scholarly journals Robust Preimplantation Genetic Testing of Huntington Disease by Combined Triplet-Primed PCR Analysis of the HTT CAG Repeat and Multi-Microsatellite Haplotyping

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Mingjue Zhao ◽  
Felicia Siew Hong Cheah ◽  
Arnold Sia Chye Tan ◽  
Mulias Lian ◽  
Gui Ping Phang ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Huntington Disease ◽  
Neurodegenerative Disorder ◽  
Cag Repeat ◽  
Pcr Analysis ◽  
Monogenic Disorder ◽  
Preimplantation Genetic Testing ◽  
Haplotype Phasing ◽  
Repeat Locus ◽  
Disease Haplotype

Abstract Huntington disease (HD) is a lethal neurodegenerative disorder caused by expansion of a CAG repeat within the huntingtin (HTT) gene. Disease prevention can be facilitated by preimplantation genetic testing for this monogenic disorder (PGT-M). We developed a strategy for HD PGT-M, involving whole genome amplification (WGA) followed by combined triplet-primed PCR (TP-PCR) for HTT CAG repeat expansion detection and multi-microsatellite marker genotyping for disease haplotype phasing. The strategy was validated and tested pre-clinically in a simulated PGT-M case before clinical application in five cycles of a PGT-M case. The assay reliably and correctly diagnosed all embryos, even where allele dropout (ADO) occurred at the HTT CAG repeat locus or at one or more linked markers. Ten of the 27 embryos analyzed were diagnosed as unaffected. Four embryo transfers were performed, two of which involved fresh cycle double embryo transfers and two were frozen-thawed single embryo transfers. Pregnancies were achieved from each of the frozen-thawed single embryo transfers and confirmed to be unaffected by amniocentesis, culminating in live births at term. This strategy enhances diagnostic confidence for PGT-M of HD and can also be employed in situations where disease haplotype phase cannot be established prior to the start of PGT-M.

scholarly journals A Case of Previously Unsuspected Huntington Disease Diagnosed at Autopsy

2017 ◽  
Vol 7 (1) ◽  
pp. 136-144
Author(s):  
Catherine R. Miller ◽  
Nobby C. Mambo ◽  
Jianli Dong ◽  
Gerald A. Campbell
Keyword(s):  
Genetic Testing ◽  
Huntington Disease ◽  
Clinical Symptoms ◽  
Neurodegenerative Disorder ◽  
Case Reports ◽  
Neuronal Loss ◽  
Cag Repeat ◽  
Cag Repeats ◽  
Psychiatric Disturbances ◽  
Personality Changes

Huntington disease (HD) is a neurodegenerative disorder with a worldwide prevalence of four to ten per 100 000. It is characterized by choreiform movements, behavioral/psychiatric disturbances, and eventual cognitive decline. Symptoms usually present between 30 and 50 years of age and the diagnosis is based on the combination of clinical symptoms, family history, and genetic testing. A variation of HD, juvenile Huntington disease (JHD), presents earlier, with more severe symptoms and with a worse prognosis. Symptoms are different in JHD, with personality changes and learning difficulties being the predominant presenting features. Seizures are common in JHD, and chorea is uncommon; movement disorders at presentation of JHD are predominantly nonchoreiform. The inheritance pattern for both HD and JHD is autosomal dominant and the disease is caused by an elongation of the CAG repeat in the huntingtin gene. There are many published case reports of Huntington disease that were confirmed at autopsy, but to our knowledge, there are no reports in the literature where the diagnosis of Huntington disease was first made at autopsy. We present a case of a 28-year-old African-American male who was in a state of neglect due to a lifetime of abuse, cognitive difficulties, and seizures, whose cause of death was pneumonia. The gross autopsy findings included bilateral caudate nucleus atrophy and lateral ventricular dilation. Microscopically, severe bilateral neuronal loss and gliosis of the caudate and putamen nuclei were seen. Genetic testing for the number of CAG repeats confirmed the diagnosis and was consistent with JHD.

scholarly journals Preimplantation Genetic Testing for Monogenic Disorders

Genes ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 871 ◽  
Author(s):  
Martine De Rycke ◽  
Veerle Berckmoes
Keyword(s):  
Genetic Testing ◽  
Whole Genome Amplification ◽  
State Of The Art ◽  
Snp Array ◽  
Genetic Data ◽  
Monogenic Disorder ◽  
Preimplantation Genetic Testing ◽  
Monogenic Disorders ◽  
The Cost ◽  
Concurrent Analysis

Preimplantation genetic testing (PGT) has evolved into a well-established alternative to invasive prenatal diagnosis, even though genetic testing of single or few cells is quite challenging. PGT-M is in theory available for any monogenic disorder for which the disease-causing locus has been unequivocally identified. In practice, the list of indications for which PGT is allowed may vary substantially from country to country, depending on PGT regulation. Technically, the switch from multiplex PCR to robust generic workflows with whole genome amplification followed by SNP array or NGS represents a major improvement of the last decade: the waiting time for the couples has been substantially reduced since the customized preclinical workup can be omitted and the workload for the laboratories has decreased. Another evolution is that the generic methods now allow for concurrent analysis of PGT-M and PGT-A. As innovative algorithms are being developed and the cost of sequencing continues to decline, the field of PGT moves forward to a sequencing-based, all-in-one solution for PGT-M, PGT-SR, and PGT-A. This will generate a vast amount of complex genetic data entailing new challenges for genetic counseling. In this review, we summarize the state-of-the-art for PGT-M and reflect on its future.

