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Objective:To compare the genotypes and phenotypes between the monozygotic twins via whole genome sequencing to further clarify the autosomal dominant inherited neurofibromatosis type 1 (NF1) variants related to congenital pseudarthrosis (CP).Methods:According to the diagnostic criteria of congenital tibial pseudarthrosis and the clinical diagnostic criteria of NF1, two pairs of monozygotic twins with NF1 were included. Both were female and only one of each pair had congenital pseudarthrosis. The other did not have congenital pseudarthrosis. Whole genome sequencing was performed using the peripheral blood of the two pairs of monozygotic twins. Customized bioinformatics analysis was then performed to identify single nucleotide variants (SNVs), short insertion deletion variants (InDel), copy number variants (CNVs), and structural variants (SVs). Classified the variants according to the American College of Medical Genetics and Genomics (ACMG) and ClinGen criteria. The germline variants within the monozygotic twins were compared to identify the CP patients' unique variants. The shared pathogenic or likely pathogenic germline variants between the unique variants in the CP patients from the twins were also analyzed. Further, the identified disease-causing variants were validated by Sanger sequencing in the family of the twins and their parents. Finally, the genotypes and phenotypes regarding the pathogenic variants of the NF1 gene among the twins were characterized. Results:Both the two monozygotic twins were identified pathogenic variants in the NF1 gene. One with c.3047_3048del (p.Cys1016SerfsTer4), and the other with c.4267A>G (p.Lys1423Glu). By Sanger sequencing validation in family quads, the two CP patients and their siblings harbored de novo heterozygous variants of the NF1 gene. In addition to the NF1 gene, no other genes were identified pathogenic or likely pathogenic variants uniquely in the CP patients compared with their twin sisters, as well as SVs and CNVs. In addition, by analyzing the rare and damaging variants in the two CP patients from the two twins, they had no overlapping genes against the SNVs, InDels, SVs, or CNVs. Conclusion:Whole genome sequencing revealed that both the two monozygotic twins with NF1 were detected pathogenic variants of gene NF1. No other pathogenic variants specific to the CP patients among the twins were identified. The two CP patients shared no other common genes from the detected likely pathogenic variants.
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Objective:To identify and analyze different proteins expression in the periosteum of congenital pseudarthrosis of the tibia (CPT) using tandem mass tags (TMT) proteomics.Methods:The samples were divided into three groups, namely CPT with neurofibromatosis type 1 (NF1) group (NF1-CPT group), CPT without NF1 group (nonNF1-CPT group) and control group (patients with open tibial fracture). A fold change ≥1.5 or ≤0.66 and P-value <0.05 was regarded as the threshold to screen differentially expressed proteins (DEPs). Subsequently, bioinformatics resources such as online tools DAVID and STRING were used to conduct GO annotation, KEGG pathways enrichment and protein-protein interaction (PPI) network with DEPs. Results:A total of 347 proteins differentially expressed in NF1-CPT group, 212 of which were up-regulated and 135 down-regulated. We identified 467 DEPs in nonNF1-CPT group, including 281 up-regulated and 186 down-regulated. Among of them, NF1-CPT group and nonNF1-CPT group shared 231 DEPs, except for HLA-DRB1 which increased in NF1-CPT group but decreased in nonNF1-CPT group. The remaining 230 DEPs showed the same expression trend in the two positive groups, including 117 up-regulated and 113 down-regulated. In particular, a total of 116 proteins were altered only in NF1-CPT group, including 94 up-regulated and 22 down-regulated. However, there were 236 proteins altered only in nonNF1-CPT group, including 164 up-regulated and 72 down-regulated. The results indicated that the pathogenesis of NF1-CPT was similar as nonNF1-CPT largely with a few differences. Finally, compared with nonNF1-CPT, there were 47 proteins changed 1.5-fold and P-value <0.05 in NF1-CPT group. Conclusion:The proteins expression in the periosteum of CPT is different from that of normal tibia. The expression of periosteal protein is also different between NF1-CPT and nonNF1-CPT. The present study will deepen our understanding of the pathogenesis of CPT in the protein level.