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URL of this page: https://medlineplus.gov/genetics/gene/flnb/

FLNB gene

filamin B

Normal Function

The FLNB gene provides instructions for making a protein called filamin B. This protein helps build the network of protein filaments (cytoskeleton) that gives structure to cells and allows them to change shape and move. Filamin B attaches (binds) to another protein called actin and helps the actin to form the branching network of filaments that makes up the cytoskeleton. It also links actin to many other proteins to perform various functions within the cell, including the cell signaling that helps determine how the cytoskeleton will change as tissues grow and take shape during development.

Filamin B is involved in the development of the skeleton before birth. It is active (expressed) in many cells and tissues of the body, including cartilage-forming cells called chondrocytes. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone (a process called ossification), except for the cartilage that continues to cover and protect the ends of bones and is present in the nose, airways (trachea and bronchi), and external ears. Filamin B appears to be important for normal cell growth and division (proliferation) and maturation (differentiation) of chondrocytes and for the ossification of cartilage.

Health Conditions Related to Genetic Changes

Atelosteogenesis type 1

At least seven FLNB gene mutations have been identified that cause atelosteogenesis type 1, a disorder that affects the development of bones throughout the body. The mutations change single protein building blocks (amino acids) in the filamin B protein or delete a small section of the protein sequence, resulting in an abnormal protein. This abnormal protein appears to have a new, atypical function that interferes with normal proliferation or differentiation of chondrocytes, impairing ossification and leading to the signs and symptoms of atelosteogenesis type 1.

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Atelosteogenesis type 3

At least six FLNB gene mutations have been identified that cause atelosteogenesis type 3, a disorder that affects the development of bones throughout the body. These mutations change single amino acids in the filamin B protein or delete a small section of the protein sequence, resulting in an abnormal protein. This abnormal protein appears to have a new, atypical function that interferes with normal proliferation or differentiation of chondrocytes, impairing ossification and leading to the signs and symptoms of atelosteogenesis type 3.

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Boomerang dysplasia

At least two FLNB gene mutations have been identified that cause boomerang dysplasia, a disorder that affects the development of bones throughout the body. These mutations change single amino acids in the filamin B protein or delete a small section of the protein sequence, resulting in an abnormal protein. This abnormal protein appears to have a new, atypical function that interferes with normal proliferation or differentiation of chondrocytes, impairing ossification and leading to the signs and symptoms of boomerang dysplasia.

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Larsen syndrome

At least 13 FLNB gene mutations have been identified that cause Larsen syndrome, a disorder that affects the development of bones throughout the body. These mutations change single amino acids in the filamin B protein or delete a small section of the protein sequence, resulting in an abnormal protein. This abnormal protein appears to have a new, atypical function that interferes with normal proliferation or differentiation of chondrocytes, impairing ossification and leading to the signs and symptoms of Larsen syndrome.

It is not clear why similar mutations in the FLNB gene can result in four different disorders: atelosteogenesis type 1, atelosteogenesis type 3, boomerang dysplasia, or Larsen syndrome. Certain mutations in regions of the FLNB gene known as exons 2 through 5 seem to have the most harmful effects, usually resulting in the more severe disorders, atelosteogenesis type 1 and boomerang dysplasia. Atelosteogenesis type 3 and Larsen syndrome, which are less severe, are usually caused by apparently milder mutations in exons 2 through 5 or by mutations in exons 27 through 33. In a few cases, the same mutation has been associated with more than one of these disorders in different people.

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Spondylocarpotarsal synostosis syndrome

At least five FLNB gene mutations have been identified that cause spondylocarpotarsal synostosis syndrome, a disorder that affects the development of bones throughout the body. These mutations, which may occur in any region of the gene, result in the production of an abnormally short filamin B protein that is unstable and breaks down rapidly. Loss of the filamin B protein appears to result in out-of-place (ectopic) ossification, resulting in fusion of the bones in the spine, wrists, and ankles and other signs and symptoms of spondylocarpotarsal synostosis syndrome.

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Other disorders

Several common variations (polymorphisms) in the FLNB gene have been associated with low bone mineral density (osteoporosis), which weakens the bones and makes them prone to fracture. FLNB gene variations may affect the maintenance of bone structure throughout the lifespan and result in differences in bone mineral density.

