Genetic counseling for FTD/ALS caused by the C9ORF72 hexanucleotide expansion

Individuals' experiences in genetic counseling and predictive testing for familial amyotrophic lateral sclerosis

As clinical genetic testing in the amyotrophic lateral sclerosis (ALS) diagnostic setting increases, the identification of at-risk family members has also expanded. No practice guidelines specifically for predictive genetic testing exist, and few studies about the psychological impacts of testing in this subgroup have occurred, limiting the ability to tailor recommendations and counseling in this community. We surveyed asymptomatic individuals at risk for inheriting an ALS-associated gene mutation. The 80-question survey was designed using a combination of validated measures (General Anxiety Disorder; FACToR; Decision Regret Scale) and original items. Ninety participants completed the survey, including those who completed predictive genetic testing (N = 42) and those who did not (N = 48). Gene positive individuals experienced greater negativity, uncertainty, and overall psychological impairment (p = 0.002; p < 0.001; p = 0.001). Individuals who had not undergone testing reported thinking about their risk multiple times per day and experiencing more decisional regret than those who tested (p = 0.006). In terms of decision-making, being prepared for potential clinical drug trials was a more important potential benefit among those who underwent testing (p = 0.026). Participants valuing preparedness for clinical drug trials supports the concept that genetic testing for ALS will increase as research in gene-targeted therapeutics progresses. This study describes factors relevant to the genetic testing decision-making process and adaptation to results from the perspective of at-risk individuals, which can ultimately guide genetic counseling practice in this population.

Small molecules targeting different cellular pathologies for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease in which the motor neuron circuitry displays progressive degeneration, affecting mostly the motor neurons in the brain and in the spinal cord. There are no effective cures, albeit three drugs, riluzole, edaravone, and AMX0035 (a combination of sodium phenylbutyrate and taurursodiol), have been approved by the Food and Drug Administration, with limited improvement in patients. There is an urgent need to build better and more effective treatment strategies for ALS. Since the disease is very heterogenous, numerous approaches have been explored, such as targeting genetic mutations, decreasing oxidative stress and excitotoxicity, enhancing mitochondrial function and protein degradation mechanisms, and inhibiting neuroinflammation. In addition, various chemical libraries or previously identified drugs have been screened for potential repurposing in the treatment of ALS. Here, we review previous drug discovery efforts targeting a variety of cellular pathologies that occur from genetic mutations that cause ALS, such as mutations in SOD1, C9orf72, FUS, and TARDP-43 genes. These mutations result in protein aggregation, which causes neuronal degeneration. Compounds used to target cellular pathologies that stem from these mutations are discussed and comparisons among different preclinical models are presented. Because the drug discovery landscape for ALS and other motor neuron diseases is changing rapidly, we also offer recommendations for a novel, more effective, direction in ALS drug discovery that could accelerate translation of effective compounds from animals to patients.

Evidence-based consensus guidelines for ALS genetic testing and counseling

OBJECTIVE

Advances in amyotrophic lateral sclerosis (ALS) gene discovery, ongoing gene therapy trials, and patient demand have driven increased use of ALS genetic testing. Despite this progress, the offer of genetic testing to persons with ALS is not yet "standard of care." Our primary goal is to develop clinical ALS genetic counseling and testing guidelines to improve and standardize genetic counseling and testing practice among neurologists, genetic counselors or any provider caring for persons with ALS.

METHODS

Core clinical questions were identified and a rapid review performed according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA-P) 2015 method. Guideline recommendations were drafted and the strength of evidence for each recommendation was assessed by combining two systems: the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) System and the Evaluation of Genomic Applications in Practice and Prevention (EGAPP). A modified Delphi approach was used to reach consensus among a group of content experts for each guideline statement.

