The FBN1 gene provides instructions for making a large protein called fibrillin-1. This protein is transported out of cells into the extracellular matrix, which is an intricate lattice of proteins and other molecules that forms in the spaces between cells. In this matrix, molecules of fibrillin-1 attach (bind) to each other and to other proteins to form threadlike filaments called microfibrils. Microfibrils form elastic fibers, which enable the skin, ligaments, and blood vessels to stretch. Microfibrils also provide support to more rigid tissues such as bones and the tissues that support the nerves, muscles, and lenses of the eyes.
Microfibrils store a protein called transforming growth factor beta (TGF-β), a critical growth factor. TGF-β affects development by helping to control the growth and division (proliferation) of cells, the process by which cells mature to carry out specific functions (differentiation), cell movement (motility), and the self-destruction of cells (apoptosis). Microfibrils help regulate the availability of TGF-β, which is turned off (inactivated) when stored in microfibrils and turned on (activated) when released.
Health Conditions Related to Genetic Changes
At least nine FBN1 gene mutations have been identified in people with acromicric dysplasia. This condition is characterized by severely short stature, short limbs, stiff joints, and distinctive facial features.
FBN1 gene mutations that cause acromicric dysplasia are located in an area of the gene called exons 41 and 42, and change single protein building blocks (amino acids) in a region of the fibrillin-1 protein called TGF-β binding-protein-like domain 5. The mutations result in a reduction and disorganization of the microfibrils. Without enough normal microfibrils to store TGF-β, the growth factor is abnormally active. These effects likely contribute to the physical abnormalities that occur in acromicric dysplasia, but the mechanisms are unclear.
It is unknown why the FBN1 gene mutations that cause acromicric dysplasia lead to short stature, while certain other FBN1 gene mutations that also increase TGF-β activity cause a disorder called Marfan syndrome (see below), which is characterized by tall stature.More About This Health Condition
Isolated ectopia lentis
More than 30 mutations in the FBN1 gene have been found to cause isolated ectopia lentis. In this condition, the lens in one or both eyes is off-center (displaced), which leads to vision problems. Most of the FBN1 gene mutations that cause this condition change single amino acids in the fibrillin-1 protein. As a result, the production of normal fibrillin-1 protein is reduced, leading to a decrease in microfibril formation or the formation of impaired microfibrils. Without enough functional microfibrils to anchor the lens in its central position at the front of the eye, the lens becomes displaced, resulting in isolated ectopia lentis and related vision problems.
Ectopia lentis is classified as isolated when it occurs alone, without signs and symptoms affecting other body systems. However, some people initially diagnosed with isolated ectopia lentis caused by FBN1 gene mutations later develop additional features typical of a condition called Marfan syndrome (described below), such as abnormalities of the large blood vessel that distributes blood from the heart to the rest of the body (the aorta). In these cases, the diagnosis often changes from isolated ectopia lentis to Marfan syndrome.More About This Health Condition
Researchers have identified more than 1,300 FBN1 gene mutations that cause Marfan syndrome, a disorder that affects the connective tissue supporting the body's joints and organs. Abnormalities in the connective tissue lead to heart and eye problems in people with this disorder. In addition, affected individuals are usually tall and slender with elongated fingers and toes and other skeletal abnormalities.
Most of the mutations that cause Marfan syndrome change a single amino acid in the fibrillin-1 protein. The remaining FBN1 gene mutations result in an abnormal fibrillin-1 protein that cannot function properly. FBN1 gene mutations that cause Marfan syndrome reduce the amount of fibrillin-1 produced by the cell, alter the structure or stability of fibrillin-1, or impair the transport of fibrillin-1 out of the cell. These mutations lead to a severe reduction in the amount of fibrillin-1 available to form microfibrils.
Without enough microfibrils, excess TGF-β growth factors are activated and elasticity in many tissues is decreased, leading to overgrowth and instability of tissues and the signs and symptoms of Marfan syndrome.More About This Health Condition
Mutations in the FBN1 gene have also been identified in Weill-Marchesani syndrome. One of the identified mutations deletes part of the gene, leading to the production of an unstable version of the fibrillin-1 protein. The unstable protein likely interferes with the assembly of microfibrils. Abnormal microfibrils weaken connective tissue, which causes the eye, heart, and skeletal abnormalities associated with Weill-Marchesani syndrome.More About This Health Condition
Familial thoracic aortic aneurysm and dissection
MedlinePlus Genetics provides information about Familial thoracic aortic aneurysm and dissectionMore About This Health Condition
MedlinePlus Genetics provides information about Geleophysic dysplasiaMore About This Health Condition
MedlinePlus Genetics provides information about Shprintzen-Goldberg syndromeMore About This Health Condition
Mutations in the FBN1 gene can cause a condition called stiff skin syndrome. This condition is characterized by very hard, thick skin covering most of the body. The abnormal skin limits movement and can lead to joint deformities called contractures that restrict the movement of certain joints. The signs and symptoms of stiff skin syndrome usually become apparent in infancy to mid-childhood.
