[Expanded carrier screening for 216 diseases in a cohort of 3 097 healthy Chinese individuals of childbearing age].

Objective: To determine the carrier frequency and hot-spot variants of a custom-designed expanded carrier screening (ECS) panel with 216 diseases (216-ECS panel) within a Chinese population of childbearing age. Methods: Whole-exome sequencing data from a cohort of 3 097 unrelated healthy individuals (including 1 424 couples) from Peking Union Medical College Hospital between January 2013 and December 2023 were analyzed. Totally 220 genes which inherited in a recessive manner of 216-ECS panel were included in the analysis. The analysis included variant carrier rate, gene carrier rate, cumulative carrier rate, at-risk couple rates, and variant spectrum. Results: (1) Pathogenic variants were identified in 1 472 (47.53%, 1 472/3 097) individuals, with an average of 0.65 pathogenic variants per individual. The rate of at-risk couples was 3.93% (56/1 424). (2) A total of 180 genes were identified, with 16 genes exhibiting a gene carrier rate of ≥1% and 33 genes having a rate of ≥0.5%, most of which were associated with inherited metabolic diseases. Noteworthy genes with higher gene carrier rates and high-frequency variants included GJB2: c.235del, PAH: c.728G>A, ATP7B: c.2333G>T, SLC26A4: c.919-2A>G, GALC: c.1901T>C, POLG: c.2890C>T, SLC22A5: c.1472C>G, USH2A: c.2802T>G, SLC25A13: c.852_855del, GAA: c.761C>T and c.752C>T. Conclusion: This study offers a focused analysis of carrier frequencies and hot-spot variants of 216 diseases of the ECS panel constructed by our laboratory among the Chinese population, laying a foundation for the development of ECS programs tailored to the Chinese population.

[Efficacy and initial clinical evaluation of optical genome mapping in the diagnosis of structural variations].

To investigate the efficacy and value of optical genome mapping (OGM) in detecting chromosomal structural variations. In a clinical study about high-precision analysis of genomic structural variation for complex genetic diseases, a retrospective study was performed on the cases with karyotyping at the department of Obstetrics and Gynecology, and Endocrinology of Peking Union Medical College Hospital from January to December 2021. Ten cases with abnormal karyotype was detected by OGM. Partial cases were verified by fluorescence in situ hybridization (FISH), SNP array or CNV-seq. Results of ten cases, nine were detected with abnormality by OGM, including unbalanced chromosomal rearrangements (n=3), translocation (n=5) and paracentric inversion (n=1), and the results were in concordance with other standard assays. However, one case with breakpoint and reconnected at centromere has not been detected. In conclusion, ten samples were comprehensively analyzed by karyotyping, FISH, SNP array or CNV-seq, and OGM, and results demonstrated that optical genome mapping as a new technology can not only detect unbalanced rearrangements such as copy number variants as well as balanced translocations and inversions, but more importantly, it can refine breakpoints and orientation of duplicated segments or insertions. So it can contribute to the diagnosis of genetic diseases and prevent birth defect. However, the current technology is not yet capable of detecting breakpoints of balanced structural variations lying within unmapped regions.

[Impact of maternal X chromosome aneuploidies on cell free DNA prenatal screening].

Objective: To investigate the impact of maternal X chromosome aneuploidies on cell free DNA (cf-DNA) prenatal screening. Methods: After genetic counseling, invasive prenatal diagnosis was provided for the 124 cases with high risk of sex chromosome aneuploidie (SCA) indicated by cf-DNA prenatal screening. For cases with discordant results of fetal prenatal diagnosis and cf-DNA prenatal screening, maternal leukocyte was collected for copy number variation sequencing (CNV-seq) to detect whether the maternal X chromosome was carrying variations. Results: Totally, 124 cases with high risks of SCA indicated by cf-DNA prenatal screening, 9 cases refused to take invasive prenatal diagnosis, while the remaining 115 cases received. Among the 115 cases, 41 cases received accordant results with cf-DNA prenatal screening while 74 cases discordant. Among the 74 cases with discordant results, 19 cases were indicated with maternal X chromosome variations by maternal leukocyte CNV-seq, which accounting for 25.7% (19/74) of the SCA false positive cases, and 15.3% (19/124) of all SCA cases. Conclusions: Pregnant women with X chromosome variations may affect the results of cf-DNA prenatal screening, resulting in false positive or false negative outcomes, it should be emphasized that the cf-DNA results may be affected by maternal X chromosome variations. In cases with discordant results of prenatal diagnosis and cf-DNA prenatal screening, maternal leukocyte CNV-seq is recommended to find the reasons of false positive or negative results. And cf-DNA prenatal screening is not recommended for pregnant women who are already known with X chromosome variations.

[Prenatal diagnosis of 17q12 microdeletion syndrome in fetal renal abnormalities].

Objectives: To analyze 3 cases of 17q12 microdeletion syndrome diagnosed prenatally, and to demonstrate clinical phenotype of the syndrome in prenatal setting. Methods: From January 2013 to July 2017, 1 370 women received invasive prenatal diagnosis and chromosome microarray analysis (CMA) in Peking Union Medical College Hospital. Among them, 3 fetuses were diagnosed as 17q12 microdeletion syndrome. All 3 cases were low-risk pregnancies. Abnormal structures in fetal kidney were found in all 3 cases, including 1 case of multiple renal cysts, 2 cases of bilateral hyperechogenic kidneys. These women accepted invasive prenatal diagnosis followed by karyotyping, parental fluorescence in situ hybridization or CMA validation. Results: The second and third trimester ultrasound showed that all 3 fetuses had bilateral renal structural abnormalities, including hyperechogenic kidney, multiple cysts and renal pelvis dilatation. The karyotyping of the 3 fetuses were normal. CMA examination showed that each case had 1.4-1.6 Mb deletion in 17q12 region. Two cases were de novo deletion and 1 case was inherited from the mother who had mild symptoms. The 3 women decided to terminate pregnancies after genetic counseling. Conclusion: 17q12 microdeletion syndrome is a recurrent chromosome microdeletion syndrome, and the unique phenotype in prenatal setting is the abnormal structure of bilateral kidneys. A few cases of 17q12 microdeletion syndrome even inherited normally phenotypical parents, and prenatal genetic counseling of 17q12 microdeletion syndrome is relatively difficult.

Chemical state analysis of sulfur and phosphorus in biological samples by X-ray fluorescence.

Double-crystal high-resolution X-ray fluorescence spectroscopy was applied to the chemical state analysis of sulfur and phosphorus in biological samples of leaves and bones. Both S(2-) and S(6+) states are present in all leaves. In plants infected with the mosaic virus, the abundance of S(2-) state was found to be less than normal.Furthermore, the total sulfur content of leaves with the mosaic virus was less than that in normal leaves. From these results we have concluded that the mosaic virus is related to the decrease in cysteine sulfur (S(2-)), which is an essential component in amino acids. Most of the phosphorus in leaves and bones was found to be in P(5+) state. A small amount of P(3+) state, however, was also detected.