Trinucleotide Repeat Sequences Research Articles

Spermidine treatment: induction of autophagy but also apoptosis?

Machado-Joseph disease (MJD), also known as spinocerebellar ataxia type 3, is a fatal neurodegenerative disease that causes loss of balance and motor co-ordination, eventually leading to paralysis. It is caused by the autosomal dominant inheritance of a long CAG trinucleotide repeat sequence within the ATXN3 gene, encoding for an expanded polyglutamine (polyQ) repeat sequence within the ataxin-3 protein. Ataxin-3 containing an expanded polyQ repeat is known to be highly prone to intraneuronal aggregation, and previous studies have demonstrated that protein quality control pathways, such as autophagy, are impaired in MJD patients and animal models of the disease. In this study, we tested the therapeutic potential of spermidine on zebrafish and rodent models of MJD to determine its capacity to induce autophagy and improve functional output. Spermidine treatment of transgenic MJD zebrafish induced autophagy and resulted in increased distances swum by the MJD zebrafish. Interestingly, treatment of the CMVMJD135 mouse model of MJD with spermidine added to drinking water did not produce any improvement in motor behaviour assays, neurological testing or neuropathology. In fact, wild type mice treated with spermidine were found to have decreased rotarod performance when compared to control animals. Immunoblot analysis of protein lysates extracted from mouse cerebellar tissue found little differences between the groups, except for an increased level of phospho-ULK1 in spermidine treated animals, suggesting that autophagy was indeed induced. As we detected decreased motor performance in wild type mice following treatment with spermidine, we conducted follow up studies into the effects of spermidine treatment in zebrafish. Interestingly, we found that in addition to inducing autophagy, spermidine treatment also induced apoptosis, particularly in wild type zebrafish. These findings suggest that spermidine treatment may not be therapeutically beneficial for the treatment of MJD, and in fact warrants caution due to the potential negative side effects caused by induction of apoptosis.

Evidence for a fragile X messenger ribonucleoprotein 1 (FMR1) mRNA gain-of-function toxicity mechanism contributing to the pathogenesis of fragile X-associated premature ovarian insufficiency.

Fragile X-associated premature ovarian insufficiency (FXPOI) is among a family of disorders caused by expansion of a CGG trinucleotide repeat sequence located in the 5' untranslated region (UTR) of the fragile X messenger ribonucleoprotein 1 (FMR1) gene on the X chromosome. Women with FXPOI have a depleted ovarian follicle population, resulting in amenorrhea, hypoestrogenism, and loss of fertility before the age of 40. FXPOI is caused by expansions of the CGG sequence to lengths between 55 and 200 repeats, known as a FMRI premutation, however the mechanism by which the premutation drives disease pathogenesis remains unclear. Two main hypotheses exist, which describe an mRNA toxic gain-of-function mechanism or a protein-based mechanism, where repeat-associated non-AUG (RAN) translation results in the production of an abnormal protein, called FMRpolyG. Here, we have developed an in vitro granulosa cell model of the FMR1 premutation by ectopically expressing CGG-repeat RNA and FMRpolyG protein. We show that expanded CGG-repeat RNA accumulated in intranuclear RNA structures, and these aggregates were able to cause significant granulosa cell death independent of FMRpolyG expression. Using an innovative RNA pulldown, mass spectrometry-based approach we have identified proteins that are specifically sequestered by CGG RNA aggregates in granulosa cells in vitro, and thus may be deregulated as consequence of this interaction. Furthermore, we have demonstrated reduced expression of three proteins identified via our RNA pulldown (FUS, PA2G4 and TRA2β) in ovarian follicles in a FMR1 premutation mouse model. Collectively, these data provide evidence for the contribution of an mRNA gain-of-function mechanism to FXPOI disease biology.

Beyond the CAG triplet number: exploring potential predictors of delayed age of onset in Huntington's disease.

