The Human Genome Project is an international cooperative project that launched in 1990 and completely finished in April 14, 2003. The discovery of pathogenic genes is promising that light up the pathogenesis of many diseases in human. In the future, the understanding of these genes is helpful for patients and physicians, but the first advantages are in diagnosis and prognosis. It’s hoped to bring about new more effective therapies tailored for each patient according to his genome in the next 5 years
Genome, Human ; Gene Conversion ; medicine

Steroid 21 hydroxylase deficiency is a major cause of congenital adrenal hyperplasia(CAH) and is caused by genetic impairment (CYP21B) of this enzyme. In the human genome, CYP21B is located within MHC class III region on the short arm of chromosome 6. Most of the genes in this region are highly polymorphic and crowded. Also the CYP21B gene is accompanied by its pseudogene (CYP21A) and tandemly arranged with two genes of fourth component of complement. This highly complex gene arrangement in this area may predispose genetic unstability of CYP21 genes,i.e. mutations. In the current study, we tried to investigate the frequency of duplication and deletion of CYP21 genes and pattern of the genetic alteration of these genes by RFLPs. We also compared the genetic alteration of CYP21 in normal subjects with those of the CAH patients. According to our study, 15% of the normal Korean population have duplication or deletion of CYP21. There was one normal subject with heterozygous deletion of CYP21B gene. Of the 5 CAH patients examined, we found abnormal patterns in 2 patients. One was a large scale gene conversion and the other was a deletion of CYP21B and C4 locus II genes with gene conversion. These results suggest that high frequency of duplication and deletion of CYP21 and C4 in the general population may provide the genetic pool of instable CYP21 genes and these duplicated or deleted genes may result in gene conversions between CYP21A(pseudogene) and CYP21B(true gene) by preventing the normal recombination event.
Adrenogenital Syndrome* ; Arm ; Chromosomes, Human, Pair 6 ; Complement System Proteins ; Gene Conversion ; Gene Order ; Genome, Human ; Humans ; Polymorphism, Restriction Fragment Length ; Pseudogenes ; Recombination, Genetic ; Steroid 21-Hydroxylase*

OBJECTIVETo study the incidence of homozygous absence of SMN1 exons 7 and 8, SMN gene conversion frequency and SMN subtle mutations in children with spinal muscular atrophy (SMA).

METHODSThe homozygous deletion was detected by PCR-RFLP in 106 Chinese children with SMA, gene conversion by RFLP and subtle mutations by sequencing.

RESULTSThe rate of deletion of SMN1 exons 7 and/or 8 was 91.5%. Deletion of SMN1 exon 8 but existence of exon 7 was noted in one child with SMA. There were no significant differences in the gene conversion frequency among children with different types of SMA and who had homozygous deletion of SMN1 exon 7 but existence of exon 8. The gene conversion frequency was 8.3% in children with homozygous deletion of SMN1 exon 7. No subtle mutations were found around SMN1 exon 7.

CONCLUSIONSDeletion of SMN1 exons 7 and/or 8 is the main cause of SMA in Chinese children. There exists a SMN gene conversion phenomenon in SMA. Deletion of exon 8 might lead to SMA. The hot area of subtle mutations of this disease might not be around SMN1 exon 7.

Child, Preschool ; Female ; Gene Conversion ; Gene Deletion ; Humans ; Infant ; Infant, Newborn ; Male ; Microsatellite Repeats ; Muscular Atrophy, Spinal ; genetics ; Survival of Motor Neuron 1 Protein ; genetics