Mutations in the FBN1 gene can cause another condition called MASS syndrome. This condition involves abnormalities in several parts of the body, including the mitral valve (one of the valves that controls blood flow through the heart), the aorta (a large blood vessel that distributes blood from the heart to the rest of the body), the skeleton, and the skin.
It is unknown why different mutations in the FBN1 gene cause such a variety of disorders.
Other Names for This Gene
- fibrillin 1 (Marfan syndrome)
Additional Information & Resources
Tests Listed in the Genetic Testing Registry
Scientific Articles on PubMed
- Ades LC, Sullivan K, Biggin A, Haan EA, Brett M, Holman KJ, Dixon J, Robertson S, Holmes AD, Rogers J, Bennetts B. FBN1, TGFBR1, and the Marfan-craniosynostosis/mental retardation disorders revisited. Am J Med Genet A. 2006 May 15;140(10):1047-58. doi: 10.1002/ajmg.a.31202. Citation on PubMed
- Arbustini E, Grasso M, Ansaldi S, Malattia C, Pilotto A, Porcu E, Disabella E, Marziliano N, Pisani A, Lanzarini L, Mannarino S, Larizza D, Mosconi M, Antoniazzi E, Zoia MC, Meloni G, Magrassi L, Brega A, Bedeschi MF, Torrente I, Mari F, Tavazzi L. Identification of sixty-two novel and twelve known FBN1 mutations in eighty-one unrelated probands with Marfan syndrome and other fibrillinopathies. Hum Mutat. 2005 Nov;26(5):494. doi: 10.1002/humu.9377. Citation on PubMed
- Brautbar A, LeMaire SA, Franco LM, Coselli JS, Milewicz DM, Belmont JW. FBN1 mutations in patients with descending thoracic aortic dissections. Am J Med Genet A. 2010 Feb;152A(2):413-6. doi: 10.1002/ajmg.a.32856. Citation on PubMed or Free article on PubMed Central
- Chandra A, Patel D, Aragon-Martin JA, Pinard A, Collod-Beroud G, Comeglio P, Boileau C, Faivre L, Charteris D, Child AH, Arno G. The revised ghent nosology; reclassifying isolated ectopia lentis. Clin Genet. 2015 Mar;87(3):284-7. doi: 10.1111/cge.12358. Epub 2014 Mar 6. Citation on PubMed
- Collod-Beroud G, Boileau C. Marfan syndrome in the third Millennium. Eur J Hum Genet. 2002 Nov;10(11):673-81. doi: 10.1038/sj.ejhg.5200876. Citation on PubMed or Free article on PubMed Central
- Dietz HC, McIntosh I, Sakai LY, Corson GM, Chalberg SC, Pyeritz RE, Francomano CA. Four novel FBN1 mutations: significance for mutant transcript level and EGF-like domain calcium binding in the pathogenesis of Marfan syndrome. Genomics. 1993 Aug;17(2):468-75. doi: 10.1006/geno.1993.1349. Citation on PubMed
- Faivre L, Collod-Beroud G, Callewaert B, Child A, Loeys BL, Binquet C, Gautier E, Arbustini E, Mayer K, Arslan-Kirchner M, Kiotsekoglou A, Comeglio P, Grasso M, Beroud C, Bonithon-Kopp C, Claustres M, Stheneur C, Bouchot O, Wolf JE, Robinson PN, Ades L, De Backer J, Coucke P, Francke U, De Paepe A, Boileau C, Jondeau G. Pathogenic FBN1 mutations in 146 adults not meeting clinical diagnostic criteria for Marfan syndrome: further delineation of type 1 fibrillinopathies and focus on patients with an isolated major criterion. Am J Med Genet A. 2009 May;149A(5):854-60. doi: 10.1002/ajmg.a.32809. Citation on PubMed