Huntington's disease (HD) is a genetic neurodegenerative disease characterized by cognitive, motor, and psychiatric dysfunction. It is caused by an expansion of the trinucleotide repeat sequence cytosine-adenine-guanine (CAG) in the Huntingtin gene on chromosome 4. Onset typically occurs in the fourth or fifth decade, ranging from childhood to late adulthood. The CAG triplet number is generally inversely proportional to the age of onset (AOO), but the repeat number only accounts for ∼70% of the variability in AOO. Several studies demonstrated the impact of genetic modifiers on age of disease onset. In addition to genetics, we also explored the demographic, anamnestic, and socio-environmental factors that can affect AOO, to help us understand the non-genetic variability of age of onset in HD. We analyzed the retrospective data of the ENROLL-HD global registry study, particularly focusing on the continuum of ages, to include sociodemographic, genetic, and anamnestic psychobehavioral variables in a multivariate regression model aimed at identifying the potential predictors of age of motor onset (n = 5053). We ran the same regression model in the sample of subjects who had the same number of triplets (41 CAG, n = 593) and in the sample whose family history was absent/unknown (n = 630). Patients with delayed onset more frequently have unknown/missing family history, are married or widowed, live in larger urbanized contexts and have a lower educational level. Individuals with earlier onset more frequently develop psychobehavioral symptoms. In the past, the HD gene was considered the epitome of genetic determinism. Our results are consistent with recent evidence that other factors might modulate its impact. These findings allow characterizing the determinants of AOO beyond the CAG expansions and provide valuable information for stratifying patients for future clinical trial designs.

Huntington disease update: new insights into the role of repeat instability in disease pathogenesis.

The causative mutation for Huntington disease (HD), an expanded trinucleotide repeat sequence in the first exon of the huntingtin gene (HTT) is naturally polymorphic and inevitably associated with disease symptoms above 39 CAG repeats. Although symptomatic medical therapies for HD can improve the motor and non-motor symptoms for affected patients, these drugs do not stop the ongoing neurodegeneration and progression of the disease, which results in severe motor and cognitive disability and death. To date, there is still an urgent need for the development of effective disease-modifying therapies to slow or even stop the progression of HD. The increasing ability to intervene directly at the roots of the disease, namely HTT transcription and translation of its mRNA, makes it necessary to understand the pathogenesis of HD as precisely as possible. In addition to the long-postulated toxicity of the polyglutamine-expanded mutant HTT protein, there is increasing evidence that the CAG repeat-containing RNA might also be directly involved in toxicity. Recent studies have identified cis- (DNA repair genes) and trans- (loss/duplication of CAA interruption) acting variants as major modifiers of age at onset (AO) and disease progression. More and more extensive data indicate that somatic instability functions as a driver for AO as well as disease progression and severity, not only in HD but also in other polyglutamine diseases. Thus, somatic expansions of repetitive DNA sequences may be essential to promote respective repeat lengths to reach a threshold leading to the overt neurodegenerative symptoms of trinucleotide diseases. These findings support somatic expansion as a potential therapeutic target in HD and related repeat expansion disorders.

Efficient and Precise Processing of the Optimized Primary Artificial MicroRNA in a Huntingtin-Lowering Adeno-Associated Viral Gene Therapy In Vitro and in Mice and Nonhuman Primates.

Huntington's disease is a fatal neurodegenerative disorder caused by an inherited mutation in the huntingtin (HTT) gene comprising an expanded cytosine-adenine-guanine (CAG) trinucleotide repeat sequence that results in a pathogenic huntingtin protein. Adeno-associated viral (AAV) gene therapy containing a primary artificial microRNA (pri-amiRNA) specifically targeting HTT messenger RNA (mRNA) has the potential to provide long-lasting therapeutic benefit, through durable reduction of mutant HTT expression after a single administration. The efficiency and precision of processing of the pri-amiRNA precursor to the mature guide (G) strand by transduced cells are critical for specific and potent HTT mRNA lowering. The selection of the optimized pri-amiRNA comprised a series of in vitro studies followed by in vivo studies in small and then large mammals. Our studies demonstrate the predictivity of certain cell culture systems and rodent models for nonhuman primates with respect to some, but not all key features of pri-amiRNA processing. In addition, our results show that the processing of pri-amiRNAs to the mature guide strand can differ greatly across different scaffolds and sequences while providing the same levels of target lowering. Importantly, our data demonstrate that there is a combinatorial effect of guide and passenger (P) strand sequences, together with the scaffold, on pri-amiRNA processing, with different guide and passenger strand sequences within the same scaffold dramatically altering pri-amiRNA processing. Taken together, our results highlight the importance of optimizing not only target lowering but also the efficiency and precision of pri-amiRNA processing in vitro, in rodents and in large mammals to identify the most potent and selective AAV gene therapy that harnesses the endogenous microRNA (miRNA) biogenesis pathway for target lowering without perturbing the endogenous cellular miRNA profile. The optimized pri-amiRNA was selected with this focus on efficiency and precision of pri-amiRNA processing in addition to its pharmacological activity on HTT mRNA lowering and general tolerability in vivo.