RESULTS

A total of 35 guideline statements were developed. In summary, all persons with ALS should be offered single-step genetic testing, consisting of a C9orf72 assay, along with sequencing of SOD1, FUS, and TARDBP, at a minimum. The key education and genetic risk assessments that should be provided before and after testing are delineated. Specific guidance regarding testing methods and reporting for C9orf72 and other genes is provided for commercial laboratories.

INTERPRETATION

These evidence-based, consensus guidelines will support all stakeholders in the ALS community in navigating benefits and challenges of genetic testing.

Expanding Clinical Spectrum of C9ORF72-Related Disorders and Promising Therapeutic Strategies: A Review

In 2011, a pathogenic hexanucleotide repeat expansion in the C9ORF72 gene was discovered to be the leading genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Before this, the C9ORF72 gene and its protein were unknown. The repeat expansion was found to cause both haploinsufficiency and gain of toxicity through aggregating RNA products and dipeptide repeat proteins. A worldwide effort was then initiated to define C9ORF72 ALS/FTD and unravel the pathogenic mechanism for the development of therapeutic options. A decade later, C9ORF72 genetic testing is readily available. There is now an increasing appreciation that C9ORF72 not only is the leading genetic cause of ALS/FTD but may contribute to a spectrum of disorders. This article reviews what is currently known about the C9ORF72 expansion and how C9ORF72 expansion manifests in ALS, FTD, psychiatric disorders, and movement disorders. With therapeutic strategies fast approaching the clinic, earlier recognition of possible C9ORF72 expansion related disorders is even more paramount to improve patient care.

Patient and Relative Experiences and Decision-making About Genetic Testing and Counseling for Familial ALS and FTD: A Systematic Scoping Review

Genetic testing and counseling is an emerging part of care for patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) and their families. This scoping review aimed to map patients' and relatives' experiences of genetic testing and counseling for familial ALS and FTD and the factors influencing their decision to proceed with testing or counseling. Informed by the Joanna Briggs Institute methodology, 5 databases were systematically searched. Thirty studies from 39 references were included. A descriptive numerical summary analysis and narrative synthesis was conducted. Mostly positive diagnostic testing experiences were reported, but issues arose due to progressive disease and discordant results. Predictive testing impacted at-risk relatives, regardless of the result received, and psychosocial sequelae ranged from relief to guilt, worry or contemplating suicide. Four reproductive testing experiences were reported. Personal, familial and practical factors, and the lived experience of disease, informed decision-making. Greater uncertainty and complexity may be faced in familial ALS/FTD than in other late-onset neurodegenerative diseases due to clinical and genetic heterogeneity, and testing limitations. Genetic counseling models of care should consider this difference to ensure that individuals with, or at risk of, ALS/FTD are effectively managed. Implications for research and practice are discussed.

Who and Why? Requests for Presymptomatic Genetic Testing for Amyotrophic Lateral Sclerosis/Frontotemporal Dementia vs Huntington Disease

Objective

We aimed to describe the population of subjects seeking presymptomatic counseling for amyotrophic lateral sclerosis and/or frontotemporal dementia (ALS/FTD) and compared them with those demanding the well-established presymptomatic test for Huntington disease (HD).

Methods

We retrospectively examined the requests of a cohort of individuals at risk of familial ALS/FTD and 1 at risk of HD over the same time frame of 11 years. The individuals were seen in the referral center of our neurogenetics unit.

Results

Of the 106 presymptomatic testing (PT) requests from subjects at risk of ALS/FTD, 65% were seen in the last 3 years. Over two-thirds of the subjects were at risk of carrying mutations responsible for ALS, FTD, or both. Sixty-two percent of the subjects came from families with a known hexanucleotide repeat expansion in C9ORF72. During the same period, we counseled 840 subjects at risk of HD. Subjects at risk of ALS/FTD had the presymptomatic test significantly sooner after being aware of their risk, but were older than those at risk of HD. The youngest subjects requesting the test had the highest disease load in the family (p < 0.05).