scholarly journals Gene expression profiles complement the analysis of genomic modifiers of the clinical onset of Huntington disease

2019 ◽  
Author(s):  
Galen E.B. Wright ◽  
Nicholas S. Caron ◽  
Bernard Ng ◽  
Lorenzo Casal ◽  
Xiaohong Xu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Huntington Disease ◽  
Neurodegenerative Disorder ◽  
Age Of Onset ◽  
Expression Profiles ◽  
Gene Expression Profiles ◽  
Cag Repeat ◽  
Biologically Relevant ◽  
Clinical Onset ◽  
Genome Wide Data

ABSTRACTHuntington disease (HD) is a neurodegenerative disorder that is caused by a CAG repeat expansion in the HTT gene. In an attempt to identify genomic modifiers that contribute towards the age of onset of HD, we performed a transcriptome wide association study assessing heritable differences in genetically determined expression in diverse tissues, employing genome wide data from over 4,000 patients. This identified genes that showed evidence for colocalization and replication, with downstream functional validation being performed in isogenic HD stem cells and patient brains. Enrichment analyses detected associations with various biologically-relevant gene sets and striatal coexpression modules that are mediated by CAG length. Further, cortical coexpression modules that are relevant for HD onset were also associated with cognitive decline and HD-related traits in a longitudinal cohort. In summary, the combination of population-scale gene expression information with HD patient genomic data identified novel modifier genes for the disorder.

scholarly journals Library preparation and MiSeq sequencing for the genotyping-by-sequencing of the Huntington disease HTT exon one trinucleotide repeat and the quantification of somatic mosaicism

2020 ◽  
Author(s):  
Marc Ciosi ◽  
Sarah A. Cumming ◽  
Asma M. Alshammari ◽  
Efthymia Symeonidi ◽  
Pawel Herzyk ◽  
...  
Keyword(s):  
Huntington Disease ◽  
Trinucleotide Repeat ◽  
Neurodegenerative Disorder ◽  
Fragment Size ◽  
Somatic Mosaicism ◽  
Genotyping By Sequencing ◽  
Amplicon Sequencing ◽  
Cag Repeat ◽  
Miseq Sequencing ◽  
Flanking Sequence

Abstract Huntington disease \(HD) is an autosomal dominant neurodegenerative disorder caused by the expansion of a CAG repeat in the first exon of the _HTT_ gene. Affected individuals inherit more than 40 repeats and the CAG repeat is genetically unstable in both the germline and soma. Molecular diagnosis and genotyping of the CAG repeat is traditionally performed by estimation of PCR fragment size. However, this approach is complicated by the presence of an adjacent polymorphic CCG repeat and provides no information on the presence of variant repeats, flanking sequence variants or on the degree of somatic mosaicism. To overcome these limitations, we have developed an amplicon-sequencing protocol that allows the sequencing of hundreds of samples in a single MiSeq run. The composition of the _HTT_ exon one trinucleotide repeat locus can be determined from the MiSeq sequencing reads generated. With sufficient sequencing depth, such MiSeq data can also be used to quantify the degree of somatic mosaicism of the _HTT_ CAG repeat in the tissue analysed.

scholarly journals Preimplantation genetic testing for Huntington disease

2019 ◽  
Vol 4 (5) ◽  
pp. e48
Author(s):  
Diogo Ferreira ◽  
Berta Carvalho ◽  
Ana P. Neto ◽  
Joaquina Silva ◽  
Ana M. Póvoa ◽  
...  
Keyword(s):  
Genetic Testing ◽  
Huntington Disease ◽  
Preimplantation Genetic Testing

scholarly journals Single-Step Scalable-Throughput Molecular Screening for Huntington Disease

2008 ◽  
Vol 54 (6) ◽  
pp. 964-972 ◽  
Author(s):  
Clara R L Teo ◽  
Wen Wang ◽  
Hai Yang Law ◽  
Caroline G Lee ◽  
Samuel S Chong
Keyword(s):  
Huntington Disease ◽  
Trinucleotide Repeat ◽  
Neurodegenerative Disorder ◽  
False Positive Rate ◽  
Screening Method ◽  
Melting Curve ◽  
Single Step ◽  
Cag Repeat ◽  
Clinical Samples ◽  
Melting Curve Analysis