Folate Deficiency Triggers the Abnormal Segregation of a Region With Large Cluster of CG-Rich Trinucleotide Repeats on Human Chromosome 2

Folate deficiency is associated with a broad range of human disorders, including anemia, fetal neural tube defects, age-associated dementia and several types of cancer. It is well established that a subgroup of rare fragile sites (RFSs) containing expanded CGG trinucleotide repeat (TNR) sequences display instability when cells are deprived of folate. However, given that folate sensitive RFSs exist in a very small percentage of the population, they are unlikely to be the cause of the widespread health problems associated with folate deficiency. We hypothesized that folate deficiency could specifically affect DNA replication at regions containing CG-rich repeat sequences. For this, we identified a region on human chromosome 2 (Chr2) comprising more than 300 CG-rich TNRs (termed “FOLD1”) by examining the human genome database. Via the analysis of chromosome shape and segregation in mitosis, we demonstrate that, when human cells are cultured under folate stress conditions, Chr2 is prone to display a “kink” or “bending” at FOLD1 in metaphase and nondisjunction in anaphase. Furthermore, long-term folate deprivation causes Chr2 aneuploidy. Our results provide new evidence on the abnormalities folate deficiency could cause in human cells. This could facilitate future studies on the deleterious health conditions associated with folate deficiency.

Sequence-dependent nucleosome formation in trinucleotide repeats evaluated by in vivo chemical mapping

Trinucleotide repeat sequences (TRSs), consisting of 10 unique classes of repeats in DNA, are members of microsatellites and abundantly and non-randomly distributed in many eukaryotic genomes. The lengths of TRSs are mutable, and the expansions of several TRSs are implicated in hereditary neurological diseases. However, the underlying causes of the biased distribution and the dynamic properties of TRSs in the genome remain elusive. Here, we examined the effects of TRSs on nucleosome formation in vivo by histone H4–S47C site-directed chemical cleavages, using well-defined yeast minichromosomes in which each of the ten TRS classes resided in the central region of a positioned nucleosome. We showed that (AAT)12 and (ACT)12 act as strong nucleosome-promoting sequences, while (AGG)12 and (CCG)12 act as nucleosome-excluding sequences in vivo. The local histone binding affinity scores support the idea that nucleosome formation in TRSs, except for (AGG)12, is mainly determined by the affinity for the histone octamers. Overall, our study presents a framework for understanding the nucleosome-forming abilities of TRSs.

Brief Review on Some Neurological Diseases Which Have Association with Trinucleotide Repeat Sequences

Trinucleotide repeat sequences can be seen in some neurological diseases. This study will briefly review some of these neurological diseases and the associated trinucleotide repeat sequences.

Cross genera transferability of microsatellite markers from other members of family Bignoniaceae to Tecomella undulata (Sm.) Seem

Transferability of SSR markers from related species/genera is a rapid and cost-effective method to enhance genomic database of genetically neglected crops. Monotypic genus Tecomella undulata, a pharmacologically important endangered timber tree, found in hyper arid regions is one such genetic resource limited species, wherein neither SSR identification nor cross transferability studies have been initiated. Transferability of 69 cross-genera SSR primers selected from other members of family bignoniaceae (Incarvillea sinensis, I. mairei, Jacaranda copaia, Tabebuia aurea and Arrabidaea chica) showed 40.58% (28 primers) transferability amplifying 1–10 amplicons ranging in the size from 80to 600 bp in 24 accessions of T. undulata. Per cent marker transferability varied from 66.67% (A. chica) to 38.89% (J. copaia) among the genera tested while no transferable markers could be identified from I. sinensis. Transferability of simple di-/tri-nucleotide repeat (34.2–37.5%) and complex nucleotide sequence (60.0%) based SSR motifs were higher as compared to penta-/hexa-nucleotide based repeat motifs. Within the 28 transferable markers, 26 (92.86%) were polymorphic while 2 (7.14%) were monomorphic. Average number of alleles per primer was 5.39 while average polymorphic alleles per locus were 5.11. The PIC values of SSR markers ranged from 0.23 to 0.85 with an average of 0.59. Efficiency of the identified cross species SSR markers was tested for diversity analysis using a set of 24 trees (8 each of yellow, orange and red flower colour morphotypes). The 24 samples clustered into six groups with similarity coefficient ranging from 0.29 to 0.67, while six accessions formed distinct out groups. Distribution of accessions in the SSR dendrogram showed no correlation with flower colour. More diversity (99%) was observed within populations compared to that existing between populations (1%). The present study can enrich the genomic background of T. undulata by identifying suitable polymorphic markers from confamiliar species that can be applied for genetic diversity studies, mapping of QTLs and cultivar identification as well.

