Doublecortin expression in the rat dentate gyrus, 21st postnatal day. Oomen et al., 2009.
Doublecortin (DCX) is a microtubule-associated protein expressed by neuronal precursor cells and immature neurons in embryonic and adult cortical structures. Neuronal precursor cells begin to express DCX while actively dividing, and their neuronal daughter cells continue to express DCX for 2–3 weeks as the cells mature into neurons. Downregulation of DCX begins after 2 weeks, and occurs at the same time that these cells begin to express NeuN, a marker for mature neurons.
Due to the nearly exclusive expression of DCX in developing neurons, this protein has been used increasingly as a marker for neurogenesis. Indeed, levels of DCX expression increase in response to exercise, and that increase occurs in parallel with increased BrdU labelling (which is currently a "gold standard" in measuring neurogenesis).
Double layer hippocampus seen in Doublecortin knock out mice (right panels) compared to the normal hippocampus in wild type mice (left panels). Figure extracted from the work of the laboratory of Fiona Francis
In mice where the Doublecortin gene has been knocked out, cortical layers are still correctly formed. However, the hippocampi of these mice show disorganisation in the CA3 region. The normally single layer of pyramidal cells in mutants is seen as a double layer. These mice also have different behavior than their wild type littermates and are epileptic.
The detailed sequence analysis of Doublecortin and Doublecortin-like proteins allowed the identification of a tandem repeat of evolutionarily conserved Doublecortin (DC) domains. These domains are found in the N terminus of proteins and consists of tandemly repeated copies of an around 80 amino acids region. It has been suggested that the first DC domain of Doublecortin binds tubulin and enhances microtubule polymerisation.
Doublecortin has been shown to influence the structure of microtubules. Microtubule nucleated in vitro in the presence of Doublecortin have almost exclusively 13 protofilaments, whereas microtubule nucleated without Doublecortin are present in a range of different sizes.
Doublecortin is mutated in X-linked lissencephaly and the double cortex syndrome, and the clinical manifestations are sex-linked. In males, X-linked lissencephaly produces a smooth brain due to lack of migration of immature neurons, which normally promote folding of the brain surface. Double cortex syndrome is characterized by abnormal migration of neural tissue during development which results in two bands of misplaced neurons within the subcortical white, generating two cortices, giving the name to the syndrome; this finding generally occurs in females. The mutation was discovered by Joseph Gleeson and Christopher A. Walsh in Boston.
^Brown JP, Couillard-Després S, Cooper-Kuhn CM, Winkler J, Aigner L, Kuhn HG (December 2003). "Transient expression of doublecortin during adult neurogenesis". J. Comp. Neurol. 467 (1): 1–10. doi:10.1002/cne.10874. PMID14574675.
^Couillard-Despres S, Winner B, Schaubeck S, Aigner R, Vroemen M, Weidner N, Bogdahn U, Winkler J, Kuhn HG, Aigner L (January 2005). "Doublecortin expression levels in adult brain reflect neurogenesis". Eur. J. Neurosci. 21 (1): 1–14. doi:10.1111/j.1460-9568.2004.03813.x. PMID15654838.
^Horesh D, Sapir T, Francis F, Wolf SG, Caspi M, Elbaum M, Chelly J, Reiner O (September 1999). "Doublecortin, a stabilizer of microtubules". Hum. Mol. Genet. 8 (9): 1599–610. doi:10.1093/hmg/8.9.1599. PMID10441322.
^Gleeson JG, Allen KM, Fox JW, Lamperti ED, Berkovic S, Scheffer I, Cooper EC, Dobyns WB, Minnerath SR, Ross ME, Walsh CA (January 1998). "Doublecortin, a brain-specific gene mutated in human X-linked lissencephaly and double cortex syndrome, encodes a putative signaling protein". Cell. 92 (1): 63–72. doi:10.1016/S0092-8674(00)80899-5. PMID9489700.
^Lowenstein DH (2011). "Seizures and Epilepsy". In Loscalzo J, Longo DL, Fauci AS, Kasper DL, Hauser SL. Harrison's Principles of Internal Medicine (18th ed.). McGraw-Hill Professional. pp. 3251–3269. ISBN0-07-174889-X.
des Portes V, Pinard JM, Billuart P, et al. (1998). "A novel CNS gene required for neuronal migration and involved in X-linked subcortical laminar heterotopia and lissencephaly syndrome". Cell. 92 (1): 51–61. doi:10.1016/S0092-8674(00)80898-3. PMID9489699.
