A new method avoids interference of ABCD1 pseudogenes in molecular diagnosis of X-linked adrenoleukodystrophy / 第二军医大学学报

Objective: To introduce a new method which can avoid the interference of ABCD1 pseudogenes in the molecular diagnosis of X-linked adrenoleukodystrophy. Methods: The coding regions of ABCD1 gene of 3 unrelated Chinese patients with X-linked adrenoleukodystrophy were amplified from the total RNA of peripheral blood by long distance RT-PCR; the product was further amplified in 4 segments in a second round PCR; and the PCR products were purified and directly sequenced. To confirm the mutations, the genomic DNA from peripheral blood cells of the patients was analyzed by direct sequencing after amplification of the ABCD1 genes by nested PCR, in which the product of the first round PCR covered the fragment starting from exon 6 and ending at 3′UTR of the ABCD1 gene. Results: The 3 Chinese patients with X-linked adrenoleukodystrophy had 3 different base substitutions(2235C>T,2065C>T and 2190A>T)in the ABCD1 genes of the 3 probands and their mothers, which resulted in 2 missense mutations (R617C and P560L) and one nonsense mutation (K602X). Conclusion: Nested PCR can rapidly and efficiently avoid the interference of ABCD1 pseudogenes in the molecular diagnosis of X-ALD.

A novel missense mutation resulting in X-linked adrenoleukodystrophy in female heterozygotes of a Chinese family / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To identify ABCD1 gene mutation in a Chinese family with three heterozygous female patients.</p><p><b>METHODS</b>Four fragments covering the entire coding sequence of the ABCD1 gene from one of the female patients were amplified by reverse transcription-PCR. The PCR products were directly sequenced. The result of sequencing was confirmed by restriction enzyme digestion of PCR products from genomic DNA. Human ABCD1 gene and ALD protein were aligned with those of rat, monkey, mouse and cattle by Clustal X 1.83. Softwares of Motif Scan, TMpred and ESYpred3D were used to predict the effect of the mutation on the structure of the ALD protein.</p><p><b>RESULTS</b>A novel missense mutation, CAC to CGC, was found at codon 283 of the ABCD1 gene from the patient, resulting in the replacement of histidine by arginine. This mutation abolished an Msl I site in the gene. Her son was free from this mutation. The mutated amino acid residue (283H) was highly conservative in evolution, and the mutation caused a dramatic change in the structure of the ALD protein.</p><p><b>CONCLUSION</b>Three female patients heterozygous for ABCD1 gene mutation were first reported in China, and a novel mutation, p.H283R, was identified in this X-ALD family.</p>

Molecular diagnosis of a Chinese pedigree with osteogenesis imperfecta type I / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To perform molecular diagnosis for a Chinese pedigree with osteogenesis imperfecta type I.</p><p><b>METHODS</b>Thirty pairs of primers were designed to amplify all the 52 exons, exon boundaries and promoter region of the COL1A1 gene from genomic DNA of peripheral blood cells of the family members. The PCR products were purified and directly sequenced. To check the mutation in normal controls, the genomic DNA from peripheral blood cells of the index patient, his mother and 60 normal controls were analyzed by amplification refractory mutation system.</p><p><b>RESULTS</b>A missense mutation of GAT>CAT was identified at codon 1441 of the COL1A1 gene from the family, which resulted in the replacement of aspartic acid by histidine (D1441H). This mutation was not found in a group of 60 normal controls.</p><p><b>CONCLUSION</b>The method for molecular diagnosis of osteogenesis imperfecta was established and a novel COL1A1 gene mutation, D1441H, was identified in the Chinese pedigree with osteogenesis imperfecta type I.</p>

Mutation analysis of SMN gene in a patient and his family with spinal muscular atrophy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To perform mutation analysis and describe the genotype of the SMN gene in a patient with spinal muscular atrophy (SMA) and his family.</p><p><b>METHODS</b>Deletion analysis of the SMN1 exon 7 by conventional PCR-restriction fragment length polymorphism (RFLP) and allele-specific PCR, and gene dosage of SMN1 and SMN2 by multiplex ligation-dependent probe amplification (MLPA) were performed for the patient and his parents; reverse transcriptase (RT)-PCR and sequencing were performed for the patient. To determine whether the SMN variant was exclusive to transcripts derived from SMN1, the RT-PCR product of the patient was subcloned and multiple clones were sequenced directly; PCR of SMN exon 5 from the genomic DNA of the parents and direct sequencing were performed to confirm the mutation.</p><p><b>RESULTS</b>In SMN1 exon 7 deletion analysis, no homozygous deletion of the SMN1 was observed in the family; the gene dosage analysis by MLPA showed that the patient had 1 copy of SMN1 and 1 copy of SMN2 his father had 2 copies of SMN1 and 2 copies of SMN2, and his mother had 1 copy of SMN1 and no SMN2. A previously unreported missense mutation of S230L was identified from the patient and this mutation was also found in his father.</p><p><b>CONCLUSION</b>A novel missense mutation of S230L was identified in the SMA family and the genotype of the family members were investigated.</p>

Prenatal diagnosis of 5 fetuses with high risk of developing spinal muscular atrophy / 中华医学遗传学杂志

<p><b>OBJECTIVE</b>To perform prenatal diagnosis for 5 pregnant women who had given birth to children with spinal muscular atrophy (SMA).</p><p><b>METHODS</b>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.</p><p><b>RESULTS</b>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.</p><p><b>CONCLUSION</b>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.</p>