Conclusions

Demands for PT for ALS/FTD have been increasingly growing, particularly since the discovery of the C9ORF72 gene. The major specificity of the genetic counseling for these diseases is the unpredictability of the clinical phenotype for most of the genes involved. Awareness of this added uncertainty does not prevent individuals from taking the test, as the dropout rate is not higher than that for HD.

C9orf72 and the Care of the Patient With ALS or FTD: Progress and Recommendations After 10 Years

The 2011 discovery of the pathogenic hexanucleotide repeat expansion (HRE) in C9orf72, the leading genetic cause of both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), marked a breakthrough in the effort to unravel the etiology of these conditions. Ten years later, clinicians are still working to integrate the implications of this discovery into the care of individuals with ALS and/or FTD. Consensus management guidelines for ALS do not comprehensively address the issue of genetic testing, and questions remain about whom to test, what counseling should be provided before and after testing, laboratory methods, and test interpretation. These challenges have contributed to inconsistent clinical practices and present barriers to patients wishing to access testing. This review summarizes the clinical impact of the discovery of the C9orf72 HRE, outlines ongoing challenges, and provides recommendations for C9orf72 testing, counseling, and research.

Membrane-Bound Meet Membraneless in Health and Disease

Membraneless organelles (MLOs) are defined as cellular structures that are not sealed by a lipidic membrane and are shown to form by phase separation. They exist in both the nucleus and the cytoplasm that is also heavily populated by numerous membrane-bound organelles. Even though the name membraneless suggests that MLOs are free of membrane, both membrane and factors regulating membrane trafficking steps are emerging as important components of MLO formation and function. As a result, we name them biocondensates. In this review, we examine the relationships between biocondensates and membrane. First, inhibition of membrane trafficking in the early secretory pathway leads to the formation of biocondensates (P-bodies and Sec bodies). In the same vein, stress granules have a complex relationship with the cyto-nuclear transport machinery. Second, membrane contributes to the regulated formation of phase separation in the cells and we will present examples including clustering at the plasma membrane and at the synapse. Finally, the whole cell appears to transit from an interphase phase-separated state to a mitotic diffuse state in a DYRK3 dependent manner. This firmly establishes a crosstalk between the two types of cell organization that will need to be further explored.

Autophagy as a common pathway in amyotrophic lateral sclerosis

Age-dependent neurodegenerative diseases are associated with a decline in protein quality control systems including autophagy. Amyotrophic lateral sclerosis (ALS) is a motor neuron degenerative disease of complex etiology with increasing connections to other neurodegenerative conditions such as frontotemporal dementia. Among the diverse genetic causes for ALS, a striking feature is the common connection to autophagy and its associated pathways. There is a recurring theme of protein misfolding as in other neurodegenerative diseases, but importantly there is a distinct common thread among ALS genes that connects them to the cascade of autophagy. However, the roles of autophagy in ALS remain enigmatic and it is still unclear whether activation or inhibition of autophagy would be a reliable avenue to ameliorate the disease. The main evidence that links autophagy to different genetic forms of ALS is discussed.

The C9orf72 hexanucleotide repeat expansion presents a challenge for testing laboratories and genetic counseling

C9orf72 hexanucleotide repeat expansions are the most common known cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Genetic testing for C9orf72 expansions in patients with ALS and/or FTD and their relatives has become increasingly available since hexanucleotide repeat expansions were first reported in 2011. The repeat number is highly variable and the threshold at which repeat size leads to neurodegeneration remains unknown. We present the case of an ALS patient who underwent genetic testing through our Motor Neurone Disease Clinic. We highlight current limitations to analysing and interpreting C9orf72 expansion test results and describe how this resulted in discordant reports of pathogenicity between testing laboratories that confounded the genetic counselling process. We conclude that patients with ALS or FTD and their at-risk family members, need to be adequately counselled about the limitations of current knowledge to ensure they are making informed decisions about genetic testing for C9orf72. Greater collaboration between clinicians, testing laboratories and researchers is required to ensure risks to patients and their families are minimised.

