OPHN1 explained

Oligophrenin-1 is a protein that in humans is encoded by the OPHN1 gene.^{[1] [2] [3]}

Function

Oligophrenin 1 has 25 exons and encodes a Rho-GTPase-activating protein. The Rho proteins are important mediators of intracellular signal transduction, which affects cell migration and cell morphogenesis.

The role of OPHN1 in the medial prefrontal cortex in the behavioural responses to stress, and learned helplessness-inducing effect of OPHN1 deletion in parvalbumin interneurons, is of recent research interest.^{[4] [5]} It is also involved in regulation in inhibitory interneurons in the olfactory bulb.^[6]

Clinical significance

Mutations in this gene are responsible for non-specific X-linked intellectual disability (previously called mental retardation).

OPHN1 syndrome is a rare disorder characterized by intellectual disability and changes in the part of the brain which controls movement and balance (cerebellum). The syndrome mainly affects males. It is characterized by low muscle tone (hypotonia), developmental and cognitive delay, early-onset seizures, abnormal behavior, characteristic facial features (long face, bulging forehead, under eye creases, deep set eyes, and large ears), crossed eyes (strabismus) and inability to coordinate movements.^{[7] [8]} A small cerebellum and large ventricles can be seen on brain imaging (MRI).^{[9] [10]} Treatment is supportive and includes physical, occupational and speech and language therapy.^[11] In 2014 an OPHN1 patient organization and website was formed to support families and promote OPHN1 syndrome research. ^[12]

OPHN1 syndrome is caused by mutations in the OPHN1 gene, which is located on the X chromosome. Inheritance is X-linked. Some females who carry a mutation in the OPHN1 gene may have mild learning disabilities, mild cognitive impairment, strabismus, and subtle facial changes.

Further reading

• Castellví-Bel S, Milà M . Genes responsible for nonspecific mental retardation . Molecular Genetics and Metabolism . 72 . 2 . 104–8 . February 2001 . 11161835 . 10.1006/mgme.2000.3128 .
• Ramakers GJ . Rho proteins, mental retardation and the cellular basis of cognition . Trends in Neurosciences . 25 . 4 . 191–9 . April 2002 . 11998687 . 10.1016/S0166-2236(00)02118-4 . 13941716 .
• Bergmann C, Zerres K, Senderek J, Rudnik-Schoneborn S, Eggermann T, Häusler M, Mull M, Ramaekers VT . Oligophrenin 1 (OPHN1) gene mutation causes syndromic X-linked mental retardation with epilepsy, rostral ventricular enlargement and cerebellar hypoplasia . Brain . 126 . Pt 7 . 1537–44 . July 2003 . 12805098 . 10.1093/brain/awg173 . free .
• Tentler D, Gustavsson P, Leisti J, Schueler M, Chelly J, Timonen E, Annerén G, Willard HF, Dahl N . Deletion including the oligophrenin-1 gene associated with enlarged cerebral ventricles, cerebellar hypoplasia, seizures and ataxia . European Journal of Human Genetics . 7 . 5 . 541–8 . July 1999 . 10439959 . 10.1038/sj.ejhg.5200320 . free .
• Billuart P, Chelly J, Carrié A, Vinet M, Couvert P, McDonell N, Zemni R, Kahn A, Moraine C, Beldjord C, Bienvenu T . Determination of the gene structure of human oligophrenin-1 and identification of three novel polymorphisms by screening of DNA from 164 patients with non-specific X-linked mental retardation . Annales de Génétique . 43 . 1 . 5–9 . 2000 . 10818214 . 10.1016/S0003-3995(00)00015-0 .
• Pinheiro NA, Caballero OL, Soares F, Reis LF, Simpson AJ . Significant overexpression of oligophrenin-1 in colorectal tumors detected by cDNA microarray analysis . Cancer Letters . 172 . 1 . 67–73 . October 2001 . 11595131 . 10.1016/S0304-3835(01)00625-5 .
• Kitano T, Schwarz C, Nickel B, Pääbo S . Gene diversity patterns at 10 X-chromosomal loci in humans and chimpanzees . Molecular Biology and Evolution . 20 . 8 . 1281–9 . August 2003 . 12777533 . 10.1093/molbev/msg134 . free .
• Philip N, Chabrol B, Lossi AM, Cardoso C, Guerrini R, Dobyns WB, Raybaud C, Villard L . Mutations in the oligophrenin-1 gene (OPHN1) cause X linked congenital cerebellar hypoplasia . Journal of Medical Genetics . 40 . 6 . 441–6 . June 2003 . 12807966 . 1735502 . 10.1136/jmg.40.6.441 .
• Xiao J, Neylon CB, Nicholson GA, Furness JB . Evidence that a major site of expression of the RHO-GTPASE activating protein, oligophrenin-1, is peripheral myelin . Neuroscience . 124 . 4 . 781–7 . 2004 . 15026118 . 10.1016/j.neuroscience.2004.01.007 . 10045850 .
• Zanni G, Saillour Y, Nagara M, Billuart P, Castelnau L, Moraine C, Faivre L, Bertini E, Durr A, Guichet A, Rodriguez D, des Portes V, Beldjord C, Chelly J . Oligophrenin 1 mutations frequently cause X-linked mental retardation with cerebellar hypoplasia . Neurology . 65 . 9 . 1364–9 . November 2005 . 16221952 . 10.1212/01.wnl.0000182813.94713.ee . 21028212 .

