Molecular and prenatal diagnosis of a pedigree with spinocerebellar ataxia / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify the type of a pedigree with spinocerebellar ataxia, and carry out asymptomatic carrier detection and prenatal diagnosis.</p><p><b>METHODS</b>The blood samples of two patients in the spinocerebellar ataxia pedigree were collected. Based on the clinical characteristics of the pedigree and the disease incidence in China, the regions containing the CAG repeat of the SCA1, SCA2 and SCA3/MJD genes were amplified by polymerase chain reaction (PCR). The numbers of CAG repeats in the normal and abnormal allele fragments were identified by using agarose gel electrophoresis and DNA sequencing. We further carried out tests on the children of the patients and fetus to identify the presence of the abnormal allele.</p><p><b>RESULTS</b>The numbers of CAG repeat in the SCA1 and SCA2 genes were in the normal range. The CAG repeat number in one allele of SCA3/MJD gene was in the normal range, while that in the other allele was in the abnormal range. One of the children of the patients and the fetus carried the abnormal allele.</p><p><b>CONCLUSION</b>It was confirmed that the pedigree was SCA3/MJD by gene diagnosis. One of the children of the patients was asymptomatic carrier and the fetus also carried the abnormal allele.</p>

Prenatal cytogenetic diagnosis study of 2782 cases of high-risk pregnant women / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Prenatal diagnoses are extremely advantageous for pregnant women with high-risk indicators and can help prevent the birth of malformed infants. However, no large-scale statistical study analyzing the correlation between fetal chromosome disorders and abnormal indicators during pregnancy has been done in China. The objectives of this study were to diagnose and analyze fetal chromosome abnormalities, determine the feasibility of the various prenatal test methods and establish diagnostic guidelines for the early, middle, and late trimesters.</p><p><b>METHODS</b>From January 2004 to May 2009, 2782 pregnant women at high-risk underwent prenatal diagnoses. Categorized data expressed as either actual counts or percentages were analyzed by the chi-square or Fisher's exact test. Chorionic villus sampling was performed in the early-trimester (10 - 12 weeks of gestation), amniocentesis in mid-trimester (16 - 28 weeks of gestation), and umbilical cord blood collection in mid- or late-trimester (16 - 37 weeks of gestation). In 51 cases either autopsy samples from intrauterine fetal deaths or placental tissues from aborted fetuses were tested.</p><p><b>RESULTS</b>Chromosomal abnormalities were observed in 3.99% (111/2782) of the samples. Overall, the success rate of cytogenetic analysis for high-risk pregnancy groups was 98.17% (2731/2782). It was significantly less successful when used to analyze data from the chorionic villus sampling compared with that from amniocentesis and umbilical cord blood (P = 0.000). Abnormal chromosome carriers had the highest percentage of abnormal chromosomes (67.86%) when compared with chromosomal abnormalities in patients with ultra-sonographic "soft markers" (11.81%), advanced maternal age (4.51%) and those who had positive serum screening results (P = 0.000).</p><p><b>CONCLUSIONS</b>Invasive prenatal diagnostic techniques are feasible tools for confirming fetal chromosomal abnormalities. Abnormal chromosomes detected in one of the parents carrying abnormal chromosome, ultrasound soft markers, advanced maternal age or positive serum screening results were associated with a higher frequency of fetal genetic diseases.</p>

Gene diagnosis for spinal muscular atrophy and its application study / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To establish an effective testing system for gene diagnosis, carrier detection and prenatal diagnosis for spinal muscular atrophy (SMA).</p><p><b>METHODS</b>Twenty-six patients with SMA were directly tested with PCR-RFLP for exon 7 deletion in the SMN1 gene. Carrier detection was carried out with multi-PCR-DHPLC. Amniotic fluid was taken at the middle stage of gestation from pregnant women who had given birth to affected children.</p><p><b>RESULTS</b>Twenty-five out of 26 patients were diagnosed as having SMN1 gene deletion. Fifty-two of their parents were found to be carriers of exon 7 deletion. Eight of 20 fetuses were diagnosed as having SMN1 gene deletion by PCR-RFLP.</p><p><b>CONCLUSION</b>PCR-RFLP and multi-PCR-DHPLC techniques can provide rapid diagnosis for exon 7 deletion detection and carrier detection. PCR-RFLP may also be adapted for prenatal gene diagnosis of exon 7 deletion in SMN1 gene.</p>

Application study on inversion diagnosis of F8 gene in hemophilia A / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To establish an effective method of genetic diagnosis on hemophilia A (HA) by detecting the inversion mutation in intron 22 of F8 gene.</p><p><b>METHODS</b>Intron 22 inversion mutation in F8 gene was detected by using long distance-polymerase chain reaction (LD-PCR) and inversion-PCR (I-PCR) in 31 HA patients. The mothers of HA patients with intron 22 inversion mutation were selected to carrier diagnosis and amniotic fluid of the pregnant women with inversion mutation was collected at intermediate stage of gestation, and used to prenatal genetic diagnosis.</p><p><b>RESULTS</b>Seven patients showed F8 gene inversion mutation in thirty-one patients. Three in four mothers of HA patients with intron 22 inversion mutation were diagnosed as carriers. The prenatal diagnosis result indicated that the fetus conceived in the HA-carrier woman was normal individual.</p><p><b>CONCLUSION</b>The detection of intron 22 inversion mutation by LD-PCR and I-PCR is time-saving, and can be used in prenatal diagnosis on HA.</p>