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.

Clinical application of non-invasive prenatal testing for twin pregnancies / 中华医学遗传学杂志

OBJECTIVE@#To evaluate the feasibility of non-invasive prenatal testing (NIPT) for the screening of fetal chromosome aneuploidies in twin pregnancies.@*METHODS@#A total of 2 745 women with twin-pregnancies were subjected for NIPT screening. Chromosomal karyotyping and chromosomal microarray analysis (CMA) were carried out on amniotic fluid samples from those with a high risk for fetal chromosome aneuploidies, and the diagnosis and pregnancy outcome were followed up. The sensitivity, specificity, positive predictive value and false positive rate of the NIPT were calculated.@*RESULTS@#Compared with other chromosomal abnormalities, NIPT had a higher efficacy for trisomy 21 and sex chromosomal aneuploidy (SCA) in twin pregnancies (with sensitivity being 100%, 100%, and specificity being 99.93%, 99.9%, respectively). It is difficult to evaluate the efficacy for trisomies 18 and 13 due to the limited data. For chromosome microdeletions and microduplications spanning 15 ~ 21 Mb, NIPT also had a certain detection rate. Compared with women with natural conception, NIPT had a higher detection rate for those with twin pregnancies by assisted reproduction (P < 0.05).@*CONCLUSION@#It is feasible to use NIPT for the detection of chromosome aneuploidies in women with twin pregnancies.

Prenatal diagnosis of a case of Pallister-Killian syndrome / 中华医学遗传学杂志

OBJECTIVE@#To carry out G-banded chromosomal karyotyping and chromosomal microarray analysis (CMA) for a fetus featuring multiple malformations.@*METHODS@#The fetus was found to have increased nuchal thickness, generalized edema, asymmetric lower limbs, tetralogy of Fallot, nasal bone anomaly and cleft palate. Following amniocentesis, G-band karyotyping and CMA were carried out.@*RESULTS@#The fetus had a karyotype of 47,XX,+i(12)(p10) [14]/46,XX[6]. CMA has identified a 33.9 Mb duplication at 12p13.33-p11.1, which was suggestive of tetrasomy 12p.@*CONCLUSION@#Combined chromosomal karyotyping and CMA can delineate the origin of abnormal chromosomal fragments during prenatal diagnosis. The fetus was diagnosed with Pallister-Killian syndrome.

Genetic analysis of a 46,XY female with sex reversal due to duplication of NR0B1 gene / 中华医学遗传学杂志

OBJECTIVE@#To explore the pathogenesis of a 46,XY female with sex reversal.@*METHODS@#Peripheral blood lymphocytes of the patient were subjected to G-banding karyotype analysis. Sex chromosomes were analyzed with fluorescence in situ hybridization (FISH). SRY gene was analyzed by Sanger sequencing. The whole exome of the patient was subjected to next generation sequencing. Copy number variations (CNVs) of the NR0B1, SF1, SRY, SOX9 and WNT4 genes were validated by multiplex ligation-dependent probe amplification (MLPA).@*RESULTS@#The patient had a 46,XY karyotype. FISH analysis showed that her sex chromosomes were X and Y. No mutation was found in the SRY gene, and no pathogenic mutation was detected in her exome. However, a duplication spanning approximately 67.31 kb encompassing the MAGEB1, MAGEB3, MAGEB4 and NR0B1 genes at Xp21, was predicted by software analysis. MLPA confirmed duplication of the NR0B1 gene in the patient and her mother.@*CONCLUSION@#A duplication fragment of Xp21 encompassing the NR0B1 gene in the 46,XY female with sex reversal is transmitted from her asymptomatic carrier mother. Attention should be paid towards the insidious nature and high morbidity of this duplication.

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>

Analysis of genetics mechanism for the phenotypic diversity in a patient carrying a rare ring chromosome 9 / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To explore the genetics mechanism for the phenotypic variability in a patient carrying a rare ring chromosome 9.</p><p><b>METHODS</b>The karyotype of the patient was analyzed with cytogenetics method. Presence of sex chromosome was confirmed with fluorescence in situ hybridization. The SRY gene was subjected to PCR amplification and direct sequencing. Potential deletion and duplication were detected with array-based comparative genomic hybridization (array-CGH).</p><p><b>RESULTS</b>The karyotype of the patient has comprised 6 types of cell lines containing a ring chromosome 9. The SRY gene sequence was normal. By array-CGH, the patient has carried a hemizygous deletion at 9p24.3-p23 (174 201-9 721 761) encompassing 30 genes from Online Mendelian Inheritance in Man.</p><p><b>CONCLUSION</b>The phenotypic variability of the 9p deletion syndrome in conjunct with ring chromosome 9 may be attributable to multiple factors including loss of chromosomal material, insufficient dosage of genes, instability of ring chromosome, and pattern of inheritance.</p>

Detection of chromosomal aneuploidies in spontaneous abortion samples by fluorescence in situ hybridization / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To analyze 81 spontaneous abortion samples with fluorescence in situ hybridization (FISH).</p><p><b>METHODS</b>Chromosome 13, 21, 16, 22, 18, X and Y probes were used to detect the samples.</p><p><b>RESULTS</b>FISH was successful in 80 cases (98.77%). Among these, 35 (43.75%) had an abnormal karyotype, which included 19 autosomal aneuploidies, 6 sex chromosome aneuploidies, 9 triploidies and 1 tetraploidy.</p><p><b>CONCLUSION</b>FISH is a rapid and easy method for detecting chromosomal aneuploidies in spontaneous abortion samples, and has a higher detection rate in early spontaneous abortion samples.</p>