MKX explained

Homeobox protein Mohawk, also known as iroquois homeobox protein-like 1, is a protein that in humans is encoded by the MKX (mohawk homeobox) gene.^[1] MKX is a member of an Iroquois (IRX) family-related class of 'three-amino acid loop extension' (TALE) atypical homeobox proteins characterized by 3 additional amino acids in the loop region between helix I and helix II of the homeodomain.^{[1] [2]}

Function

MKX is a transcription factor that regulates tendon differentiation during embryological development. Knocking out this gene in mouse embryos results in them developing hypoplastic tendons containing less type I collagen.^[3] MKX binds directly to the promoter of MyoD and represses its expression, negatively regulating muscle differentiation.^[4]

Expression of MKX is maintained in adult tendon tissues, decreasing as a result of ageing or osteoarthritis. Collagen fibres in tendons become more dense and thick following mechanical stimulation as a result of exercise,^[5] and MKX is essential in this mechanosensory process.^[6]

Further reading

• Robertson NG, Khetarpal U, Gutiérrez-Espeleta GA, Bieber FR, Morton CC . Isolation of novel and known genes from a human fetal cochlear cDNA library using subtractive hybridization and differential screening . Genomics . 23 . 1 . 42–50 . September 1994 . 7829101 . 10.1006/geno.1994.1457 .
• Weinmann A, Galle PR, Teufel A . In silico characterization of an Iroquois family-related homeodomain protein . International Journal of Molecular Medicine . 16 . 3 . 443–8 . September 2005 . 16077953 . 10.3892/ijmm.16.3.443 .
• Anderson DM, Arredondo J, Hahn K, Valente G, Martin JF, Wilson-Rawls J, Rawls A . Mohawk is a novel homeobox gene expressed in the developing mouse embryo . Developmental Dynamics . 235 . 3 . 792–801 . March 2006 . 16408284 . 10.1002/dvdy.20671 . 29018840 . free .
• Barbe L, Lundberg E, Oksvold P, Stenius A, Lewin E, Björling E, Asplund A, Pontén F, Brismar H, Uhlén M, Andersson-Svahn H . Toward a confocal subcellular atlas of the human proteome . Molecular & Cellular Proteomics . 7 . 3 . 499–508 . March 2008 . 18029348 . 10.1074/mcp.M700325-MCP200 . free .

Notes and References

1. Web site: Entrez Gene: mohawk homeobox.
2. Anderson DM, Arredondo J, Hahn K, Valente G, Martin JF, Wilson-Rawls J, Rawls A . Mohawk is a novel homeobox gene expressed in the developing mouse embryo . Developmental Dynamics . 235 . 3 . 792–801 . March 2006 . 16408284 . 10.1002/dvdy.20671 . 29018840 . free .
3. Ito Y, Toriuchi N, Yoshitaka T, Ueno-Kudoh H, Sato T, Yokoyama S, Nishida K, Akimoto T, Takahashi M, Miyaki S, Asahara H . The Mohawk homeobox gene is a critical regulator of tendon differentiation . Proceedings of the National Academy of Sciences of the United States of America . 107 . 23 . 10538–42 . June 2010 . 20498044 . 2890854 . 10.1073/pnas.1000525107 . 2010PNAS..10710538I . free .
4. Chuang HN, Hsiao KM, Chang HY, Wu CC, Pan H . The homeobox transcription factor Irxl1 negatively regulates MyoD expression and myoblast differentiation . The FEBS Journal . 281 . 13 . 2990–3003 . July 2014 . 24814716 . 10.1111/febs.12837 . 19733342 . free .
5. Nakahara H, Hasegawa A, Otabe K, Ayabe F, Matsukawa T, Onizuka N, Ito Y, Ozaki T, Lotz MK, Asahara H . Transcription factor Mohawk and the pathogenesis of human anterior cruciate ligament degradation . Arthritis and Rheumatism . 65 . 8 . 2081–9 . August 2013 . 23686683 . 3840305 . 10.1002/art.38020 .
6. Kayama T, Mori M, Ito Y, Matsushima T, Nakamichi R, Suzuki H, Ichinose S, Saito M, Marumo K, Asahara H . Gtf2ird1-Dependent Mohawk Expression Regulates Mechanosensing Properties of the Tendon . Molecular and Cellular Biology . 36 . 8 . 1297–309 . April 2016 . 26884464 . 4836271 . 10.1128/MCB.00950-15 .