The MAPT gene provides instructions for making a protein called tau. This protein is found throughout the nervous system, including in nerve cells (neurons) in the brain. It is involved in assembling and stabilizing microtubules, which are rigid, hollow fibers that make up the cell's structural framework (the cytoskeleton). Microtubules help cells maintain their shape, assist in the process of cell division, and are essential for the transport of materials within cells.
Six different versions (isoforms) of the tau protein are produced in the adult brain. The isoforms vary in length from 352 to 441 protein building blocks (amino acids). A region of the protein called the microtubule-binding domain, which is the part of the protein that attaches (binds) to microtubules, also varies among the isoforms. In three of the isoforms, the microtubule-binding domain contains three repeated segments. In the other three isoforms, this domain contains four repeated segments. Typically, the brain has approximately the same amount of three-repeat isoforms and four-repeat isoforms. This balance appears to be essential for the normal function of neurons.
Health Conditions Related to Genetic Changes
Frontotemporal dementia with parkinsonism-17
More than 40 mutations in the MAPT gene have been found to cause frontotemporal dementia with parkinsonism-17 (FTDP-17). Some of these mutations change single amino acids in the tau protein, most often in the microtubule-binding region. These mutations reduce tau's ability to bind to microtubules, which disrupts many important cell functions.
Other MAPT gene mutations change the way the gene's instructions are used to build the tau protein. Most of these mutations increase the production of tau with four repeated segments compared to the production of tau with three repeated segments. The resulting imbalance of tau isoforms in the brain interferes with the normal functions of brain cells.
In ways that are not fully understood, the MAPT gene mutations responsible for FTDP-17 lead to an accumulation of abnormal tau in neurons and other brain cells. These clumps of defective tau build up over time, although it is unclear what effect they have on cell function and survival. FTDP-17 is characterized by the gradual death of cells in areas of the brain called the frontal and temporal lobes. The frontal lobes are involved in reasoning, planning, judgment, and problem-solving, while the temporal lobes help process hearing, speech, memory, and emotion. The loss of cells in these brain regions leads to the major features of FTDP-17, including changes in personality and behavior, speech and language abnormalities, and problems with movement.More About This Health Condition
Progressive supranuclear palsy
Several mutations in the MAPT gene have been found to cause progressive supranuclear palsy. However, mutations in this gene appear to be a rare cause of this disorder.
At least one normal variation (polymorphism) in the MAPT gene has been associated with an increased risk of developing progressive supranuclear palsy. This polymorphism, known as the H1 haplotype, is found much more frequently in people with progressive supranuclear palsy than in the general population. It is unclear exactly how this genetic variation increases the risk of developing this disease.
The features of progressive supranuclear palsy appear to be related to abnormalities in the tau protein. In people with MAPT gene mutations, genetic changes disrupt the protein's normal structure and function. However, abnormal tau is also found in people without MAPT gene mutations. The defective tau protein assembles into abnormal clumps within neurons and other brain cells, although it is unclear what effect these clumps have on cell function and survival. Progressive supranuclear palsy is characterized by the gradual death of brain cells, particularly in structures deep within the brain that are essential for coordinating movement. This loss of brain cells underlies the major features of progressive supranuclear palsy, including problems with movement, vision, speech, and thinking (cognition).More About This Health Condition
Idiopathic pulmonary fibrosis
MedlinePlus Genetics provides information about Idiopathic pulmonary fibrosisMore About This Health Condition
Mutations in the MAPT gene have also been found to cause other brain disorders similar to FTDP-17 and progressive supranuclear palsy. These disorders include corticobasal degeneration, tauopathy with respiratory failure, and a form of dementia with seizures (epilepsy). Although these conditions have somewhat different patterns of signs and symptoms, they all involve changes in personality, behavior, or cognition and problems with movement. The MAPT gene mutations responsible for these disorders lead to a buildup of abnormal tau in brain cells. Although the effect of tau accumulation on cell function and survival is unknown, these disorders are characterized by the death of brain cells in regions of the brain essential for cognition, emotion, and coordinating movement.
Because all of these diseases are characterized by an abnormal buildup of tau in the brain, they are known as tauopathies. Some researchers suggest that, instead of being described as separate disorders, the group of tauopathies caused by mutations in the MAPT gene should be considered as part of a spectrum with varying signs and symptoms.
