C9ORF72 expansion in a family with bipolar disorder

C9orf72 Repeat Expansion Initially Presenting as Late-Onset Bipolar Disorder With Psychosis

INTRODUCTION

C9orf72 expansion is the most common genetic abnormality in behavioral variant frontotemporal dementia (bvFTD) and amyotrophic lateral sclerosis. Although psychiatric prodromes are common in C9orf72 expansion carriers, there are only scattered reported cases of primary psychiatric disorders, such as bipolar disorder, diagnosed at disease onset. Moreover, C9orf72 carrier status is rarely identified in bipolar disorder genetic studies.

CASE REPORT

A 51-year-old, right-handed woman with 16 years of education presented for evaluation of long-standing cognitive and behavioral change. She initially displayed symptoms of mania and florid, multimodal psychotic symptoms at age 39. Her bipolar disorder symptoms were initially responsive to medication; however, she later developed executive dysfunction and behavioral symptoms consistent with bvFTD. She became progressively nonverbal, and her limited speech was notable for speech apraxia. At the time of presentation, she demonstrated cortical sensory deficit, ideomotor and oral-buccal apraxia, and unstable gait. Neuroimaging revealed diffuse brain atrophy. Postmortem histopathological evaluation revealed frontotemporal lobar degeneration with TDP-43 inclusions, type B, and genetic study identified C9orf72 expansion. A detailed review of family history found a strong paternal history of bipolar disorder and substance use disorder.

CONCLUSIONS

We describe a rare case of C9orf72 expansion initially characterized by late-onset bipolar disorder and florid, multimodal psychotic symptoms, followed years later by bvFTD diagnosis. This report emphasizes the importance of completing a neurological examination, obtaining a detailed family history, and pursuing genetic screening to distinguish between primary psychiatric disorder and bvFTD in individuals who meet the criteria for late-onset bipolar disorder.

C9ORF72 Gene GGGGCC Hexanucleotide Expansion: A High Clinical Variability from Amyotrophic Lateral Sclerosis to Frontotemporal Dementia

The expanded GGGGCC hexanucleotide repeat (HRE) in the non-coding region of the C9ORF72 gene (C9ORF72-HRE) is the most common genetic cause of familial forms of amyotrophic lateral sclerosis (ALS), FTD, and concurrent ALS and FTD (ALS-FTD), in addition to contributing to the sporadic forms of these diseases. Both syndromes overlap not only genetically, but also sharing similar clinical and neuropathological findings, being considered as a spectrum. In this paper we describe the clinical-genetic findings in a Basque family with different manifestations within the spectrum, our difficulties in reaching the diagnosis, and a narrative review, carried out as a consequence, of the main features associated with C9ORF72-HRE. Family members underwent a detailed clinical assessment, neurological examination, and genetic analysis by repeat-primed PCR. We studied 10 relatives of a symptomatic carrier of the C9ORF72-HRE expansion. Two of them presented the expansion in the pathological range, one of them was symptomatic whereas the other one remained asymptomatic at 72 years. Given the great intrafamilial clinical variability of C9ORF72-HRE, the characterization of patients and family members with particular clinical and genetic subgroups within ALS and FTD becomes a bottleneck for medication development, in particular for genetically focused medicines for ALS and FTD.

Bipolar Disorder and Manic-Like Symptoms in Alzheimer's, Vascular and Frontotemporal Dementia: A Systematic Review

BACKGROUND

An increased risk of manic episodes has been reported in patients with neurodegenerative disorders, but the clinical features of bipolar disorder (BD) in different subtypes of dementia have not been thoroughly investigated.

OBJECTIVES

The main aim of this study is to systematically review clinical and therapeutic evidence about manic syndromes in patients with Alzheimer's disease (AD), vascular dementia (VaD), and frontotemporal dementia (FTD). Since manic-mixed episodes have been associated to negative outcomes in patients with dementia and often require medical intervention, we also critically summarized selected studies with relevance for the treatment of mania in patients with cognitive decline.

METHODS

A systematic review of the literature was conducted according to PRISMA guidelines. PubMed, Scopus, and Web of Science databases were searched up to February 2022. Sixty-one articles on patients with AD, VaD, or FTD and BD or (hypo) mania have been included.

RESULTS

Manic symptoms seem to be associated to disease progression in AD, have a greatly variable temporal relationship with cognitive decline in VaD, and frequently coincide with or precede cognitive impairment in FTD. Overall, mood stabilizers, and electroconvulsive therapy may be the most effective treatments, while the benefits of short-term treatment with antipsychotic agents must be balanced with the associated risks. Importantly, low-dose lithium salts may exert neuroprotective activity in patients with AD.

CONCLUSION

Prevalence, course, and characteristics of manic syndromes in patients with dementia may be differentially affected by the nature of the underlying neurodegenerative conditions.

Behavioral and psychological symptoms in neurodegenerative dementias: harbinger, follower, or constant collateral?

Neurodegenerative dementias such as the behavioral variant of frontotemporal dementia, Alzheimer’s disease, and Parkinson’s disease dementia are linked to various behavioral and psychological abnormalities. Whether these abnormalities precede, coincide or follow the onset of cognitive symptoms is still controversial in existing literature, with trajectories available so far dependent on types of dementia. The authors aim to review the different kinds of premorbid behavioral symptoms/personality traits associated with an increased risk of developing specific types of neurodegenerative dementia. Neuroticism has been associated with an increased risk of Alzheimer’s disease and late-onset behavioral abnormalities with the behavioral variant of frontotemporal dementia. The presence of obsessive–compulsive spectrum disorders in Parkinson’s disease dementia is also not rare. Analyzing this evidence, we propose “behavioral biomarkers” as neuroticism in Alzheimer’s disease, late-onset behavioral abnormalities in behavioral variant of frontotemporal dementia, and obsessive–compulsive traits in Parkinson’s disease dementia. These noninvasive behavioral biomarkers will be of immense help, particularly in developing countries, and will prevent the need for costlier investigations and aid in therapeutic strategies.

