Lewy bodies are the inclusion bodies – abnormal aggregations of protein – that develop inside nerve cells affected by Parkinson's disease (PD), the Lewy body dementias, and some other disorders. They are also seen in cases of multiple system atrophy, particularly the parkinsonian variant (MSA-P).
Frontotemporal dementia (FTD), frontotemporal degeneration disease, or frontotemporal neurocognitive disorder encompasses several types of dementia involving the progressive degeneration of the brain's frontal and temporal lobes. FTDs broadly present as behavioral or language disorders with gradual onsets. Common signs and symptoms include significant changes in social and personal behavior, apathy, blunting of emotions, and deficits in both expressive and receptive language. Signs and symptoms tend to appear in late adulthood, typically between the ages of 45 and 65. Men and women appear to be equally affected. FTD is the second most prevalent type of early onset dementia after Alzheimer's disease. Currently, there is no cure, but there are treatments that help alleviate symptoms.
The tau proteins are a group of six highly soluble protein isoforms produced by alternative splicing from the gene MAPT. They have roles primarily in maintaining the stability of microtubules in axons and are abundant in the neurons of the central nervous system (CNS), where the cerebral cortex has the highest abundance. They are less common elsewhere but are also expressed at very low levels in CNS astrocytes and oligodendrocytes.
Semantic dementia (SD), also known as semantic variant primary progressive aphasia (svPPA), is a progressive neurodegenerative disorder characterized by loss of semantic memory in both the verbal and non-verbal domains. However, the most common presenting symptoms are in the verbal domain. Semantic dementia is a disorder of semantic memory that causes patients to lose the ability to match words or images to their meanings. However, it is fairly rare for patients with semantic dementia to develop category specific impairments, though there have been documented cases of it occurring. Typically, a more generalized semantic impairment results from dimmed semantic representations in the brain.
Hippocampal sclerosis (HS) or mesial temporal sclerosis (MTS) is a neuropathological condition with severe neuronal cell loss and gliosis in the hippocampus. Neuroimaging tests such as magnetic resonance imaging (MRI) and positron emission tomography (PET) may identify individuals with hippocampal sclerosis. Hippocampal sclerosis occurs in 3 distinct settings: mesial temporal lobe epilepsy, adult neurodegenerative disease and acute brain injury.
Hereditary inclusion body myopathies (HIBM) are a group of rare genetic disorders which have different symptoms. Generally, they are neuromuscular disorders characterized by muscle weakness developing in young adults. Hereditary inclusion body myopathies comprise both autosomal recessive and autosomal dominant muscle disorders that have a variable expression (phenotype) in individuals, but all share similar structural features in the muscles.
Corticobasal degeneration (CBD) is a rare neurodegenerative disease involving the cerebral cortex and the basal ganglia. CBD symptoms typically begin in people from 50 to 70 years of age, and typical survival before death is eight years. It is characterized by marked disorders in movement and cognition, and is classified as one of the Parkinson plus syndromes. Diagnosis is difficult, as symptoms are often similar to those of other disorders, such as Parkinson's disease, progressive supranuclear palsy, and dementia with Lewy bodies, and a definitive diagnosis of CBD can only be made upon neuropathologic examination.
Tauopathies are neurodegenerative diseases involving the aggregation of abnormal tau protein. Tangles are formed by hyperphosphorylation of the microtubule protein known as tau, causing the protein to dissociate from microtubules and form insoluble aggregate. Various neuropathologic phenotypes are identified based on the specific engagement of anatomical regions, cell types, and the presence of unique isoforms of tau within pathological deposits. The designation 'primary tauopathy' is assigned to disorders where the predominant feature is the deposition of tau protein. Alternatively, diseases exhibiting tau pathologies attributed to different and varied underlying causes are termed 'secondary tauopathies. Some neuropathologic phenotypes involving tau protein is Alzheimer’s disease, Pick disease, Progressive supranuclear palsy and corticobasal degeneration.
Valosin-containing protein (VCP) or transitional endoplasmic reticulum ATPase also known as p97 in mammals and CDC48 in S. cerevisiae, is an enzyme that in humans is encoded by the VCP gene. The TER ATPase is an ATPase enzyme present in all eukaryotes and archaebacteria. Its main function is to segregate protein molecules from large cellular structures such as protein assemblies, organelle membranes and chromatin, and thus facilitate the degradation of released polypeptides by the multi-subunit protease proteasome.
