Discovery and validation of dominantly inherited Alzheimer\u27s disease mutations in populations from Latin America

BACKGROUND: In fewer than 1% of patients, AD is caused by autosomal dominant mutations in either the presenilin 1 (PSEN1), presenilin 2 (PSEN2), or amyloid precursor protein (APP) genes. The full extent of familial AD and frequency of these variants remains understudied in Latin American (LatAm) countries. Due to the rare nature of these variants, determining the pathogenicity of a novel variant in these genes can be challenging. Here, we use a systematic approach to assign the likelihood of pathogenicity in variants from densely affected families in Latin American populations. METHODS: Clinical data was collected from LatAm families at risk for DIAD. Symptomatic family members were identified and assessed by local clinicians and referred for genetic counseling and testing. To determine the likelihood of pathogenicity among variants of unknown significance from LatAm populations, we report pedigree information, frequency in control populations, in silico predictions, and cell-based models of amyloid-beta ratios. RESULTS: We identified five novel variants in the presenilin1 (PSEN1) gene from Brazilian and Mexican families. The mean age at onset in newly identified families was 43.5 years (range 36-54). PSEN1 p.Val103_Ser104delinsGly, p.Lys395Ile, p.Pro264Se, p.Ala275Thr, and p.Ile414Thr variants have not been reported in PubMed, ClinVar, and have not been reported in dominantly inherited AD (DIAD) families. We found that PSEN1 p.Val103_Ser104delinsGly, p.Lys395Ile, p.Pro264Se, and p.Ala275Thr produce Aβ profiles consistent with known AD pathogenic mutations. PSEN1 p.Ile414Thr did not alter Aβ in a manner consistent with a known pathogenic mutation. CONCLUSIONS: Our study provides further insights into the genetics of AD in LatAm. Based on our findings, including clinical presentation, imaging, genetic, segregations studies, and cell-based analysis, we propose that PSEN1 p.Val103_Ser104delinsGly, p.Lys395Ile, p.Pro264Se, and p.Ala275Thr are likely pathogenic variants resulting in DIAD, whereas PSEN1 p.Ile414Thr is likely a risk factor. This report is a step forward to improving the inclusion/engagement of LatAm families in research. Family discovery is of great relevance for the region, as new initiatives are underway to extend clinical trials and observational studies to families living with DIAD

The impact of SARS-CoV-2 in dementia across Latin America : A call for an urgent regional plan and coordinated response

The SARS-CoV-2 global pandemic will disproportionately impact countries with weak economies and vulnerable populations including people with dementia. Latin American and Caribbean countries (LACs) are burdened with unstable economic development, fragile health systems, massive economic disparities, and a high prevalence of dementia. Here, we underscore the selective impact of SARS-CoV-2 on dementia among LACs, the specific strain on health systems devoted to dementia, and the subsequent effect of increasing inequalities among those with dementia in the region. Implementation of best practices for mitigation and containment faces particularly steep challenges in LACs. Based upon our consideration of these issues, we urgently call for a coordinated action plan, including the development of inexpensive mass testing and multilevel regional coordination for dementia care and related actions. Brain health diplomacy should lead to a shared and escalated response across the region, coordinating leadership, and triangulation between governments and international multilateral networks

Dementia in Latin America : paving the way towards a regional action plan

Regional challenges faced by Latin American and Caribbean countries (LACs) to fight dementia, such as heterogeneity, diversity, political instabilities, and socioeconomic disparities, can be addressed more effectively grounded in a collaborative setting based on the open exchange of knowledge. In this work, the Latin American and Caribbean Consortium on Dementia (LAC-CD) proposes an agenda for integration to deliver a Knowledge to Action Framework (KtAF). First, we summarize evidence-based strategies (epidemiology, genetics, biomarkers, clinical trials, nonpharmacological interventions, networking and translational research) and align them to current global strategies to translate regional knowledge into actions with transformative power. Then, by characterizing genetic isolates, admixture in populations, environmental factors, and barriers to effective interventions and mapping these to the above challenges, we provide the basic mosaics of knowledge that will pave the way towards a KtAF. We describe strategies supporting the knowledge creation stage that underpins the translational impact of KtAF

Mutations in GRN and plasma progranulin levels in a Brazilian cohort of Frontotemporal Lobar Degeneration

