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AliasesNKX3-2, NK3 homeobox 2, BAPX1, NKX3.2, NKX3B, SMMD
External IDsOMIM: 602183 MGI: 108015 HomoloGene: 68168 GeneCards: NKX3-2
Gene location (Human)
Chromosome 4 (human)
Chr.Chromosome 4 (human)[1]
Chromosome 4 (human)
Genomic location for NKX3-2
Genomic location for NKX3-2
Band4p15.33Start13,540,830 bp[1]
End13,545,050 bp[1]
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 4: 13.54 – 13.55 MbChr 5: 41.76 – 41.76 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

NK3 homeobox 2 also known as NKX3-2 is a human gene. It is a homolog of bagpipe (bap) in Drosophila and therefore also known as Bapx1 (bagpipe homeobox homolog 1). The protein encoded by this gene is a homeodomain containing transcription factor.[5]


NKX3-2 plays a role in the development of the axial and limb skeleton.[6] Mutations disrupting the function of these gene are associated with spondylo-megaepiphyseal-metaphyseal dysplasia (SMMD)[7]. Nkx3-2 in mice also regulates patterning in the middle ear.[8] Two small bones in the middle ear, the malleus and incus, are homologous to the articular and quadrate, the bones of the proximal jaw joint in fish and other non-mammalian jawed vertebrates. NKX3-2 expression is required to pattern the articulated joint between these jaw bones, as knockdowns or knockouts of this gene result in the loss of the jaw joint in zebrafish,[9] chicken,[10] and amphibians[11].


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000109705 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000049691 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:".
  4. ^ "Mouse PubMed Reference:".
  5. ^ Yoshiura KI, Murray JC (October 1997). "Sequence and chromosomal assignment of human BAPX1, a bagpipe-related gene, to 4p16.1: a candidate gene for skeletal dysplasia". Genomics. 45 (2): 425–8. doi:10.1006/geno.1997.4926. PMID 9344671.
  6. ^ Lettice L, Hecksher-Sørensen J, Hill R (2001). "The role of Bapx1 (Nkx3.2) in the development and evolution of the axial skeleton". J. Anat. 199 (Pt 1–2): 181–7. doi:10.1111/j.1469-7580.2008.00944.x. PMC 1594973. PMID 11523821.
  7. ^ Hellemans, Jan; Simon, Marleen; Dheedene, Annelies; Alanay, Yasemin; Mihci, Ercan; Rifai, Laila; Sefiani, Abdelaziz; van Bever, Yolande; Meradji, Morteza (2009). "Homozygous Inactivating Mutations in the NKX3-2 Gene Result in Spondylo-Megaepiphyseal-Metaphyseal Dysplasia". The American Journal of Human Genetics. 85 (6): 916–922. doi:10.1016/j.ajhg.2009.11.005. PMC 2790567. PMID 20004766.
  8. ^ Tucker AS, Watson RP, Lettice LA, Yamada G, Hill RE (2004). "Bapx1 regulates patterning in the middle ear: altered regulatory role in the transition from the proximal jaw during vertebrate evolution". Development. 131 (6): 1235–1245. doi:10.1242/dev.01017. PMID 14973294.
  9. ^ Miller, C. T. (2003). "Two endothelin 1 effectors, hand2 and bapx1, pattern ventral pharyngeal cartilage and the jaw joint". Development. 130 (7): 1353–1365. doi:10.1242/dev.00339.
  10. ^ Wilson, Joanne; Tucker, Abigail S (2004). "Fgf and Bmp signals repress the expression of Bapx1 in the mandibular mesenchyme and control the position of the developing jaw joint". Developmental Biology. 266 (1): 138–150. doi:10.1016/j.ydbio.2003.10.012.
  11. ^ Lukas, Paul; Olsson, Lennart (2018). "Bapx1 is required for jaw joint development in amphibians". Evolution & Development. 20 (6): 192–206. doi:10.1111/ede.12267. ISSN 1525-142X.

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