CCG Repeats Research Articles

Repeat-associated non-AUG translation from antisense CCG repeats in fragile X tremor/ataxia syndrome.

Repeat-associated non-AUG (RAN) translation drives production of toxic proteins from pathogenic repeat sequences in multiple untreatable neurodegenerative disorders. Fragile X-associated tremor/ataxia syndrome (FXTAS) is one such condition, resulting from a CGG trinucleotide repeat expansion in the 5' leader sequence of the FMR1 gene. RAN proteins from the CGG repeat accumulate in ubiquitinated inclusions in FXTAS patient brains and elicit toxicity. In addition to the CGG repeat, an antisense mRNA containing a CCG repeat is also transcribed from the FMR1 locus. We evaluated whether this antisense CCG repeat supports RAN translation and contributes to pathology in FXTAS patients. We generated a series of CCG RAN translation-specific reporters and utilized them to measure RAN translation from CCG repeats in multiple reading frames in transfected cells. We also developed antibodies against predicted CCG RAN proteins and used immunohistochemistry and immunofluorescence on FXTAS patient tissues to measure their accumulation and distribution. RAN translation from CCG repeats is supported in all 3 potential reading frames, generating polyproline, polyarginine, and polyalanine proteins, respectively. Their production occurs whether or not the natural AUG start upstream of the repeat in the proline reading frame is present. All 3 frames show greater translation at larger repeat sizes. Antibodies targeted to the antisense FMR polyproline and polyalanine proteins selectively stain nuclear and cytoplasmic aggregates in FXTAS patients and colocalize with ubiquitinated neuronal inclusions. RAN translation from antisense CCG repeats generates novel proteins that accumulate in ubiquitinated inclusions in FXTAS patients. Ann Neurol 2016;80:871-881.

Fluorescence Probe for Detecting CCG Trinucleotide Repeat DNA Expansion and Slip-Out.

Trinucleotide repeat expansion in genomic DNA causes severe neurodegenerative diseases. Fluorescence probes that bind to trinucleotide repeats have potential as diagnostic tools of trinucleotide repeat disorders. Here, we report a novel tricyclic ligand that binds to CCG trinucleotide repeat DNA. The expansion of the aromatic ring system of the 2-amino-1,8-naphthyridine chromophore from the bicyclic to the tricyclic improved the binding ability to the CCG/CCG motif without losing the selectivity and emissive character. The fluorescence sensitively decreased in response to binding to the CCG trinucleotide repeat. The degree of quenching depended on the number of CCG repeats. In addition, the fluorescence detection was applicable to CCG slip-out DNA.

Synthesis of 1H-pyrrolo[3,2-h]quinoline-8-amine derivatives that target CTG trinucleotide repeats

We describe a new molecular design, synthesis, and investigation of small molecules that bind to CTG trinucleotide repeats in DNA. 1H-Pyrrolo[3,2-h]quinoline-8-amine (PQA) has a tricyclic aromatic system with unique non-linear hydrogen-bonding surface complementary to thymine. We have synthesized a series of PQA derivatives with different alkylamino linkers. These PQAs showed binding to pyrimidine bulge DNAs and CNG (N=T and C) repeats depending on the linker structure, while quinoline derivatives lacking the pyrrole ring showed much lower binding affinity. PQA is a useful molecular unit for both CTG and CCG repeat binding.

Huntington's Disease: Relationship Between Phenotype and Genotype.

Huntington's disease (HD) is an autosomal dominant inherited neurodegenerative disease with the typical manifestations of involuntary movements, psychiatric and behavior disorders, and cognitive impairment. It is caused by the dynamic mutation in CAG triplet repeat number in exon 1 of huntingtin (HTT) gene. The symptoms of HD especially the age at onset are related to the genetic characteristics, both the CAG triplet repeat and the modified factors. Here, we reviewed the recent advancement on the genotype-phenotype relationship of HD, mainly focus on the characteristics of different expanded CAG repeat number, genetic modifiers, and CCG repeat number in the 3' end of CAG triplet repeat and their effects on the phenotype. We also reviewed the special forms of HD (juvenile HD, atypical onset HD, and homozygous HD) and their phenotype-genotype correlations. The review will aid clinicians to predict the onset age and disease course of HD, give the genetic counseling, and accelerate research into the HD mechanism.

