Identification of pathogenic variants in three Chinese patients with McCune-Albright syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for three Chinese patients with McCune-Albright syndrome (MAS).@*METHODS@#Three children who had respectively presented at Shandong Provincial Hospital in April 2019 and Peking Union Medical College Hospital in August 2020 and May 2021 were selected as the research subjects. Peripheral blood samples of the probands and their family members were taken for the extraction of genomic DNA. Potential variants were screened by whole exome sequencing (WES), and candidate variants were validated by Sanger sequencing of the patients and their family members.@*RESULTS@#The proband from family 1 was found to harbor a heterozygous c.601C>T (p.R201C) missense variant in exon 8 of the GNAS gene, whilst the probands from families 2 and 3 were both found to harbor a heterozygous c.602G>A (p.R201H) missense variant in exon 8 of the GNAS gene. Both variants were known to be pathogenic, and all probands were found to be mosaics for the corresponding variants but with various degrees.@*CONSLUSION@#WES can effectively diagnose MAS and other somatic genetic disorders. In this study, the combined WES and Sanger sequencing have verified the degree of mosaicisms of pathogenic variants in the three MAS patients, albeit no apparent correlation was found between the degree of mosaicisms and the phenotype of patients. Above finding has provided a basis for genetic counseling and prenatal diagnosis for the affected families.

Genetic analysis of two families with Short-rib thoracic dysplasia type 3 / 中华医学遗传学杂志

OBJECTIVE@#To explore the pathogenic variants and clinical classification of two fetuses with Short-rib thoracic dysplasia with or without polydactyly (SRTD).@*METHODS@#With informed consent obtained, the phenotypic characteristics of the fetuses were comprehensively examined, and genomic DNA was extracted from fetal skin tissue and peripheral blood samples of the parents with conventional phenol-chloroform method. Whole exome sequencing (WES) was carried out on both fetuses, and the candidate variants were validated by Sanger sequencing. The pathogenicity of the candidate variants was analyzed using bioinformatic software VarCards, and the impact of the variants on the protein structure was predicted with Swiss-Pdb-viewer.@*RESULTS@#Both fetuses were found to harbor compound heterozygous variants of the DYNC2H1 gene, including c.515C>A (p.Pro172Gln) and c.5983G>A (p.Ala1995Thr) in fetus 1, and c.5920G>T (pGly1974) and c.9908T>C (p.He3303Thr) in fetus 2. The parents of both fetuses were heterozygous carriers.@*CONCLUSION@#The compound heterozygous variants of the DYNC2H1 gene probably underlay the SRTD3 in the two fetuses.

Identification of potential splicing variants in two Chinese patients with osteogenesis imperfecta / 中华骨科杂志

Objective:To identify pathogenicity of the potential splicing variants in two Chinese Han patients with osteogenesis imperfecta.Methods:Genomic DNA was extracted using the conventional phenol-chloroform method; whole exome sequencing (WES) was used to analysis the disease-related variants in the two probands; Minigene assay was used to identify pathogenicity of the variants found in the patients' genome that possibly affect RNA splicing.Results:Two potential splicing variants, c.858+1_858+5delGTAAG in intron 12 of COL1A1 and c.1405-7C>T in intron 24 of COL1A2, were found in proband 1 and proband 2, respectively. In addition, a missense mutation, c.2972G>T (p.G991V) in exon 45 of COL1A2, was detected in proband 2. Minigene assay revealed that the variant in proband 1 caused the skipping of exon 12, while the variant in proband 2 did not lead to aberrant splicing. G199 of the COL1A2 in proband 2 was a highly conserved amino acid site, and the results suggested that c.2972G>T (p.G991V) may be the real pathogenic variant by the means of bioinformatics analysis.Conclusion:The variant c.858+1_858+5delGTAAG in COL1A1 was a causative variant that led to OI in proband 1, while the missense variant c.2972G>T (p.G991V) in COL1A2 was the cause of OI in proband 2, instead of the variant c.1405-7C>T. Minigene assay for potential splicing variants detected by WES could not only validate the pathogenicity of the candidate variants and enrich the mutation spectrum of OI, but also lay the foundation for patients' prenatal diagnosis and subsequent mechanism research.