Polyglutamine (Poly Q) diseases are a group of neurodegenerative disorders, caused by the formation of PolyQ mutants due to trinucleotide repeats expansion in coding regions of disease-causing genes, which eventually lead to selective neuronal degeneration and death with unclarified pathogenesis. As a new type of genetic regulatory factor, microRNA (miRNA) plays an important role in modulating gene expression in eukaryote. During the recent years, more attention was paid to roles and related mechanism of miRNA involving in neurodegenerative disease, especially PolyQ diseases. This review is focused on research progress in roles of miRNA in the pathogenesis of PolyQ diseases.
Eukaryota ; MicroRNAs ; genetics ; physiology ; Nerve Degeneration ; Neurodegenerative Diseases ; genetics ; Peptides ; genetics ; Trinucleotide Repeat Expansion ; genetics ; Trinucleotide Repeats ; genetics

Trinucleotide repeat (TNR) instability can cause a variety of human genetic diseases including myotonic dystrophy and Huntington's disease. Recent genetic data show that instability of the CAG/CTG repeat DNA is dependent on its length and replication origin. In yeast, the RAD27 (human FEN-1 homologue) null mutant has a high expansion frequency at the TNR loci. We demonstrate here that FEN-1 processes the 5'-flap DNA of CTG/CAG repeats, which is dependent on the length in vitro. FEN-1 protein can cleave the 5'-flap DNA containing triplet repeating sequence up to 21 repeats, but the activity decreases with increasing size of flap above 11 repeats. In addition, FEN-1 processing of 5'-flap DNA depends on sequence, which play a role in the replication origin-dependent TNR instability. Interestingly, FEN-1 can cleave the 5'-flap DNA of CTG repeats better than CAG repeats possibly through the flap-structure. Our biochemical data of FEN-1's activity with triplet repeat DNA clearly shows length dependence, and aids our understanding on the mechanism of TNR instability.
Base Sequence ; DNA, Single-Stranded/*metabolism ; Endodeoxyribonucleases/genetics/*metabolism ; Flap Endonucleases ; Gene Expression Regulation ; Genetic Diseases, Inborn/*genetics ; Human ; Nucleic Acid Conformation ; Trinucleotide Repeat Expansion ; *Trinucleotide Repeats

Trinucleotide repeat (TNR) instability can cause a variety of human genetic diseases including myotonic dystrophy and Huntington's disease. Recent genetic data show that instability of the CAG/CTG repeat DNA is dependent on its length and replication origin. In yeast, the RAD27 (human FEN-1 homologue) null mutant has a high expansion frequency at the TNR loci. We demonstrate here that FEN-1 processes the 5'-flap DNA of CTG/CAG repeats, which is dependent on the length in vitro. FEN-1 protein can cleave the 5'-flap DNA containing triplet repeating sequence up to 21 repeats, but the activity decreases with increasing size of flap above 11 repeats. In addition, FEN-1 processing of 5'-flap DNA depends on sequence, which play a role in the replication origin-dependent TNR instability. Interestingly, FEN-1 can cleave the 5'-flap DNA of CTG repeats better than CAG repeats possibly through the flap-structure. Our biochemical data of FEN-1's activity with triplet repeat DNA clearly shows length dependence, and aids our understanding on the mechanism of TNR instability.
Base Sequence ; DNA, Single-Stranded/*metabolism ; Endodeoxyribonucleases/genetics/*metabolism ; Flap Endonucleases ; Gene Expression Regulation ; Genetic Diseases, Inborn/*genetics ; Human ; Nucleic Acid Conformation ; Trinucleotide Repeat Expansion ; *Trinucleotide Repeats