Short CCG repeat in huntingtin gene is an obstacle for replicative DNA polymerases, potentially hampering progression of replication fork.

Trinucleotide repeats (TNRs) are highly unstable in genomes, and their expansions are linked to human disorders. DNA replication is reported to be involved in TNR instability, but the current models are insufficient in explaining TNR expansion is induced during replication. Here, we investigated replication fork progression across huntingtin (HTT)-gene-derived fragments using an Escherichia coli oriC plasmid DNA replication system. We found most of the forks to travel smoothly across the HTT fragments even when the fragments had a pathological length of CAG/CTG repeats (approximately 120 repeats). A little fork stalling in the fragments was observed, but it occurred within a short 3'-flanking region downstream of the repeats. This region contains another short TNR, (CCG/CGG)7 , and the sense strand containing CCG repeats appeared to impede the replicative DNA polymerase Pol III. Examining the behavior of the human leading and lagging replicative polymerases Pol epsilon (hPolε) and Pol delta (hPolδ) on this sequence, we found hPolδ replicating DNA across the CCG repeats but hPolε stalling at the CCG repeats even if the secondary structure is eliminated by a single-stranded binding protein. These findings offer insights into the distinct behavior of leading and lagging polymerases at CCG/CGG repeats, which may be important for understanding the process of replication arrest and genome instability at the HTT gene.

The Significance of Fragile X Mental Retardation Gene 1 CGG Repeat Sizes in the Normal and Intermediate Range in Women With Primary Ovarian Insufficiency

Primary ovarian insufficiency (POI) refers to the cessation of menses before the age of 40 years and occurs in 1% to 2% of women. The specific cause of POI is unknown in the majority of cases. Known causes include gene mutations of fragile X mental retardation 1 (FMR1), a gene located on the X chromosome. This gene codes for a protein essential for normal cognitive development and female reproductive function. FMR1 contains a CCG trinucleotide segment in an untranslated region of its DNA that is repeated less than 45 times in normal individuals (normal range of repeats). Mutation of FMR1 results in abnormal expansion of an unstable CGG triplet, leading to impaired cognitive and reproductive function. Between 55 and 200 CCG repeats is called premutation; affected individuals with premutation are at risk for POI and further expansion of repeats in subsequent generations. People with 45 to 54 CCG repeats (intermediate range of repeats) are considered to be at borderline risk for POI and further expansion of repeats. This case-control study was designed to determine whether the risk of POI is associated with CGG repeat length of normal and intermediate range (up to 55 repeats) in a large cohort of Dutch women with idiopathic POI. The second aim of the study was to examine a possible association between the number of CGG repeats and age at first manifestation of POI as a measurement for the severity of POI. The study population was composed of 375 well-phenotyped Dutch women diagnosed with POI; control subjects were 3368 women with natural menopause at 40 years or older. The FMR1 CGG repeat number was determined by polymerase chain reaction amplification of DNA extracted from blood samples drawn from each patient. Fisher exact test was used to assess the prevalence of intermediate-size CGG repeats in POI cases and control subjects. Analysis of variance tested differences in mean CGG repeat lengths on alleles 1 and 2 between POI cases and control subjects. Allele 1 has the lowest triple repeat number, and allele 2 has the highest triple repeat number. There was no significant difference between POI cases and control subjects in the frequency of intermediate-size CGG repeats on allele 2 (POI 2.7 vs control subjects 3.8%; the odds ratio was 0.72, with a 95% confidence interval of 0.38–1.39; P = 0.38). Linear regression analysis showed no association between the number of CGG repeats and age at first POI manifestation (β = 20.019, P = 0.72). These data suggest that intermediate-size CGG repeats are not associated with risk of POI. Therefore, evaluation of normal and intermediate FMR1 repeat size appears to be of little or no value in the diagnostic workup of women affected by POI or in the prognostic assessment of women at risk of developing POI. Reasons for caution in interpreting these results are as follows: (1) FMR1 CGG repeat lengths in POI cases and control subjects were genotyped in 2 different laboratories; technical differences could have affected the results; (2) distributions of CGG repeats could vary among ethnic populations; (3) women with primary amenorrhea (n = 17) were included in the POI group. The last 2 possible limitations were unlikely because exclusion of data from nonwhite women or women with primary amenorrhea did not affect the results.