A proteomic network approach across the ALS-FTD disease spectrum resolves clinical phenotypes and genetic vulnerability in human brain

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are neurodegenerative diseases with overlap in clinical presentation, neuropathology, and genetic underpinnings. The molecular basis for the overlap of these disorders is not well established. We performed a comparative unbiased mass spectrometry‐based proteomic analysis of frontal cortical tissues from postmortem cases clinically defined as ALS, FTD, ALS and FTD (ALS/FTD), and controls. We also included a subset of patients with the C9orf72 expansion mutation, the most common genetic cause of both ALS and FTD. Our systems‐level analysis of the brain proteome integrated both differential expression and co‐expression approaches to assess the relationship of these differences to clinical and pathological phenotypes. Weighted co‐expression network analysis revealed 15 modules of co‐expressed proteins, eight of which were significantly different across the ALS‐FTD disease spectrum. These included modules associated with RNA binding proteins, synaptic transmission, and inflammation with cell‐type specificity that showed correlation with TDP‐43 pathology and cognitive dysfunction. Modules were also examined for their overlap with TDP‐43 protein–protein interactions, revealing one module enriched with RNA‐binding proteins and other causal ALS genes that increased in FTD/ALS and FTD cases. A module enriched with astrocyte and microglia proteins was significantly increased in ALS cases carrying the C9orf72 mutation compared to sporadic ALS cases, suggesting that the genetic expansion is associated with inflammation in the brain even without clinical evidence of dementia. Together, these findings highlight the utility of integrative systems‐level proteomic approaches to resolve clinical phenotypes and genetic mechanisms underlying the ALS‐FTD disease spectrum in human brain.

Intrafamilial Phenotypic Variability in the C9orf72 Gene Expansion: 2 Case Studies

The C9orf72 genetic mutation is the most common cause of familial frontotemporal dementia (FTD) and motor neuron disease (MND). Previous family studies suggest that while some common clinical features may distinguish gene carriers from sporadic patients, the clinical features, age of onset and disease progression vary considerably in affected patients. Whilst disease presentations may vary across families, age at disease onset appears to be relatively uniform within each family. Here, we report two individuals with a C9orf72 repeat expansion from two generations of the same family with markedly different age at disease onset, clinical presentation and disease progression: one who developed motor neuron and behavioural symptoms in their mid 40s and died 3 years later with confirmed TDP-43 pathology and MND; and a second who developed cognitive and mild behavioural symptoms in their mid 70s and 8 years later remains alive with only slow deterioration. This report highlights the phenotypic variability, including age of onset, within a family with the C9orf72 repeat expansion.

(C2G4)n repeat expansion sequences from the C9orf72 gene form an unusual DNA higher-order structure in the pH range of 5-6

Massive expansion of a DNA hexanucleotide sequence repeat (C₂G₄) within the human C9orf72 gene has been linked to a number of neurodegenerative diseases. In sodium or potassium salt solutions, single-stranded d(C₂G₄)_n DNAs fold to form G-quadruplexes. We have found that in magnesium or lithium salt solutions, especially under slightly acidic conditions, d(C₂G₄)_n oligonucleotides fold to form a distinctive higher order structure whose most striking feature is an “inverted” circular dichroism spectrum, which is distinguishable from the spectrum of the left handed DNA double-helix, Z-DNA. On the basis of CD spectroscopy, gel mobility as well as chemical protection analysis, we propose that this structure, which we call “iCD-DNA”, may be a left-handed Hoogsteen base-paired duplex, an unorthodox G-quadruplex/i-motif composite, or a non-canonical, “braided” DNA triplex. Given that iCD-DNA forms under slightly acidic solution conditions, we do not know at this point in time whether or not it forms within living cells.