Overlap of Neuroanatomical Involvement in Frontotemporal Dementia and Primary Psychiatric Disorders: A Meta-analysis

BACKGROUND

Despite significant symptomatic overlap between behavioral variant frontotemporal dementia (bvFTD) and primary psychiatric disorders (PPDs), a potential overlap in their structural anatomical changes has not been studied systematically.

METHODS

In this magnetic resonance imaging-based meta-analysis, we included studies on bvFTD, schizophrenia, bipolar disorder, and autism spectrum disorder that 1) used voxel-based morphometry analysis to assess regional gray matter volumes (GMVs) and 2) reported the coordinates of the regional GMV. Separate analyses were performed comparing clusters of coordinate-based changes in the GMVs (n = 24,183) between patients and control subjects, and overlapping brain regions between bvFTD and each PPD were examined.

RESULTS

We found that GMV alterations in the prefrontal and anterior cingulate cortices, temporal lobe, amygdala, and insula comprise the transdiagnostic brain alterations in bvFTD and PPD.

CONCLUSIONS

Our meta-analysis revealed significant anatomical overlap that paves the way for future investigations of shared pathophysiological pathways, and our cross-disorder approach would provide new insights to better understand the relationship between bvFTD and PPD.

Bipolar disorder and frontotemporal dementia: A systematic review

OBJECTIVES

To detail the biological, clinical and neurocognitive characteristics differentiating bipolar disorder (BD) from frontotemporal dementia (FTD) and to investigate whether BD is a risk factor for FTD.

METHODS

A total of 16 studies were included in this systematic review. Five studies described biological and/or neurocognitive characteristics between patients with BD and FTD, and 11 studies investigated whether BD was a risk factor for FTD.

RESULTS

Individuals with FTD presented higher levels of serum neurofilament light chain, greater grey matter reduction in frontal, parietal and temporal lobes, and increased slow wave oscillations in channels F3, F4, T3, T5, T4 and T6 within an electroencephalogram (EEG), relative to individuals with BD. Patients with FTD presented greater deficits in executive function and theory of mind compared to patients with BD in a euthymic state, and more deficits in verbal fluency compared to patients with BD in a current mood episode. Patients with BD in a current mood episode showed greater impairment in attention, working memory, verbal memory and executive function relative to individuals with FTD. In addition, retrospective studies showed that 10.2%-11.6% of patients with behavioural variant FTD (bvFTD) had a preceding history of BD.

CONCLUSION

Biological and neurocognitive characteristics help to distinguish between BD and FTD, and it may help to reach a more precise diagnosis. In addition, individuals with BD are at higher risk of developing FTD. More studies are needed to identify the predictors of the conversion between BD to FTD.

Exploring Signatures of Neurodegeneration in Early-Onset Older-Age Bipolar Disorder and Behavioral Variant Frontotemporal Dementia

Introduction: Older-age bipolar disorder (OABD) may involve neurocognitive decline and behavioral disturbances that could share features with the behavioral variant of frontotemporal dementia (bvFTD), making the differential diagnosis difficult in cases of suspected dementia.

Objective: To compare the neuropsychological profile, brain morphometry, and structural connectivity patterns between patients diagnosed with bvFTD, patients classified as OABD with an early onset of the disease (EO-OABD), and healthy controls (HC).

Methods: bvFTD patients (n = 25, age: 66 ± 7, female: 64%, disease duration: 6 ± 4 years), EO-OABD patients (n = 17, age: 65 ± 9, female: 71%, disease duration: 38 ± 8 years), and HC (n = 28, age: 62 ± 7, female: 64%) were evaluated through neuropsychological tests concerning attention, memory, executive function, praxis, and language. Brain morphometry was analyzed through surface-based morphometry (SBM), while structural brain connectivity was assessed through diffusion tensor imaging (DTI).

Results: Both bvFTD and EO-OABD patients showed lower performance in neuropsychological tests of attention, verbal fluency, working memory, verbal memory, and praxis than HC. Comparisons between EO-OABD and bvFTD showed differences limited to cognitive flexibility delayed recall and intrusion errors in the memory test. SBM analysis demonstrated that several frontal, temporal, and parietal regions were altered in both bvFTD and EO-OABD compared to HC. In contrast, comparisons between bvFTD and EO-OABD evidenced differences exclusively in the right temporal pole and the left entorhinal cortex. DTI analysis showed alterations in association and projection fibers in both EO-OABD and bvFTD patients compared to HC. Commissural fibers were found to be particularly affected in EO-OABD. The middle cerebellar peduncle and the pontine crossing tract were exclusively altered in bvFTD. There were no significant differences in DTI analysis between EO-OABD and bvFTD.

Discussion: EO-OABD and bvFTD may share an overlap in cognitive, brain morphometry, and structural connectivity profiles that could reflect common underlying mechanisms, even though the etiology of each disease can be different and multifactorial.

Older Age Bipolar Disorder

Further understanding of older age bipolar disorder (OABD) may lead to more specific recommendations for treatment adjusted to the specific characteristics and needs caused by age-related somatic and cognitive changes. Late-onset mania has a broad differential diagnosis and requires full psychiatric and somatic work-up, including brain imaging. Research on pharmacotherapy in OABD is limited. First-line treatment of OABD is similar to that for adult bipolar disorder (BD), with specific attention to vulnerability to side effects and somatic comorbidity. Because findings in younger adults with BD cannot be extrapolated to OABD, more research in OABD is warranted.

Intermediate lengths of the C9ORF72 hexanucleotide repeat expansion may synergistically contribute to attention deficit hyperactivity disorder in child and his father: case report

We have summarized the abstract section as follows: "We report a son and his father affected by Attention Deficit Hyperactivity Disorder (ADHD). They belonged to a larger cohort (116 ADHD children, 20 related parents, 77 controls) wholly genotyped forC9ORF72 expansion. Ten ADHD susceptibility genes were further investigated in the family. We revealed that son and father shared an intermediateC9ORF72 expansion and common variants inCDH23, ITGAE and MTRR. Bioinformatics highlighted aC9ORF72-MTRR interaction. This case-report underlines that in relatives with ADHD, carrying variants in ADHD susceptibility genes, the intermediateC9ORF72 repeats might have a potentially pathogenetic synergistic effect, supporting the multifactorial polygenic aetiopathogenetic profile of disease".

