HNF1 homeobox B
The HNF1B gene provides instructions for making a protein that attaches (binds) to specific regions of DNA and regulates the activity of other genes. On the basis of this role, the protein produced from the HNF1B gene is called a transcription factor. The HNF1B protein is part of a large group of transcription factors called homeodomain proteins. The homeodomain is a region of the protein that allows it to bind to DNA.
The HNF1B protein is found in many organs and tissues, including the lungs, liver, intestines, pancreas, kidneys, reproductive system, and urinary tract. Researchers suspect that this protein may play a role in the development of many of these parts of the body.
17q12 deletion syndrome is a condition that results from the deletion of a small piece of chromosome 17 in each cell. Signs and symptoms of 17q12 deletion syndrome can include abnormalities of the kidneys (particularly fluid-filled sacs, called cysts, in the kidneys) and a form of diabetes called maturity-onset diabetes of the young type 5 (MODY5). The combination of kidney cysts and MODY5 is sometimes referred to as renal cysts and diabetes (RCAD) syndrome. Other features of 17q12 deletion syndrome include abnormalities of the urinary tract and reproductive system, delayed development, intellectual disability, and behavioral or psychiatric disorders. The health problems associated with 17q12 deletion syndrome vary widely, even among affected members of the same family.
The part of chromosome 17 that is deleted is on the long (q) arm of the chromosome at a position designated q12. This region of the chromosome contains at least 15 genes, including HNF1B. A deletion of this region results in a loss of one copy of the HNF1B gene in each cell, leading to a reduced amount of HNF1B protein. A shortage of this protein likely disrupts the regulation of genes that are necessary for the normal development of several organs, including the kidneys and pancreas. Studies suggest that a loss of one copy of the HNF1B gene underlies the kidney and urinary tract abnormalities, as well as MODY5, in people with 17q12 deletion syndrome.
Mutations within the HNF1B gene are found in people with abnormalities of the kidneys and other structures of the urinary system but without other features of 17q12 deletion syndrome (described above). These abnormalities vary in severity and are grouped together as congenital anomalies of kidney and urinary tract (CAKUT). The most severe CAKUT abnormalities can cause kidney damage and life-threatening kidney failure.
Mutations associated with CAKUT occur in one copy of the HNF1B gene in each cell. Many change single protein building blocks (amino acids) in the HNF1B protein. Others lead to an abnormally shaped protein or prevent the production of any functional protein from one copy of the gene. A shortage of functional HNF1B protein likely disrupts the regulation of genes that help direct development of the kidneys and urinary tract. It is unclear why only structures of the urinary system are affected in these individuals.
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HNF1B gene mutations can also cause abnormalities of multiple organ systems. Some of the features associated with HNF1B gene mutations are the same as those of 17q12 deletion syndrome (described above), including RCAD syndrome and abnormalities of the urinary tract, reproductive system, and other organs. Like the signs and symptoms of those syndromes, the health problems associated with HNF1B gene mutations vary widely among affected individuals. However, unlike 17q12 deletions, mutations in the HNF1B gene have not been found to cause delayed development, intellectual disability, or behavioral or psychiatric disorders.
More than 200 mutations in the HNF1B gene have been identified. As in CAKUT (described above), the mutations lead to a shortage of functional HNF1B protein, which likely disrupts the regulation of genes that are necessary for the normal development of several organs. It is unclear why these mutations can affect different organ systems in different people.
- hepatocyte nuclear factor 1B
- HNF1 beta A
- homeoprotein LFB3
- transcription factor 2, hepatic