Identification of a novel variant of NHS gene underlying Nance-Horan syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for a pedigree affected with Nance-Horan syndrome.@*METHODS@#Clinical manifestation of the patients was analyzed. Genomic DNA was extracted from peripheral blood samples of the pedigree members and 100 unrelated healthy controls. A panel of genes for congenital cataract was subjected to next-generation sequencing (NGS), and candidate variant was verified by Sanger sequencing and bioinformatic analysis based on guidelines of American College of Medical Genetics and Genomics (ACMG). mRNA expression was determined by reverse transcriptase-PCR (RT-PCR). Linkage analysis based on short tandem repeats was carried out to confirm the consanguinity.@*RESULTS@#A small insertional variant c.766dupC (p.Leu256Profs*21) of the NHS gene was identified in the proband and his affected mother, but not among unaffected members and the 100 healthy controls. The variant was unreported in Human Gene Mutation Database (HGMD) and other databases. Based on the ACMG guideline, the variant is predicted to be pathogenic (PVS1+PM2+PM6+PP4).@*CONCLUSION@#The novel variant c.766dupC of the NHS gene probably underlay the X-linked dominant Nance-Horan syndrome in this pedigree.

Identification of a novel splicing variant of IDS gene in a pedigree affected with type II glycosaminoglycan product storage disease / 中华医学遗传学杂志

OBJECTIVE@#To analyze variant of IDS gene in a pedigree affected with mucopolysaccharidosis type II (MPS II).@*METHODS@#The proband was subjected to next generation sequencing and Sanger sequencing to identify potential variants. Suspected variant was analyzed by its co-segregation with the disease in the pedigree. Its impact on mRNA splicing was analyzed by using reverse transcription PCR (RT-PCR).@*RESULTS@#A hemizygous IVS1-3T>G variant was found in the IDS gene in the proband. RT-PCR results revealed two abnormal cDNA fragments of 600 bp and 300 bp. The 600 bp fragment had inserted 216 nucleotides at the 3' end of intron 1, while the 300 bp fragment had lost 109 nucleotides at the 5' end of exon 2, which resulted in two truncated proteins comprising 38 and 92 amino acids, respectively, instead of the normal product (550 amino acids). The proband and his mother were respectively hemizygous and heterozygous for the variant. The same variant was not found among 100 normal controls.@*CONCLUSION@#The IVS1-3T>G variant of the IDS gene probably underlies the MPS II in this pedigree by causing reduction or elimination of the IDS protein.

Identification of a novel variant of COL4A5 gene in a pedigree affected with Alport syndrome / 中华医学遗传学杂志

OBJECTIVE@#To explore the genetic basis for a pedigree affected with Alport syndrome.@*METHODS@#Next generation sequencing and Sanger sequencing was carried out to detect potential variant of the COL4A5 gene among members from the pedigree and 100 unrelated healthy controls.@*RESULTS@#A novel missense c.3293G>T (p.Gly1098Val) variant was found in the COL4A5 gene among 6 affected members but not the unaffected members of the pedigree or the 100 healthy controls. According to the American College of Medical Genetics and Genomics standards and guidelines, the c.3293G>T variant was classified as pathogenic (PP1-strong+PM1+PM2+PP3+PP4).@*CONCLUSION@#By destructing the Gly-X-Y structure of its protein product, the c.3293G>T variant of the COL4A5 gene probably underlies the Alport syndrome in this pedigree. Above finding has enriched the spectrum of COL4A5 variants.

Novel mutations of XPC gene detected in a family affected with xeroderma pigmentosum group C / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect mutations of the XPC (XPC complex subunit, DNA damage recognition and repair factor) gene in a family affected with xeroderma pigmentosum group C (XP-C).</p><p><b>METHODS</b>The patient was subjected to next-generation sequencing and Sanger sequencing. Suspected mutations were validated by Sanger sequencing. Effect of splicing mutation was confirmed by reverse transcription-PCR (RT-PCR).</p><p><b>RESULTS</b>Compound heterozygous mutations of c.2098G to T and c.2034-7_2040del were found in the XPC gene in the proband. Among these, c.2098G to T (p.G700X) is a nonsense mutation resulting in a truncated XPC protein. C.2034-7_2040del involves the -1 position, which may alter the splice donor site of the intron 11 of XPC and result in a truncated XPC protein with loss of amino acids from 940 to 679 positions. The two mutations were not detected among 100 unrelated healthy controls.</p><p><b>CONCLUSION</b>Mutations of c.2098 G to T and c.2034-7_2040del of the XPC gene may lead to abnormal XPC expression and reduction or elimination of normal XPC functions, which may underlie the disease in this family.</p>

Application of droplet digital PCR for non-invasive prenatal diagnosis of single gene disease in two families / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To assess the value of droplet digital PCR (ddPCR) for non-invasive prenatal diagnosis of single gene disease in two families.</p><p><b>METHODS</b>Paternal mutation in cell-free DNA derived from the maternal blood and amniotic fluid DNA was detected by ddPCR. Suspected mutation in the amniotic fluid DNA was verified with Sanger sequencing.</p><p><b>RESULTS</b>The result of ddPCR and Sanger sequencing indicated that the fetuses have carried pathogenic mutations from the paternal side in both families.</p><p><b>CONCLUSION</b>Droplet digital PCR can accurately detect paternal mutation carried by the fetus, and it is sensitive and reliable for analyzing trace samples. This method may be applied for the diagnosis of single gene diseases caused by paternal mutation using peripheral blood sample derived from the mother.</p>