Survival and Prognostic Factors in C9orf72 Repeat Expansion Carriers: A Systematic Review and Meta-analysis

Importance

The c9orf72 repeat expansion (c9 or c9orf72RE) confers a survival disadvantage in amyotrophic lateral sclerosis (ALS); its effect on prognosis in frontotemporal dementia (FTD) remains uncertain. Data on prognostic factors in c9orf72RE disorders could inform patient care, genetic counseling, and trial design.

Objective

To examine prognostic factors in c9ALS, c9FTD, c9ALS-FTD, and atypical phenotypes.

Data Sources

The MEDLINE, Embase, Amed, ProQuest, PsychINFO, CINAHL, and LILACS databases were searched between January 2011 and January 2019. Keywords used were c9orf72 and chromosome 9 open reading frame 72. Reference lists, citations of eligible studies, and review articles were also searched by hand.

Study Selection

Studies reporting disease duration for patients with a confirmed c9orf72RE and a neurological and/or psychiatric disorder were included. A second author independently reviewed studies classified as irrelevant by the first author. Analysis began in January 2019.

Data Extraction and Synthesis

Data were extracted by 1 author; a further author independently extracted 10% of data. Data were synthesized in univariate and multivariable Cox regression and are displayed as hazard ratios (HR) and 95% confidence intervals.

Main Outcomes and Measures

Survival after symptom onset.

Results

Overall, 206 studies reporting on 1060 patients were included from 2878 publications identified (c9ALS: n = 455; c9FTD: n = 296; c9ALS-FTD: n = 198; atypical phenotypes: n = 111); 197 duplicate cases were excluded. The median (95% CI) survival (in years) differed significantly between patients with c9ALS (2.8 [2.67-3.00]), c9FTD (9.0 [8.09-9.91]), and c9ALS-FTD (3.0 [2.73-3.27]); survival in atypical phenotypes varied substantially. Older age at onset was associated with shorter survival in c9ALS (HR, 1.03; 95% CI, 1.02-1.04; P < .001), c9FTD (HR, 1.04; 95% CI, 1.02-1.06; P < .001), and c9ALS-FTD (HR, 1.02; 95% CI, 1.004-1.04; P = .016). Bulbar onset was associated with shorter survival in c9ALS (HR, 1.64; 95% CI, 1.27-2.08; P < .001). Age at onset and bulbar onset ALS remained significant in multivariable regression including variables indicating potential diagnostic ascertainment bias, selection bias, and reporting bias. Family history, sex, study continent, FTD subtype, or the presence of additional pathogenic sequence variants were not significantly associated with survival. Clinical phenotypes in patients with neuropathologically confirmed frontotemporal lobar degeneration-TDP-43, motor neuron disease-TDP-43 and frontotemporal lobar degeneration-motor neuron disease-TDP-43 were heterogenous and impacted on survival.

Conclusions and Relevance

Several factors associated with survival in c9orf72RE disorders were identified. The inherent limitations of our methodological approach must be considered; nonetheless, the reported prognostic factors were not significantly associated with the bias indicators examined.

Degenerative dementias: Alterations of emotions and mood disorders

Degenerative dementias such as Alzheimer's disease and frontotemporal dementia result in distinct alterations in emotional processing, emotional experiences, and mood. The neuropathology of these dementias extends to structures involved in emotional processing, including the basolateral limbic network (orbitofrontal cortex, anterior temporal lobe, amygdala, and thalamus), the insula, and ventromedial frontal lobe. Depression is the most common emotion and mood disorder affecting patients with Alzheimer's disease. The onset of depression can be a prodromal sign of this dementia. Anxiety can also be present early in the course of Alzheimer's disease and especially among patients with early-onset forms of the disease. In contrast, patients with behavioral variant frontotemporal dementia demonstrate hypoemotionality, deficits in the recognition of emotion, and decreased psychophysiological reactivity to emotional stimuli. They typically have a disproportionate impairment in emotional and cognitive empathy. One other unique feature of behavioral variant frontotemporal dementia is the frequent occurrence of bipolar disorder. The management strategies for these alterations of emotion and mood in degenerative dementias primarily involve the judicious use of the psychiatric armamentarium of medications.

The carboxyl termini of RAN translated GGGGCC nucleotide repeat expansions modulate toxicity in models of ALS/FTD

An intronic hexanucleotide repeat expansion in C9ORF72 causes familial and sporadic amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). This repeat is thought to elicit toxicity through RNA mediated protein sequestration and repeat-associated non-AUG (RAN) translation of dipeptide repeat proteins (DPRs). We generated a series of transgenic Drosophila models expressing GGGGCC (G₄C₂) repeats either inside of an artificial intron within a GFP reporter or within the 5' untranslated region (UTR) of GFP placed in different downstream reading frames. Expression of 484 intronic repeats elicited minimal alterations in eye morphology, viability, longevity, or larval crawling but did trigger RNA foci formation, consistent with prior reports. In contrast, insertion of repeats into the 5' UTR elicited differential toxicity that was dependent on the reading frame of GFP relative to the repeat. Greater toxicity correlated with a short and unstructured carboxyl terminus (C-terminus) in the glycine-arginine (GR) RAN protein reading frame. This change in C-terminal sequence triggered nuclear accumulation of all three RAN DPRs. A similar differential toxicity and dependence on the GR C-terminus was observed when repeats were expressed in rodent neurons. The presence of the native C-termini across all three reading frames was partly protective. Taken together, these findings suggest that C-terminal sequences outside of the repeat region may alter the behavior and toxicity of dipeptide repeat proteins derived from GGGGCC repeats.

