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Early growth response protein 2 is a protein that in humans is encoded by the EGR2 gene. EGR2 (also termed Krox20) is a transcription regulatory factor, containing two zinc finger DNA-binding sites, and is highly expressed in a population of migrating neural crest cells.[1][2][3] It is later expressed in the neural crest derived cells of the cranial ganglion. The protein encoded by Krox20 contains two cys2his2-type zinc fingers. Krox20 gene expression is restricted to the early hindbrain development.[2][4] It is evolutionarily conserved in vertebrates, humans, mice, chicks, and zebra fish.[5] In addition, the amino acid sequence and most aspects of the embryonic gene pattern is conserved among vertebrates, further implicating its role in hindbrain development.[3][6][7][8] When the Krox20 is deleted in mice, the protein coding ability of the Krox20 gene (including the DNA-binding domain of the zinc finger) is diminished. These mice are unable to survive after birth and exhibit major hindbrain defects.[2][4] These defects include but are not limited to defects in formation of cranial sensory ganglia, partial fusion of the trigeminal nerve (V) with the facial (VII) and auditory (VII) nerves, the proximal nerve roots coming off of these ganglia were disorganized and intertwined among one another as they entered the brainstem, and there was fusion of the glossopharyngeal (IX) nerve complex.[9][10][11]


The early growth response protein 2 is a transcription factor with three tandem C2H2-type zinc fingers. Mutations in this gene are associated with the autosomal dominant Charcot-Marie-Tooth disease, type 1D,[12] Dejerine–Sottas disease,[13] and Congenital Hypomyelinating Neuropathy.[14] Two studies have linked EGR2 expression to proliferation of osteoprogenitors [15] and cell lines derived from Ewing sarcoma, which is a highly aggressive bone-associated cancer.[16]

New research suggests that Krox20 - or the lack of it - is the reason for male baldness.[17]


  1. Chavrier P, Janssen-Timmen U, Mattéi MG, Zerial M, Bravo R, Charnay P (February 1989). "Structure, chromosome location, and expression of the mouse zinc finger gene Krox-20: multiple gene products and coregulation with the proto-oncogene c-fos". Molecular and Cellular Biology. 9 (2): 787–97. doi:10.1128/mcb.9.2.787. PMC 362656. PMID 2496302.
  2. 2.0 2.1 2.2 Swiatek PJ, Gridley T (November 1993). "Perinatal lethality and defects in hindbrain development in mice homozygous for a targeted mutation of the zinc finger gene Krox20". Genes & Development. 7 (11): 2071–84. doi:10.1101/gad.7.11.2071. PMID 8224839.
  3. 3.0 3.1 Wilkinson DG, Bhatt S, Chavrier P, Bravo R, Charnay P (February 1989). "Segment-specific expression of a zinc-finger gene in the developing nervous system of the mouse". Nature. 337 (6206): 461–4. doi:10.1038/337461a0. PMID 2915691.
  4. 4.0 4.1 Bradley LC, Snape A, Bhatt S, Wilkinson DG (January 1993). "The structure and expression of the Xenopus Krox-20 gene: conserved and divergent patterns of expression in rhombomeres and neural crest". Mechanisms of Development. 40 (1–2): 73–84. doi:10.1016/0925-4773(93)90089-g. PMID 8443108.
  5. Bhat RV, Worley PF, Cole AJ, Baraban JM (April 1992). "Activation of the zinc finger encoding gene krox-20 in adult rat brain: comparison with zif268". Brain Research. Molecular Brain Research. 13 (3): 263–6. doi:10.1016/0169-328x(92)90034-9. PMID 1317498.
  6. Wilkinson DG, Bhatt S, Cook M, Boncinelli E, Krumlauf R (October 1989). "Segmental expression of Hox-2 homoeobox-containing genes in the developing mouse hindbrain". Nature. 341 (6241): 405–9. doi:10.1038/341405a0. PMID 2571936.
  7. Hunt P, Gulisano M, Cook M, Sham MH, Faiella A, Wilkinson D, Boncinelli E, Krumlauf R (October 1991). "A distinct Hox code for the branchial region of the vertebrate head". Nature. 353 (6347): 861–4. doi:10.1038/353861a0. PMID 1682814.
  8. Oxtoby E, Jowett T (March 1993). "Cloning of the zebrafish krox-20 gene (krx-20) and its expression during hindbrain development". Nucleic Acids Research. 21 (5): 1087–95. doi:10.1093/nar/21.5.1087. PMC 309267. PMID 8464695.
  9. Frohman MA, Boyle M, Martin GR (October 1990). "Isolation of the mouse Hox-2.9 gene; analysis of embryonic expression suggests that positional information along the anterior-posterior axis is specified by mesoderm". Development. 110 (2): 589–607. PMID 1983472.
  10. Murphy P, Davidson DR, Hill RE (September 1989). "Segment-specific expression of a homoeobox-containing gene in the mouse hindbrain". Nature. 341 (6238): 156–9. doi:10.1038/341156a0. PMID 2571087.
  11. Nieto MA, Bradley LC, Wilkinson DG (1991). "Conserved segmental expression of Krox-20 in the vertebrate hindbrain and its relationship to lineage restriction". Development. Suppl 2: 59–62. PMID 1688180.
  12. "Entrez Gene: EGR2 early growth response 2 (Krox-20 homolog, Drosophila)".
  13. Boerkoel CF, Takashima H, Bacino CA, Daentl D, Lupski JR (July 2001). "EGR2 mutation R359W causes a spectrum of Dejerine-Sottas neuropathy". Neurogenetics. 3 (3): 153–7. doi:10.1007/s100480100107. PMID 11523566.
  14. Warner LE, Mancias P, Butler IJ, McDonald CM, Keppen L, Koob KG, Lupski JR (April 1998). "Mutations in the early growth response 2 (EGR2) gene are associated with hereditary myelinopathies". Nature Genetics. 18 (4): 382–4. doi:10.1038/ng0498-382. PMID 9537424.
  15. Chandra A, Lan S, Zhu J, Siclari VA, Qin L (July 2013). "Epidermal growth factor receptor (EGFR) signaling promotes proliferation and survival in osteoprogenitors by increasing early growth response 2 (EGR2) expression". The Journal of Biological Chemistry. 288 (28): 20488–98. doi:10.1074/jbc.M112.447250. PMC 3711314. PMID 23720781.
  16. Grünewald TG, Bernard V, Gilardi-Hebenstreit P, Raynal V, Surdez D, Aynaud MM, et al. (September 2015). "Chimeric EWSR1-FLI1 regulates the Ewing sarcoma susceptibility gene EGR2 via a GGAA microsatellite". Nature Genetics. 47 (9): 1073–8. doi:10.1038/ng.3363. PMC 4591073. PMID 26214589.
  17. Le, Lu. "Scientists find skin cells at the root of balding, gray hair". UT Southwestern Medical Center. Retrieved 9 May 2017.

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