Objective:To explore the clinical phenotype and genetic variant in a Chinese pedigree affected with Hunter syndrome and create immortalized cell lines for the affected pedigree members.Methods:A pedigree of six members who had visited Xi′an Children′s Hospital in July 2022 was selected as the study subject. Clinical data was collected. Whole exome sequencing was carried out for the pedigree members. Candidate variant was verified by Sanger sequencing. In addition, peripheral B lymphocytes were transfected with Epstein-Barr virus to create immortalized cell lines, which were then subjected to enzyme activity analysis.Results:The patient, a five-year-and-seven-month-old boy, had exhibited stiff limbs and enlarged joints. He had developed hernia, scaphocephaly, and barrel chest from 3 months of age. His uncle also had stiff limbs, poor hearing, blindness, and right oblique inguinal hernia. Above features had resembled those of Hunter syndrome. Genetic testing revealed that both the child and his uncle had harbored an IDS (NM_000202.8): c. 823G>A (p.D275N) variant, which was unreported previously. Bioinformatic analysis indicated that the D275 to be a highly conserved site, and the D275N variant may affect the stability of the protein′s spatial conformation, thereby decrease the catalytic activity of the enzyme. The successfully constructed immortalized lymphoblastoid cell lines for the child and his parents showed increased volume, irregular shape, burr structure and cluster growth. And the value of IDS activity of the patient′s immortalized lymphoblastoid cells was below the limit of detection. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was classified as likely pathogenic (PS3+ PM2_Supporting+ PM5+ PP1+ PP3). Conclusion:Above finding has enriched the phenotypic and mutational spectra of Hunter syndrome, and provided a basis for the genetic counseling for this pedigree. The creation of immortalized cell lines has offered a model for further investigation of the impact of variant on the function of IDS and development of targeted drugs.

Objective:To analyze the clinical characteristics of a child with Congenital disorder of glycosylation due to compound heterozygous variants of COG6 gene ( COG6-CDG). Methods:A child who was admitted to Xi′an Children′s Hospital on January 10, 2023 was selected as the study subject. Clinical data were collected. Pathogenic variants were analyzed by whole exome sequencing, and candidate variants were verified by Sanger sequencing, in vitro experiments and bioinformatic analysis. This study was approved by the Medical Ethics Committee of Xi′an Children′s Hospital (No. 20230101). Results:The child, a 1-month-8-day-old male, was admitted for diarrhea and weight loss for one month. He had presented with cholestasis, diarrhea, facial dysmorphism, poor response, bilateral Simian crease, and brain atrophy. After discharge, he had continued to have high fever, feeding difficulty, and deceased finally. Whole exome sequencing results showed that he had harbored compound heterozygous variants of the COG6 gene, namely c. 807delT (p.F269Lfs*37) and c. 1746+ 1G>C (p.Gly565_Met582del). Sanger sequencing verified that the variants were inherited from his father and mother, respectively. In vitro experiments verified that the c. 1746+ 1G>C variant could affect the mRNA splicing and produce a truncated protein, whilst the c. 807delT variant could significantly reduce gene expression at both mRNA and protein levels. Based on the guidelines from the American College of Medical Genetics and Genomics and the Association for Molecular Pathology (ACMG-AMP), the variants were classified as pathogenic (PVS1+ PM3+ PM2_Supporting) and likely pathogenic (PVS1+ PM2_Supporting), respectively. Conclusion:The c. 807delT (p.F269Lfs*37) and c. 1746+ 1G>C (p.Gly565_Met582del) compound heterozygous variants of the COG6 gene probably underlay the pathogenesis of this child. Above finding has enriched the mutational spectrum of COG6-CDG and provided a basis for the genetic counseling for this family.

Objective:To analyze the gene variants of a patient affected with Duchenne/Becker muscular dystrophy in a pedigree and further explore the genotype-phenotype correlation for providing basis for family genetic counseling.Methods:The clinical features and family history of family members were collected.Multiplex ligation-dependent probe amplification(MLPA)was utilized to detect copy number variation of target genes.The pathogenic variations were ana-lyzed by whole exome sequencing(WES).The suspected gene variations were verified by Sanger sequencing.For the splice site mutations,mini-gene was constructed and expressed in vitro to detect the number of transcript and cDNA se-quence.Results:The proband of this family is a male,with no obvious involvement of the lower limbs.Laboratory tests showed an elevated level of creatine kinase(CK)in peripheral blood(700-1600 U/L),and electromyography showed myogenic damage.MLPA did not detect pathogenic exon copy number variation in dystrophin(DMD)gene.Genetic testing showed the proband carried a maternal hemizygotic splicing variation of DMD gene(NM_004006.2):c.2622+2T＞C.An in vitro mini-gene splicing assay confirmed that this splicing mutation could affect RNA splicing.According to clinical features and genetic testing results,the proband was speculated first proof of Duchenne/Becker muscular dys-trophy(DMD/BMD)caused by DMD gene mutation.Conclusion:This study identified the pathogenic variation of a proband with DMD/BMD of DMD gene,which enriched the variation spectrum of DMD/BMD in China.It was con-firmed that the splicing variation of the DMD gene c.2622+2T＞C can produce multiple transcripts leading to different functional impairments,and based on the specificity of temporal and spatial expression,it corresponded to the mild clin-ical manifestations of the patient,providing some reference value for the correlation between genotype and phenotype.