Bipolar Disorder Among Patients Diagnosed With Frontotemporal Dementia

OBJECTIVE

Previous studies have documented manic and hypomanic symptoms in behavioral variant frontotemporal dementia (bvFTD), suggesting a relationship between bipolar disorder and bvFTD.

METHODS

The investigators conducted a literature review as well as a review of the psychiatric histories of 137 patients with bvFTD, and patients with a prior diagnosis of bipolar disorder were identified. The clinical characteristics of patients' bipolar disorder diagnosis, family history, features of bvFTD, and results from fluorodeoxyglucose positron emission tomography (FDG-PET), as well as autopsy findings, were evaluated.

RESULTS

Among the 137 patients, 14 (10.2%) had a psychiatric diagnosis of bipolar disorder, eight of whom met criteria for bipolar disorder (type I, N=6; type II, N=2) 6-12 years preceding onset of classic symptoms of progressive bvFTD. Seven of the eight patients with bipolar disorder had a family history of mood disorders, four had bitemporal predominant hypometabolism on FDG-PET, and two had a tauopathy involving temporal lobes on autopsy. Three additional patients with late-onset bipolar I disorder proved to have a nonprogressive disorder mimicking bvFTD. The remaining three patients with bvFTD had prior psychiatric symptoms that did not meet criteria for a diagnosis of bipolar disorder. The literature review and the findings for one patient further suggested a shared genetic mutation in some patients.

CONCLUSIONS

Manic or hypomanic episodes years before other symptoms of bvFTD may be a prodrome of this dementia, possibly indicating anterior temporal involvement in bvFTD. Other patients with late-onset bipolar disorder exhibit the nonprogressive frontotemporal dementia phenocopy syndrome. Finally, a few patients with bvFTD have a genetic predisposition for both disorders.

Behavioral variant frontotemporal dementia in patients with previous severe mental illness: a systematic and critical review

ABSTRACT Objectives: To explore the relationship between severe/serious mental illness (SMI) and the behavioral variant of frontotemporal dementia (bvFTD), as the patterns of symptoms and cognitive performance that characterize both disorders share similarities. Methods: We performed a systematic review investigating what has already been published regarding the relationship between bvFTD and SMI. Studies were selected from PubMed and LILACS databases, including those published up to February 12, 2018. The search strategy included the following terms: “frontotemporal dementia” plus “bipolar”, OR “frontotemporal dementia” plus “schizophrenia”, OR “frontotemporal dementia” plus “schizoaffective”. Publications without abstracts, case reports with absent genetic or histopathological confirmation, reviews and non-English language papers were excluded across the search process. Results: The search on PubMed retrieved 186 articles, of which 42 met eligibility criteria. On the LILACS database, none met the requirements. Generally, three major research aims were identified: 1) to look for frontotemporal lobar degeneration-associated genetic abnormalities in patients with prior SMI; 2) to compare the cognitive profile between patients affected by neurodegenerative disorders and schizophrenic patients; 3) to highlight the association between bvFTD and preceding psychiatric conditions and/or distinguish them both. The investigated mutations were found infrequently in the studied SMI samples. Cross-sectional studies comparing cognitive performance between bvFTD and psychiatric disorders mostly found no remarkable differences. There were only a few case reports identifying definite frontotemporal lobar degeneration in patients with previous psychiatric diagnoses. Conclusions: The available evidence demonstrates how fragile the current understanding is regarding the association between bvFTD and prior SMI.

A review on shared clinical and molecular mechanisms between bipolar disorder and frontotemporal dementia

Mental disorders are highly prevalent and important causes of medical burden worldwide. Co-occurrence of neurological and psychiatric symptoms are observed among mental disorders, representing a challenge for their differential diagnosis. Psychiatrists and neurologists have faced challenges in diagnosing old adults presenting behavioral changes. This is the case for early frontotemporal dementia (FTD) and bipolar disorder. In its initial stages, FTD is characterized by behavioral or language disturbances in the absence of cognitive symptoms. Consequently, patients with the behavioral subtype of FTD (bv-FTD) can be initially misdiagnosed as having a psychiatric disorder, typically major depression disorder (MDD) or bipolar disorder (BD). Bipolar disorder is associated with a higher risk of dementia in older adults and with cognitive impairment, with a subset of patients presents a neuroprogressive pattern during the disease course. No mendelian mutations were identified in BD, whereas three major genetic causes of FTD have been identified. Clinical similarities between BD and bv-FTD raise the question whether common molecular pathways might explain shared clinical symptoms. Here, we reviewed existing data on clinical and molecular similarities between BD and FTD to propose biological pathways that can be further investigated as common or specific markers of BD and FTD.

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.

Older Age Bipolar Disorder

Further understanding of older age bipolar disorder (OABD) may lead to more specific recommendations for treatment adjusted to the specific characteristics and needs caused by age-related somatic and cognitive changes. Late-onset mania has a broad differential diagnosis and requires full psychiatric and somatic work-up, including brain imaging. Research on pharmacotherapy in OABD is limited. First-line treatment of OABD is similar to that for adult bipolar disorder (BD), with specific attention to vulnerability to side effects and somatic comorbidity. Because findings in younger adults with BD cannot be extrapolated to OABD, more research in OABD is warranted.

Manic behavior and asymmetric right frontotemporal dementia from a novel progranulin mutation

Studies suggest a relationship of manic behavior and bipolar disorder (BD) with behavioral variant frontotemporal dementia (bvFTD). The nature of this relationship is unclear. This report presents a patient with initial manic behavior as the main manifestation of familial bvFTD from a novel progranulin (GRN) mutation. In contrast, there are other reports of a long background of BD preceding a diagnosis of bvFTD. A review of the literature and this patient suggest that manic symptoms result from damage to right frontotemporal neural structures from longstanding BD, as well as from bvFTD and other focal neurological disorders. In addition, there is a subgroup of patients with a probable genetic predisposition to both BD and bvFTD.