J38 Disease-associated Htt Haplotypes In The South African Population

Background Huntington disease (HD) is an inherited neurodegenerative disorder resulting from an expanded CAG-tract in the huntingtin (HTT) gene. Disease prevalence varies worldwide with the highest figures reported in populations of European ancestry. Average CAG-tract size in the general population and population-specific haplotypes have been previously associated with HD prevalence in different regions. HD in South Africa (SA) occurs in all three subpopulations; similar occurrence has been reported in the Caucasian and mixed ancestry groups, with a significantly lower estimate in the black subpopulation. Aims To assess the distribution of CAG-tract size in the South African general population and to determine what population-specific haplotypes are present in patient and control individuals. Methods Haplotypes were constructed based on the genotypes of 96 SNPs across the HTT gene, for 72 affected and 311 unaffected chromosomes. CAG-sizing was performed for over 1000 individuals taken from the general population and representative of the three subpopulations. The polymorphic CCG repeat adjacent to the CAG-tract was also investigated in the control cohort. Results Expanded alleles from Caucasian and mixed ancestry patients were predominantly associated with haplogroup A, signifying a similar European origin; while those from black patients were found on haplogroup B suggesting distinct origins of the mutation. In addition, average CAG-tract size in the general population could be associated with reported minimum prevalence estimates. Conclusion This data is crucial to the understanding of the genetic background of the HD gene in African populations and may contribute to the development of silencing therapeutics for HD patients.

Investigation of optimum concentrations of betaine for improving the resolution of sequencing G-C rich DNA with trinucleotide repeats

To develop an optimal sequencing system which can improve the resolution of sequencing G-C rich DNA with abundant trinucleotide repeats by applying concentration gradients of betaine to the Sanger sequencing system. Concentration gradients of betaine were introduced into the sequencing system by taking the 5' terminal of Nogo-B cDNA (Am-Nogo-B) (G-C%=72%, without trinucleotide repeats) and 5' terminal of Huntingtin cDNA (Am-HTT) (G-C%=74%, with abundant CAG and CCG repeats) the results of sequencing were compared. The optimum concentration of betaine for sequencing Am-Nogo-B has differed from that for Am-HTT. Result of sequencing Am-Nogo-B has achieved the best quality when the concentration of betaine was at 0.8-1.2 mol/L, whereas the result of sequencing Am-HTT obtained the best quality when the concentration of betaine was at 1.6 -2.4 mol/L. The results were reproducible. G-C rich DNA with similar G-C% required different concentrations of betaine in the sequencing system due to base pair compositions. The sequencing system developed for improving the resolution of sequencing of G-C rich DNA with abundant trinucleotide repeats can be used as a reference for similar studies.