Abstract Background: Huntington disease (HD) is a fatal autosomal dominant neurodegenerative disorder caused by an unstable expansion of the CAG trinucleotide repeat in exon 1 of the HTT (huntingtin) gene and typically has an adult onset. Molecular diagnosis and screening for HD currently involve separate amplification and detection steps. Methods: We evaluated a novel, rapid microplate-based screening method for HD that combines the amplification and detection procedures in a single-step, closed-tube format. We carried out both the PCR for the HTT CAG-repeat region and the subsequent automated melting-curve analysis of the amplicon in the same wells on the plate. To establish cutoff melting temperatures (Tms) for each allelic class, we used a panel of reference DNA samples of known CAG-repeat sizes that represent a range of HTT alleles [normal (≤26 repeats), intermediate (27–35 repeats), reduced penetrance expanded (36–39 repeats), and fully penetrant expanded (≥40 repeats)]. We also measured well-to-well variation in Tm across the thermal block and validated cutoff Tms with DNA samples from 5 different populations. We also conducted a blinded validation analysis of clinical samples from an additional 40 HD-affected and 30 unaffected individuals. Results: We observed a strong correlation between CAG-repeat size and amplicon Tm among the reference DNA samples. Use of the Tm cutoffs we established revealed that 5 samples from unaffected individuals had been misclassified as affected (1.1% false-positive rate). All samples from HD-affected and unaffected individuals were correctly identified in the blinded analysis. Conclusions: This simple and scalable homogeneous assay may serve as a convenient, rapid, and accurate screen to detect the presence of pathologic expanded HD alleles in symptomatic patients.

scholarly journals Early white matter pathology in the fornix of the limbic system in Huntington disease

2021 ◽  
Vol 142 (5) ◽  
pp. 791-806
Author(s):  
Sanaz Gabery ◽  
Jing Eugene Kwa ◽  
Rachel Y. Cheong ◽  
Barbara Baldo ◽  
Costanza Ferrari Bardile ◽  
...  
Keyword(s):  
Transcription Factor ◽  
White Matter ◽  
Limbic System ◽  
Huntington Disease ◽  
Neurodegenerative Disorder ◽  
Cag Repeat ◽  
Polycomb Repressive Complex 2 ◽  
Transcription Factor Target ◽  
Motor Component ◽  
White Matter Pathology

AbstractHuntington disease (HD) is a fatal neurodegenerative disorder caused by an expanded CAG repeat in the huntingtin (HTT) gene. The typical motor symptoms have been associated with basal ganglia pathology. However, psychiatric and cognitive symptoms often precede the motor component and may be due to changes in the limbic system. Recent work has indicated pathology in the hypothalamus in HD but other parts of the limbic system have not been extensively studied. Emerging evidence suggests that changes in HD also include white matter pathology. Here we investigated if the main white matter tract of the limbic system, the fornix, is affected in HD. We demonstrate that the fornix is 34% smaller already in prodromal HD and 41% smaller in manifest HD compared to controls using volumetric analyses of MRI of the IMAGE-HD study. In post-mortem fornix tissue from HD cases, we confirm the smaller fornix volume in HD which is accompanied by signs of myelin breakdown and reduced levels of the transcription factor myelin regulating factor but detect no loss of oligodendrocytes. Further analyses using RNA-sequencing demonstrate downregulation of oligodendrocyte identity markers in the fornix of HD cases. Analysis of differentially expressed genes based on transcription-factor/target-gene interactions also revealed enrichment for binding sites of SUZ12 and EZH2, components of the Polycomb Repressive Complex 2, as well as RE1 Regulation Transcription Factor. Taken together, our data show that there is early white matter pathology of the fornix in the limbic system in HD likely due to a combination of reduction in oligodendrocyte genes and myelin break down.

scholarly journals Advances in Huntington Disease Drug Discovery

2013 ◽  
Vol 19 (2) ◽  
pp. 191-204 ◽  
Author(s):  
Jonathan Bard ◽  
Michael D. Wall ◽  
Ovadia Lazari ◽  
Jamshid Arjomand ◽  
Ignacio Munoz-Sanjuan
Keyword(s):  
Huntington Disease ◽  
Molecular Mechanisms ◽  
Mononuclear Cells ◽  
Neurodegenerative Disorder ◽  
Embryonic Stem ◽  
Cellular Systems ◽  
Cag Repeat ◽  
Amino Terminal ◽  
Cellular Models ◽  
Wide Range

Huntington disease is a monogenic, autosomal dominant, progressive neurodegenerative disorder caused by a trinucleotide CAG repeat expansion in exon 1 of the huntingtin ( HTT) gene; age of onset of clinical symptoms inversely correlates with expanded CAG repeat length. HD leads to extensive degeneration of the basal ganglia, hypothalamic nuclei, and selected cortical areas, and a wide range of molecular mechanisms have been implicated in disease pathology in animal or cellular models expressing mutated HTT (mHTT) proteins, either full-length or amino-terminal fragments. However, HD cellular models that recapitulate the slow progression of the disease have not been available due to the toxicity of overexpressed exogenous mHTT or to limitations with using primary cells for long-term studies. Most investigations of the effects of mHTT relied on cytotoxicity or aggregation end points in heterologous systems or in primary embryonic neuroglial cultures derived from HD mouse models. More innovative approaches are currently under active investigation, including screening using electrophysiological endpoints, as well as the recent use of primary blood mononuclear cells and of human embryonic stem cells derived from a variety of HD research participants. Here we describe how these cellular systems are being used to investigate HD biology as well as to identify mechanisms with therapeutic potential.

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