Update on the Epidemiology, Diagnosis, and Treatment of Mania in Older-Age Bipolar Disorder

PURPOSE OF REVIEW

The population over age 60 is growing more rapidly than the general population. Given the projected increase and need for data that can inform treatment, this review provides a brief description of newer publications focused on mania in older-age bipolar disorder (OABD), including epidemiology, diagnosis, and treatments.

RECENT FINDINGS

Age cutoffs to define OABD range from 50 to 65 years. OABD clinical presentation and course of illness is highly variable, often characterized by mood episode recurrence, medical comorbidity, cognitive deficits, and impaired functioning. There is little pharmacotherapy data on mania in OABD. Lithium and valproate have been tested in a single randomized controlled trial and there is data of more limited quality with other compounds. Treating OABD is challenging due to medical complexity, comorbidity, diminished tolerance to treatment, and a limited evidence base. More data is needed to keep pace with clinical demand.

Genetics of FTLD: overview and what else we can expect from genetic studies

Frontotemporal lobar degeneration (FTLD) comprises a highly heterogeneous group of disorders clinically associated with behavioral and personality changes, language impairment, and deficits in executive functioning, and pathologically associated with degeneration of frontal and temporal lobes. Some patients present with motor symptoms including amyotrophic lateral sclerosis. Genetic research over the past two decades in FTLD families led to the identification of three common FTLD genes (microtubule-associated protein tau, progranulin, and chromosome 9 open reading frame 72) and a small number of rare FTLD genes, explaining the disease in almost all autosomal dominant FTLD families but only a minority of apparently sporadic patients or patients in whom the family history is less clear. Identification of additional FTLD (risk) genes is therefore highly anticipated, especially with the emerging use of next-generation sequencing. Common variants in the transmembrane protein 106 B were identified as a genetic risk factor of FTLD and disease modifier in patients with known mutations. This review summarizes for each FTLD gene what we know about the type and frequency of mutations, their associated clinical and pathological features, and potential disease mechanisms. We also provide an overview of emerging disease pathways encompassing multiple FTLD genes. We further discuss how FTLD specific issues, such as disease heterogeneity, the presence of an unclear family history and the possible role of an oligogenic basis of FTLD, can pose challenges for future FTLD gene identification and risk assessment of specific variants. Finally, we highlight emerging clinical, genetic, and translational research opportunities that lie ahead. Genetic research led to the identification of three common FTLD genes with rare variants (MAPT, GRN, and C9orf72) and a small number of rare genes. Efforts are now ongoing, which aimed at the identification of rare variants with high risk and/or low frequency variants with intermediate effect. Common risk variants have also been identified, such as TMEM106B. This review discusses the current knowledge on FTLD genes and the emerging disease pathways encompassing multiple FTLD genes.

Unstable repeat expansion in major psychiatric disorders: two decades on, is dynamic DNA back on the menu?

For a period in the mid-1990s, soon after the discovery of the involvement of trinucleotide repeat expansions in fragile-X syndrome (both A and E), Huntington's disease, myotonic dystrophy, and a number of hereditary ataxias, there was a clear sense that this new disease mechanism might provide answers for psychiatric disorders. Given the then failures to replicate initial genetic linkage findings for schizophrenia (SCZ) and bipolar disorder (BD), a greater emphasis was placed on the role of complex and non-Mendelian mechanisms, and repeat instability appeared to have the potential to provide adequate explanations for numerous apparently non-Mendelian features such as anticipation, incomplete penetrance, sporadic occurrence, and nonconcordance of monozygotic twins. Initial molecular studies using a ligation-based amplification method (repeat expansion detection) appeared to support the involvement of CAG•CTG repeat expansion in SCZ and BD. However, subsequent studies that dissected the large repeats responsible for much of the positive signal showed that there were three main loci where CAG•CTG repeat expansion was occurring (on 13q21.33, 17q21.33-q22, and 18q21.2). None of the expansions at these loci appeared to segregate with SCZ or BD, and research into repeat expansions in psychiatric illness petered out in the early 2000s. The 13q expansion occurs within a noncoding RNA and appears to be associated with spinocerebellar ataxia 8 (SCA8), but with a still unexplained dichotomy in penetrance - either very high or very low. The 17q expansion occurs within an intron of the carbonic anhydrase-like gene, CA10. The 18q expansion is located within an intron of the TCF4 gene. Mutations in TCF4 are a known cause of Pitt-Hopkins syndrome. Also, pertinently, genome-wide association studies have shown a well-replicated association between TCF4 and SCZ. Two decades on, in 2016, it appears to be an appropriate juncture to reflect on what we have learned, and, with the arrival of newer technologies, whether there is any mileage to be made in revisiting the unstable DNA hypothesis for psychiatric illness.

The Confluence of Psychiatric Symptoms and Neurodegenerative Disease: Impact on Genetic Counseling

Hereditary neurodegenerative diseases can present with a psychiatric prodrome that overlaps with psychiatric symptoms that are not primary to these diseases. When individuals present for predictive testing while experiencing such symptoms, clinicians including genetic counselors, must proceed with caution and evaluate each situation on a case-by-case basis. Legitimate reasons may exist for moving forward with testing. Additionally predicting the consequences of testing is unrealistic so that the clinicians must do their best to prepare patients for both positive and negative results. A multidisciplinary team following the Huntington disease protocol remains the gold standard care for predictive testing for such patients. We discuss 3 case histories that demonstrate the complex nature of genetic counseling and testing in the presence of psychiatric symptoms, whether emanating from the disease itself or the results of living in an affected family.

Psychiatric disorders prior to amyotrophic lateral sclerosis

It is recognized that neuropsychiatric conditions are overrepresented in amyotrophic lateral sclerosis (ALS) patient kindreds and psychiatric symptoms may precede the onset of motor symptoms. Using a hospital record linkage database, hospitalization with a diagnosis of schizophrenia, bipolar disorder, depression, or anxiety was significantly associated with a first diagnosis of ALS within the following year. This is likely to specifically reflect the clinicopathological overlap of ALS with frontotemporal dementia. A diagnosis of depression was significantly associated with a first record of ALS ≥5 years later, in keeping with growing evidence for major depressive disorder as an early marker of cerebral neurodegeneration. Ann Neurol 2016;80:935-938.

