SIX homeobox 3
Last updated 18 Aug 2020
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The SIX3 gene provides instructions for making a protein that plays an important role in the development of the eyes and front part of the brain (forebrain). This protein is a transcription factor, which means that it attaches (binds) to specific regions of DNA and helps control the activity of certain genes. The SIX3 protein regulates genes involved in several signaling pathways that are important for embryonic development. Some of these genes are turned on (activated) by the SIX3 protein and others are turned off (repressed).
Normal function
The SIX3 gene provides instructions for making a protein that plays an important role in the development of the eyes and front part of the brain (forebrain). This protein is a transcription factor, which means that it attaches (binds) to specific regions of DNA and helps control the activity of certain genes. The SIX3 protein regulates genes involved in several signaling pathways that are important for embryonic development. Some of these genes are turned on (activated) by the SIX3 protein and others are turned off (repressed).
One gene that is activated by the SIX3 protein is the SHH gene, which provides instructions for making a protein called Sonic Hedgehog. Among its many functions, Sonic Hedgehog helps establish the right and left halves (hemispheres) of the forebrain. The SIX3 protein also regulates genes involved in the formation of the lens of the eye and the specialized tissue at the back of the eye that detects light and colour (the retina).
Conditions referring to this gene or chromosome
Other names
homeobox protein SIX3
HPE2
sine oculis homeobox homolog 3
SIX3_HUMAN
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Further reading and references
- SIX homeobox 3; MedlinePlus, National Library of Medicine.
- Domene S, Roessler E, El-Jaick KB, Snir M, Brown JL, Velez JI, Bale S, Lacbawan F, Muenke M, Feldman B. Mutations in the human SIX3 gene in holoprosencephaly are loss of function. Hum Mol Genet. 2008 Dec 15;17(24):3919-28. doi: 10.1093/hmg/ddn294. Epub 2008 Sep 12.
- Geng X, Speirs C, Lagutin O, Inbal A, Liu W, Solnica-Krezel L, Jeong Y, Epstein DJ, Oliver G. Haploinsufficiency of Six3 fails to activate Sonic hedgehog expression in the ventral forebrain and causes holoprosencephaly. Dev Cell. 2008 Aug;15(2):236-47. doi: 10.1016/j.devcel.2008.07.003.
- Hehr U, Pineda-Alvarez DE, Uyanik G, Hu P, Zhou N, Hehr A, Schell-Apacik C, Altus C, Daumer-Haas C, Meiner A, Steuernagel P, Roessler E, Winkler J, Muenke M. Heterozygous mutations in SIX3 and SHH are associated with schizencephaly and further expand the clinical spectrum of holoprosencephaly. Hum Genet. 2010 Mar;127(5):555-61. doi: 10.1007/s00439-010-0797-4. Epub 2010 Feb 16.
- Jeong Y, Leskow FC, El-Jaick K, Roessler E, Muenke M, Yocum A, Dubourg C, Li X, Geng X, Oliver G, Epstein DJ. Regulation of a remote Shh forebrain enhancer by the Six3 homeoprotein. Nat Genet. 2008 Nov;40(11):1348-53. doi: 10.1038/ng.230. Epub 2008 Oct 5.
- Lacbawan F, Solomon BD, Roessler E, El-Jaick K, Domene S, Velez JI, Zhou N, Hadley D, Balog JZ, Long R, Fryer A, Smith W, Omar S, McLean SD, Clarkson K, Lichty A, Clegg NJ, Delgado MR, Levey E, Stashinko E, Potocki L, Vanallen MI, Clayton-Smith J, Donnai D, Bianchi DW, Juliusson PB, Njolstad PR, Brunner HG, Carey JC, Hehr U, Musebeck J, Wieacker PF, Postra A, Hennekam RC, van den Boogaard MJ, van Haeringen A, Paulussen A, Herbergs J, Schrander-Stumpel CT, Janecke AR, Chitayat D, Hahn J, McDonald-McGinn DM, Zackai EH, Dobyns WB, Muenke M. Clinical spectrum of SIX3-associated mutations in holoprosencephaly: correlation between genotype, phenotype and function. J Med Genet. 2009 Jun;46(6):389-98. doi: 10.1136/jmg.2008.063818. Epub 2009 Apr 2.
- Ribeiro LA, El-Jaick KB, Muenke M, Richieri-Costa A. SIX3 mutations with holoprosencephaly. Am J Med Genet A. 2006 Dec 1;140(23):2577-83. doi: 10.1002/ajmg.a.31377.
- Roessler E, Muenke M. The molecular genetics of holoprosencephaly. Am J Med Genet C Semin Med Genet. 2010 Feb 15;154C(1):52-61. doi: 10.1002/ajmg.c.30236.
- Solomon BD, Lacbawan F, Jain M, Domene S, Roessler E, Moore C, Dobyns WB, Muenke M. A novel SIX3 mutation segregates with holoprosencephaly in a large family. Am J Med Genet A. 2009 May;149A(5):919-25. doi: 10.1002/ajmg.a.32813.
- Solomon BD, Mercier S, Velez JI, Pineda-Alvarez DE, Wyllie A, Zhou N, Dubourg C, David V, Odent S, Roessler E, Muenke M. Analysis of genotype-phenotype correlations in human holoprosencephaly. Am J Med Genet C Semin Med Genet. 2010 Feb 15;154C(1):133-41. doi: 10.1002/ajmg.c.30240.
- Tekendo-Ngongang C, Muenke M, Kruszka P. Holoprosencephaly Overview. 2000 Dec 27 [updated 2026 Jun 9]. In: Adam MP, Bick S, Mirzaa GM, Wallace SE, Amemiya A, editors. GeneReviews(R) [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2026. Available from http://www.ncbi.nlm.nih.gov/books/NBK1530/
- Wallis DE, Roessler E, Hehr U, Nanni L, Wiltshire T, Richieri-Costa A, Gillessen-Kaesbach G, Zackai EH, Rommens J, Muenke M. Mutations in the homeodomain of the human SIX3 gene cause holoprosencephaly. Nat Genet. 1999 Jun;22(2):196-8. doi: 10.1038/9718.
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