Other Names for This Gene

  • ABP-278
  • ABP-280 homolog
  • actin binding protein 278
  • actin-binding-like protein
  • beta-filamin
  • FH1
  • filamin B, beta
  • filamin homolog 1
  • filamin-3
  • filamin-B
  • FLN-B
  • FLN1L
  • FLNB_HUMAN
  • LRS1
  • TABP
  • TAP
  • thyroid autoantigen
  • truncated ABP
  • truncated actin-binding protein

Additional Information & Resources

Tests Listed in the Genetic Testing Registry

Scientific Articles on PubMed

Catalog of Genes and Diseases from OMIM

Gene and Variant Databases

References

  • Bicknell LS, Farrington-Rock C, Shafeghati Y, Rump P, Alanay Y, Alembik Y, Al-Madani N, Firth H, Karimi-Nejad MH, Kim CA, Leask K, Maisenbacher M, Moran E, Pappas JG, Prontera P, de Ravel T, Fryns JP, Sweeney E, Fryer A, Unger S, Wilson LC, Lachman RS, Rimoin DL, Cohn DH, Krakow D, Robertson SP. A molecular and clinical study of Larsen syndrome caused by mutations in FLNB. J Med Genet. 2007 Feb;44(2):89-98. doi: 10.1136/jmg.2006.043687. Epub 2006 Jun 26. Citation on PubMed or Free article on PubMed Central
  • Bicknell LS, Morgan T, Bonafe L, Wessels MW, Bialer MG, Willems PJ, Cohn DH, Krakow D, Robertson SP. Mutations in FLNB cause boomerang dysplasia. J Med Genet. 2005 Jul;42(7):e43. doi: 10.1136/jmg.2004.029967. Citation on PubMed or Free article on PubMed Central
  • Farrington-Rock C, Firestein MH, Bicknell LS, Superti-Furga A, Bacino CA, Cormier-Daire V, Le Merrer M, Baumann C, Roume J, Rump P, Verheij JB, Sweeney E, Rimoin DL, Lachman RS, Robertson SP, Cohn DH, Krakow D. Mutations in two regions of FLNB result in atelosteogenesis I and III. Hum Mutat. 2006 Jul;27(7):705-10. doi: 10.1002/humu.20348. Citation on PubMed
  • Isidor B, Cormier-Daire V, Le Merrer M, Lefrancois T, Hamel A, Le Caignec C, David A, Jacquemont S. Autosomal dominant spondylocarpotarsal synostosis syndrome: phenotypic homogeneity and genetic heterogeneity. Am J Med Genet A. 2008 Jun 15;146A(12):1593-7. doi: 10.1002/ajmg.a.32217. Citation on PubMed
  • Krakow D, Robertson SP, King LM, Morgan T, Sebald ET, Bertolotto C, Wachsmann-Hogiu S, Acuna D, Shapiro SS, Takafuta T, Aftimos S, Kim CA, Firth H, Steiner CE, Cormier-Daire V, Superti-Furga A, Bonafe L, Graham JM Jr, Grix A, Bacino CA, Allanson J, Bialer MG, Lachman RS, Rimoin DL, Cohn DH. Mutations in the gene encoding filamin B disrupt vertebral segmentation, joint formation and skeletogenesis. Nat Genet. 2004 Apr;36(4):405-10. doi: 10.1038/ng1319. Epub 2004 Feb 29. Citation on PubMed
  • Li GH, Kung AW, Huang QY. Common variants in FLNB/CRTAP, not ARHGEF3 at 3p, are associated with osteoporosis in southern Chinese women. Osteoporos Int. 2010 Jun;21(6):1009-20. doi: 10.1007/s00198-009-1043-6. Epub 2009 Sep 1. Citation on PubMed or Free article on PubMed Central
  • Sawyer GM, Clark AR, Robertson SP, Sutherland-Smith AJ. Disease-associated substitutions in the filamin B actin binding domain confer enhanced actin binding affinity in the absence of major structural disturbance: Insights from the crystal structures of filamin B actin binding domains. J Mol Biol. 2009 Jul 31;390(5):1030-47. doi: 10.1016/j.jmb.2009.06.009. Epub 2009 Jun 6. Citation on PubMed
  • Wilson SG, Jones MR, Mullin BH, Dick IM, Richards JB, Pastinen TM, Grundberg E, Ljunggren O, Surdulescu GL, Dudbridge F, Elliott KS, Cervino AC, Spector TD, Prince RL. Common sequence variation in FLNB regulates bone structure in women in the general population and FLNB mRNA expression in osteoblasts in vitro. J Bone Miner Res. 2009 Dec;24(12):1989-97. doi: 10.1359/jbmr.090530. Citation on PubMed
  • Yang CF, Wang CH, Siong H'ng W, Chang CP, Lin WD, Chen YT, Wu JY, Tsai FJ. Filamin B Loss-of-Function Mutation in Dimerization Domain Causes Autosomal-Recessive Spondylocarpotarsal Synostosis Syndrome with Rib Anomalies. Hum Mutat. 2017 May;38(5):540-547. doi: 10.1002/humu.23186. Epub 2017 Feb 27. Citation on PubMed
  • Zhang D, Herring JA, Swaney SS, McClendon TB, Gao X, Browne RH, Rathjen KE, Johnston CE, Harris S, Cain NM, Wise CA. Mutations responsible for Larsen syndrome cluster in the FLNB protein. J Med Genet. 2006 May;43(5):e24. doi: 10.1136/jmg.2005.038695. Citation on PubMed or Free article on PubMed Central

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