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Reviewed January 2014

What is the official name of the AFF2 gene?

The official name of this gene is “AF4/FMR2 family member 2.”

AFF2 is the gene's official symbol. The AFF2 gene is also known by other names, listed below.

Read more about gene names and symbols on the About page.

What is the normal function of the AFF2 gene?

The AFF2 gene provides instructions for making a protein that is found in the nucleus of cells but whose function is not well understood. Some studies suggest that it acts as a transcription factor, which means that it attaches (binds) to specific regions of DNA and helps control the activity of other genes, although the identity of these genes is unknown. Other studies show that the protein can attach to specific regions of messenger RNA (mRNA), which is a chemical cousin of DNA that serves as the genetic blueprint for protein production. It is thought that the AFF2 protein helps control the process by which the mRNA blueprint is cut and rearranged to produce different versions of proteins (alternative splicing).

One region of the AFF2 gene contains a particular DNA segment known as a CCG trinucleotide repeat, so called because this segment of three DNA building blocks (nucleotides) is repeated multiple times within the gene. In most people, the number of CCG repeats ranges from 4 to about 40.

How are changes in the AFF2 gene related to health conditions?

fragile XE syndrome - caused by mutations in the AFF2 gene

Mutations in the AFF2 gene cause fragile XE syndrome, a condition characterized by mild intellectual disability and learning difficulties. Nearly all cases are caused by a mutation called a CCG trinucleotide repeat expansion, in which the CCG trinucleotide is abnormally repeated more than 200 times, which makes this region of the gene unstable. As a result, the AFF2 gene is turned off (silenced), and no protein is produced from it. It is unclear how a shortage of this protein leads to problems with intellectual functioning.

Rarely, small deletions of genetic material from the AFF2 gene are associated with fragile XE syndrome, although how these deletions affect the protein and lead to intellectual disability is unknown.

Where is the AFF2 gene located?

Cytogenetic Location: Xq28

Molecular Location on the X chromosome: base pairs 148,500,619 to 149,000,663

(Homo sapiens Annotation Release 107, GRCh38.p2) (NCBIThis link leads to a site outside Genetics Home Reference.)

The AFF2 gene is located on the long (q) arm of the X chromosome at position 28.

The AFF2 gene is located on the long (q) arm of the X chromosome at position 28.

More precisely, the AFF2 gene is located from base pair 148,500,619 to base pair 149,000,663 on the X chromosome.

See How do geneticists indicate the location of a gene? in the Handbook.

Where can I find additional information about AFF2?

You and your healthcare professional may find the following resources about AFF2 helpful.

You may also be interested in these resources, which are designed for genetics professionals and researchers.

What other names do people use for the AFF2 gene or gene products?

  • AF4/FMR2 family, member 2
  • FMR2
  • FMR2P
  • fragile X E mental retardation syndrome protein
  • fragile X mental retardation 2 protein
  • MRX2
  • OX19
  • protein FMR-2

Where can I find general information about genes?

The Handbook provides basic information about genetics in clear language.

These links provide additional genetics resources that may be useful.

What glossary definitions help with understanding AFF2?

alternative splicing ; disability ; DNA ; gene ; mental retardation ; messenger RNA ; mRNA ; mutation ; nucleus ; protein ; RNA ; splicing ; syndrome ; transcription ; transcription factor ; trinucleotide repeat

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.

See also Understanding Medical Terminology.

References (11 links)


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? in the Handbook.

Reviewed: January 2014
Published: February 1, 2016