Nestin-expressing progenitor cells: function, identity and therapeutic implications

The neuroepithelial stem cell protein, or Nestin, is a cytoskeletal intermediate filament initially characterized in neural stem cells. However, current extensive evidence obtained in in vivo models and humans shows presence of Nestin+ cells with progenitor and/or regulatory functions in a number of additional tissues, remarkably bone marrow. This review presents the current knowledge on the role of Nestin in essential stem cell functions, including self-renewal/proliferation, differentiation and migration, in the context of the cytoskeleton. We further discuss the available in vivo models for the study of Nestin+ cells and their progeny, their function and elusive nature in nervous system and bone marrow, and their potential mechanistic role and promising therapeutic value in preclinical models of disease. Future improved in vivo models and detection methods will allow to determine the true essence of Nestin+ cells and confirm their potential application as therapeutic target in a range of diseases.

Frontotemporal dementia

Frontotemporal dementia (FTD) is a neurodegenerative disorder characterized by progressive changes in behavior, personality, and language with involvement of the frontal and temporal regions of the brain. About 40% of FTD cases have a positive family history, and about 10% of these cases are inherited in an autosomal-dominant pattern. These gene defects present with distinct clinical phenotypes. As the diagnosis of FTD becomes more recognizable, it will become increasingly important to keep these gene mutations in mind. In this chapter, we review the genes with known associations to FTD. We discuss protein functions, mutation frequencies, clinical phenotypes, imaging characteristics, and pathology associated with these genes.

Patients with sporadic and familial amyotrophic lateral sclerosis found value in genetic testing

Background

Amyotrophic lateral sclerosis (ALS) is increasingly recognized as a genetic disease. There is no consensus, however, as to the role of genetic testing in the care of the ALS patient.

Methods

We conducted a survey to study patient access, attitudes, and experience with ALS genetic testing among patients enrolled in a US ALS registry.

Results

Among 449 survey respondents, 156 (34.7%) were offered testing and 105 of 156 (67.3%) completed testing. The majority of respondents with familial ALS (fALS) (31/45, 68.9%) were offered testing, while a minority of respondents with sporadic ALS (sALS) (111/404, 27.5%) were offered testing (p = .00001). Comparison of mean test experience scores between groups revealed that respondents with fALS were no more likely to report a favorable experience with genetic testing than those with sALS (p = .51). Respondents who saw a genetic counselor did not have significantly different test experience scores, compared to those who did not (p = .14). In addition, no differences in test experience scores were observed between those who received positive or negative genetic test results (p = .98).

Conclusion

These data indicate that patients with ALS found value in clinical genetic testing.

Current Advances and Limitations in Modeling ALS/FTD in a Dish Using Induced Pluripotent Stem Cells

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are two age-dependent multifactorial neurodegenerative disorders, which are typically characterized by the selective death of motor neurons and cerebral cortex neurons, respectively. These two diseases share many clinical, genetic and pathological aspects. During the past decade, cell reprogramming technologies enabled researchers to generate human induced pluripotent stem cells (iPSCs) from somatic cells. This resulted in the unique opportunity to obtain specific neuronal and non-neuronal cell types from patients which could be used for basic research. Moreover, these in vitro models can mimic not only the familial forms of ALS/FTD, but also sporadic cases without known genetic cause. At present, there have been extensive technical advances in the generation of iPSCs, as well as in the differentiation procedures to obtain iPSC-derived motor neurons, cortical neurons and non-neuronal cells. The major challenge at this moment is to determine whether these iPSC-derived cells show relevant phenotypes that recapitulate complex diseases. In this review, we will summarize the work related to iPSC models of ALS and FTD. In addition, we will discuss potential drawbacks and solutions for establishing more trustworthy iPSC models for both ALS and FTD.

