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Iroquois homeobox 3
Symbols IRX3 ; IRX-1; IRXB1
External IDs OMIM612985 MGI1197522 HomoloGene7385 GeneCards: IRX3 Gene
Species Human Mouse
Entrez 79191 16373
Ensembl ENSG00000177508 ENSMUSG00000031734
UniProt P78415 P81067
RefSeq (mRNA) NM_024336 NM_001253822
RefSeq (protein) NP_077312 NP_001240751
Location (UCSC) Chr 16:
54.28 – 54.29 Mb
Chr 8:
91.8 – 91.8 Mb
PubMed search [1] [2]

Iroquois-class homeodomain protein IRX-3, also known as Iroquois homeobox protein 3, is a protein that in humans is encoded by the IRX3 gene.[1]


IRX3 is a member of the Iroquois homeobox gene family and plays a role in an early step of neural development.[2] Members of this family appear to play multiple roles during pattern formation of vertebrate embryos.[1][3] Specifically, IRX3 contributes to pattern formation in the spinal cord where it tranlates a morphogen gradient into transcriptional events, and is directly regulated by NKX2-2. [4]

Clinical significance[edit]

Association with obesity[edit]

Obesity-associated noncoding sequences within FTO interact with the promoter of IRX3 and FTO in human, mouse, and zebrafish. Obesity-associated single nucleotide polymorphisms are related to the expression of IRX3 (not FTO) in the human brain. A direct connection between the expression of IRX3 and body mass and composition was shown through the decrease in body weight of 25-30% in IRX3-deficient mice. This suggests that IRX3 influences obesity.[5]


  1. ^ a b "Entrez Gene: iroquois homeobox 3". 
  2. ^ Bellefroid EJ, Kobbe A, Gruss P, Pieler T, Gurdon JB, Papalopulu N (Jan 1998). "Xiro3 encodes a Xenopus homolog of the Drosophila Iroquois genes and functions in neural specification". The EMBO Journal 17 (1): 191–203. doi:10.1093/emboj/17.1.191. PMC 1170370. PMID 9427753. 
  3. ^ Lewis MT, Ross S, Strickland PA, Snyder CJ, Daniel CW (Jun 1999). "Regulated expression patterns of IRX-2, an Iroquois-class homeobox gene, in the human breast". Cell and Tissue Research 296 (3): 549–54. doi:10.1007/s004410051316. PMID 10370142. 
  4. ^ Lovrics A, Gao Y, Juhász B, Bock I, Byrne HM, Dinnyés A et al. (November 2014). "Boolean modelling reveals new regulatory connections between transcription factors orchestrating the development of the ventral spinal cord". PloS One 9 (11): e111430. doi:10.1371/journal.pone.0111430. PMID 25398016. 
  5. ^ Smemo S, Tena JJ, Kim KH, Gamazon ER, Sakabe NJ, Gómez-Marín C et al. (Mar 2014). "Obesity-associated variants within FTO form long-range functional connections with IRX3". Nature 507 (7492): 371–5. doi:10.1038/nature13138. PMID 24646999. 

Further reading[edit]

This article incorporates text from the United States National Library of Medicine, which is in the public domain.