Introdução: A demência frontotemporal (DFT) inclui a variante comportamental da demência frontotemporal (vcDFT), a variante semântica da afasia progressiva primária (vsAPP), e a variante não fluente da APP (vnfAPP). Os genes em que são encontradas mutações causadoras de DFT mais frequentemente são: GRN (que codifica a progranulina), MAPT (que codifica a proteína tau) e C9orf72. Métodos: Foram incluídos probandos diagnosticados com vcDFT, vsAPP ou vnfAPP, com base com os critérios diagnósticos mais recentes, e um grupo de indivíduos cognitivamente normais. Os éxons 2-12 de GRN e os éxons 1, 9-13 de MAPT foram sequenciados pelo método de Sanger, e foi realizada dosagem de progranulina no plasma. Resultados: foram incluídos 62 probandos, sendo 44 com vcDFT, 9 com vsAPP, e 9 com vnfAPP. Antecedente familiar de demência foi positivo em 45,1% dos probandos, e de DFT, em 24,1%. Os 60 indivíduos do grupo controle tinham idade média de 60,8±8,5 anos. Foram identificadas seis mutações nulas em GRN (p.Q130X, p.V200Gfs*18, p.Q257Pfs*26, p.Q300X, p.S301Cfs*60 e p.D317Afs*11) e uma mutação patogênica em MAPT (p.N279K). A dosagem média de progranulina plasmática nos pacientes com mutações de GRN foi de 29,8±11,9ng/ml Conclusões: A frequência de mutações patogênicas em GRN nesta casuística foi de 9,6%, e a de mutações em MAPT foi de 1,6%. Entre casos familiais de DFT, a frequência de mutações em GRN foi de 33,3%, e em MAPT foi de 6,7%. Duas das mutações encontradas em GRN (p.Q130X e p.D317Afs*11) ainda não foram descritas em casos de DFT. O valor de corte de 70ng/ml identificou as mutações nulas de GRN com sensibilidade e especificidade de 100%Introduction: Frontotemporal dementia (FTD) encompasses behavioral variant of frontotemporal dementia (bvFTD), semantic variant of primary progressive aphasia (svPPA), and nonfluent variant PPA (nfvPPA). The genes in which FTD-causing mutations are most frequently found are: GRN (which encodes progranulin), MAPT (which encodes tau protein) and C9orf72. Methods: We included probands diagnosed with bvFTD, svPPA or nfvPPA, based on the most recent diagnostic criteria, and a group of cognitively normal individuals. GRN exons 2-12 and MAPT exons 1, 9-13 were sequenced by the Sanger method, and plasma progranulin levels were measured. Results: we included 62 probands (44 with bvFTD, 9 with svPPA, and 9 with nfvPPA). Family history of dementia was positive in 45.1% of probands, and of DFT, in 24.1%. The control group of 60 individuals had a mean age of 60.8±8.5 years. Six null GRN mutations were identified in (p.Q130X, p.V200Gfs*18, p.Q257Pfs*26, p.Q300X, p.S301Cfs*60 e p.D317Afs*11) and one MAPT pathogenic mutation (p.N279K). The mean plasma progranulin level in patients with GRN mutations was 29.8±11,9ng/ml. Conclusions: The frequency of pathogenic mutations in GRN was 9.6%, and of MAPT mutations was 1.6%. Among cases of familial FTD, the frequency of GRN mutations was 33.3%, and of MAPT mutations was 6.7%. Two of the mutations found in GRN (p.Q130X and p.D317Afs*11) are novel. The cutoff value of 70ng/ml identified null GRN mutations with sensitivity and specificity of 100

Neuropathology of frontotemporal lobar degeneration: A review

ABSTRACT Frontotemporal lobar degeneration (FTLD) is the second most common cause of presenile dementia. Three main clinical variants are widely recognized within the FTLD spectrum: the behavioural variant of frontotemporal dementia (bvFTD), semantic dementia (SD) and progressive non-fluent aphasia (PNFA). FTLD represents a highly heterogeneous group of neurodegenerative disorders which are best classified according to the main protein component of pathological neuronal and glial inclusions. The most common pathological class of FTLD is associated with the TDP-43 protein (FTLD-TDP), while FTLD-Tau is considered slightly less common while the FTLD-FUS (Fused in sarcoma protein) pathology is rare. In this review, these three major pathological types of FTLD are discussed

Charles Bonnet Syndrome: Case series

Abstract Since its first description in 1760, Charles Bonnet syndrome (CBS) has been reported in many studies. The main characteristics are visual hallucinations, preserved awareness of unreal visions, and absence of psychotic symptoms. CBS can occur with lesions located anywhere along the central visual pathway, from the eye to the calcarine fissure. Objective: To describe patients with CBS and carry out a review of the literature. Methods: Six patients with visual hallucinations were evaluated in an outpatient memory clinic between 2001 and 2008, and their clinical characteristics recorded. Results: Four patients were female, and the mean age was 74.5±16.9 years. Three patients had visual loss secondary to eye disease and three due to cerebral lesions. The visions consisted of animals, persons, moving objects, bizarre creatures or colored forms, and were considered disturbing by five patients. Five patients received treatment, and only three reported partial benefit from the therapy. Complete recovery was not seen in any of the subjects. Conclusions: CBS is relatively rare and its recognition is important to avoid misdiagnoses with psychiatric or dementing illnesses

Non-inflammatory cerebral amyloid angiopathy as a cause of rapidly progressive dementia: A case study

Abstract A 77 year-old men developed a subacute-onset, rapidly progressive cognitive decline. After 6 months of evolution, he scored 6 on the Mini-Mental State Examination and had left hemiparesis and hemineglect. The patient died 11 months after the onset of cognitive symptoms. Brain MRI showed microhemorrhages on gradient-echo sequence and confluent areas of white matter hyperintensities on T2-weighted images. Brain biopsy revealed amyloid-b peptide deposition in vessel walls, some of them surrounded by micro-bleeds. In this case report, we discuss the role of cerebral amyloid angiopathy (CAA) in cognitive decline, due to structural lesions associated with hemorrhages and infarcts, white matter lesions and co-morbidity of Alzheimer's disease, as well as the most recently described amyloid angiopathy-related inflammation