Molecular diagnosis of X-linked adrenoleukodystrophy: experience from a clinical genetic laboratory in mainland China with report of 13 novel mutations.

BACKGROUND: X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative disorder characterized by progressive demyelination of the nervous system, adrenocortical insufficiency and increase of very long chain fatty acids (VLCFAs) in the plasma and tissues. METHODS: A total of 131 individuals from 30 Chinese pedigrees were involved in this study, including 42 symptomatic patients, 44 female carriers, and 15 high-risk fetuses from 13 families. The mutation was first pinpointed through long distance RT-PCR-based RNA approach and confirmed through peripheral blood DNA approach. RESULTS: A total of 28 mutations were identified, of which 19 were missense, 3 nonsense and 6 frame-shift mutations. Thirteen mutations were novel, i.e. p.R280L, p.P580L, p.G343V, p.S108X, p.R259W, p.P534R, p.fs A246, p.L576P, p.K602X, p.A314P, p.N148D, p.H283R, and p.fs R89. Two mutations occurred de novo, for they were not found in somatic cells of their parents. Three females from the same family developed AMN-like symptoms and they were heterozygous for the p.H283R mutation. Four asymptomatic boys were diagnosed as X-ALD patients and prenatal molecular diagnosis were provided for 13 X-ALD-stricken families. CONCLUSIONS: Our work extended the spectrum of mutations in X-ALD and benefited genetic counseling through reliable identification of heterozygous females and asymptomatic males.

A rapid and sensitive protocol for prenatal molecular diagnosis of X-linked adrenoleukodystrophy.

BACKGROUND: X-linked adrenoleukodystrophy (X-ALD) is a neurodegenerative genetic disease characterized by progressive demylination of the brain, adrenal insufficiency and elevated VLCFA level. ABCD1gene is the disease gene and more than 500 unique mutations in the ABCD1gene have been recorded in the database, approximately 60% of which are noncurrent ones. Although great progress has been made in the treatment of X-ALD, prenatal diagnosis is still badly needed by X-ALD-stricken families. METHODS: Twelve high-risk fetuses entered this study. Amniotic fluid (AF) was divided into two parts, with one part being used directly to isolate genomic DNA and debris from the other part for amniotic fluid cells (AFC) culturing. STR profiling was performed to evaluate maternal contamination of AFC genomic DNA. Two different molecular approaches, be they any two of direct sequencing, PCR-RFLP, ARMS, dot hybridization and DHPLC, were applied to determine whether the mutation identified in the index patient was found in the fetus. RESULTS: The genotypes of all 12 fetuses were determined, among which 2 were diagnosed as ALD males, 5 unaffected males, 1 heterozygote, and 4 normal unaffected females. A total of 9 families sent samples of umbilical blood at the time of delivery, and results of molecular checking of these samples agreed with those of prenatal diagnosis. Up until now, no ALD-related abnormalities were reported postnatally. CONCLUSION: An in-house protocol for the prenatal molecular diagnosis of X-ALD was established, and this protocol would provide accurate and rapid prenatal genetic service to X-ALD-stricken families.

[Prenatal molecular diagnosis of four fetuses at high risk for X-linked adrenoleukodystrophy].

OBJECTIVE: To investigate methods for prenatal molecular diagnosis of fetuses at high risk for X-linked adrenoleukodystrophy (X-ALD). METHODS: The amniotic fluid was obtained and genomic DNA was isolated from amniotic fluid cells. Maternal contamination was evaluated by paternity test. PCR-RFLP, sequencing and denaturing high performance liquid chromatography (DHPLC) were used to detect the ABCD1 gene of fetal genome. RESULTS: In the pedigree 1, the PCR product (799 bp) of the fetus 1 and her father (normal control) could be digested with BcnI. No P560L mutation, which was present in the index patient, was detected in the ABCD1 gene from the genomic DNA of the fetus 1 using direct sequencing. In the pedigree 2, the PCR product (232 bp) of the fetus 2 and her father could not be digested with MaeI and no Q177X mutation, which was present in the propositus, was detected in the ABCD1 gene from the genomic DNA of the fetus 2 using direct sequencing. In the pedigree 3, the PCR product (271 bp) was digested with AciI, the pattern of the fetus 3 and the propositus being the same, and the R617C mutation was found in the ABCD1 gene from the genomic DNA of the fetus 3 using direct sequencing. In the pedigree 4, the PCR product (269 bp) was analyzed with the DHPLC, and the pattern of elution peaks of the fetus 4 and her father was similar, but different from that of the propositus. No K276E mutation was detectable in the ABCD1 gene from the genomic DNA of the fetus 4 by using direct sequencing. Judging from the sex of the fetuses, fetuses 1 and 2 were normal homozygotes, fetus 3 was an ALD hemizygote, and fetus 4 was a normal hemizygote. CONCLUSION: A new protocol for X-ALD prenatal molecular diagnosis is proposed, which would ensure the accuracy of prenatal diagnosis.