Identification of a novel splicing mutation of PHEX gene in a pedigree affected with X-linked hypophosphatemia / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify potential mutation of PHEX gene in two patients from a family affected with X-linked hypophosphatemia (XLH).</p><p><b>METHODS</b>PCR and Sanger sequencing were performed on blood samples from the patients and 100 healthy controls. Reverse transcription-PCR (RT-PCR) was used to determine the mRNA expression in patient samples.</p><p><b>RESULTS</b>A splicing site mutation, IVS21+2T>G, was found in the PHEX gene in both patients but not among the 100 healthy controls. RT-PCR confirmed that exon 21 of the PHEX gene was deleted.</p><p><b>CONCLUSION</b>The novel splicing mutation IVS21+2T>G of the PHEX gene probably underlies the XLH in this pedigree. At the mRNA level, the mutation has led to removal of exon 21 and shift of the open reading frame (p.Val691fsx), resulting in premature termination of protein translation.</p>

A novel mutation of GLI3 gene underlying synpolydactyly in a family / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect mutation of GLI3 gene in a family affected with autosomal dominant synpolydactyly.</p><p><b>METHODS</b>Genomic DNA was extracted from peripheral blood samples from members of the family and 100 unrelated healthy controls. Potential mutation was screened by next-generation sequencing and confirmed by Sanger sequencing.</p><p><b>RESULTS</b>A heterozygous frameshift mutation c.480dupC was identified in the GLI3 gene among all patients from the family. The same mutation was not found in unaffected family members and the 100 healthy controls.</p><p><b>CONCLUSION</b>The c.480dupC of the GLI3 gene probably underlies the synpolydactyly in this family.</p>

Application of droplet digital PCR technology for genetic testing and prenatal diagnosis of spinal muscular atrophy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the clinical application of droplet digital PCR (ddPCR) for genetic testing and prenatal diagnosis of spinal muscular atrophy (SMA) with deletion of SMN1 gene exon 7.</p><p><b>METHODS</b>A total of 138 clinical samples, including 121 peripheral blood, 13 amniotic fluid, 2 umbilical cord blood and 2 chorionic villi from 56 SMA families, were tested by both ddPCR and multiplex ligation-dependent probe amplification (MLPA). Results of the two approaches were analyzed with commercial software QuantaSoft (ddPCR) and Coffalyser (MLPA), respectively.</p><p><b>RESULTS</b>Among the 138 cases, 25 had two copies, 84 had one copy, and 29 had null copy of exon 7 of the SMN1 gene. The results of ddPCR and MLPA were completely consistent.</p><p><b>CONCLUSION</b>As a rapid, precise and economically efficient method, ddPCR will provide a new choice for genetic testing of SMA.</p>

Identification of a novel splicing mutation of PKD1 gene in a pedigree affected with autosomal dominant polycystic kidney disease / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify potential mutations of PKD1 gene in a family affected with autosomal dominant polycystic kidney disease (ADPKD).</p><p><b>METHODS</b>The coding regions of the PKD1 gene were subjected to PCR and Sanger sequencing. Reverse transcription-PCR (RT-PCR) was used to determine the relative mRNA expression in the patient.</p><p><b>RESULTS</b>A splicing site mutation, c.8791+1_8791+5delGTGCG (IVS23+1_+5delGTGCG), was detected in the PKD1 gene in all 5 patients from the pedigree but not in 6 phenotypically normal relatives and 40 healthy controls. Sequencing of RNA has confirmed that there were 8 bases inserted in the 3' end of exon 23 of the PKD1 gene.</p><p><b>CONCLUSION</b>The novel c.8791+1_8791+5delGTGCG mutation has created a new splice site and led to a frameshift, which probably underlies the ADPKD in the family. Above finding has enriched the mutation spectrum of the PKD1 gene.</p>

A novel pathogenic mutation of CRYGD gene in a congenital cataract family / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect the disease-causing mutation in a pedigree affected with autosomal dominant congenital cataract.</p><p><b>METHODS</b>Genomic DNA was extracted and purified from peripheral blood samples from members of the pedigree and 100 healthy controls. Coding regions of 18 candidate genes were screened with PCR and Sanger sequencing. Identified mutations were verified among 100 healthy individuals to exclude single nucleotide polymorphisms.</p><p><b>RESULTS</b>A heterozygous nonsense mutation c.471G>A of the CRYGD gene, which resulted in p.Trp157Term, was identified in all three patients. The same mutation was not found in the two normal individuals from the family and 100 healthy controls. The nonsense mutation was predicted to be "disease causing" by Mutation t@sting program.</p><p><b>CONCLUSION</b>The nonsense mutation c.471G>A of the CRYGD gene probably underlies the congenital cataract in the pedigree.</p>