Chromosome fragility and the abnormal replication of the FMR1 locus in fragile X syndrome

Fragile X Syndrome (FXS) is a learning disability seen in individuals who have >200 CGG•CCG repeats in the 5' untranslated region of the X-linked FMR1 gene. Such alleles are associated with a fragile site, FRAXA, a gap or constriction in the chromosome that is coincident with the repeat and is induced by folate stress or thymidylate synthase inhibitors like fluorodeoxyuridine (FdU). The molecular basis of the chromosome fragility is unknown. Previous work has suggested that the stable intrastrand structures formed by the repeat may be responsible, perhaps via their ability to block DNA synthesis. We have examined the replication dynamics of normal and FXS cells with and without FdU. We show here that an intrinsic problem with DNA replication exists in the FMR1 gene of individuals with FXS even in the absence of FdU. Our data suggest a model for chromosome fragility in FXS in which the repeat impairs replication from an origin of replication (ORI) immediately adjacent to the repeat. The fact that the replication problem occurs even in the absence of FdU suggests that this phenomenon may have in vivo consequences, including perhaps accounting for the loss of the X chromosome containing the fragile site that causes Turner syndrome (45, X0) in female carriers of such alleles. Our data on FRAXA may also be germane for the other FdU-inducible fragile sites in humans, that we show here share many common features with FRAXA.

The Mismatch Repair Protein MSH2 is Rate Limiting for Repeat Expansion in a Fragile X Premutation Mouse Model

Fragile X-associated tremor and ataxia syndrome, Fragile X-associated primary ovarian insufficiency, and Fragile X syndrome are Repeat Expansion Diseases caused by expansion of a CGG•CCG-repeat microsatellite in the 5 UTR of the FMR1 gene. To help understand the expansion mechanism responsible for these disorders, we have crossed mice containing∼147 CGG•CCG repeats in the endogenous murine Fmr1 gene with mice containing a null mutation in the gene encoding the mismatch repair protein MSH2. MSH2 mutations are associated with elevated levels of generalized microsatellite instability. However, we show here for the first time that in the FX mouse model, all maternally and paternally transmitted expansions require Msh2. Even the loss of one Msh2 allele reduced the intergenerational expansion frequency significantly. Msh2 is also required for all somatic expansions and loss of even one functional Msh2 allele reduced the extent of somatic expansion in some organs. Tissues with lower levels of MSH2 were more sensitive to the loss of a single Msh2 allele. This suggests that MSH2 is rate limiting for expansion in this mouse model and that MSH2 levels may be a key factor that accounts for tissue-specific differences in expansion risk.

The Trouble with Triples: Elucidating the Behavior of Trinucleotide Repeats in Chromatin

Trinucleotide repeats (TNRs) occur throughout the genome and their expansion can affect varied cellular processes such as gene expression, mRNA processing, and protein folding. TNR expansion, facilitated by formation of stable non-canonical secondary structures (e.g. hairpins), has been linked to several neurodegenerative diseases, such as Huntington's Disease, Myotonic Dystrophy (both caused by expansion of CAG•CTG repeats), and Fragile X Mental Retardation (caused by expansion of CGG•CCG repeats). TNR structure and expansion has been studied in vitro using both oligonucleotides and TNRs incorporated into plasmids; however, genomic DNA is packaged into chromatin, and little is know about the effect of packaging on the ability of repetitive DNA to expand. Previous studies have shown that disease-length, expanded CAG•CTG repeats readily incorporate into the basic unit of chromatin packing, the nucleosome core particle (NCP), composed of 146 base pairs of DNA wrapped around a core of eight histone proteins. However, long CGG•CCG repeats exclude NCP formation. Here, we seek to investigate not only the properties associated with shorter repeats (those that have not expanded) incorporated into NCPs, but also the effect of the flanking, disease-associated gene sequence. To assess the global forces regulating interaction between the TNRs and the histone core, we performed competitive nucleosome exchanges to determine the efficiency with which various TNR sequences incorporate into NCPs. We then used enzymatic and chemical probing to determine the effect of histone occupancy on the TNRs, including the formation of possible non-canonical structures. Understanding the intricacies underlying the interaction between unexpanded TNRs and the histone core is important to understanding how TNRs expand in the genome.

