Charcot–Marie–Tooth disease (CMT) is a hereditary motor and sensory neuropathy of the peripheral nervous system characterized by progressive loss of muscle tissue and touch sensation across various parts of the body. This disease is the most commonly inherited neurological disorder, affecting about one in 2,500 people. It is named after those who classically described it: the Frenchman Jean-Martin Charcot (1825–1893), his pupil Pierre Marie (1853–1940), and the Briton Howard Henry Tooth (1856–1925).
Dejerine–Sottas disease, also known as, Dejerine–Sottas neuropathy, Dejerine–Sottas syndrome, progressive hypertrophic interstitial polyneuropathy of childhood, demyelinating polyneuropathy of childhood, and onion bulb neuropathy, is a hereditary neurological disorder characterised by damage to the peripheral nerves, demyelination, and resulting progressive muscle wasting and somatosensory loss. The condition is caused by mutations in a various genes and currently has no known cure.
Laminopathies are a group of rare genetic disorders caused by mutations in genes encoding proteins of the nuclear lamina. They are included in the more generic term nuclear envelopathies that was coined in 2000 for diseases associated with defects of the nuclear envelope. Since the first reports of laminopathies in the late 1990s, increased research efforts have started to uncover the vital role of nuclear envelope proteins in cell and tissue integrity in animals.
Myelin protein zero is a single membrane glycoprotein which in humans is encoded by the MPZ gene. P0 is a major structural component of the myelin sheath in the peripheral nervous system (PNS). Myelin protein zero is expressed by Schwann cells and accounts for over 50% of all proteins in the peripheral nervous system, making it the most common protein expressed in the PNS. Mutations in myelin protein zero can cause myelin deficiency and are associated with neuropathies like Charcot–Marie–Tooth disease and Dejerine–Sottas disease.
Fukutin is a eukaryotic protein necessary for the maintenance of muscle integrity, cortical histogenesis, and normal ocular development. Mutations in the fukutin gene have been shown to result in Fukuyama congenital muscular dystrophy (FCMD) characterised by brain malformation - one of the most common autosomal-recessive disorders in Japan. In humans this protein is encoded by the FCMD gene, located on chromosome 9q31. Human fukutin exhibits a length of 461 amino acids and a predicted molecular mass of 53.7 kDa.
Gap junction beta-1 protein (GJB1), also known as connexin 32 (Cx32) is a transmembrane protein that in humans is encoded by the GJB1 gene. Gap junction beta-1 protein is a member of the gap junction connexin family of proteins that regulates and controls the transfer of communication signals across cell membranes, primarily in the liver and peripheral nervous system.
Early growth response protein 2 is a protein that in humans is encoded by the EGR2 gene. EGR2 is a transcription regulatory factor, containing three zinc finger DNA-binding sites, and is highly expressed in a population of migrating neural crest cells. It is later expressed in the neural crest derived cells of the cranial ganglion. The protein encoded by Krox20 contains two cys2his2-type zinc fingers. Krox20 gene expression is restricted to the early hindbrain development. It is evolutionarily conserved in vertebrates, humans, mice, chicks, and zebra fish. In addition, the amino acid sequence and most aspects of the embryonic gene pattern is conserved among vertebrates, further implicating its role in hindbrain development. When the Krox20 is deleted in mice, the protein coding ability of the Krox20 gene is diminished. These mice are unable to survive after birth and exhibit major hindbrain defects. These defects include but are not limited to defects in formation of cranial sensory ganglia, partial fusion of the trigeminal nerve (V) with the facial (VII) and auditory (VII) nerves, the proximal nerve roots coming off of these ganglia were disorganized and intertwined among one another as they entered the brainstem, and there was fusion of the glossopharyngeal (IX) nerve complex.
Glycine—tRNA ligase also known as glycyl–tRNA synthetase is an enzyme that in humans is encoded by the GARS1 gene.
Myotubularin is a protein that in humans is encoded by the MTM1 gene.
Lipopolysaccharide-induced tumor necrosis factor-alpha factor is a protein that in humans is encoded by the LITAF gene.
