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The official name of this gene is “cubilin.”
CUBN is the gene's official symbol. The CUBN gene is also known by other names, listed below.
The CUBN gene provides instructions for making a protein called cubilin. This protein is involved in the uptake of vitamin B12 (also called cobalamin) from food into the body. Vitamin B12, which cannot be made in the body and can only be obtained from food, is essential for the formation of DNA and proteins, the production of cellular energy, and the breakdown of fats. This vitamin is involved in the formation of red blood cells and maintenance of the brain and spinal cord (central nervous system).
The cubilin protein is primarily found associated with kidney cells and cells that line the small intestine. Cubilin is anchored to the outer membrane of these cells by its attachment to another protein called amnionless. Cubilin can interact with molecules and proteins passing through the small intestine and kidneys, including vitamin B12. During digestion, vitamin B12 is released from food. As the vitamin passes through the small intestine, cubilin attaches (binds) to it. Amnionless helps transfer the cubilin-vitamin B12 complex into the intestinal cell. From there, the vitamin is released into the blood and transported throughout the body. In the kidneys, cubilin and amnionless are involved in the reabsorption of certain proteins that would otherwise be released in urine.
At least 35 mutations in the CUBN gene have been found to cause a condition called Imerslund-Gräsbeck syndrome. This condition is characterized by low levels of vitamin B12 in the body, which leads to a blood disorder known as megaloblastic anemia. About half of affected individuals also have excess protein in their urine (proteinuria), and some have neurological problems.
The most common CUBN gene mutation, which is found in people of Finnish heritage, changes a single protein building block (amino acid) in the cubilin protein; the amino acid proline is replaced by the amino acid leucine at position 1297 (written as Pro1297Leu or P1297L). The protein alteration impairs cubilin's ability to bind to vitamin B12. Instead of being taken up into intestinal cells, the vitamin is released from the body. A shortage of this essential vitamin impairs the proper development of red blood cells, leading to megaloblastic anemia. In addition, low levels of vitamin B12 can affect the central nervous system, causing neurological problems.
Other CUBN gene mutations prevent cubilin from attaching to the amnionless protein or lead to a reduction in the amount or function of the cubilin protein. These changes impair cubilin's function in the kidneys as well as in the small intestine. Without amnionless function in the kidneys, proteins are not reabsorbed into the body and are instead released in the urine, leading to proteinuria. Individuals with these mutations develop megaloblastic anemia and proteinuria.
Cytogenetic Location: 10p12.31
Molecular Location on chromosome 10: base pairs 16,823,966 to 17,130,249
The CUBN gene is located on the short (p) arm of chromosome 10 at position 12.31.
More precisely, the CUBN gene is located from base pair 16,823,966 to base pair 17,130,249 on chromosome 10.
See How do geneticists indicate the location of a gene? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genelocation) in the Handbook.
You and your healthcare professional may find the following resources about CUBN helpful.
You may also be interested in these resources, which are designed for genetics professionals and researchers.
See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.
amino acid ; anemia ; breakdown ; cell ; central nervous system ; cobalamin ; digestion ; DNA ; endocytosis ; gene ; intestine ; kidney ; leucine ; megaloblastic anemia ; mutation ; nervous system ; neurological ; precursor ; proline ; protein ; proteinuria ; receptor ; syndrome ; vitamin B12
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
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 healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.