Molecular diagnosis of OTC gene mutation in a Chinese family with ornithine transcarbamylase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect potential mutations of OTC gene in a male infant affected with ornithine transcarbamylase deficiency.</p><p><b>METHODS</b>Genomic DNA were isolated from peripheral blood samples of family members and 100 healthy individuals. Potential mutations of the 10 exons of OTC gene were screened with PCR and Sanger sequencing.</p><p><b>RESULTS</b>A homozygous missense mutation c.917G>C in exon 9, which results in p.R306T, was identified in the infant. Sequencing of the mother and two female members of the family indicated a heterozygous status for the same mutation. The same mutation was not found in other members of the family and 100 healthy controls.</p><p><b>CONCLUSION</b>A missense mutation c.917G>C in the OTC gene is responsible for the pathogenesis of the disease. Identification of the mutation can facilitate prenatal diagnosis and genetic counseling for the family.</p>

Development and application of a method for molecular diagnosis of 21-hydroxylase deficiency / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To develop a method for elucidating genetic basis of 21-hydroxylase deficiency.</p><p><b>METHODS</b>Sanger sequencing of entire 21-hydroxylase coding gene CYP21A2 was carried out to detect point mutations, and multiplex ligation-dependent probe amplification (MLPA) and locus-specific PCR/enzyme restriction method were used to detect large deletions and conversion mutations.</p><p><b>RESULTS</b>Nine children were analyzed. Point mutations of the CYP21A2 gene have been identified as: IVS2 13A/C>G (9 alleles), p.Arg356Trp (1 allele), Cluster E6 (1 allele), p.Gln318X (1 allele), and Prom conv (1 allele). While the former 4 mutations are pathogenic, the role of Prom conv mutation in the pathogenesis was uncertain. Three cases had entire CYP21A2 gene deletions (3 alleles), three had CYP21A1P/CYP21A2 chimeric mutations (3 alleles). The genotypes of all patients were determined. And all of the mutations were inherited from parents.</p><p><b>CONCLUSION</b>A rational method for detecting point mutations and large deletions/conversions of CYP21A2 gene has been established.</p>

Prenatal diagnosis of two fetuses with de novo small supernumerary markers by single nucleotide polymorphism array based comparative genomic hybridization / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the origins of small de novo mosaic supernumerary marker chromosomes (mars) in two fetuses, and to assess the feasibility of single nucleotide polymorphism array-based comparative genomic hybridization (SNP-array CGH) for prenatal molecular cytogenetic diagnosis.</p><p><b>METHODS</b>Two fetuses with de novo were identified. SNP-array marker chromosomes was applied to define the location and range of marker chromosomes. The karyotype of fetus I was determined to be 47,XX,+ mar[23]/46,XX[16], and that of fetus II was 47,XX,+ mar. Multiplex ligation-dependent probe amplification (MLPA) was applied to verify the genomic imbalance found in fetus II. The karyotypes of parents were normal in both families.</p><p><b>RESULTS</b>SNP-array CGH has indicated a 8.3 Mb duplication at 9p21.1-p21.3 in fetus I, and a 10.8 Mb duplication at 15q11.2-q13.3 in fetus II. MLPA has also confirmed a 15q terminal duplication in fetus II.</p><p><b>CONCLUSION</b>Above cases have illustrated that SNP-array CGH is a rapid, powerful and sensitive technique which may be used for identify the origins of marker chromosomes in prenatal diagnosis.</p>

Array-based comparative genomic hybridization detection of copy number variations in a fetus with hypoplastic left-heart syndrome / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect the copy number variations (CNVs) of a fetus with hypoplastic left-heart syndrome, and to assess the value of array-based comparative genomic hybridization (array-CGH) for molecular cytogenetic diagnosis.</p><p><b>METHODS</b>The whole genome of a fetus with normal karyotype by G-banding was scanned and analyzed by array-CGH, and the CNVs was confirmed by multiplex ligation-dependent probe amplification (MLPA).</p><p><b>RESULTS</b>Two submicroscopic CNVs [del(11)(q24.1-ter)(121951443-134449216, -12.50 Mb),dup(15)(q26.3)(96889082-100215359, -3.33 Mb)] were identified and mapped by array-CGH. MLPA test confirmed both CNVs.</p><p><b>CONCLUSION</b>Del (11) (q24.1-ter) may contribute to hypoplastic left-heart syndrome of the fetus. For its high-resolution and high-accuracy, array-CGH has provided a powerful tool for detection of genomic imbalance.</p>