Periaxin is a protein that in humans is encoded by the PRX gene.
Myotubularin-related protein 2 also known as phosphatidylinositol-3,5-bisphosphate 3-phosphatase or phosphatidylinositol-3-phosphate phosphatase is a protein that in humans is encoded by the MTMR2 gene.
SH3 domain and tetratricopeptide repeats-containing protein 2 is a protein that in humans is encoded by the SH3TC2 gene. It is believed to be expressed in the Schwann cells that wrap the myelin sheath around nerves.
Myotubularin-related protein 13 is a protein that in humans is encoded by the SBF2 gene.
FYVE, RhoGEF and PH domain-containing protein 4 is a protein that in humans is encoded by the FGD4 gene.
Neurofilament light polypeptide, also known as neurofilament light chain, abbreviated to NF-L or Nfl and with the HGNC name NEFL is a member of the intermediate filament protein family. This protein family consists of over 50 human proteins divided into 5 major classes, the Class I and II keratins, Class III vimentin, GFAP, desmin and the others, the Class IV neurofilaments and the Class V nuclear lamins. There are four major neurofilament subunits, NF-L, NF-M, NF-H and α-internexin. These form heteropolymers which assemble to produce 10nm neurofilaments which are only expressed in neurons where they are major structural proteins, particularly concentrated in large projection axons. Axons are particularly sensitive to mechanical and metabolic compromise and as a result axonal degeneration is a significant problem in many neurological disorders. The detection of neurofilament subunits in CSF and blood has therefore become widely used as a biomarker of ongoing axonal compromise. The NF-L protein is encoded by the NEFL gene. Neurofilament light chain is a biomarker that can be measured with immunoassays in cerebrospinal fluid and plasma and reflects axonal damage in a wide variety of neurological disorders. It is a useful marker for disease monitoring in amyotrophic lateral sclerosis, multiple sclerosis, Alzheimer's disease, and more recently Huntington's disease. It is also promising marker for follow-up of patients with brain tumors. Higher levels of blood or CSF NF-L have been associated with increased mortality, as would be expected as release of this protein reflects ongoing axonal loss. Recent work performed as a collaboration between EnCor Biotechnology Inc. and the University of Florida showed that the NF-L antibodies employed in the most widely used NF-L assays are specific for cleaved forms of NF-L generated by proteolysis induced by cell death. Methods used in different studies for NfL measurement are sandwich enzyme-linked immunosorbent assay (ELISA), electrochemiluminescence, and high-sensitive single molecule array (SIMOA).
Hereditary sensory and autonomic neuropathy (HSAN) or hereditary sensory neuropathy (HSN) is a condition used to describe any of the types of this disease which inhibit sensation.
Hereditary neuropathy with liability to pressure palsy (HNPP) is a peripheral neuropathy, a condition that affects the nerves. Pressure on the nerves can cause tingling sensations, numbness, pain, weakness, muscle atrophy and even paralysis of the affected area. In normal individuals, these symptoms disappear quickly, but in sufferers of HNPP even a short period of pressure can cause the symptoms to occur. Palsies can last from minutes or days to weeks or even months.
Distal hereditary motor neuropathy type V is a particular type of neuropathic disorder. In general, distal hereditary motor neuropathies affect the axons of distal motor neurons and are characterized by progressive weakness and atrophy of muscles of the extremities. It is common for them to be called "spinal forms of Charcot-Marie-Tooth disease (CMT)", because the diseases are closely related in symptoms and genetic cause. The diagnostic difference in these diseases is the presence of sensory loss in the extremities. There are seven classifications of dHMNs, each defined by patterns of inheritance, age of onset, severity, and muscle groups involved. Type V is a disorder characterized by autosomal dominance, weakness of the upper limbs that is progressive and symmetrical, and atrophy of the small muscles of the hands.
Autosomal dominant Charcot–Marie–Tooth disease type 2 with giant axons is a rare subtype of hereditary motor and sensory neuropathy of the axons which is characterized by symptoms similar to those from Charcot–Marie–Tooth disease and autosomal dominant inheritance.