Granulin is a protein that in humans is encoded by the GRN gene. Each granulin protein is cleaved from the precursor progranulin, a 593 amino-acid-long and 68.5 kDa protein. While the function of progranulin and granulin have yet to be determined, both forms of the protein have been implicated in development, inflammation, cell proliferation and protein homeostasis. The 2006 discovery of the GRN mutation in a population of patients with frontotemporal dementia has spurred much research in uncovering the function and involvement in disease of progranulin in the body. While there is a growing body of research on progranulin's role in the body, studies on specific granulin residues are still limited.
RNA-binding protein FUS/TLS, also known as heterogeneous nuclear ribonucleoprotein P2 is a protein that in humans is encoded by the FUS gene.
TAR DNA-binding protein 43 is a protein that in humans is encoded by the TARDBP gene.
Transmembrane protein 106B is a protein that is encoded by the TMEM106B gene. It is found primarily within neurons and oligodendrocytes in the central nervous system with its subcellular location being in lysosomal membranes. TMEM106B helps facilitate important functions for maintaining a healthy lysosome, and therefore certain mutations and polymorphisms can lead to issues with proper lysosomal function. Lysosomes are in charge of clearing out mis-folded proteins and other debris, and thus, play an important role in neurodegenerative diseases that are driven by the accumulation of various mis-folded proteins and aggregates. Due to its impact on lysosomal function, TMEM106B has been investigated and found to be associated to multiple neurodegenerative diseases.
C9orf72 is a protein which in humans is encoded by the gene C9orf72.
Multisystem proteinopathy (MSP) is a dominantly inherited, pleiotropic, degenerative disorder of humans that can affect muscle, bone, and/or the central nervous system. MSP can manifest clinically as classical amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), inclusion body myopathy (IBM), Paget's disease of bone (PDB), or as a combination of these disorders. Historically, several different names have been used to describe MSP, most commonly "inclusion body myopathy with early-onset Paget disease and frontotemporal dementia (IBMPFD)" or "inclusion body myopathy with frontotemporal dementia, Paget's disease of bone, and amyotrophic lateral sclerosis (IBMPFD/ALS)." However, IBMPFD and IBMPFD/ALS are now considered outdated classifications and are more properly referred to as MSP, as the disease is clinically heterogeneous and its phenotypic spectrum extends beyond IBM, PDB, FTD, and ALS to include motor neuron disease, Parkinson's disease features, and ataxia features. Although MSP is rare, growing interest in this syndrome derives from the molecular insights the condition provides into the etiological relationship between common age-related degenerative diseases of muscle, bone, and brain.
Primary age-related tauopathy (PART) is a neuropathological designation introduced in 2014 to describe the neurofibrillary tangles (NFT) that are commonly observed in the brains of normally aged and cognitively impaired individuals that can occur independently of the amyloid plaques of Alzheimer's disease (AD). The term and diagnostic criteria for PART were developed by a large group of neuropathologists, spearheaded by Drs. John F. Crary and Peter T. Nelson. Despite some controversy, the term PART has been widely adopted, with the consensus criteria cited over 1130 times as of April 2023 according to Google Scholar.
Virginia Man-Yee Lee is a Chinese-born American biochemist and neuroscientist who specializes in the research of Alzheimer's disease. She is the current John H. Ware 3rd Endowed Professor in Alzheimer's Research at the Department of Pathology and Laboratory Medicine, and the director of the Center for Neurodegenerative Disease Research and co-director of the Marian S. Ware Alzheimer Drug Discovery Program at the Perelman School of Medicine, University of Pennsylvania. She received the 2020 Breakthrough Prize in Life Sciences.
There are more than 25 genes known to be associated with amyotrophic lateral sclerosis (ALS) as of June 2018, which collectively account for about 70% of cases of familial ALS (fALS) and 10% of cases of sporadic ALS (sALS). About 5–10% of cases of ALS are directly inherited. Overall, first-degree relatives of an individual with ALS have a 1% risk of developing ALS. ALS has an oligogenic mode of inheritance, meaning that mutations in two or more genes are required to cause disease.
Corticobasal syndrome (CBS) is a rare, progressive atypical Parkinsonism syndrome and is a tauopathy related to frontotemporal dementia. CBS is typically caused by the deposit of tau proteins forming in different areas of the brain.
LATE is a term that describes a prevalent condition with impaired memory and thinking in advanced age, often culminating in the dementia clinical syndrome. In other words, the symptoms of LATE are similar to those of Alzheimer's disease.