Erratum: Haplotype analysis of the CAG and CCG repeats in 21 Brazilian families with Huntington’s disease

Erratum: Haplotype analysis of the CAG and CCG repeats in 21 Brazilian families with Huntington’s disease

Haplotype analysis of the CAG and CCG repeats in 21 Brazilian families with Huntington’s disease

We studied the allelic profile of CAG and CCG repeats in 61 Brazilian individuals in 21 independent families affected by Huntington's disease (HD). Thirteen individuals had two normal alleles for HD, two had one mutable normal allele and no HD phenotype, and forty-six patients carried at least one expanded CAG repeat allele. Forty-five of these individuals had one expanded allele and one individual had one mutable normal allele (27 CAG repeats) and one expanded allele (48 CAG repeats). Eleven of these forty-five subjects had a mutant allele with reduced penetrance, and thirty-four patients had a mutant allele with complete penetrance. Inter- and intragenerational investigations of CAG repeats were also performed. We found a negative correlation between the number of CAG repeats and the age of disease onset (r=-0.84; P<0.001) and no correlation between the number of CCG repeats and the age of disease onset (r=0.06). We found 40 different haplotypes and the analysis showed that (CCG)(10) was linked to a CAG normal allele in 19 haplotypes and to expanded alleles in two haplotypes. We found that (CCG)(7) was linked to expanded CAG repeats in 40 haplotypes (95.24%) and (CCG)(10) was linked to expanded CAG repeats in only two haplotypes (4.76%). Therefore, (CCG)(7) was the most common allele in HD chromosomes in this Brazilian sample. It was also observed that there was a significant association of (CCG)(7) with the expanded CAG alleles (χ(2)=6.97, P=0.0084). Worldwide, the most common CCG alleles have 7 or 10 repeats. In Western Europe, (CCG)(7) is the most frequent allele, similarly to our findings.

Somatic Expansion in Mouse and Human Carriers of Fragile X Premutation Alleles

Repeat expansion diseases result from expansion of a specific tandem repeat. The three fragile X-related disorders (FXDs) arise from germline expansions of a CGG•CCG repeat tract in the 5' UTR (untranslated region) of the fragile X mental retardation 1 (FMR1) gene. We show here that in addition to germline expansion, expansion also occurs in the somatic cells of both mice and humans carriers of premutation alleles. Expansion in mice primarily affects brain, testis, and liver with very little expansion in heart or blood. Our data would be consistent with a simple two-factor model for the organ specificity. Somatic expansion in humans may contribute to the mosaicism often seen in individuals with one of the FXDs. Because expansion risk and disease severity are related to repeat number, somatic expansion may exacerbate disease severity and contribute to the age-related increased risk of expansion seen on paternal transmission in humans. As little somatic expansion occurs in murine lymphocytes, our data also raise the possibility that there may be discordance in humans between repeat numbers measured in blood and that present in brain. This could explain, at least in part, the variable penetrance seen in some of these disorders.

Purifying Selection Bias against Microsatellites in Gene Rich Segmental Duplications in the Rice Genome.

Little data is available on microsatellite dynamics in the duplicated regions of the rice genome, even though efforts have been made in the past to align genome sequences of its two sub-species. Based on the coordinates of duplicated sequences in the indica genome as available in the public domain, we identified microsatellites in these regions. CCG and GAAAA repeats occurred most frequently. In all, 259 microsatellites could be identified in the duplicated sequences using the criteria of minimum 90% alignability spread over a minimum of 1 Kb sequence. More than 25% of the repeats in duplicated regions occurred in the genic sequences. Only 45 (17%) of these 259 microsatellites were found conserved in the duplicated paralogues. Among these repeats, 40% maintained both sequence and length conservation. The effect of mutability of nearby regions could also be clearly seen in microsatellite regions. The overall purpose of this study was to investigate, whether microsatellites follow an independent course of evolutionary dynamics subsequent to events like genome reshuffling that simply drives these elements to different locations in the genome. To the best of our knowledge, this is the first comprehensive analysis of microsatellite conservation in the duplicated regions of any genome.