Neuroanatomical and Neuropsychological Markers of Amnestic MCI: A Three-Year Longitudinal Study in Individuals Unaware of Cognitive Decline

Structural brain changes underlying mild cognitive impairment (MCI) have been well-researched, but most previous studies required subjective cognitive complaints (SCC) as a diagnostic criterion, diagnosed MCI based on a single screening test or lacked analyses in relation to neuropsychological impairment. This longitudinal voxel-based morphometry study aimed to overcome these limitations: The relationship between regional gray matter (GM) atrophy and behavioral performance was investigated over the course of 3 years in individuals unaware of cognitive decline, identified as amnestic MCI based on an extensive neuropsychological test battery. Region of interest analyses revealed GM atrophy in the left amygdala, hippocampus, and parahippocampus in MCI individuals compared to normally aging participants, which was specifically related to verbal memory impairment and evident already at the first measurement point. These findings demonstrate that GM atrophy is detectable in individuals with amnestic MCI despite unawareness of beginning cognitive decline. Thus, individuals with GM atrophy in regions associated with verbal memory impairment do not necessarily need to experience SCC before meeting neuropsychological criteria for MCI. These results have important implications for future research and diagnostic procedures of MCI.

Patients with Amyotrophic Lateral Sclerosis Have High Interest in and Limited Access to Genetic Testing

Although genetic testing for amyotrophic lateral sclerosis (ALS) is widely available, it is unknown what proportion of patients with ALS have access to genetic counseling and testing, and patient attitudes towards ALS genetic testing have not been studied. We conducted a national survey of ALS patients enrolled in the Agency for Toxic Substances and Disease Registry, which consisted of multiple choice questions and two 12 item Likert scale series assessing respondents' experience with and attitude toward genetic testing. The survey had an 8 % response rate, with 449 completed responses. Genetic testing was offered to 33.4 % and completed by 67.1 % of those offered. A minority of respondents (12.5 %) saw a genetic counselor, and were much more likely to be offered genetic testing (p = 0.0001). Respondents with a family history of ALS (8.4 %) were more likely to be offered testing (p = 0.0001) and complete testing (p = 0.05). Respondents with a family history of ALS were more likely to report a favorable attitude towards genetic testing (p = 0.0003), as were respondents who saw a genetic counselor (p = 0.02). The majority of respondents (82.7 %) felt that genetic testing should be offered to all patients with ALS. Our results indicate that ALS patients may have limited access to genetic testing, but perceive benefit from this service. Development of practice guidelines for genetic testing in ALS, to include the routine offer of genetic counseling, may result in broader and more consistent access to these services.

The C9orf72 repeat size correlates with onset age of disease, DNA methylation and transcriptional downregulation of the promoter

Pathological expansion of a G4C2 repeat, located in the 5' regulatory region of C9orf72, is the most common genetic cause of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). C9orf72 patients have highly variable onset ages suggesting the presence of modifying factors and/or anticipation. We studied 72 Belgian index patients with FTLD, FTLD-ALS or ALS and 61 relatives with a C9orf72 repeat expansion. We assessed the effect of G4C2 expansion size on onset age, the role of anticipation and the effect of repeat size on methylation and C9orf72 promoter activity. G4C2 expansion sizes varied in blood between 45 and over 2100 repeat units with short expansions (45-78 units) present in 5.6% of 72 index patients with an expansion. Short expansions co-segregated with disease in two families. The subject with a short expansion in blood but an indication of mosaicism in brain showed the same pathology as those with a long expansion. Further, we provided evidence for an association of G4C2 expansion size with onset age (P<0.05) most likely explained by an association of methylation state of the 5' flanking CpG island and expansion size in blood (P<0.0001) and brain (P<0.05). In several informative C9orf72 parent-child transmissions, we identified earlier onset ages, increasing expansion sizes and/or increasing methylation states (P=0.0034) of the 5' CpG island, reminiscent of disease anticipation. Also, intermediate repeats (7-24 units) showed a slightly higher methylation degree (P<0.0001) and a decrease of C9orf72 promoter activity (P<0.0001) compared with normal short repeats (2-6 units). Decrease of transcriptional activity was even more prominent in the presence of small deletions flanking G4C2 (P<0.0001). Here we showed that increased methylation of CpGs in the C9orf72 promoter may explain how an increasing G4C2 size lead to loss-of-function without excluding repeat length-dependent toxic gain-of-function. These data provide insights into disease mechanisms and have important implications for diagnostic counseling and potential therapeutic approaches.