ASS1 mutation leading to citrullinemia I in a Chinese Han family / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To investigate potential mutation of the ASS1 gene in a male infant with acute citrullinemia type I.</p><p><b>METHODS</b>Genomic DNA was prepared from peripheral blood samples of the family members. Mutation analysis of the 14 ASS1 exons was carried out by PCR and direct DNA sequencing.</p><p><b>RESULTS</b>A homozygous missense mutation of c.970G>A located in exon 13, which results in p.G324S, was identified in the child. Sequencing of the parents showed a heterozygous status for the same mutation.</p><p><b>CONCLUSION</b>A missense mutation of c.970G>A in the ASS1 gene is responsible for the pathogenesis of the disease in the infant.</p>

Application of multiplex ligation-dependent probe amplification for rapid detection of aneuploidies in prenatal diagnosis / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To determine the applicability of multiplex ligation-dependent probe amplification (MLPA) for rapid detection of aneuploidies in prenatal diagnosis.</p><p><b>METHODS</b>A total of 561 prenatal samples were analyzed in parallel by MLPA and traditional karyotyping. Another 20 clinical samples with known common chromosome abnormalities were also determined by MLPA to evaluate the accuracy and reliability of MLPA. The results obtained from MLPA were compared with that from traditional karyotyping.</p><p><b>RESULTS</b>The results were available within 48 h. A total of 38 aneuploidies were identified by MLPA, including 20 cases of trisomy 21, 10 cases of trisomy 18, 1 case of trisomy 13, 4 cases of Turner syndrome, 1 case of Klinefelter syndrome, 1 case of 47, XYY trisomy and 1 case of 48,XYY, +18. MLPA was able to detect all the expected aneuploidies with 100% accuracy. The results obtained from MLPA agreed with traditional karyotyping. Among 561 prenatal samples, the results of 550 samples were concordant with those of karyotyping, and the coincidence rate of MLPA was 98.04%.</p><p><b>CONCLUSION</b>MLPA is a rapid, simple and reliable method for detection of the most common chromosome aneuploidies in prenatal diagnosis. MLPA is a valuable tool in prenatal clinical practice.</p>

Detection of cryptic copy number variations in a fetus with congenital heart disease by array-based comparative genomic hybridization / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To detect the copy number variation (CNV) of a fetus with interrupted aortic arch and ventricular septal defect, in order to explore the underlying genetic causes of the congenital malformation, and investigate the feasibility of array-based comparative genomic hybridization (array-CGH) in molecular cytogenetic diagnosis.</p><p><b>METHODS</b>The whole genome of the fetus with de novo apparently balanced translocations [46,XX,t(7;9)(q12;q21)] diagnosed by G-banding was scanned and analyzed by array-CGH, and the copy number variation was confirmed by fluorescence in situ hybridization (FISH).</p><p><b>RESULTS</b>A pathologic submicroscopic CNV [del(22) (q11.2) (17 370 128-19 790 009, -2.42 Mb)] was identified and mapped by array-CGH. FISH test confirmed the microdeletion detected by array-CGH.</p><p><b>CONCLUSION</b>The cryptic 22q11.2 deletion might be the reason leading to the congenital malformation of the fetus. This study provides evidence that apparently balanced translocations classified by conventional cytogenetic techniques may host additional submicroscopic CNVs which are not located at the breakpoints. Due to the high-resolution, high-throughput and high-accuracy, array-CGH is considered to be a powerful tool for submicroscopic CNVs detection.</p>