Hair Cell Loss, Spiral Ganglion Degeneration, and Progressive Sensorineural Hearing Loss in Mice with Targeted Deletion of Slc44a2/Ctl2

SLC44A2 (solute carrier 44a2), also known as CTL2 (choline transporter-like protein 2), is expressed in many supporting cell types in the cochlea and is implicated in hair cell survival and antibody-induced hearing loss. In mice with the mixed C57BL/6-129 background, homozygous deletion of Slc44a2 exons 3–10 (Slc44a2^Δ/Δ) resulted in high-frequency hearing loss and hair cell death. To reduce effects associated with age-related hearing loss (ARHL) in these strains, mice carrying the Slc44a2^Δ allele were backcrossed to the ARHL-resistant FVB/NJ strain and evaluated after backcross seven (N7) (99 % FVB). Slc44a2^Δ/Δ mice produced abnormally spliced Slc44a2 transcripts that contain a frameshift and premature stop codons. Neither full-length SLC44A2 nor a putative truncated protein could be detected in Slc44a2^Δ/Δ mice, suggesting a likely null allele. Auditory brain stem responses (ABRs) of mice carrying the Slc44a2^Δ allele on an FVB/NJ genetic background were tested longitudinally between the ages of 2 and 10 months. By 6 months of age, Slc44a2^Δ/Δ mice exhibited hearing loss at 32 kHz, but at 12 and 24 kHz had sound thresholds similar to those of wild-type Slc44a2^+/+ and heterozygous +/Slc44a2^Δ mice. After 6 months of age, Slc44a2^Δ/Δ mutants exhibited progressive hearing loss at all frequencies and +/Slc44a2^Δ mice exhibited moderate threshold elevations at high frequency. Histologic evaluation of Slc44a2^Δ/Δ mice revealed extensive hair cell and spiral ganglion cell loss, especially in the basal turn of the cochlea. We conclude that Slc44a2 function is required for long-term hair cell survival and maintenance of hearing.

High-resolution chromosome ideogram representation of recognized genes for bipolar disorder

Bipolar disorder (BPD) is genetically heterogeneous with a growing list of BPD associated genes reported in recent years resulting from increased genetic testing using advanced genetic technology, expanded genomic databases, and better awareness of the disorder. We compiled a master list of recognized susceptibility and genes associated with BPD identified from peer-reviewed medical literature sources using PubMed and by searching online databases, such as OMIM. Searched keywords were related to bipolar disorder and genetics. Our compiled list consisted of 290 genes with gene names arranged in alphabetical order in tabular form with source documents and their chromosome location and gene symbols plotted on high-resolution human chromosome ideograms. The identified genes impacted a broad range of biological pathways and processes including cellular signaling pathways particularly cAMP and calcium (e.g., CACNA1C, CAMK2A, CAMK2D, ADCY1, ADCY2); glutamatergic (e.g., GRIK1, GRM3, GRM7), dopaminergic (e.g., DRD2, DRD4, COMT, MAOA) and serotonergic (e.g., HTR1A, HTR2A, HTR3B) neurotransmission; molecular transporters (e.g., SLC39A3, SLC6A3, SLC8A1); and neuronal growth (e.g., BDNF, IGFBP1, NRG1, NRG3). The increasing prevalence of BPD calls for better understanding of the genetic etiology of this disorder and associations between the observed BPD phenotype and genes. Visual representation of genes for bipolar disorder becomes a tool enabling clinical and laboratory geneticists, genetic counselors, and other health care providers and researchers easy access to the location and distribution of currently recognized BPD associated genes. Our study may also help inform diagnosis and advance treatment developments for those affected with this disorder and improve genetic counseling for families.

The clinical spectrum of sporadic and familial forms of frontotemporal dementia

The term frontotemporal dementia (FTD) describes a clinically, genetically and pathologically diverse group of neurodegenerative disorders. Symptoms of FTD can present in individuals in their 20s through to their 90s, but the mean age at onset is in the sixth decade. The most common presentation is with a change in personality and impaired social conduct (behavioural variant FTD). Less frequently patients present with language problems (primary progressive aphasia). Both of these groups of patients can develop motor features consistent with either motor neuron disease (usually the amyotrophic lateral sclerosis variant) or parkinsonism (most commonly a progressive supranuclear palsy or corticobasal syndrome). In about a third of cases FTD is familial, with mutations in the progranulin, microtubule-associated protein tau and chromosome 9 open reading frame 72 genes being the major causes. Mutations in a number of other genes including TANK-binding kinase 1 are rare causes of familial FTD. This review aims to clarify the often confusing terminology of FTD, and outline the various clinical features and diagnostic criteria of sporadic and familial FTD syndromes. It will also discuss the current major challenges in FTD research and clinical practice, and potential areas for future research. This review clarifies the terminology of frontotemporal dementia (FTD) and summarizes the various clinical features and most recent diagnostic criteria of sporadic and familial FTD syndromes. It also discusses the current major challenges in FTD research and clinical practice, and highlights potential areas for future research.

Screening for novel hexanucleotide repeat expansions at ALS- and FTD-associated loci

OBJECTIVE

To determine whether GGGGCC (G4C2) repeat expansions at loci other than C9orf72 serve as common causes of amyotrophic lateral sclerosis (ALS).

METHODS

We assessed G4C2 repeat number in 28 genes near known ALS and frontotemporal dementia (FTD) loci by repeat-primed PCR coupled with fluorescent fragment analysis in 199 patients with ALS (17 familial, 182 sporadic) and 136 healthy controls. We also obtained blood from patients with ALS4 for evaluation of repeats surrounding the SETX gene locus. C9orf72 expansions were evaluated in parallel.