[Genetics of dementia]

Most psychiatric diseases in adulthood have a multifactorial origin. This also applies for most cases of dementia; however, rare familial forms of Alzheimer's disease and frontotemporal lobar degeneration follow an autosomal dominant (Mendelian) inheritance pattern. Alzheimer's disease that is caused by mutations in the genes for presenilin 1, presenilin 2 and amyloid precursor protein has an onset under the age of 65 years in most cases. Approximately 10 % of frontotemporal lobar degeneration cases display an autosomal dominant inheritance pattern. According to the current S3 guidelines on dementia of the German Association for Psychiatry, Psychotherapy and Psychosomatics and the German Society of Neurology, genetic counseling should be offered if an autosomal dominant disease pattern is suspected. Genetic counseling must conform to the German Genetic Diagnostics Act (Gendiagnostikgesetz).

The Spectrum of C9orf72-mediated Neurodegeneration and Amyotrophic Lateral Sclerosis

The discovery that a hexanucleotide repeat expansion in C9orf72 is the most numerous genetic variant of both amyotrophic lateral sclerosis and frontotemporal dementia has opened a rapidly growing field, which may provide long hoped for advances in the understanding and treatment of these devastating diseases. In this review we describe the various phenotypes, clinical and pathological, associated with expansion of C9orf72, which go beyond amyotrophic lateral sclerosis and frontotemporal dementia to include neurodegeneration more broadly. Next we take a step back and summarize the current understanding of the C9orf72 expansion and its protein products at a molecular level. Three mechanisms are prominent: toxicity mediated directly by RNA transcribed from the repeat; toxicity mediated by dipeptide repeat proteins translated from the repeat sequence; and haploinsufficiency resulting from reduced transcription of the C9orf72 exonic sequence. A series of exciting advances have recently described how dipeptide repeat proteins might interfere with the normal role of the nucleolus in maturation of RNA binding proteins and in production of ribosomes. Importantly, these mechanisms are unlikely to be mutually exclusive. We draw attention to the fact that clinical and pathological similarities to other genetic variants without a repeat expansion must not be overlooked in ascribing a pathogenic mechanism to C9orf72-disease. Finally, with a view to impact on patient care, we discuss current practice with respect to genetic screening in patients with and without a family history of disease, and the most promising developments towards therapy that have been reported to date.

Arizona Study of Aging and Neurodegenerative Disorders and Brain and Body Donation Program

The Brain and Body Donation Program (BBDP) at Banner Sun Health Research Institute (http://www.brainandbodydonationprogram.org) started in 1987 with brain-only donations and currently has banked more than 1600 brains. More than 430 whole-body donations have been received since this service was commenced in 2005. The collective academic output of the BBDP is now described as the Arizona Study of Aging and Neurodegenerative Disorders (AZSAND). Most BBDP subjects are enrolled as cognitively normal volunteers residing in the retirement communities of metropolitan Phoenix, Arizona. Specific recruitment efforts are also directed at subjects with Alzheimer's disease, Parkinson's disease and cancer. The median age at death is 82. Subjects receive standardized general medical, neurological, neuropsychological and movement disorders assessments during life and more than 90% receive full pathological examinations by medically licensed pathologists after death. The Program has been funded through a combination of internal, federal and state of Arizona grants as well as user fees and pharmaceutical industry collaborations. Subsets of the Program are utilized by the US National Institute on Aging Arizona Alzheimer's Disease Core Center and the US National Institute of Neurological Disorders and Stroke National Brain and Tissue Resource for Parkinson's Disease and Related Disorders. Substantial funding has also been received from the Michael J. Fox Foundation for Parkinson's Research. The Program has made rapid autopsy a priority, with a 3.0-hour median post-mortem interval for the entire collection. The median RNA Integrity Number (RIN) for frozen brain and body tissue is 8.9 and 7.4, respectively. More than 2500 tissue requests have been served and currently about 200 are served annually. These requests have been made by more than 400 investigators located in 32 US states and 15 countries. Tissue from the BBDP has contributed to more than 350 publications and more than 200 grant-funded projects.

