Objective:To identify the pathogenic gene of a pedigree with symphalangism and to prove the pathogenicity of this locus in vitro.Methods:The clinical data of patients’families were collected at Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, peripheral blood was collected and genomic DNA was extracted and NOG, FGF9, GDF5 exon regions were amplified by PCR, and the exon gene mutations were detected by first-generation sequencing technique. The structure of noggin-GDF5 protein complex was simulated in silicon. COS-7 cells were transfected with 5 μg empty plasmid, wild type plasmid and V202G mutant plasmid in vitro. Each group of plasmids was transfected into 3 well cells. The experiment was repeated for 3 times, and the expression of noggin protein was detected by Western blotting. C2C12 cells were also transfected with the above plasmids in vitro for osteogenic differentiation. By applying alkaline phosphatase staining and quantitative assay. Relative expression level of osteoblast-related genes Col1α1, ALP and Runx2 were detected by qRT-PCR. Each group of plasmids was transfected into 3 well cells, and the experiment was repeated for 3 times. All statistical analysis were performed by Prism 6 software. The result were shown as mean±standard deviation, and the comparison between groups was done by unpaired t-test. Data were considered statistically significant when P value is less than 0.05. Results:Both the proband and his mother suffered from symphalangism. The result of Sanger sequencing showed that there was a heterozygous missense mutation of NOG gene (p.V202G) in all patients in this pedigree. No disease-related mutations were detected in FGF9 and GDF5. Computer three-dimensional mechanism simulation showed that the site was located at the α helix. The result of Western blotting showed that the expression of mutant protein was significantly lower than that of wild type. Osteogenic differentiation in vitro showed that the inhibitory effect of V202G mutant protein on osteogenic differentiation decreased. The quantitative result of alkaline phosphatase staining showed that the alkaline phosphatase activity in the vector group was (12.3±0.8) U/L, and the alkaline phosphatase activity in the wild type plasmid group was (2.6±0.3) U/L, which was significantly lower than that in the vector group ( t=11.550, P<0.001). The alkaline phosphatase activity in the mutant plasmid group was (10.8±0.3) U/L. There was no significant difference between the mutant group and the vector group ( t=1.830, P=0.141). The mRNA expression level of osteogenesis-related genes was consistent with the above result . Compared with vector group, the expression of osteogenesis-related genes in wild-type noggin group decreased significantly ALP、 Col1α1 and Runx2 ( t=5.987, 4.498, 4.170; P=0.004, 0.011, 0.014). There was no significant difference between mutant plasmid group and blank vector group in ALP、 Col1α1 and Runx2 ( t=0.433, 0.177, 1.159; P=0.688, 0.868, 0.311). Conclusions:NOG gene c. 605T < G p. V202G is a novel mutation in symphalangism, which is located in the α helix of noggin protein, leading to the decrease of the expression of noggin protein and the manifestation of ankylosis.