Notes and References

1. Bienvenu T, Der-Sarkissian H, Billuart P, Tissot M, Des Portes V, Brüls T, Chabrolle JP, Chauveau P, Cherry M, Kahn A, Cohen D, Beldjord C, Chelly J, Cherif D . Mapping of the X-breakpoint involved in a balanced X;12 translocation in a female with mild mental retardation . European Journal of Human Genetics . 5 . 2 . 105–9 . Aug 1997 . 9195162 . 10.1159/000484743.
2. Billuart P, Bienvenu T, Ronce N, des Portes V, Vinet MC, Zemni R, Roest Crollius H, Carrié A, Fauchereau F, Cherry M, Briault S, Hamel B, Fryns JP, Beldjord C, Kahn A, Moraine C, Chelly J . Oligophrenin-1 encodes a rhoGAP protein involved in X-linked mental retardation . Nature . 392 . 6679 . 923–6 . April 1998 . 9582072 . 10.1038/31940 . 1998Natur.392..923B . 4355919 .
3. Web site: Entrez Gene: OPHN1 oligophrenin 1.
4. Wang M, Gallo NB, Tai Y, Li B, Van Aelst L . Oligophrenin-1 moderates behavioral responses to stress by regulating parvalbumin interneuron activity in the medial prefrontal cortex . Neuron . 109 . 10 . 1636–1656.e8 . May 2021 . 33831348 . 10.1016/j.neuron.2021.03.016. 8141044 .
5. Cvetkovska V, Bagot RC . Ophn1 regulation of prefrontal inhibition: A mechanism for stress susceptibility in intellectual disability . Neuron . 109 . 10 . 1583–1584 . May 2021 . 34015262 . 10.1016/j.neuron.2021.04.030 . 235074402 . free .
6. Redolfi N, Galla L, Maset A, Murru L, Savoia E, Zamparo I, Gritti A, Billuart P, Passafaro M, Lodovichi C . 6 . Oligophrenin-1 regulates number, morphology and synaptic properties of adult-born inhibitory interneurons in the olfactory bulb . Human Molecular Genetics . 25 . 23 . 5198–5211 . December 2016 . 27742778 . 10.1093/hmg/ddw340 . free .
7. Zanni G, Bertini ES . X-linked disorders with cerebellar dysgenesis . Orphanet Journal of Rare Diseases . 6 . 24 . May 2011 . 21569638 . 3115841 . 10.1186/1750-1172-6-24 . free .
8. OPHN1 . Genetics Home Reference . 2016 . 2018-09-29 . 2018-09-29 . https://web.archive.org/web/20180929080408/https://ghr.nlm.nih.gov/gene/OPHN1#conditions . dead .
9. Web site: Zanni G . X-linked intellectual disability-cerebellar hypoplasia syndrome. . Orphanet . February 2013 .
10. Bedeschi MF, Novelli A, Bernardini L, Parazzini C, Bianchi V, Torres B, Natacci F, Giuffrida MG, Ficarazzi P, Dallapiccola B, Lalatta F . Association of syndromic mental retardation with an Xq12q13.1 duplication encompassing the oligophrenin 1 gene . American Journal of Medical Genetics. Part A . 146A . 13 . 1718–24 . July 2008 . 18512229 . 10.1002/ajmg.a.32365 . 39448434 .
11. Web site: OPHN1 therapies . Oligophrenin-1 Syndrome Foundation .
12. Web site: OPHN1 therapies . Oligophrenin-1 Syndrome Foundation .