BACKGROUND: Trinucleotide repeat (TNR) expanded disorders represent a novel class of human mutations, which are characterized by abnormal elongation of the triplet repeat sequence in the human genome and is caused by heritable DNA instability. The aim of this study is to determine the relative frequency, distribution of alleles, and the clinical manifestation of TNR expanded disorders in Korean patients with progressive ataxia. METHODS: A total of 76 clinical specimens that were suspicous of hereditary cerebellar ataxia were submitted from January 1999 to August 2001 and tested for TNR expanded disorders by PCR analysis. RESULTS: Spinocerebellar ataxia (SCA) type 1 was the most common hereditary ataxia (5.3%), while SCA2, SCA3, SCA6, SCA7, and dentatorubral and pallidoluysian atrophy (DRPLA) represented 2.6%, 3.9%, 2.6%, 2.6%, and 1.3% of progressive ataxia patients, respectively. This result is different from previous reports concerning Caucasian, Chinese and Koreans. CONCLUSIONS: This study may provide the basis for the study of TNR expanded disorders in Korean patients. To elucidate the prevalence and frequencies of mutation types in Koreans, a large scale study should be performed.
Alleles* ; Asian Continental Ancestry Group ; Ataxia* ; Atrophy ; Cerebellar Ataxia ; DNA ; Genome, Human ; Humans ; Polymerase Chain Reaction ; Prevalence ; Spinocerebellar Ataxias ; Spinocerebellar Degenerations ; Trinucleotide Repeat Expansion* ; Trinucleotide Repeats

OBJECTIVES: The genetic facotrs have been suggested for the etiology of mood disorders but the mode of inheritance is complex. Increased severity and an earlier onset of the bipolar and major depressive disorder over generations within families(Anticipation) were reported. In order to test the hypothesis that trinucleotide repeat expansions underlie the genetic basis of Bipolar and major depressive disorders, we have analyzed the extent of CAG reapeats in genomic DNA from mood disorder patients. METHODS: 55 bipolar disorder, 67 major depressive disorder patients were recruited according to the DSM-III-R criteria. 89 normal controls were recruited from the medical personnel, students and the visitors to the health services center who had no history of psychiatric illness and show normal profile of MMPI. The genomic DNA of patients and controls was analyzed by use of the(CTG) 17 oligonucleotide and the repeat expansion detection(RED) method. The Mann-Whitney U test was used to compare the distribution of the number of CAG repeats among the groups. RESULTS: when the bipolar disorder, major depressive disorder patients were compared with the control group, no significant differences were observed. CONCLUSION: Our results do not support the hypothesis that expanding CAG repeats are causing the observed genetic anticipation in bipolar disorders and major depressive disorders.
Anticipation, Genetic ; Bipolar Disorder ; Depressive Disorder, Major ; DNA ; Family Characteristics ; Health Services ; Humans ; MMPI ; Mood Disorders* ; Trinucleotide Repeat Expansion ; Trinucleotide Repeats ; Wills

OBJECTIVE: To screen for mutations of fragile X mental retardation 1 (FMR1) gene during early and middle pregnancy and provide prenatal diagnosis for those carrying high-risk CGG trinucleotide expansions. METHODS: Peripheral blood samples of 2316 pregnant women at 12 to 21(+6) gestational weeks were collected for the extraction of genomic DNA. CGG repeats of the FMR1 gene were detected by fluorescence PCR and capillary electrophoresis. Genetic counseling and prenatal diagnosis were provided for 3 women carrying the premutations. RESULTS: The carrier rate of CGG repeats of the FMR1 gene was 1 in 178 for the intermediate type and 1 in 772 for the premutation types. The highest frequency allele of CGG was 29 repeats, which accounted for 49.29%, followed by 30 repeats (28.56%) and 36 repeats (8.83%). In case 1, the fetus had a karyotype of 45,X, in addition with premutation type of CGG expansion of the FMR1 gene. Following genetic counseling, the couple chose to terminate the pregnancy through induced labor. The numbers of CGG repeats were respectively 70/- and 29/30 for the husband and wife. In case 2, amniocentesis was performed at 20 weeks of gestation. The number of CGG repeats of the FMR1 gene was 29/-. No abnormality was found in the fetal karyotype and chromosomal copy number variations. The couple chose to continue with the pregnancy. Case 3 refused prenatal diagnosis after genetic counseling and gave birth to a girl at full term, who had a birth weight of 2440 g and no obvious abnormality found during follow-up. CONCLUSION Pregnant women should be screened for FMR1 gene mutations during early and middle pregnancy, and those with high-risk CGG expansions should undergo prenatal diagnosis, genetic counseling and family study.
DNA Copy Number Variations ; Female ; Fragile X Mental Retardation Protein/genetics* ; Fragile X Syndrome/genetics* ; Genetic Counseling ; Humans ; Mutation ; Pregnancy ; Trinucleotide Repeat Expansion ; Trinucleotide Repeats