[Prenatal diagnosis of 5 fetuses with high risk of developing spinal muscular atrophy].

OBJECTIVE: To perform prenatal diagnosis for 5 pregnant women who had given birth to children with spinal muscular atrophy (SMA). METHODS: Thirty to forty mililiters of amniotic fluid was obtained by amniocentesis under ultrasonic monitoring. DNA was extracted directly from sediment of amniotic fluid. Short tandem repeat (STR) profiling was carried out to evaluate the contamination of amniotic DNA by maternal genomic DNA. Two methods, PCR-restriction fragment length polymorphism (PCR-RFLP) and allele-specific PCR, were used to analyze exon 7 of SMN gene from amniotic DNA. RESULTS: Comparing the 16 STR sites of each fetus with those of his/her parents, there was no or little contamination of amniotic DNA by maternal genomic DNA. In conventional PCR-RFLP, part of the PCR product (189 bp) from amniotic DNA of fetus A, C, or D remained intact after digestion with Dra I, while the PCR product from amniotic DNA of fetus B or E was completely digested by Dra I. In allele-specific PCR, exon 7 of both SMN1 and SMN2 gene could be seen when amniotic DNA of fetuses A, C, or D was analyzed, while only exon 7 of SMN2 could be seen when amniotic DNA of fetuses B or E was analyzed. CONCLUSION: Homozygous deletion of SMN1 is not detected in fetuses A, C, and D, predicting that the risk of developing SMA after birth would be extremely low. Homozygous deletion of SMN1 was present in fetuses B and E suggesting high risk of developing SMA after birth.

Prenatal molecular diagnosis of adrenoleukodystrophy.

OBJECTIVE: To carry out prenatal diagnosis on two fetuses of different pedigrees with X-linked adrenoleukodystrophy (ALD). METHODS: The amniotic fluid was obtained with the help of a clinical doctor and the genomic DNA was isolated from it. Maternal DNA contamination was excluded by fluorescent STR profiling, The R617G mutation found in the first pedigree was searched in genomic DNA of amniotic fluid cells (AFC) from fetus 1 by amplification refractory mutation system (ARMS) and dot DNA hybridization while the P534R mutation found in pedigree 2 was analyzed in the AFC genomic DNA of fetus 2 by restrictive digestion with Hae II and DNA direct sequencing. RESULTS: A specific band (185 bp) was detected from the genomic DNA of the first fetus and his mother by using mutation primer in ARMS but not from that of the first fetus's father and unrelated controls. DNA dots were visualized only in the fetus 1 and carrier when using the mutation probe in DNA hybridization. In the other ALD family, the PCR product (506 bp) of the second fetus which spanned the site of P534R mutation could not be digested with Hae II and no mutation was detected in the ABCD1 gene from the genomic DNA of the fetus 2 by using DNA direct sequencing. CONCLUSION: Fetus 1 had R617G mutation on his ABCD1 gene and he was an adrenoleukodystrophy hemizygote. Fetus 2 had no P534R mutation on his ABCD1 gene and he was a normal hemizygote.

[Mutational analysis of three Chinese pedigrees with adrenoleukodystrophy].

