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The official name of this gene is “RAB27A, member RAS oncogene family.”
RAB27A is the gene's official symbol. The RAB27A gene is also known by other names, listed below.
The RAB27A gene provides instructions for making a protein that is involved in a process called vesicle trafficking, which moves proteins and other molecules within cells in sac-like structures called vesicles. Although the Rab27a protein is found in cells and tissues throughout the body, it appears to be most critical in pigment-producing cells called melanocytes and in certain immune system cells.
In melanocytes, the Rab27a protein helps transport structures called melanosomes. These structures produce a pigment called melanin, which is the substance that gives skin, hair, and eyes their color (pigmentation). Rab27a interacts with proteins produced from the MLPH and MYO5A genes to form a complex that transports melanosomes to the outer edges of melanocytes. From there, the melanosomes are transferred to other types of cells, where they provide the pigment needed for normal hair, skin, and eye coloring.
The Rab27a protein also plays an important role in immune system cells called T-lymphocytes. These cells recognize and attack foreign invaders, such as viruses and bacteria, to prevent infection and illness. Specifically, Rab27a is involved in cytotoxic granule exostosis, which is the process by which T-lymphocytes release cell-killing (cytotoxic) compounds to destroy foreign invaders.
The RAB27A gene belongs to a family of genes called RAB (RAB, member RAS oncogene family).
A gene family is a group of genes that share important characteristics. Classifying individual genes into families helps researchers describe how genes are related to each other. For more information, see What are gene families? (http://ghr.nlm.nih.gov/handbook/howgeneswork/genefamilies) in the Handbook.
At least 24 mutations in the RAB27A gene have been found in people with Griscelli syndrome. These mutations cause a form of the condition designated type 2, which is characterized by unusually light (hypopigmented) skin, silvery-gray hair, and immune system abnormalities. The known mutations either prevent the production of any Rab27a protein or lead to the production of an abnormal or unstable protein that cannot form a complex with the proteins produced from the MLPH and MYO5A genes. A shortage of functional Rab27a protein impairs the normal transport of melanosomes to the edges of melanocytes. Instead, these structures clump near the center of melanocytes, trapping melanin within these cells and preventing normal pigmentation of skin and hair. A loss of Rab27a function in T-lymphocytes impairs cytotoxic granule exocytosis, making people with Griscelli syndrome type 2 prone to recurrent infections.
Through mechanisms that are not well understood, a shortage of Rab27a in immune system cells also leads to a condition called hemophagocytic lymphohistiocytosis (HLH) in people with Griscelli syndrome type 2. This condition triggers the immune system to produce too many activated T-lymphocytes and other immune cells called macrophages (histiocytes). Overactivity of these cells can damage organs and tissues throughout the body, causing life-threatening complications if the condition is untreated.
Cytogenetic Location: 15q15-q21.1
Molecular Location on chromosome 15: base pairs 55,202,965 to 55,289,831
The RAB27A gene is located on the long (q) arm of chromosome 15 between positions 15 and 21.1.
More precisely, the RAB27A gene is located from base pair 55,202,965 to base pair 55,289,831 on chromosome 15.
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 RAB27A 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.
bacteria ; cell ; gene ; GTP ; immune system ; infection ; melanin ; melanocytes ; oncogene ; pigment ; pigmentation ; protein ; RAS ; RAS oncogene ; syndrome ; vesicle
You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://ghr.nlm.nih.gov/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.