PURPOSE: The trinucleotide repeat expansion in the 3' untanslated resion of the gene is known to be the cause of myotonic dystrophy which is one of most common neurodegenerative disorder manifested by myotonia, cataract, mental retardation and even respiratory distress in neonates. The hereditary pattern of myotonic dystrophy shows more severe symptoms and shows earlier onset with successive generations and congenital cases, the most severe form of myotonic dystrophy,. Occurs by maternal transmission. This genetic transmission mode does not follow Mendelian genetic trait. To find the molecular genetic abnormalities of Korean myotonic dystrophy patients, we investigated the general distribution of myotonic dystrophy alleles and compared the results with referred patients. METHODS: During an 8 month study, from June 1995 to February 1996, 5 patients were referred with presumed diagnosis of myotonicdystrophy. Among these patients, four cases were confirmed to have the disease by clinical and electrophysiological findings. We included family members of the studied probands and 50 normal blood donor DNAs were included as controls. The DNAs of the enrolled cases were evaluated by Southern blot. Subsequently, copy numbers of the repeats were determined using PCR amplification. RESULTS: (1) Two peaks were found in the distribution of trinucleotide repeats in the normal Korean population. One peak had 5 copies and the other had 11 to 13 copies. The highest number of copies was 27. (2) Of the referred cases, 4 pedigrees showed typical expanded repeats. (3) The minimum expanded copy number was 55 and we were able to detect the expanded band only by PCR in 2 cases. In other cases, expaded bands were visible by Southern blotting. (4) There were trend of earlier onset of the disease, progressive worsening symptoms and larger expanded bands with successive generations. CONCLUSION: We established the methodology for myotonic dystrophy DNA diagnosis using Southern blot and PCR amplification based on the normal Korean allele distribution. These methods might be useful in genetic counselling and detection of minimally affected myotonic dystrophy patients.
Alleles ; Blood Donors ; Blotting, Southern ; Cataract ; Diagnosis ; DNA ; Family Characteristics ; Humans ; Infant, Newborn ; Intellectual Disability ; Molecular Biology ; Myotonia ; Myotonic Dystrophy* ; Neurodegenerative Diseases ; Polymerase Chain Reaction ; Trinucleotide Repeat Expansion* ; Trinucleotide Repeats*

OBJECTIVETo compare the distribution of (CAG)n and (GGN)n repeats polymorphisms of androgen receptor (AR) gene between Hui and Han ethnic Chinese from Ningxia.

METHODSGenotypes of above repeats were determined with DNA sequencing method.

RESULTSThe distribution of (GGN)n repeats was significantly different between the two ethnic groups (P< 0.01), though no such difference was detected with (CAG)n repeats (P> 0.05). Particularly, Han Chinese women carrying 23 GGN repeats were significantly fewer (48.4%) than Hui women (64.7%, P=0.01).

CONCLUSIONThe distribution of GGN repeat is significantly differently among Hui and Han Chinese ethnics from Ningxia.

Alleles ; Asian Continental Ancestry Group ; genetics ; Base Sequence ; China ; ethnology ; Female ; Genotype ; Humans ; Male ; Molecular Sequence Data ; Polymorphism, Genetic ; Population Groups ; genetics ; Receptors, Androgen ; genetics ; Trinucleotide Repeat Expansion ; Trinucleotide Repeats

Polyglutamine (polyQ) diseases are a group of hereditary neurodegenerative disorders caused by expansion of a glutamine repeat in responsible gene products. To date, the pathogenesis of polyQ diseases is still not very clear, but many researches suggest that phosphorylation of mutant proteins plays a critical role on the process of Huntington's disease, dentatorubral-pallidoluysian atrophy, spinal bulbar muscular atrophy, spinocerebellar ataxia1 and spinocerebellar ataxia 3/Machado-Joseph disease.
Heredodegenerative Disorders, Nervous System ; genetics ; metabolism ; Humans ; Huntington Disease ; genetics ; metabolism ; Machado-Joseph Disease ; genetics ; metabolism ; Muscular Atrophy, Spinal ; Peptides ; genetics ; metabolism ; Phosphorylation ; physiology ; Spinocerebellar Degenerations ; genetics ; metabolism ; Trinucleotide Repeat Expansion ; genetics ; physiology ; Trinucleotide Repeats ; genetics

No abstract available.
Spinocerebellar Ataxias* ; Trinucleotide Repeats