Gleeson JG, Allen KM, Fox JW, et al. (1998). "Doublecortin, a brain-specific gene mutated in human X-linked lissencephaly and double cortex syndrome, encodes a putative signaling protein". Cell. 92 (1): 63–72. doi:10.1016/S0092-8674(00)80899-5. PMID9489700.
des Portes V, Francis F, Pinard JM, et al. (1999). "doublecortin is the major gene causing X-linked subcortical laminar heterotopia (SCLH)". Hum. Mol. Genet. 7 (7): 1063–70. doi:10.1093/hmg/7.7.1063. PMID9618162.
Sossey-Alaoui K, Hartung AJ, Guerrini R, et al. (1998). "Human doublecortin (DCX) and the homologous gene in mouse encode a putative Ca2+-dependent signaling protein which is mutated in human X-linked neuronal migration defects". Hum. Mol. Genet. 7 (8): 1327–32. doi:10.1093/hmg/7.8.1327. PMID9668176.
Pilz DT, Matsumoto N, Minnerath S, et al. (1999). "LIS1 and XLIS (DCX) mutations cause most classical lissencephaly, but different patterns of malformation". Hum. Mol. Genet. 7 (13): 2029–37. doi:10.1093/hmg/7.13.2029. PMID9817918.
Kato M, Kimura T, Lin C, et al. (1999). "A novel mutation of the doublecortin gene in Japanese patients with X-linked lissencephaly and subcortical band heterotopia". Hum. Genet. 104 (4): 341–4. doi:10.1007/s004390050963. PMID10369164.
Pilz DT, Kuc J, Matsumoto N, et al. (2000). "Subcortical band heterotopia in rare affected males can be caused by missense mutations in DCX (XLIS) or LIS1". Hum. Mol. Genet. 8 (9): 1757–60. doi:10.1093/hmg/8.9.1757. PMID10441340.
Sakamoto M, Ono J, Okada S, et al. (2000). "Genetic alteration of the DCX gene in Japanese patients with subcortical laminar heterotopia or isolated lissencephaly sequence". J. Hum. Genet. 45 (3): 167–70. doi:10.1007/s100380050204. PMID10807542.
Matsumoto N, Leventer RJ, Kuc JA, et al. (2001). "Mutation analysis of the DCX gene and genotype/phenotype correlation in subcortical band heterotopia". Eur. J. Hum. Genet. 9 (1): 5–12. doi:10.1038/sj.ejhg.5200548. PMID11175293.
Demelas L, Serra G, Conti M, et al. (2001). "Incomplete penetrance with normal MRI in a woman with germline mutation of the DCX gene". Neurology. 57 (2): 327–30. doi:10.1212/wnl.57.2.327. PMID11468322.
Friocourt G, Chafey P, Billuart P, et al. (2001). "Doublecortin interacts with mu subunits of clathrin adaptor complexes in the developing nervous system". Mol. Cell. Neurosci. 18 (3): 307–19. doi:10.1006/mcne.2001.1022. PMID11591131.
Kato M, Kanai M, Soma O, et al. (2001). "Mutation of the doublecortin gene in male patients with double cortex syndrome: somatic mosaicism detected by hair root analysis". Ann. Neurol. 50 (4): 547–51. doi:10.1002/ana.1231. PMID11601509.
des Portes V, Abaoub L, Joannard A, et al. (2002). "So-called 'cryptogenic' partial seizures resulting from a subtle cortical dysgenesis due to a doublecortin gene mutation". Seizure : the journal of the British Epilepsy Association. 11 (4): 273–7. doi:10.1053/seiz.2001.0607. PMID12027577.
Kizhatil K, Wu YX, Sen A, Bennett V (2002). "A new activity of doublecortin in recognition of the phospho-FIGQY tyrosine in the cytoplasmic domain of neurofascin". J. Neurosci. 22 (18): 7948–58. PMID12223548.
D'Agostino MD, Bernasconi A, Das S, et al. (2002). "Subcortical band heterotopia (SBH) in males: clinical, imaging and genetic findings in comparison with females". Brain. 125 (Pt 11): 2507–22. doi:10.1093/brain/awf248. PMID12390976.
Meyer G, Perez-Garcia CG, Gleeson JG (2003). "Selective expression of doublecortin and LIS1 in developing human cortex suggests unique modes of neuronal movement". Cereb. Cortex. 12 (12): 1225–36. doi:10.1093/cercor/12.12.1225. PMID12427674.