Crystallographic characterization of CCG repeats

CCG repeats are highly over-represented in exons of the human genome. Usually they are located in the 5′ UTR but are also abundant in translated sequences. The CCG repeats are associated with three tri-nucleotide repeat disorders: Huntington’s disease, myotonic dystrophy type 1 and chromosome X-linked mental retardation (FRAXE). In this study, we present two crystal structures containing double-stranded CCG repeats: one of an RNA in the native form, and one containing LNA nucleotides. Both duplexes form A-helices but with strands slipped in the 5′ (native structure) or the 3′ direction (LNA-containing structure). As a result, one of two expected C-C pairs is eliminated from the duplex. Each of the three observed C-C pairs interacts differently, forming either one weak H-bond or none. LNA nucleotides have no apparent effect on the helical parameters but the base stacking is increased compared to the native duplex and the distribution of electrostatic potential in the major groove is changed. The CCG crystal structures explain the thermodynamic fragility of CCG runs and throw light on the observation that the MBNL1 protein recognises CCG runs, as well as CUG and CAG, but not the relatively stable CGG repeats.

Variants in Exon 11 of MEF2A Gene and Coronary Artery Disease: Evidence from a Case-Control Study, Systematic Review, and Meta-Analysis

BackgroundCoronary artery disease (CAD) is the most common heart disease worldwide. Association of CAD with variants in the myocyte enhancer factor 2A (MEF2A) gene, the first identified CAD-causing gene, has attracted special attention but the results are controversial. We aimed to evaluate this genetic association via a case-control study and meta-analysis.Methodology/Principal FindingsWe performed a case-control association study to investigate the relationship between variations in exon 11 of MEF2A gene and CAD in 1045 sporadic patients and 1008 controls enrolled angiographically among southern Chinese population, and then the data from this study were compared and discussed in a systematic review and meta-analysis with all available published studies on MEF2A gene and CAD. In total, eight variants were identified (21-bp deletion, CAG repeats, CCG repeats, a CCA deletion and four SNPs). No significant link was observed between the common (CAG)n polymorphism and CAD, whereas the rare 21-bp deletion was detected only in five affected individuals. The meta-analysis of (CAG)n polymorphism and CAD risk, including nine studies with 3801 CAD patients and 4020 controls, also provided no convincing evidence for the genetic association, even upon stratification by race (mainly Whites and Chinese). However, the 21-bp deletion was regarded as a potentially logical, albeit undetermined, candidate for CAD in the following systematic review.Conclusions/SignificanceOur findings failed to demonstrate a correlation between (CAG)n polymorphism with CAD, however, we concluded that the rare 21-bp deletion might have a more compelling effect on CAD than the common (CAG)n polymorphism, and MEF2A genetic variant might be a rare but specific cause of CAD/MI.

Analysis of SSRs Information in Capsicum spp. from EST Database

Abstract SSR markers are useful in pepper linkage mapping and gene location. 446 SSR markers have been reported, but they are insufficient. It is costly to develop SSR markers from DNA library, whereas it seems much easy to find in EST sequences in the GenBank of pepper through internet. In this study, attempts have been made to develop SSR markers in the EST sequences by using bioinformatics. EST sequences were trimmed by ‘est-trimmer.pr software, while 116915EST sequences were obtained without poly ‘A’ or poly ‘T’, ranged between 100 and 700 bp. Using ‘e-PCR’ and ‘del.pl’ softwares, SSR sequences were identified. 2 508 micro satellite loci (larger than 20 repeats) were established and 755 SSR primers were designed using SSR finder software and Primer 3 software. There were 498 (0.43%) mono-, 1 026 (0.89%) di-, 518 (0.45%) tn-, 245 (0.21%) tetra-, 114 (0.10%) penta-, and 107 (0.09%) hexa-nucleotide SSRs. The estimated frequency of SSRs was approximately 1/25.12 kb. According to the distribution of SSRs in pepper, the mean length of pepper SSRs was 22.68 bp and the adenine rich repeats such as A/T, AG, AT, AAG, AAAT, and AAAC were predominant in each type of SSRs (mono-, di-, tri-, tetra-, penta-, and hexa-), whereas the C/G, CG, CCG repeats were less abundant. 210 primers were tested in 8 pepper cultivars and the PCR result revealed the existence of polymorphism among 127 (60.48%) SSR primers within 8 pepper cultivars. It is confirmed that pepper EST database could be efficiently exploited for availability of SSR markers.