Folate stress induces SLX1- and RAD51-dependent mitotic DNA synthesis at the fragile X locus in human cells

Folate deprivation drives the instability of a group of rare fragile sites (RFSs) characterized by CGG trinucleotide repeat (TNR) sequences. Pathological expansion of the TNR within the FRAXA locus perturbs DNA replication and is the major causative factor for fragile X syndrome, a sex-linked disorder associated with cognitive impairment. Although folate-sensitive RFSs share many features with common fragile sites (CFSs; which are found in all individuals), they are induced by different stresses and share no sequence similarity. It is known that a pathway (termed MiDAS) is employed to complete the replication of CFSs in early mitosis. This process requires RAD52 and is implicated in generating translocations and copy number changes at CFSs in cancers. However, it is unclear whether RFSs also utilize MiDAS and to what extent the fragility of CFSs and RFSs arises by shared or distinct mechanisms. Here, we demonstrate that MiDAS does occur at FRAXA following folate deprivation but proceeds via a pathway that shows some mechanistic differences from that at CFSs, being dependent on RAD51, SLX1, and POLD3. A failure to complete MiDAS at FRAXA leads to severe locus instability and missegregation in mitosis. We propose that break-induced DNA replication is required for the replication of FRAXA under folate stress and define a cellular function for human SLX1. These findings provide insights into how folate deprivation drives instability in the human genome.

The newly developed genomic-SSR markers uncover the genetic characteristics and relationships of olive accessions.

BackgroundOlive (Olea europaea L.) is an important oil and fruit crop worldwide, owning a rich germplasm with a large number of cultivars. Simple sequence repeats (SSRs) are excellent markers and have been used for the identification of olive cultivars. However, the limited number of SSR markers and the occurrence of confusion on the names of cultivars, as well as the possible appearance of clonal variation make it difficult to identify cultivars and interpret relationships among olive cultivars.MethodSSR markers were designed based on trinucleotide repeat sequences by screening the whole genome of olive, and the polymorphic SSR markers were developed that were applied to the identification of 53 olive accessions. The genetic characteristics and relationships of these olive accessions were evaluated based on the developed SSR markers.ResultsTwenty-one highly polymorphic genomic-SSR markers were developed, covering most chromosomes of olive. These SSR markers could well distinguish all 53 olive accessions, confirming their effectiveness. DNA fingerprints of the 53 olive accessions were constructed based on the 21 SSR markers. The dendrogram clearly divided the tested accessions into two main groups, which was also supported by the results of principal coordinate analysis. A total of 31 private alleles were detected in 15 olive accessions, which reflected the genetic diversity within 53 olive accessions to some extent. Six homonymy cases were also clarified by genetic analysis. These results suggest that the newly developed olive SSR markers are informative for the exploitation, preservation and breeding of olive.

Hyperactivity, Memory Defects, and Craniofacial Abnormalities in Zebrafish fmr1 Mutant Larvae.

Fragile X syndrome (FXS) is a heritable mental retardation disease caused by unstable trinucleotide repeat sequences in FMR1. FXS is characterized by delayed development, hyperactivity, and autism behavior. Zebrafish is an excellent model to study FXS and the underlying function of fmr1. However, at present, fmr1 function is mainly studied via morpholinos or generated mutants using targeting induced local lesions in genomes. However, both of these methods generate off-target effects, making them suboptimal techniques for studying FXS. In this study, CRISPR/Cas9 technology was used to generate two zebrafish fmr1 mutant lines. High-throughput behavior analysis, qRT-PCR, and alcian blue staining experiments were employed to investigate fmr1 function. The fmr1 mutant line showed abnormal behavior, learning memory defects, and impaired craniofacial cartilage development. These features are similar to the human FXS phenotype, indicating that the fmr1 mutant generated in this study can be used as a new model for studying the molecular pathology of FXS. It also provides a suitable model for high-throughput screening of small molecule drugs for FXS therapeutics.