RESULTS

Expansions of G4C2 repeats in C9orf72 explained 8.8% of sporadic and 47% of familial ALS cases analyzed. Repeat variance was observed at one other locus, RGS14, but no large expansions were observed, and repeat sizes were not different between cases and controls. No G4C2 repeat expansions were identified at other ALS or FTD risk loci or in ALS4 cases.

CONCLUSIONS

G4C2 expansions near known ALS and FTD loci other than C9orf72 are not a common cause of ALS.

The behavioural variant frontotemporal dementia (bvFTD) syndrome in psychiatry

The primary goal of this article is to critically discuss the syndromic overlap that exists between early behavioural variant frontotemporal dementia (bvFTD)--the most common clinical syndrome associated with frontotemporal lobar degeneration (FTLD)--and several primary psychiatric disorders. We begin by summarising the current state of knowledge regarding FTLD, including the recent discovery of FTLD-causative genetic mutations. Clinicopathological correlations in FTLD are subsequently discussed, while emphasising that clinical syndromes of FTD are dictated by the distribution of FTLD pathology in the brain. We then review a large number of cases with suspected and confirmed bvFTD that had previously been diagnosed with a primary psychiatric disorder. The clinical and neuroscientific implications of this overlap are discussed, focusing on the importance of early diagnosis for clinical and therapeutic reasons. We propose that largely due to the paucity of biomarkers for primary psychiatric disorders, and the limited use of FTLD-related biomarkers by psychiatrists at present, it is very difficult to separate patients with early bvFTD from those with primary psychiatric disorders based on clinical grounds. Furthermore, specific limitations of the Diagnostic and Statistical Manual of Mental Disorders (DSM) 5 criteria for bvFTD may inadvertently discourage recognition of bvFTD in mental health settings. Clinically, more research is needed to develop tools that allow early differentiation of bvFTD from primary psychiatric disease, as bvFTD therapies will likely be most effective in the earliest stages of disease. From a neuroscience perspective, we argue that bvFTD provides an excellent paradigm for investigating the neural basis of psychiatric disorders.

Late life bipolar disorder evolving into frontotemporal dementia mimic

OBJECTIVES

Although bipolar disorder has been understood classically as a cyclic disease with full recovery between mood episodes, in the last decade, evidence has accumulated supporting progressive features. The clinical picture of advanced or end-stage bipolar disorder is heterogeneous with possible deficits in cognition and behavior, as illustrated by our case series.

CASES

From our neuropsychiatric outpatient clinic, we describe four cases with bipolar disorder gradually developing a clinical syndrome, including apathy, disinhibition, loss of empathy, stereotypical behavior, and compulsiveness, fulfilling the criteria for possible behavioral variant frontotemporal dementia. All cases were diagnosed with bipolar 1 disorder at least 10 years before the onset of the current symptoms, which were not due to recent mood episodes or switches of medication. In all cases, 3-7 years of follow-up yielded no progression. Repeated neuroimaging was within normal limits. Cerebrospinal fluid biomarker studies were not supportive of underlying neurodegenerative pathology. C9orf72 mutation status was negative in all cases.

CONCLUSION

Symptoms fitting the criteria for possible behavioral variant frontotemporal dementia may be present in end-stage of bipolar disorder. An alternative neurodegenerative nature seems unlikely based on repeated normal neuroimaging and the absence of clinical progression. Functional involvement of the frontal-subcortical networks might play a role.

Large-scale screening in sporadic amyotrophic lateral sclerosis identifies genetic modifiers in C9orf72 repeat carriers

Sporadic amyotrophic lateral sclerosis (ALS) is considered to be a complex disease with multiple genetic risk factors contributing to the pathogenesis. Identification of genetic risk factors that co-occur frequently could provide relevant insight into underlying mechanisms of motor neuron degeneration. To dissect the genetic architecture of sporadic ALS, we undertook a large sequencing study in 755 apparently sporadic ALS cases and 959 controls, analyzing 10 ALS genes: SOD1, C9orf72, TARDBP, FUS, ANG, CHMP2B, ATXN2, NIPA1, SMN1, and UNC13A. We observed sporadic cases with multiple genetic risk variants in 4.1% compared with 1.3% in controls. The overall difference was not in excess of what is to be expected by chance (binomial test, p = 0.59). We did, however, observe a higher frequency than expected of C9orf72 repeat carriers with co-occurring susceptibility variants (ATXN2, NIPA1, and SMN1; p = 0.001), which is mainly because of the co-occurrence of NIPA1 repeats in 15% of C9orf72 repeat carriers (p = 0.006).

Expression of microRNAs in human post-mortem amyotrophic lateral sclerosis spinal cords provides insight into disease mechanisms

Amyotrophic lateral sclerosis is a late-onset and terminal neurodegenerative disease. The majority of cases are sporadic with unknown causes and only a small number of cases are genetically linked. Recent evidence suggests that post-transcriptional regulation and epigenetic mechanisms, such as microRNAs, underlie the onset and progression of neurodegenerative disorders; therefore, altered microRNA expression may result in the dysregulation of key genes and biological pathways that contribute to the development of sporadic amyotrophic lateral sclerosis. Using systems biology analyses on postmortem human spinal cord tissue, we identified dysregulated mature microRNAs and their potential targets previously implicated in functional process and pathways associated with the pathogenesis of ALS. Furthermore, we report a global reduction of mature microRNAs, alterations in microRNA processing, and support for a role of the nucleotide binding protein, TAR DNA binding protein 43, in regulating sporadic amyotrophic lateral sclerosis-associated microRNAs, thereby offering a potential underlying mechanism for sporadic amyotrophic lateral sclerosis.

