Reviewed April 2008
What is the official name of the TTPA gene?
The official name of this gene is “tocopherol (alpha) transfer protein.”
TTPA is the gene's official symbol. The TTPA gene is also known by other names, listed below.
What is the normal function of the TTPA gene?
The TTPA gene provides instructions for making the α-tocopherol transfer protein (αTTP), which is found in the liver and brain. This protein controls the distribution of vitamin E obtained from the diet (also called α-tocopherol) to cells and tissues throughout the body. Vitamin E is an antioxidant that protects cells in the body from the damaging effects of unstable molecules called free radicals. Normally, vitamin E derived from food is absorbed in the intestine and then transported into the liver on molecules called chylomicrons. After a meal, chylomicrons are formed to transport fat-soluble vitamins (such as vitamin E), dietary fats, and cholesterol from the intestine to the liver. Once in the liver, αTTP transfers vitamin E from chylomicrons to very low-density lipoproteins (VLDLs), which carry fat, fat-soluble vitamins, and cholesterol from the liver to other tissues throughout the body. The VLDLs are then released into the bloodstream so the accompanying vitamin E can be used in the body. The αTTP protein is also thought to transport vitamin E to nerve cells (neurons) in the brain.
How are changes in the TTPA gene related to health conditions?
- ataxia with vitamin E deficiency - caused by mutations in the TTPA gene
At least 18 mutations in the TTPA gene have been found to cause ataxia with vitamin E deficiency. Some of these mutations cause no functional protein to be made, while others change a single protein building block (amino acid) in the αTTP protein, reducing its function. One mutation that is found in the Japanese population changes the amino acid histidine to the amino acid glutamine at position 101 in the αTTP protein (written as His101Glu or H101Q). Along with causing ataxia with vitamin E deficiency, this mutation is associated with the development of an eye disorder called retinitis pigmentosa that causes vision loss.
Mutations in the TTPA gene that cause no functional αTTP protein to be made are associated with a severe form of ataxia that begins at a young age. Mutations that reduce but do not eliminate the protein's function are associated with milder ataxia that occurs at a later age and progresses more slowly.
Where is the TTPA gene located?
Cytogenetic Location: 8q12.3
Molecular Location on chromosome 8: base pairs 63,972,046 to 63,998,611
The TTPA gene is located on the long (q) arm of chromosome 8 at position 12.3.
More precisely, the TTPA gene is located from base pair 63,972,046 to base pair 63,998,611 on chromosome 8.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
Where can I find additional information about TTPA?
You and your healthcare professional may find the following resources about TTPA helpful.
Educational resources - Information pages
- Basic Neurochemistry (sixth edition, 1999): The brain depends on select vitamins and closely related compounds as antioxidants to control potentially damaging free radicals (http://www.ncbi.nlm.nih.gov/books/NBK28242/)
- Eurekah Bioscience Collection: Fat-Soluble Vitamin Deficiency (http://www.ncbi.nlm.nih.gov/books/NBK6420/)
- Gene Reviews - Clinical summary (http://www.ncbi.nlm.nih.gov/books/NBK1241/)
Genetic Testing Registry - Repository of genetic test information
- GTR: Genetic tests for TTPA (http://www.ncbi.nlm.nih.gov/gtr/tests/?term=7274%5Bgeneid%5D)
You may also be interested in these resources, which are designed for genetics professionals and researchers.
- PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/pubmed?term=((TTPA%5BTIAB%5D)%20OR%20(tocopherol%20transfer%20protein%5BTIAB%5D))%20OR%20(alpha-tocopherol%20transfer%20protein%5BTIAB%5D)%20AND%20((Genes%5BMH%5D)%20OR%20(Genetic%20Phenomena%5BMH%5D))%20AND%20english%5Bla%5D%20AND%20human%5Bmh%5D%20AND%20%22last%201800%20days%22%5Bdp%5D)
- OMIM - Genetic disorder catalog (http://omim.org/entry/600415)
Research Resources - Tools for researchers
- Atlas of Genetics and Cytogenetics in Oncology and Haematology (http://atlasgeneticsoncology.org/Genes/GC_TTPA.html)
- Entrez Gene (http://www.ncbi.nlm.nih.gov/gene/7274)
- GeneCards (http://www.genecards.org/cgi-bin/carddisp.pl?id_type=entrezgene&id=7274)
- HUGO Gene Nomenclature Committee (http://www.genenames.org/data/hgnc_data.php?hgnc_id=12404)
What other names do people use for the TTPA gene or gene products?
- alpha-tocopherol transfer protein
- ataxia (Friedreich-like) with vitamin E deficiency
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
What glossary definitions help with understanding TTPA?
amino acid ;
free radicals ;
low-density lipoproteins ;
You may find definitions for these and many other terms in the Genetics Home Reference
- Entrez Gene (http://www.ncbi.nlm.nih.gov/gene/7274)
- Mariotti C, Gellera C, Rimoldi M, Mineri R, Uziel G, Zorzi G, Pareyson D, Piccolo G, Gambi D, Piacentini S, Squitieri F, Capra R, Castellotti B, Di Donato S. Ataxia with isolated vitamin E deficiency: neurological phenotype, clinical follow-up and novel mutations in TTPA gene in Italian families. Neurol Sci. 2004 Jul;25(3):130-7. (http://www.ncbi.nlm.nih.gov/pubmed/15300460?dopt=Abstract)
- Meier R, Tomizaki T, Schulze-Briese C, Baumann U, Stocker A. The molecular basis of vitamin E retention: structure of human alpha-tocopherol transfer protein. J Mol Biol. 2003 Aug 15;331(3):725-34. (http://www.ncbi.nlm.nih.gov/pubmed/12899840?dopt=Abstract)
- Morley S, Panagabko C, Shineman D, Mani B, Stocker A, Atkinson J, Manor D. Molecular determinants of heritable vitamin E deficiency. Biochemistry. 2004 Apr 13;43(14):4143-9. (http://www.ncbi.nlm.nih.gov/pubmed/15065857?dopt=Abstract)
- OMIM: TOCOPHEROL TRANSFER PROTEIN, ALPHA (http://omim.org/entry/600415)
- Pang J, Kiyosawa M, Seko Y, Yokota T, Harino S, Suzuki J. Clinicopathological report of retinitis pigmentosa with vitamin E deficiency caused by mutation of the alpha-tocopherol transfer protein gene. Jpn J Ophthalmol. 2001 Nov-Dec;45(6):672-6. (http://www.ncbi.nlm.nih.gov/pubmed/11754917?dopt=Abstract)
- Qian J, Atkinson J, Manor D. Biochemical consequences of heritable mutations in the alpha-tocopherol transfer protein. Biochemistry. 2006 Jul 11;45(27):8236-42. (http://www.ncbi.nlm.nih.gov/pubmed/16819822?dopt=Abstract)
- Yokota T, Shiojiri T, Gotoda T, Arita M, Arai H, Ohga T, Kanda T, Suzuki J, Imai T, Matsumoto H, Harino S, Kiyosawa M, Mizusawa H, Inoue K. Friedreich-like ataxia with retinitis pigmentosa caused by the His101Gln mutation of the alpha-tocopherol transfer protein gene. Ann Neurol. 1997 Jun;41(6):826-32. (http://www.ncbi.nlm.nih.gov/pubmed/9189046?dopt=Abstract)
The resources on this site should not be used as a substitute for
professional medical care or advice. Users seeking information about
a personal genetic disease, syndrome, or condition should consult with a qualified
See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.