Molecular Crowding Effects on Stability and Kinetics of Trinucleotide Repeat Hairpins

Numerous genetic disorders arise from the propensity of certain repetitive DNA sequences to form intrastrand, non-helical structures, such as hairpins, due to extensive self-complementarity. Within the cellular environment, the formation of these non-helical structures occurs within highly crowded conditions. Using single-molecule FRET microscopy, the effect of molecular crowding on the stability and dynamics of individual DNA hairpins containing the trinucleotide repeat sequences (CAG)N and (CTG)N were explored. These repeat sequences have central mismatches within each repeat unit that reduce the stability of intrastrand contacts between repeat units in the stem, leading to highly dynamic behavior for their hairpins. The structural dynamics for (CAG)N and (CTG)N trinucleotide repeat hairpins were quantified in the presence of molecular crowding agents (polyethylene glycol; PEG) with different sizes. Analysis of the transitions rates between the unstructured and closer conformations shows that an increase in molecular crowding promotes the formation of the hairpins. Strikingly, the crowding agents induce a greater acceleration of hairpin melting and overall destabilization, which contrasts with observations from controls with fully paired DNA hairpins. Under these conditions, the high mismatch content of these repeat hairpins becomes more destabilizing in the presence of PEG. The findings indicate that molecular crowding may confer some protective benefit to genomic DNA by disrupting these deleterious structures at smaller repeat sizes.

Characterization and application of fluidic properties of trinucleotide repeat sequences by wax-on-plastic microfluidics.

Trinucleotide repeat (TNR) sequences introduce sequence-directed flexibility in the genomic makeup of all living species leading to unique non-canonical structure formation. In humans, the expansions of TNR sequences are responsible for almost 24 neurodegenerative and neuromuscular diseases because their unique structures disrupt cell functions. The biophysical studies of these sequences affect their electrophoretic mobility and spectroscopic signatures. Here, we demonstrate a novel strategy to characterize and discriminate the TNR sequences by monitoring their capillary flow in the absence of an external driving force using wax-on-plastic microchannels. The wax-on-plastic microfluidic system translates the sequence-directed flexibility of TNR into differential flow dynamics. Several variables were used to characterize sequences including concentration, single- vs. double-stranded samples, type of repeat sequence, length of the repeat sequence, presence of mismatches in duplex, and presence of metal ion. All these variables were found to influence the flow velocities of TNR sequences as these factors directly affect the structural flexibility of TNR at the molecular level. An overall trend was observed as the higher flexibility in the TNR structure leads to lower capillary flow. After testing samples derived from relevant cells harboring expanded TNR sequences, it is concluded that this approach may transform into a reagent-free and pump-free biosensing platform to detect microsatellite expansion diseases.

Limits of using oligonucleotides for allele-selective inhibition at trinucleotide repeat sequences – targeting the CAG repeat within ataxin-1

Trinucleotide repeats are responsible for many genetic diseases. Previous studies have shown that duplex RNAs (dsRNAs) can be used to target expression of a mutant repeat allele while leaving expression of the wild-type allele untouched, creating opportunities for allele-selective inhibition and better therapeutic outcomes. In contrast to successes with other genes, we report here that we cannot achieve allele-selective inhibition when targeting the expanded CAG repeat within Ataxin-1 (ATXN1), the cause of spinal cerebellar ataxia-1 (SCA1). The most likely explanation for this unfavorable outcome is that the mean CAG repeat number within wild-type ATXN1 is relatively high compared to other trinucleotide repeat diseases. Because the wild-type repeat number is high, it is likely that there is poor discrimination between the mutant and wild-type repeat and less opportunity for allele-selective inhibition across the entire spectrum of mutations found in SCA1 patients. Our data support the conclusion that the potential for multiple cooperative binding interactions is a critical factor governing allele-selective recognition of trinucleotide repeat genes by duplex RNAs. These results should be helpful in predicting which diseases and which patients are most likely to benefit from allele-selective targeting of expanded repeats.