CYP21A2 mutation analysis of congenital adrenal hyperplasia (CAH) is challenging because of the genomic presence of a homologous CYP21A2 pseudogene and the significant incidence of pseudogene conversion and large deletions. The objective of this study was to accurately analyze the CYP21A2 genotype in Korean CAH patients using a combination of complementary methods. Long-range PCR and restriction fragment length polymorphism analyses were performed to confirm valid amplification of CYP21A2 and to detect large gene conversions and deletions before direct sequencing. Multiple ligation-dependent probe amplification (MLPA) analysis was conducted concurrently in 14 CAH-suspected patients and six family members of three patients. We identified 27 CYP21A2 mutant alleles in 14 CAH-suspected patients. The c.293-13A>G (or c.293-13C>G) was the most common mutation, and p.Ile173Asn was the second, identified in 25% and 17.9% of alleles, respectively. A novel frame-shift mutation of c.492delA (p.Glu 164Aspfs*24) was detected. Large deletions were detected by MLPA in 10.7% of the alleles. Mutation studies of the six familial members for three of the patients aided in the identification of haplotypes. In summary, we successfully identified CYP21A2 mutations using both long-range PCR and sequencing and dosage analyses. Our data correspond relatively well with the previously reported mutation spectrum analysis.
Adrenal Hyperplasia, Congenital* ; Alleles ; Gene Conversion ; Genotype ; Haplotypes ; Humans ; Incidence ; Korea ; Polymerase Chain Reaction* ; Polymorphism, Restriction Fragment Length* ; Pseudogenes ; Spectrum Analysis

OBJECTIVES: Congenital adrenal hyperplasia (CAH) is an autosomal recessive disease which is most often caused by a deficiency in steroid 21-hydroxylase (21-OH), a microsomal enzyme encoded by the CYP21 gene. Although several CAH causing mutations have been identified in the CYP21 gene of patients with 21-OH deficiency, genotyping of the 21-OH locus is quite complex because of the high frequency of gene conversion and the presence of multiple mutations on single CAH alleles. This study was aimed to analyze the complete characterization of the CYP21 gene coding region in a Korean CAH patient and to conform the PCR-based single strand conformation polymorphism (SSCP) and heteroduplex analysis as a diagnostic tool. METHODS: We used a highly sensitive, non-radioactive method allowing PCR-based single strand conformation polymorphism (SSCP) analysis. This method was applied to the characterization of all the exons and intron-exon junctions of the CYP21 gene in one patients affected by the salt wasting form and 4 normal controls. RESULTS: In all samples showing SSCP abnormal band patterns, sequence analysis showed the presence of sequence variants. In particular, one mutation (I172N) which is already known to cause the disease and 3 silent mutations were detected. CONCLUSION: PCR-based single strand conformation polymorphism (SSCP) and heteroduplex analysis should be useful for the clinical application as a diagnostic tool for the detection of 21-hydroxylase gene mutations.
Adrenal Hyperplasia, Congenital* ; Alleles ; Clinical Coding ; Diagnosis* ; Exons ; Gene Conversion ; Heteroduplex Analysis ; Humans ; Polymorphism, Single-Stranded Conformational ; Sequence Analysis ; Steroid 21-Hydroxylase* ; Virilism

OBJECTIVETo investigate the type and frequency of gene conversion from SMN1 to SMN2 in Chinese patients affected with spinal muscular atrophy (SMA), and to explore the relationship between gene conversion and clinical phenotype.

METHODSNon-homozygous deletion of SMN1 gene exon 8 was screened among 417 patients with SMN1 exon 7 homozygous deletions. To analyze and verify the types of gene conversion, genomic DNA sequencing, multiplex ligation-dependent probe amplification (MLPA), and gene subcloning and sequencing were carried out.

RESULTSThirty-one patients (7.4% of all) with non-homozygous deletions of SMN1 exon 8 were detected. Through series of experiments, the fusion genes SMN1/SMN2 in all cases were delineated. Five types of gene conversions were identified, which included SMN2-I7b/SMN1 E8, SMN2-I7a/SMN1 I7b, SMN2-E7/SMN1 I7a, SMN1 I6/SMN2 E7/SMN1 I7a and SMN2-E7/SMN1 I7a/SMN2 I7b. Such conversions were found in the type I-III patients. For 10 patients with type I-III SMA and 3 copies of SMN2 gene produced by conversion, the average survival age was 5 year and 4 months.