Objective:To identify the pathogenic gene of a pedigree with symphalangism and to prove the pathogenicity of this locus in vitro.Methods:The clinical data of patients’families were collected at Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, peripheral blood was collected and genomic DNA was extracted and NOG, FGF9, GDF5 exon regions were amplified by PCR, and the exon gene mutations were detected by first-generation sequencing technique. The structure of noggin-GDF5 protein complex was simulated in silicon. COS-7 cells were transfected with 5 μg empty plasmid, wild type plasmid and V202G mutant plasmid in vitro. Each group of plasmids was transfected into 3 well cells. The experiment was repeated for 3 times, and the expression of noggin protein was detected by Western blotting. C2C12 cells were also transfected with the above plasmids in vitro for osteogenic differentiation. By applying alkaline phosphatase staining and quantitative assay. Relative expression level of osteoblast-related genes Col1α1, ALP and Runx2 were detected by qRT-PCR. Each group of plasmids was transfected into 3 well cells, and the experiment was repeated for 3 times. All statistical analysis were performed by Prism 6 software. The result were shown as mean±standard deviation, and the comparison between groups was done by unpaired t-test. Data were considered statistically significant when P value is less than 0.05. Results:Both the proband and his mother suffered from symphalangism. The result of Sanger sequencing showed that there was a heterozygous missense mutation of NOG gene (p.V202G) in all patients in this pedigree. No disease-related mutations were detected in FGF9 and GDF5. Computer three-dimensional mechanism simulation showed that the site was located at the α helix. The result of Western blotting showed that the expression of mutant protein was significantly lower than that of wild type. Osteogenic differentiation in vitro showed that the inhibitory effect of V202G mutant protein on osteogenic differentiation decreased. The quantitative result of alkaline phosphatase staining showed that the alkaline phosphatase activity in the vector group was (12.3±0.8) U/L, and the alkaline phosphatase activity in the wild type plasmid group was (2.6±0.3) U/L, which was significantly lower than that in the vector group ( t=11.550, P<0.001). The alkaline phosphatase activity in the mutant plasmid group was (10.8±0.3) U/L. There was no significant difference between the mutant group and the vector group ( t=1.830, P=0.141). The mRNA expression level of osteogenesis-related genes was consistent with the above result . Compared with vector group, the expression of osteogenesis-related genes in wild-type noggin group decreased significantly ALP、 Col1α1 and Runx2 ( t=5.987, 4.498, 4.170; P=0.004, 0.011, 0.014). There was no significant difference between mutant plasmid group and blank vector group in ALP、 Col1α1 and Runx2 ( t=0.433, 0.177, 1.159; P=0.688, 0.868, 0.311). Conclusions:NOG gene c. 605T < G p. V202G is a novel mutation in symphalangism, which is located in the α helix of noggin protein, leading to the decrease of the expression of noggin protein and the manifestation of ankylosis.

Objective:To explore the genetic etiology of a Chinese pedigree affected with Branchio-oculo-facial syndrome (BOFS) and summarize the prenatal phenotype of BOFS patients.Methods:A pedigree with BOFS which had presented at the Genetics and Prenatal Diagnosis Center of the First Affiliated Hospital of Zhengzhou University in December 2021 was selected as the study subject. Clinical data of the pedigree was collected. The fetus was subjected to routine prenatal ultrasound scan. Trio-whole exome sequencing (trio-WES) was carried out for the fetus and its parents, and candidate variant was verified by Sanger sequencing. Relevant literature was searched from the database to summarize the prenatal phenotype of BOFS patients. This study was approved by the First Affiliated Hospital of Zhengzhou University (Ethics No. KS-2018-KY-36).Results:Ultrasound exam suggested the fetus had cleft lip and palate. Its father had presented with high palatal arch, prematurely grayed hair, occult cleft lip, congenital preauricular fistula, red-green color blindness and unilateral renal agenesis. Its grandfather also had high palatal arch, prematurely gray hair, protruding ears, congenital preauricular fistula and hearing disorders. Trio-WES revealed that the fetus and its father had both harbored a heterozygous c. 890-1G>A variant of the TFAP2A gene. The same variant was not found in its mother. Sanger sequencing confirmed that its grandfather had also harbored the same variant. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was rated as likely pathogenic (PVS1+ PM2_Supporting). Combined with 36 similar cases retrieved from the literature, the prenatal phenotypes of BOFS patients had included growth restriction (25/37), renal abnormalities (10/37), cleft lip and palate (5/37) and oligohydramnios (5/37). Conclusion:The c. 890-1G>A variant of the TFAP2A gene probably underlay the pathogenesis of BOFS in this pedigree. Discovery of the novel variant has enriched the mutational spectrum of the TFAP2A gene. The common prenatal phenotypes of BOFS have included growth restriction, renal abnormalities, cleft lip and palate and oligohydramnios. Delineation of the intrauterine phenotype of BOFS may facilitate its prenatal diagnosis, clinical diagnosis, treatment and genetic counseling.