Genetic counselling in ALS: facts, uncertainties and clinical suggestions

The clinical approach to patients with amyotrophic lateral sclerosis (ALS) has been largely modified by the identification of novel genes, the detection of gene mutations in apparently sporadic patients, and the discovery of the strict genetic and clinical relation between ALS and frontotemporal dementia (FTD). As a consequence, clinicians are increasingly facing the dilemma on how to handle genetic counselling and testing both for ALS patients and their relatives. On the basis of existing literature on genetics of ALS and of other late-onset life-threatening disorders, we propose clinical suggestions to enable neurologists to provide optimal clinical and genetic counselling to patients and families. Genetic testing should be offered to ALS patients who have a first-degree or second-degree relative with ALS, FTD or both, and should be discussed with, but not offered to, all other ALS patients, with special emphasis on its major uncertainties. Presently, genetic testing should not be proposed to asymptomatic at-risk subjects, unless they request it or are enrolled in research programmes. Genetic counselling in ALS should take into account the uncertainties about the pathogenicity and penetrance of some genetic mutations; the possible presence of mutations of different genes in the same individual; the poor genotypic/phenotypic correlation in most ALS genes; and the phenotypic pleiotropy of some genes. Though psychological, social and ethical implications of genetic testing are still relatively unexplored in ALS, we recommend multidisciplinary counselling that addresses all relevant issues, including disclosure of tests results to family members and the risk for genetic discrimination.

Association analysis of four candidate genetic variants with sporadic amyotrophic lateral sclerosis in a Chinese population

Recently, four single nucleotide polymorphisms (SNPs), including rs2814707 in the 9p21, rs12608932 in the UNC13A gene, rs13048019 in the TIMA1 gene, and rs2228576 in the SCNN1A gene have been reported to be associated with the risk for developing amyotrophic lateral sclerosis (ALS) in Caucasian population. However, this association is not consistent among different studies and yet to be tested in ALS patients in Mainland China. This study included 397 sporadic ALS (SALS) patients and 287 unrelated Chinese healthy controls from Southwest China. Four SNPs listed above were genotyped by using Sequenom's iPLEX assay. No significant differences in the genotype distributions or minor allele frequencies in all SNPs were found between ALS group and control group, between the spinal-onset group and bulbar-onset group, and between the early-onset group and the late-onset group. Our results suggest that these SNPs are unlikely to be common cause of SALS in Chinese population.

The C9ORF72 mutation brings more answers and more questions

The clinical, neuropsychiatric and neuroimaging features of patients who carry the important new C9ORF72 mutation are discussed in this special series of Alzheimer's Research & Therapy. First reported in November 2011, the C9ORF72 mutation is the most common mutation associated with both frontotemporal dementia and amyotrophic lateral sclerosis in the Western hemisphere and Europe. It is a gene with strong penetrance, and the vast majority of subjects with the C9ORF72 mutation die from a neurodegenerative condition. The most common clinical manifestation of disease in gene carriers is behavioral variant frontotemporal dementia. An extremely long hexanucleotide repeat (usually greater than 400), appears to lead to ribonucleic acid aggregates within the nucleus and suppression of gene expression. Finding therapies for C9ORF72 will be difficult and require novel therapeutic approaches that involve suppression of the expression of the C9ORF72 repeat.