CONCLUSIONPartial conversions of SMN1 gene have been found among Chinese SMA patients. The type of conversion and frequency seem to be different from those of other races. Gene conversion to some extent may impact on survival time and rate of SMA patients, especially type I SMA.

Base Sequence ; Child ; Child, Preschool ; Exons ; Female ; Gene Conversion ; Gene Order ; Homozygote ; Humans ; Infant ; Male ; Muscular Atrophy, Spinal ; genetics ; Phenotype ; Sequence Analysis, DNA ; Survival of Motor Neuron 1 Protein ; genetics ; Survival of Motor Neuron 2 Protein ; genetics

BACKGROUND: Spinal muscular atrophy (SMA) is the second most common disease with autosomal recessive mode of inheritance in children and characterized by degeneration of anterior horn cells of the spinal cord resulting in weakness and wasting of voluntary muscles. This disease is caused by deletion of many candidate genes including SMN, p44, NAIP on chromosome 5q11.2-13.3. Although molecular characteristics of candidate genes were identified, genotype-phenotype correlation has not been clearly elucidated yet. Nevertheless, gene conversion, previously described as simply as gene deletion, appears to be very important mechanism as a molecular pathogenesis, and even makes more difficult to pursue the correlation. PURPOSE: This study was aimed to define the correlation between genotype and phenotype of SMA in Korean patients. The significance of SMN gene as well as NAIP gene, p44 gene in the progress of disease process and phenotypic correlation with gene conversion was evaluated. This study was also undertaken to determine the frequency of gene rearrangements in normal population. METHOD: Eight type I SMA patients and two type II SMA patients were studied. SMN, NAIP, and p44 gene deletion were analyzed by PCR amplification and restriction enzyme digestion with DraI, DdeI and AluI, respectively. p44 gene was also analyzed by SSCP. Gene conversion was defined by centromeric and telomeric SMN gene exon 7 to exon 8 PCR amplification followed by DdeI restiction enzyme digestion. RESULT: 1) Five of eight type I patients showed deletion of SMN, NAIP and p44 gene, while the rest of type 1 and all type II patients showed deletion of SMN gene only. 2) We examined SMN and NAIP gene deletion on 100 normal newborns, which showed the deletion of centromeric SMN gene in two newborns, the relative frequency of 2% in gene rearrangement. 3) There was one case of type I SMA showing deletion of telomeric SMN exon 7 but not SMN exon 8 suggestive of gene conversion occurred during the recombination as a molecular pathogenesis. CONCLUSION: The major deletion of SMA candidate genes, SMN, NAIP, and p44 gene appear to be involved in severe phenotype since these three candidate genes deletion were noted only in type 1 cases. However, SMN gene deletion only identified both in type 1 and type 2 explains that SMN gene may plan an major role in the pathogenesis of SMA and also suggests that other factors may be affecting the severity in spinal muscular atrophy. One patient with type I which showed the conversion of the centromeric SMN gene to the teleomeric gene strongly supports that SMN gene copy number may not be correlated with the severity in SMA. Our molecular findings suggest that phenotype is not clearly correlated with genotype. Prenatal screening should be carefully undertaken to interpretate because of high frequency of gene rearrangements in normal populations.
Anterior Horn Cells ; Child ; Digestion ; Exons ; Gene Conversion ; Gene Deletion ; Gene Dosage ; Gene Rearrangement ; Genetic Association Studies ; Genotype* ; Humans ; Infant, Newborn ; Muscle, Skeletal ; Muscular Atrophy, Spinal* ; Phenotype* ; Polymerase Chain Reaction ; Polymorphism, Single-Stranded Conformational ; Prenatal Diagnosis ; Recombination, Genetic ; Spinal Cord ; Wills