigated the distribution of D4Z4 repeats in 100 unrelated healthy individuals from the Chinese Han population using peripheral blood samples and DLS labelling method. Additionally, prenatal diagnosis using OGM was performed in 12 FSHD families at Peking Union Medical College Hospital between January 2021 and December 2023. The prenatal samples included 2 amniotic cell cultures and 10 chorionic villus samples (CVS), with 9 labeled using DLS and 4 using NLRS method. Results Among the 100 healthy controls, the distribution of D4Z4 repeats varied, with 3 individuals having borderline 10 repeat counts on 4qA, and the most frequent count being 14 units. One individual with mosaicism was also identified. In the cohort of 12 FSHD families,14 prenatal diagnoses were performed. Of these 14 cases, 4 fetuses tested positive for 4qA contraction, with repeat counts ranging from 2 to 4. In both families that underwent two rounds of prenatal diagnosis, the first diagnosis indicated the presence of FSHD, leading to pregnancy termination, while the second diagnosis confirmed the presence of healthy fetuses. The overall positive rate was 28.57%. Conclusion Our findings demonstrate that OGM is an accurate and effective method for the prenatal diagnosis of FSHD. The application of OGM in prenatal settings could offer significant benefits to families affected by FSHD with reproductive concerns.

Abstract Optical genome mapping (OGM) offers high consistency in simultaneously detecting structural and copy number variants. This study aimed to retrospectively evaluate the efficacy and potential applications of OGM in preconception genetic counseling. Herein, 74 samples from 37 families were included, and their results of OGM were compared to conventional methods, namely karyotyping (KT) and chromosomal microarray analysis (CMA), which identified 27 variants across 16 positive families. Notably, OGM achieved a concordance rate of 94.7% and 100% with KT and CMA, respectively, presenting an overall concordance of 96.3%, as it missed detecting a centromeric translocation. Additionally, OGM detected two cryptic balanced translocations and a small deletion in three families that were missed by conventional methods, improving the diagnostic rate by 5.4%, along with assisting in the diagnoses of six families (16.2%) by identifying complex rearrangements and confirming cryptic translocations. The combination of KT with OGM yielded the highest diagnostic rate in all families. Overall, the findings of this study present the notable potential of OGM for its application, combined with KT per requirement, in clinical settings to improve the efficiency and accuracy of diagnoses and rapid screening of individuals seeking preconception genetic counseling.

Abstract Background Congenital muscular dystrophies (CMDs) and myopathies (CMYOs) are a clinically and genetically heterogeneous group of neuromuscular disorders that share common features, such as muscle weakness, hypotonia, characteristic changes on muscle biopsy and motor retardation. In this study, we recruited eleven families with early-onset neuromuscular disorders in China, aimed to clarify the underlying genetic etiology. Methods Essential clinical tests, such as biomedical examination, electromyography and muscle biopsy, were applied to evaluate patient phenotypes. Whole exome sequencing was used to screen for prospective variants responsible for muscular diseases, followed by co-segregation analysis in the families and prenatal diagnosis via Sanger sequencing, if appropriate. Nanopore sequencing and optical genome mapping were applied for detecting complicated genome rearrangements. Results Fourteen variants in nine genes (ATL1, LMNA, KLHL40, FKRP, DMD, ACTA1, MSTO1, RYR1 and LAMA2) associated with congenital muscular conditions were identified in the ten families mentioned above. Among them, five novel variants, c.1153_1155del in LMNA, c.577 A > G in ACTA1, c.694T > G in MSTO1, c.5938del in LAMA2, and a rare genome fusion ogm[GRCh38] fus(X; X)(p22.31;p21.1) involving DMD, have not been recorded in public databases to the best of our knowledge. Conclusions CMDs and CMYOs were probably responsible for most of the cases (9/11) of genetic muscular defects in this study. Molecular analysis is highly beneficial for the precise diagnosis, genetic counseling and prenatal diagnosis of families suspected of having genetic muscular disorders. Clinical trial number Not applicable.