- Faivre L, Collod-Beroud G, Loeys BL, Child A, Binquet C, Gautier E, Callewaert B, Arbustini E, Mayer K, Arslan-Kirchner M, Kiotsekoglou A, Comeglio P, Marziliano N, Dietz HC, Halliday D, Beroud C, Bonithon-Kopp C, Claustres M, Muti C, Plauchu H, Robinson PN, Ades LC, Biggin A, Benetts B, Brett M, Holman KJ, De Backer J, Coucke P, Francke U, De Paepe A, Jondeau G, Boileau C. Effect of mutation type and location on clinical outcome in 1,013 probands with Marfan syndrome or related phenotypes and FBN1 mutations: an international study. Am J Hum Genet. 2007 Sep;81(3):454-66. doi: 10.1086/520125. Epub 2007 Jul 25. Citation on PubMed or Free article on PubMed Central
- Faivre L, Gorlin RJ, Wirtz MK, Godfrey M, Dagoneau N, Samples JR, Le Merrer M, Collod-Beroud G, Boileau C, Munnich A, Cormier-Daire V. In frame fibrillin-1 gene deletion in autosomal dominant Weill-Marchesani syndrome. J Med Genet. 2003 Jan;40(1):34-6. doi: 10.1136/jmg.40.1.34. Citation on PubMed or Free article on PubMed Central
- Glesby MJ, Pyeritz RE. Association of mitral valve prolapse and systemic abnormalities of connective tissue. A phenotypic continuum. JAMA. 1989 Jul 28;262(4):523-8. Citation on PubMed
- Le Goff C, Mahaut C, Wang LW, Allali S, Abhyankar A, Jensen S, Zylberberg L, Collod-Beroud G, Bonnet D, Alanay Y, Brady AF, Cordier MP, Devriendt K, Genevieve D, Kiper PO, Kitoh H, Krakow D, Lynch SA, Le Merrer M, Megarbane A, Mortier G, Odent S, Polak M, Rohrbach M, Sillence D, Stolte-Dijkstra I, Superti-Furga A, Rimoin DL, Topouchian V, Unger S, Zabel B, Bole-Feysot C, Nitschke P, Handford P, Casanova JL, Boileau C, Apte SS, Munnich A, Cormier-Daire V. Mutations in the TGFbeta binding-protein-like domain 5 of FBN1 are responsible for acromicric and geleophysic dysplasias. Am J Hum Genet. 2011 Jul 15;89(1):7-14. doi: 10.1016/j.ajhg.2011.05.012. Epub 2011 Jun 16. Citation on PubMed or Free article on PubMed Central
- Loeys BL, Gerber EE, Riegert-Johnson D, Iqbal S, Whiteman P, McConnell V, Chillakuri CR, Macaya D, Coucke PJ, De Paepe A, Judge DP, Wigley F, Davis EC, Mardon HJ, Handford P, Keene DR, Sakai LY, Dietz HC. Mutations in fibrillin-1 cause congenital scleroderma: stiff skin syndrome. Sci Transl Med. 2010 Mar 17;2(23):23ra20. doi: 10.1126/scitranslmed.3000488. Citation on PubMed or Free article on PubMed Central
- Mizuguchi T, Matsumoto N. Recent progress in genetics of Marfan syndrome and Marfan-associated disorders. J Hum Genet. 2007;52(1):1-12. doi: 10.1007/s10038-006-0078-1. Epub 2006 Oct 24. Citation on PubMed
- Robinson PN, Arteaga-Solis E, Baldock C, Collod-Beroud G, Booms P, De Paepe A, Dietz HC, Guo G, Handford PA, Judge DP, Kielty CM, Loeys B, Milewicz DM, Ney A, Ramirez F, Reinhardt DP, Tiedemann K, Whiteman P, Godfrey M. The molecular genetics of Marfan syndrome and related disorders. J Med Genet. 2006 Oct;43(10):769-87. doi: 10.1136/jmg.2005.039669. Epub 2006 Mar 29. Citation on PubMed or Free article on PubMed Central
- Rommel K, Karck M, Haverich A, von Kodolitsch Y, Rybczynski M, Muller G, Singh KK, Schmidtke J, Arslan-Kirchner M. Identification of 29 novel and nine recurrent fibrillin-1 (FBN1) mutations and genotype-phenotype correlations in 76 patients with Marfan syndrome. Hum Mutat. 2005 Dec;26(6):529-39. doi: 10.1002/humu.20239. Citation on PubMed