DAX1 (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1) is a nuclear receptor protein that in humans is encoded by the NR0B1gene (nuclear receptor subfamily 0, group B, member 1).[5][6][7] The NR0B1 gene is located on the short (p) arm of the X chromosome between bands Xp21.3 and Xp21.2, from base pair 30,082,120 to base pair 30,087,136.
Function
This gene encodes a protein that lacks the normal DNA-binding domain contained in other nuclear receptors.[8] The encoded protein acts as a dominant-negative regulator of transcription of other nuclear receptors including steroidogenic factor 1.[9] This protein also functions as an anti-testis gene by acting antagonistically to SRY. Mutations in this gene result in both X-linked congenital adrenal hypoplasia and hypogonadotropic hypogonadism.[5]
DAX1 plays an important role in the normal development of several hormone-producing tissues. These tissues include the adrenal glands above each kidney, the pituitary gland and hypothalamus, which are located in the brain, and the reproductive structures (the testes and ovaries). DAX1 controls the activity of certain genes in the cells that form these tissues during embryonic development. Proteins that control the activity of other genes are known as transcription factors. DAX1 also plays a role in regulating hormone production in these tissues after they have been formed.
Role in disease
X-linked adrenal hypoplasia congenita is caused by mutations in the NR0B1 gene. More than 90 NR0B1 mutations that cause X-linked adrenal hypoplasia congenita have been identified. Many of these mutations delete all or part of the NR0B1 gene, preventing the production of DAX1 protein. Some mutations cause the production of an abnormally short protein. Other mutations cause a change in one of the building blocks (amino acids) of DAX1. These mutations are thought to result in a misshapen, nonfunctional protein. Loss of DAX1 function leads to adrenal insufficiency and hypogonadotropic hypogonadism,[10] which are the main characteristics of this disorder.
Duplication of genetic material on the X chromosome in the region that contains the NR0B1 gene can cause a condition called dosage-sensitive sex reversal. The extra copy of the NR0B1 gene prevents the formation of male reproductive tissues. People who have this duplication usually appear to be female, but are genetically male with both an X and a Y chromosome.
In some cases, genetic material is deleted from the X chromosome in a region that contains several genes, including NR0B1. This deletion results in a condition called adrenal hypoplasia congenita with complex glycerol kinase deficiency. In addition to the signs and symptoms of adrenal hypoplasia congenita, individuals with this condition may have elevated levels of lipids in their blood and urine and may have problems regulating blood sugar levels. In rare cases, the amount of genetic material deleted is even more extensive and affected individuals also have Duchenne muscular dystrophy.
^Tab. 1.1 of Stefan White & Andrew Sinclair: The Molecular Basis of Gonadal Development and Disorders of Sex Development, in: John M. Hutson, Garry L. Warne, & Sonia R. Grover (eds): Disorders of Sex Development. An Integrated Approach to Management, Springer 2012, ISBN978-3-642-22963-3, e-ISBN978-3-642-22964-0, DOI: 10.1007/978-3-642-22964-0.
Franzese A, Brunetti-Pierri N, Spagnuolo MI, Spadaro R, Giugliano M, Mukai T, Valerio G (May 2005). "Inappropriate tall stature and renal ectopy in a male patient with X-linked congenital adrenal hypoplasia due to a novel missense mutation in the DAX-1 gene". American Journal of Medical Genetics Part A. 135 (1): 72–4. doi:10.1002/ajmg.a.30670. PMID15800903. S2CID39583218.
Petersen KE, Bille T, Jacobsen BB, Iversen T (Nov 1982). "X-linked congenital adrenal hypoplasia. A study of five generations of a Greenlandic Family". Acta Paediatrica Scandinavica. 71 (6): 947–51. doi:10.1111/j.1651-2227.1982.tb09554.x. PMID6891556. S2CID43416274.
Burris TP, Guo W, Le T, McCabe ER (Sep 1995). "Identification of a putative steroidogenic factor-1 response element in the DAX-1 promoter". Biochemical and Biophysical Research Communications. 214 (2): 576–81. doi:10.1006/bbrc.1995.2324. PMID7677767.
Bardoni B, Zanaria E, Guioli S, Floridia G, Worley KC, Tonini G, Ferrante E, Chiumello G, McCabe ER, Fraccaro M (Aug 1994). "A dosage sensitive locus at chromosome Xp21 is involved in male to female sex reversal". Nature Genetics. 7 (4): 497–501. doi:10.1038/ng0894-497. PMID7951319. S2CID20673267.
Zanaria E, Muscatelli F, Bardoni B, Strom TM, Guioli S, Guo W, Lalli E, Moser C, Walker AP, McCabe ER (Dec 1994). "An unusual member of the nuclear hormone receptor superfamily responsible for X-linked adrenal hypoplasia congenita". Nature. 372 (6507): 635–41. Bibcode:1994Natur.372..635Z. doi:10.1038/372635a0. PMID7990953. S2CID4363344.
Muscatelli F, Strom TM, Walker AP, Zanaria E, Récan D, Meindl A, Bardoni B, Guioli S, Zehetner G, Rabl W (Dec 1994). "Mutations in the DAX-1 gene give rise to both X-linked adrenal hypoplasia congenita and hypogonadotropic hypogonadism". Nature. 372 (6507): 672–6. Bibcode:1994Natur.372..672M. doi:10.1038/372672a0. PMID7990958. S2CID4314671.
Guo W, Burris TP, McCabe ER (Oct 1995). "Expression of DAX-1, the gene responsible for X-linked adrenal hypoplasia congenita and hypogonadotropic hypogonadism, in the hypothalamic-pituitary-adrenal/gonadal axis". Biochemical and Molecular Medicine. 56 (1): 8–13. doi:10.1006/bmme.1995.1049. PMID8593542.
Schwartz M, Blichfeldt S, Müller J (Jan 1997). "X-linked adrenal hypoplasia in a large Greenlandic family. Detection of a missense mutation (N4401) in the DAX-1 gene; implication for genetic counselling and carrier diagnosis". Human Genetics. 99 (1): 83–7. doi:10.1007/s004390050316. PMID9003500. S2CID31266597.
Takahashi T, Shoji Y, Shoji Y, Haraguchi N, Takahashi I, Takada G (Mar 1997). "Active hypothalamic-pituitary-gonadal axis in an infant with X-linked adrenal hypoplasia congenita". The Journal of Pediatrics. 130 (3): 485–8. doi:10.1016/S0022-3476(97)70217-8. PMID9063431.