Other Names for This Gene
- G protein beta1/gamma2 subunit-interacting factor 1
- microtubule-associated protein tau
- neurofibrillary tangle protein
- paired helical filament-tau
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
- Baker M, Litvan I, Houlden H, Adamson J, Dickson D, Perez-Tur J, Hardy J, Lynch T, Bigio E, Hutton M. Association of an extended haplotype in the tau gene with progressive supranuclear palsy. Hum Mol Genet. 1999 Apr;8(4):711-5. doi: 10.1093/hmg/8.4.711. Citation on PubMed
- Conrad C, Andreadis A, Trojanowski JQ, Dickson DW, Kang D, Chen X, Wiederholt W, Hansen L, Masliah E, Thal LJ, Katzman R, Xia Y, Saitoh T. Genetic evidence for the involvement of tau in progressive supranuclear palsy. Ann Neurol. 1997 Feb;41(2):277-81. doi: 10.1002/ana.410410222. Citation on PubMed
- Goedert M. Tau protein and neurodegeneration. Semin Cell Dev Biol. 2004 Feb;15(1):45-9. doi: 10.1016/j.semcdb.2003.12.015. Citation on PubMed
- Hutton M, Lendon CL, Rizzu P, Baker M, Froelich S, Houlden H, Pickering-Brown S, Chakraverty S, Isaacs A, Grover A, Hackett J, Adamson J, Lincoln S, Dickson D, Davies P, Petersen RC, Stevens M, de Graaff E, Wauters E, van Baren J, Hillebrand M, Joosse M, Kwon JM, Nowotny P, Che LK, Norton J, Morris JC, Reed LA, Trojanowski J, Basun H, Lannfelt L, Neystat M, Fahn S, Dark F, Tannenberg T, Dodd PR, Hayward N, Kwok JB, Schofield PR, Andreadis A, Snowden J, Craufurd D, Neary D, Owen F, Oostra BA, Hardy J, Goate A, van Swieten J, Mann D, Lynch T, Heutink P. Association of missense and 5'-splice-site mutations in tau with the inherited dementia FTDP-17. Nature. 1998 Jun 18;393(6686):702-5. doi: 10.1038/31508. Citation on PubMed
- Lee VM, Goedert M, Trojanowski JQ. Neurodegenerative tauopathies. Annu Rev Neurosci. 2001;24:1121-59. doi: 10.1146/annurev.neuro.24.1.1121. Citation on PubMed
- Ludolph AC, Kassubek J, Landwehrmeyer BG, Mandelkow E, Mandelkow EM, Burn DJ, Caparros-Lefebvre D, Frey KA, de Yebenes JG, Gasser T, Heutink P, Hoglinger G, Jamrozik Z, Jellinger KA, Kazantsev A, Kretzschmar H, Lang AE, Litvan I, Lucas JJ, McGeer PL, Melquist S, Oertel W, Otto M, Paviour D, Reum T, Saint-Raymond A, Steele JC, Tolnay M, Tumani H, van Swieten JC, Vanier MT, Vonsattel JP, Wagner S, Wszolek ZK; Reisensburg Working Group for Tauopathies With Parkinsonism. Tauopathies with parkinsonism: clinical spectrum, neuropathologic basis, biological markers, and treatment options. Eur J Neurol. 2009 Mar;16(3):297-309. doi: 10.1111/j.1468-1331.2008.02513.x. Citation on PubMed or Free article on PubMed Central
- Nicholl DJ, Greenstone MA, Clarke CE, Rizzu P, Crooks D, Crowe A, Trojanowski JQ, Lee VM, Heutink P. An English kindred with a novel recessive tauopathy and respiratory failure. Ann Neurol. 2003 Nov;54(5):682-6. doi: 10.1002/ana.10747. Citation on PubMed
- Pastor P, Ezquerra M, Tolosa E, Munoz E, Marti MJ, Valldeoriola F, Molinuevo JL, Calopa M, Oliva R. Further extension of the H1 haplotype associated with progressive supranuclear palsy. Mov Disord. 2002 May;17(3):550-6. doi: 10.1002/mds.10076. Citation on PubMed
- Rademakers R, Melquist S, Cruts M, Theuns J, Del-Favero J, Poorkaj P, Baker M, Sleegers K, Crook R, De Pooter T, Bel Kacem S, Adamson J, Van den Bossche D, Van den Broeck M, Gass J, Corsmit E, De Rijk P, Thomas N, Engelborghs S, Heckman M, Litvan I, Crook J, De Deyn PP, Dickson D, Schellenberg GD, Van Broeckhoven C, Hutton ML. High-density SNP haplotyping suggests altered regulation of tau gene expression in progressive supranuclear palsy. Hum Mol Genet. 2005 Nov 1;14(21):3281-92. doi: 10.1093/hmg/ddi361. Epub 2005 Sep 29. Citation on PubMed
- Spillantini MG, Van Swieten JC, Goedert M. Tau gene mutations in frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Neurogenetics. 2000 Mar;2(4):193-205. doi: 10.1007/pl00022972. Citation on PubMed
- van Swieten J, Spillantini MG. Hereditary frontotemporal dementia caused by Tau gene mutations. Brain Pathol. 2007 Jan;17(1):63-73. doi: 10.1111/j.1750-3639.2007.00052.x. Citation on PubMed