Characterization, development and mapping of Unigene-derived microsatellite markers in sorghum [Sorghum bicolor (L.) Moench

Molecular variation within known genes controlling specific functions provide candidate gene-based markers which are tightly linked with the trait of interest. Unigene-derived microsatellite markers, with their unique identity and positions, offer the advantage of unraveling variation in the expressed component of the genome. We characterized ≥12-bp-long microsatellite loci from 13,899 unique sequences of sorghum [Sorghum bicolor (L.) Moench] available in the NCBI unigene database for their abundance and possible use in sorghum breeding. Analysis of 12,464 unigenes (≥200-bp) using MISA software identified 14,082 simple sequence repeats (SSRs) in 7,370 unigenes, from which 1,519 unigene SSR markers were developed. The average frequency of SSR was 1 per1.6 kb and 1.0 per 1.1 unigene; hexamers followed by trimers were found in abundance, of which 33.3% AT-rich and CCG repeats were the most abundant. Of the 302 unigene SSRs tested, 60 (19.8%) were polymorphic between the two parents, M35-1 and B35 of a recombinant inbred line (RIL) mapping population. A mapping population consisting of 500 RILs was developed using the above two parents, and a subset of random 245 RILs was used for genotyping with polymorphic SSRs. We developed a linkage map containing 231 markers, of which 228 (174 genomic and 54 genic) were microsatellites and three were morphological markers. Markers were distributed over 21 linkage groups, and spanned a genetic distance of 1235.5 cM. This map includes 81 new SSRs, of which 35 (21 unigene and 14 genomic) were developed in the present study and 46 from other studies. The order of the SSR markers mapped in the present study was confirmed physically by BLAST search against the whole-genome shotgun sequence of sorghum. Many unigene sequences used for marker development in this study include genes coding for important regulatory proteins and functional proteins that are involved in stress-related metabolism. The unigene SSR markers used together with other SSR markers to construct the sorghum genetic map will have applications in studies on comparative mapping, functional diversity analysis and association mapping, and for quantitative trait loci detection for drought and other agronomically important traits in sorghum.

Intermediate alleles at the FRAXA and FRAXE loci in Parkinson’s disease

Background It is debatable whether the size of triplet repeats of the fragile X mental retardation genes FMR1 and FMR2 (found at the FRAXA and FRAXE loci) is associated with Parkinson’s disease (PD). The aims of the current study were to investigate the relationship between these genes and PD and to determine whether these genes affected clinical manifestations of PD. Methods We recruited 206 PD patients and 227 control subjects from southern Spain. All subjects were screened for the size of CGG and CCG repeats at the FRAXA and FRAXE loci, respectively. Clinical features of each patient were examined in detail to study possible association between these features and genotype. Results Frequencies of FRAXA and FRAXE intermediate alleles were similar between PD and control groups. Clinical characteristics in PD patients, including severity of the disease, motor and non-motor symptoms, and motor complications and fluctuations were not affected by intermediate alleles at either locus. Two patients carrying FRAXA premutation alleles were identified showing clinical manifestations indistinguishable from idiopathic PD. Conclusions FRAXA and FRAXE intermediate alleles do not seem to affect the risk for PD or modify clinical features in PD patients.