Study of GCN repeats of PHOX2B gene among individuals from southwest China and diagnosis of two patients with Congenital central hypoventilation syndrome / 中华医学遗传学杂志

OBJECTIVE@#To study the trinucleotide repeats of GCN (GCA, GCT, GCC, GCG) encoding Alanine in exon 3 of the PHOX2B gene among healthy individuals from southwest China and two patients with Congenital central hypoventilation syndrome (CCHS).@*METHODS@#The number and sequence of the GCN repeats of the PHOX2B gene were analyzed by capillary electrophoresis, Sanger sequencing and cloning sequencing of 518 healthy individuals and two newborns with CCHS, respectively.@*RESULTS@#Among the 1036 alleles of the 518 healthy individuals, five alleles were identified, including (GCN)7, (GCN)13, (GCN)14, (GCN)15 and (GCN)20. The frequency of the (GCN)20 allele was the highest (94.79%). And five genotypes were identified, which included (GCN)7/(GCN)20, (GCN)13/(GCN)20, (GCN)14/(GCN)20, (GCN)15/(GCN)20, (GCN)20/(GCN)20. The homozygous genotypes were all (GCN)20/(GCN)20, and the carrier rate was 89.58%. Four GCN sequences of the (GCN)20 homozygous genotypes were identified among the 464 healthy individuals. The GCN repeat numbers in the exon 3 of the PHOX2B gene showed no significant difference between the expected and observed values, and had fulfilled the,Hardy-Weinberg equilibrium. The genotypes of the two CCHS patients were (GCN)20/(GCN)25 and (GCN)20/(GCN)30, respectively.@*CONCLUSION@#It is important to determine the GCN repeats and genotypic data of the exon 3 of the PHOX2B gene among the healthy individuals. The number of GCN repeats in 518 healthy individuals was all below 20. The selection of appropriate methods can accurately detect the polyalanine repeat mutations (PARMs) of the PHOX2B gene, which is conducive to the early diagnosis, intervention and treatment of CCHS.

Application of quantitative fluorescencet-PCR in the prenatal diagnosis of chromosomale aneuploidies / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To assess the accuracy of quantitative fluorescence PCR(QF-PCR) for the detection of fetal chromosomal aneuploidies and its values for prenatal diagnosis.</p><p><b>METHODS</b>QF-PCR and chromosomal karyotyping were used to analyze 6066 amniotic fluid samples derived from 6034 pregnant women.</p><p><b>RESULTS</b>Both QF-PCR and karyotyping analysis have detected 135 cases of fetal aneuploidies involving chromosomes 21, 18, 13, X, and Y. The QF-PCR assay was also successful in 67 cases for which amniotic fluid culture has failed. Furthermore, it has identified maternal cell contamination in 7 cases. By determining the consistency of short tandem repeat (STR) sites, the QF-PCR assay has identified 22 dizygotic twins among 32 twins with double chorions and double amniotic sacs. In 12 cases, it has signaled numerical chromosomal aberration by critical or partial abnormal values for the fluorescence peak area ratio, which were verified by karyotyping analysis as mosaicisms of chromosome aneuploidies.</p><p><b>CONCLUSION</b>The QF-PCR can provide an useful supplement for chromosomal karyotyping and has an important role in rapid prenatal diagnosis.</p>