Ratiometric electrochemical biosensor based on Exo III-Assisted recycling amplification for the detection of CAG trinucleotide repeats

Electrochemical detection of specific nucleic acid sequence remains a hot topic in current bioanalytical research. Here, a novel ratiometric electrochemical biosensor based on Exo III-assisted recycling amplification and graphene-modified electrode was fabricated for quantitative detection of trinucleotide repeat sequence d(CAG)n. The double-signals used are the hairpin DNAs labeled with ferrocene and methylene blue respectively as report DNAs, which can hybridize to target DNA. The hybridized DNA was digested by Exo III, resulting in the release of target and report fragments. The graphene-modified electrode can selectively adsorb the released report fragments to generate double electrochemical signals. The signal ratio (F/M) of ferrocene and methylene blue was used to determine the repeat length accurately: a linear relationship was found between F/M and numbers of repeats (n), F/M = 0.061 n + 1.97, with a correlation coefficient of 0.992. Moreover, any electrochemical signal can be used to test repeat concentration with detection limit of 0.22 pM. Therefore, this novel ratiometric electrochemical biosensor provided a reliable and efficient method for the analysis of d(CAG)n trinucleotide repeat and a potential simplified clinical tool for neurodegenerative diseases.

Long-Range Hairpin Slippage Reconfiguration Dynamics in Trinucleotide Repeat Sequences.

Trinucleotide repeat (TNR) sequences, which are responsible for several neurodegenerative genetic diseases, fold into hairpins that interfere with the protein machinery in replication or repair, thus leading to dynamic mutation -abnormal expansions of the genome. Despite their high thermodynamic stability, these hairpins can undergo configurational rearrangements, which may be crucial for continuous dynamic mutation. Here, we used CTG repeats as a model system to study their structural dynamics at the single-molecule level. A unique dynamic two-state configuration interchange was discovered over a wide range of odd-numbered CTG repeat sequences. Employing repeat-number-dependent kinetic analysis, we proposed a bulge translocation model, which is driven by the local instability and can be extended reasonably to longer (pathologically relevant) hairpins, implying the potential role in error accumulation in repeat expansion.

Folate deficiency drives mitotic missegregation of the human FRAXA locus

The instability of chromosome fragile sites is implicated as a causative factor in several human diseases, including cancer [for common fragile sites (CFSs)] and neurological disorders [for rare fragile sites (RFSs)]. Previous studies have indicated that problems arising during DNA replication are the underlying source of this instability. Although the role of replication stress in promoting instability at CFSs is well documented, much less is known about how the fragility of RFSs arises. Many RFSs, as exemplified by expansion of a CGG trinucleotide repeat sequence in the fragile X syndrome-associated FRAXA locus, exhibit fragility in response to folate deficiency or other forms of "folate stress." We hypothesized that such folate stress, through disturbing the replication program within the pathologically expanded repeats within FRAXA, would lead to mitotic abnormalities that exacerbate locus instability. Here, we show that folate stress leads to a dramatic increase in missegregation of FRAXA coupled with the formation of single-stranded DNA bridges in anaphase and micronuclei that contain the FRAXA locus. Moreover, chromosome X aneuploidy is seen when these cells are exposed to folate deficiency for an extended period. We propose that problematic FRAXA replication during interphase leads to a failure to disjoin the sister chromatids during anaphase. This generates further instability not only at FRAXA itself but also of chromosome X. These data have wider implications for the effects of folate deficiency on chromosome instability in human cells.

Common Chromosomal Fragile Sites-Conserved Failure Stories.

In order to pass on an intact copy of the genome during cell division, complete and faithful DNA replication is crucial. Yet, certain areas of the genome are intrinsically challenging to replicate, which manifests as high local mutation propensity. Such regions include trinucleotide repeat sequences, common chromosomal fragile sites (CFSs), and early replicating fragile sites (ERFSs). Despite their genomic instability CFSs are conserved, suggesting that they have a biological function. To shed light on the potential function of CFSs, this review summarizes the similarities and differences of the regions that challenge DNA replication with main focus on CFSs. Moreover, we review the mechanisms that operate when CFSs fail to complete replication before entry into mitosis. Finally, evolutionary perspectives and potential physiological roles of CFSs are discussed with emphasis on their potential role in neurogenesis.

A novel electrochemical method based on screen-printed electrodes and magnetic beads for detection of trinucleotide repeat sequence d(CAG)n

The combination of SPCE and magnetic beads simplifies the experimental procedure, which is useful for early diagnosis of trinucleotide repeat diseases.