OBJECTIVE: To identify the mutational genotype of three Chinese families with X-linked adrenoleukodystrophy (X-ALD: MIM#300100). METHODS: Total RNA was extracted from the peripheral blood leukocytes of patients 1, 2 and the mother of patient 3, using RNA blood Mini kit (QIAGEN). After reverse transcription, cDNA was amplified in four overlapping segments. The PCR products were purified and directly sequenced. To confirm the mutations, the genomic DNA was isolated from the patients and their family members using DNA blood isolation kit (MO-BIO) and analyzed by PCR-restrictive digestion or amplification refractory mutation system. RESULTS: Three distinct mutations were detected in the ABCD1 gene of the three pedigrees. A mutation of CCC-->CGC was detected at codon 534 of the ABCD1 gene from patient 1, resulting in the arginine for proline substitution. A change of GGG-->AGG was found at codon 266 of the second patient's gene, accompanied with the replacement of glycine by arginine. A mutation of CGC-->GGC was found at codon 617 in one ABCD1 allele of the third patient's mother, leading to the glycine for arginine substitution. The three mutations were confirmed through restriction analysis or amplification refractory mutation system. CONCLUSION: Three ABCD1 gene missense mutations were detected in three unrelated Chinese families with X-linked adrenoleukodystrophy, one of which, the mutation (P534R), is novel in Chinese with ALD, and the other two G266R and R617G mutations, have been reported outside China.

[Changes of cerebral vascular hemodynamics from normal population to stroke].

OBJECTIVE: To probe into changes of cerebral vascular hemodynamics indexes (CVHI) from normal population to different clinical stage before and after occurring of stroke. METHODS: Participants were selected from 25,355 stroke cohort study population aged 35 years and over in Northeast of China and 55 acute stroke patients were selected from Fuzhou PLA General Hospital. CVHI indexes were checked during baseline investigation or within one week after acute stroke. Participant enlisted in the study were divided into following 5 groups, normal population, high risk population, individuals before stroke, acute stroke patients and convalescence stroke patients. Characteristics of CVHI indexes in different population were analyzed and compared. RESULTS: V(min) of cerebral vascular in previous defined 5 group participants were 11.39 +/- 3.27, 9.66 +/- 3.18, 6.71 +/- 3.30, 4.13 +/- 1.27, 6.78 +/- 3.09, respectively. V(mean) and V(max) were with the same decreasing trends as V(min). However, RV in 5 group participants were 62.35 +/- 21.11, 82.32 +/- 31.16, 122.72 +/- 52.73, 137.46 +/- 49.56 and 115.89 +/- 55.51, respectively. Zcv, WV, DR and CP were also with the same increasing trends as RV. Abnormal rate of CVHI score (< 75 points) from normal population to convalescence stroke patients were 13.3%, 34.7%, 74.1%, 100% and 66.7%, respectively. CONCLUSION: From normal population to clinical stage of stroke, cerebral vascular velocity showed decreasing trends while other indexes, such as RV, Zcv, WV, DR and CP were increasing.

[Study on a test of screening to predict stroke-using cerebral vascular hemodynamic indexes].

OBJECTIVE: To evaluate efficacy and optimal cut-off-point through cerebral vascular hemodynamic indexes (CVHI) examination to predict stroke. METHODS: A number of 20,333 people at 35 years old and over were checked by CVHI and accumulative score was calculated according to the value of detected indexes. Risk factors of stroke were investigated simultaneously. One hundred and sixty-eight patients with stroke occurred during 4-year following up. Typical syndromes and signs stroke were used as golden standard to evaluate screening efficacy of CVHI. RESULTS: Score of optimal cut-off-point of cerebral vascular hemodynamic indexes was under 75 in ROC curve analyses. Sensitivity, specificity, accuracy, positive and negative predictive values, positive and negative likelihood ratios as well as Youden's index for predicting stroke within 4 years after examination were found to be 87.50%, 67.70%, 67.86%, 2.21%, 99.85%, 2.71, 0.18 and 0.55 respectively. Sensitivity and positive predict values for predicting cerebral vascular thrombosis were superior to predicting cerebral hemorrhage. Positive predicting value in risk exposure population was higher than that of overall population. Coefficiency of variation of cerebral vascular hemodynamic examination was 4.03%. The agreement rate of examination between two physicians was 97.62% and Kappa value was 0.94. CONCLUSION: The score of optimal cut-off-point of cerebral vascular hemodynamic indexes examination was 75. Both Efficacy and reliability for predicting stroke seemed to be good, especially for predicting cerebral vascular thrombosis.