Emerging role of RNA•DNA hybrids in C9orf72-linked neurodegeneration

RNA plays an active role in structural polymorphism of the genome through the formation of stable RNA•DNA hybrids (R-loops). R-loops can modulate normal physiological processes and are also associated with pathological conditions, such as those related to nucleotide repeat expansions. A guanine-rich hexanucleotide repeat expansion in chromosome 9 open reading frame 72 (C9orf72) has been linked to a spectrum of neurological conditions including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we discuss the possible roles, both locally and genome-wide, of R-loops that may arise from the C9orf72 hexanucleotide repeat. R-loops have the potential to influence the pathological processes identified in many repeat expansion diseases, such as repeat instability, transcriptional dysregulation, epigenetic modification, and antisense-mediated gene regulation. We propose that, given the wide-ranging consequences of R-loops in the cell, these structures could underlie multiple pathological processes in C9orf72-linked neurodegeneration.

Post-Mortem evaluation of amyloid-dopamine terminal positron emission tomography dementia classifications

Clinical classification of early dementia and mild cognitive impairment (MCI) is imprecise. We reported previously that molecular imaging classification of early dementia and MCI with dual amyloid and dopamine terminal positron emission tomography differs significantly from expert clinical classification. We now report pathological diagnoses in a substantial subset of our previously imaged subjects. Among 36 subjects coming to autopsy, imaging classifications and pathological diagnosis were concordant in 33 cases (κ = 0.85). This approach enhanced specificity of Alzheimer's disease diagnosis. The strong concordance of imaging-based classifications and pathological diagnoses suggests that this imaging approach will be useful in establishing more accurate and convenient classification biomarkers for dementia research.

C9orf72-related disorders: expanding the clinical and genetic spectrum of neurodegenerative diseases

Neurodegenerative diseases represent a heterogeneous group of neurological conditions primarily involving dementia, motor neuron disease and movement disorders. They are mostly related to different pathophysiological processes, notably in family forms in which the clinical and genetic heterogeneity are lush. In the last decade, much knowledge has been acumulated about the genetics of neurodegenerative diseases, making it essential in cases of motor neuron disease and frontotemporal dementia the repeat expansions of C9orf72 gene. This review analyzes the main clinical, radiological and genetic aspects of the phenotypes related to the hexanucleotide repeat expansions (GGGGCC) of C9orf72 gene. Future studies will aim to further characterize the neuropsychological, imaging and pathological aspects of the extra-motor features of motor neuron disease, and will help to provide a new classification system that is both clinically and biologically relevant.

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.

Screening a UK amyotrophic lateral sclerosis cohort provides evidence of multiple origins of the C9orf72 expansion

An expanded hexanucleotide repeat in the C9orf72 gene is the most common genetic cause of amyotrophic lateral sclerosis and frontotemporal dementia (C9ALS/FTD). Although 0-30 hexanucleotide repeats are present in the general population, expansions >500 repeats are associated with C9ALS/FTD. Large C9ALS/FTD expansions share a common haplotype and whether these expansions derive from a single founder or occur more frequently on a predisposing haplotype is yet to be determined and is relevant to disease pathomechanisms. Furthermore, although cases carrying 50-200 repeats have been described, their role and the pathogenic threshold of the expansions remain to be identified and carry importance for diagnostics and genetic counseling. We present clinical and genetic data from a UK ALS cohort and report the detailed molecular study of an atypical somatically unstable expansion of 90 repeats. Our results across different tissues provide evidence for the pathogenicity of this repeat number by showing they can somatically expand in the central nervous system to the well characterized pathogenic range. Our results support the occurrence of multiple expansion events for C9ALS/FTD.

No abnormal hexanucleotide repeat expansion of C9ORF72 in Japanese schizophrenia patients

Abnormal hexanucleotide repeat expansion of C9ORF72 is known to cause neurodegenerative disorders such as frontotemporal dementia. Additionally, patients with psychotic symptoms are more likely to have abnormal hexanucleotide repeat expansion than are patients without them. We investigated the hexanucleotide repeat sizes of C9ORF72 in 466 Japanese schizophrenia patients. We found no abnormal hexanucleotide repeat expansion. In conclusion, C9ORF72 may not be responsible for schizophrenia susceptibility in the Japanese population.

Familial benign frontotemporal deterioration with C9ORF72 hexanucleotide expansion

BACKGROUND

In recent years, a benign variant of frontotemporal lobar degeneration (FTLD) has been recognized, with a particularly slow progression of cognitive deficits and scarce frontotemporal atrophy or hypoperfusion in neuroimaging studies. Patients with FTLD have been considered "phenocopies," with an underlying nondegenerative neurologic process.

RESULTS

We report the first family with three affected members having benign FTLD associated with C9ORF72 gene hexanucleotide expansion. Onset of symptoms occurred during the fifth decade, with naming and memory problems as the main features. Two siblings have stabilized at mild cognitive impairment or incipient dementia for more than a decade, and remain quite independent for their activities of daily living at the current ages of 69 and 65 years, respectively. Their mother's cognitive deterioration evolved slowly during >30 years.

CONCLUSION

This family demonstrates that a benign evolution can be part of the growing spectrum of clinical phenotypes associated with neurodegenerative diseases caused by the C9ORF72 hexanucleotide expansion. Screening of this genetic marker should be considered in cases with this slow deterioration, especially if there is a family history.

C9ORF72 hexanucleotide repeat expansion is a rare cause of schizophrenia

A hexanucleotide repeat expansions in the first intron of C9ORF72 has been shown to be responsible for a high number of familial cases of amyotrophic lateral sclerosis and/or frontotemporal lobar degeneration. The same mutation has been described in a patient with bipolar disorder, but up to now, not in patients suffering from schizophrenia. We determined the frequency of the C9ORF72 hexanucleotide repeat expansions in a population of 298 patients with schizophrenia or schizoaffective disorder. The pathogenic repeat expansion was detected in 2 patients (0.67%). Both of them presented with auditory hallucinations and had comorbid alcohol abuse. In addition, a positive family history for psychiatric and/or neurodegenerative diseases was present. The repeat expansion in the C9ORF72 gene is a rare, but possible, cause of schizophrenic spectrum disorders. We cannot rule out however whether the number of repeats influence the phenotype.