The power of linkage analysis on PAH gene in prenatal gene diagnosis is improved with three additional short tandem repeat markers / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To increase the success rate of prenatal diagnosis for classical phenylketonuria(PKU).</p><p><b>METHODS</b>Three new short tandem repeat (STR) markers (PAH26, PAH32 and PAH9) within and surrounding phenylalanine hydroxylase(PAH) gene were selected for amplified fragment length polymorphism. The allele frequencies and polymorphism information contests (PIC) were determined in Chinese population.</p><p><b>RESULTS</b>The PIC of these three new STR markers was 0.518 (PAH26), 0.413 (PAH32) and 0.362 (PAH9) respectively. There was linkage disequilibrium between PAH9 marker and PAH-STR marker (TCTA)n in the intron 3 of PAH gene. The linkage phase of the mutant genes and the markers was established using the combination of PAH-STR, PAH26 and PAH32 in 95% families. Prenatal diagnosis was performed successfully with these markers in four cases.</p><p><b>CONCLUSION</b>By selecting or combining the three STR markers, the mutant genes could be distinguished from the normal allele in up to 95% of families with classical PKU.</p>

Postnatal and prenatal diagnosis of mucopolysaccharidosis type II (Hunter syndrome) / 中华儿科杂志

<p><b>OBJECTIVE</b>Mucopolysaccharidosis type II (MPS II, Hunter syndrome, OMIM 309900) is an X-linked recessive lysosomal storage disease resulting from a deficiency of iduronte-2-sulphate sulphatase (IDS). The present study aimed to establish an enzyme assay method for IDS activity for carrying out postnatal and prenatal diagnosis of MPS II by means of IDS activity assay on plasma, uncultured chorionic villi (CV) and cultured amniotic fluid cells (AF cell) using a new synthesized substrate.</p><p><b>METHODS</b>A fluorigenic substrate (4-methylumbelliferyl-alpha-iduronate-2-sulphate, MU-alpha-Idu-2S) was used for the assay of IDS activity. IDS activity in plasma was determined for diagnosis of the proband. Prenatal diagnosis in 10 pregnancies at risk was carried out according to IDS activity on uncultured CV at 11th week or on cultured AF cell at 18th week of gestation. At the same time, IDS activity was also determined in the maternal plasmas to observe the change of IDS activity in pregnancy. The fetal sex determination was performed by PCR amplification of the ZFX/ZFY genes.</p><p><b>RESULT</b>The IDS activity in plasma of normal controls and obligate heterozygotes were 240.2 - 668.2 nmol/(4 hxml) and 88.7 - 547.9 nmol/(4 hxml), respectively, while the enzyme activities in plasmas were in the range of 0.3 - 18.6 nmol/(4 hxml) in affected male. The IDS activities were 37.2 - 54.9 nmol/(4 hxmg protein) and 21.4 - 74.4 nmol/(4 hxmg protein) in CV and cultured AF cells respectively. Out of 50 suspected cases, 46 were diagnosed as having MPS II and 4 were excluded. Prenatal diagnosis was performed on 10 pregnancies at risk. Four of 5 male fetuses [IDS activity were 4.7, 1.8, 7.0 nmol/(4hxmg protein) in CV, 0.6 nmol/(4 hxmg protein) in AF cell] were diagnosed as having MPS II and the other 5 fetuses were normal females [IDS activity were: 48.7, 5.9, 25.2 nmol/(4 hxmg protein) in CV, 55.2, 40.9 nmol/(4 hxmg protein) in AF cell]. Increased IDS activity was observed in plasma of the pregnant women with unaffected fetuses, while the IDS activity decreased in pregnancies with affected fetuses. IDS activity of one female fetus was very low [5.9 nmol/(4 hxmg protein)], but the IDS activity in maternal plasmas increased, this fetus was a normal female.</p><p><b>CONCLUSIONS</b>The method using a synthesized fluorigenic 4-methylumbelliferyl-substrate was a sensitive, rapid and convenient assay of IDS activity and was reliable for early prenatal diagnosis. Determination of fetal sex would be helpful in excluding the female fetus with low IDS activity from being considered as an affected male fetus. It would be further helpful if IDS activity in maternal plasma was taken into account.</p>

Detection of the gene-deleted female carriers of Duchenne/Becker muscular dystrophy using a fluorescent in situ hybridization based method / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To set up a fluorescent in situ hybridization (FISH) based method to detect the gene-deleted female carriers of Duchenne/Becker muscular dystrophy (DMD/BMD).</p><p><b>METHODS</b>Multiplex polymerase chain reaction was used to identify the gene deletion DMD/BMD probands and their female relatives were checked by double-color FISH.</p><p><b>RESULTS</b>Two probands whose exon 46 of dystrophin gene was deleted, one had a positive pedigree and the other was a sporatic patient. In the case of the positive pedigree, four carriers were detected. In the case of the sporatic family, FISH showed that the mother of the proband was a somatic mosaicism.</p><p><b>CONCLUSION</b>Combined with multiplex PCR, double-color FISH is a simple, fast, directly visual and accurate method. It is feasible to identify the carrier status of the female relatives of the gene deletion DMD/BMD probands. The detection of the somatic mosaicism is a prominent feature of FISH.</p>

Screening by maternal serum markers for Down's syndrome / 中国医学科学院学报

<p><b>OBJECTIVE</b>To investigate the optimal method of screening for Down's syndrome (DS) with maternal serum mankers.</p><p><b>METHODS</b>Screening by maternal serum markers for Down's syndrome was offered to all 2886 pregnant women in Peking Union Medical Hospital during 1996.11-2001.3. Alpha-fetoprotein (AFP), human chorionic gonadotrophin (free beta-HCG) were used as markers during the first year of pregnancy. Alpha-fetoprotein, free human chorionic gonadotrophin (HCG) and pregnancy-associated plasma protein A (PAPP-A) were used as mid pregnancy and first-trimester markers in next three years. Amniocentesis and (CVS) were done in those defined as risk cases.</p><p><b>RESULTS</b>The detection rate of Down's syndrome by maternal serum markers was 3.8% (11/2886). The proportion of false positive results in group of triple markers (alpha FP, free beta-HCG, PAPP-A) was 5%.</p><p><b>CONCLUSIONS</b>The PAPP-A was a good marker to detect Down's syndrome in early pregnancy and may be used to predict the outcome during mid trimester of pregnancy. The AFP and free beta-HCG can be useful markers to detect Down's syndrome and fetal abnormality. While prenatal diagnostics can be shifted to an early pregnant period.</p>

Study on the correlation of serum folate and red blood cell folate level with birth defects and unexplained recurrent pregnancy loss / 中华妇产科杂志

0.05). The RBC folate level of birth defect group except the urinary defect was significantly lower compared with the control group(233-547 vs 689 nmol/L,P