MERTK gene

Overview

Gene (OMIM No.)
Function of gene/protein
  • Protein: MER proto-oncogene, tyrosine kinase
  • Regulates many physiological processes such as cell survival, migration, differentiation and phagocytosis of apoptotic cells
  • Regulates RPE phagocytosis of shed photoreceptor outer segments
Clinical phenotype
(OMIM phenotype no.)
Inheritance
  • Autosomal recessive
Signs for AR-RP
  • Optic disc pallor
  • Vessel attenuation
  • Scarce bone spicule pigmentation in the mid-periphery
  • Subtle white dots/RPE mottling in the periphery in some cases
  • Early macular involvement with a range of abnormalities RPE mottling, and yellowish-white deposits, bull’s eye maculopathy and macular atrophy)
  • Posterior sub-capsular cataract
Visual function
  • Nyctalopia within the first two decades of life
  • VF may be preserved into the 2nd decade but tend to deteriorate gradually thereafter
  • Some patients have relatively preserved BCVA (as good as 6/6) in the 2nd decade; progressive decline over time with most reaching PL vision by the 6th decade
  • Dyschromatopsia
Systemic features
  • No extraocular features reported
Key investigations
  • Full field ERG: rod-cone dystrophy initially; unrecordable or significantly reduced rod and cone responses in later stages
  • Pattern ERG: Early loss of responses
  • FAF: Foveal hyper AF surrounded by a ring of decreased AF or atrophic patches centrally in advanced stages
  • Multifocal fine hyper-AF dots in the posterior pole can be observed in younger patients
  • OCT: Severe ONL thinning with disruption/loss of EZ and ELM; hyper-reflective dots above the RPE/Bruch’s complex may correspond to some of the hyper-AF dots but this finding is not specific to MERTK-retinopathy
Molecular diagnosisNext generation sequencing
  • Targeted gene panels (retinal)
  • Whole exome sequencing
  • Whole genome sequencing
Management
Therapies under research
Further information
PL: Perception of light vision

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Additional information

Pathogenic mutations in MERTK account for 2-3% of AR-RP cases.[1-3]

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References

  1.  Audo I, Mohand-Said S, Boulanger-Scemama E, et al. MERTK mutation update in inherited retinal diseases. Hum Mutat. 2018;39(7):887-913
  2.  Patel N, Aldahmesh MA, Alkuraya H, et al. Expanding the clinical, allelic, and locus heterogeneity of retinal dystrophies. Genet Med. 2016;18(6):554-562
  3.  Ostergaard E, Duno M, Batbayli M, Vilhelmsen K, Rosenberg T. A novel MERTK deletion is a common founder mutation in the Faroe Islands and is responsible for a high proportion of retinitis pigmentosa cases. Mol Vis. 2011;17:1485-1492
  4.  D’Cruz PM, Yasumura D, Weir J, et al. Mutation of the receptor tyrosine kinase gene Mertk in the retinal dystrophic RCS rat. Hum Mol Genet. 2000;9(4):645-651
  5.  Feng W, Yasumura D, Matthes MT, LaVail MM, Vollrath D. Mertk triggers uptake of photoreceptor outer segments during phagocytosis by cultured retinal pigment epithelial cells. J Biol Chem. 2002;277(19):17016-17022
  6.  Gal A, Li Y, Thompson DA, et al. Mutations in MERTK, the human orthologue of the RCS rat retinal dystrophy gene, cause retinitis pigmentosa. Nat Genet. 2000;26(3):270-271
  7.  Charbel Issa P, Bolz HJ, Ebermann I, Domeier E, Holz FG, Scholl HP. Characterisation of severe rod-cone dystrophy in a consanguineous family with a splice site mutation in the MERTK gene. Br J Ophthalmol. 2009;93(7):920-925
  8.  Tschernutter M, Jenkins SA, Waseem NH, et al. Clinical characterisation of a family with retinal dystrophy caused by mutation in the Mertk gene. Br J Ophthalmol. 2006;90(6):718-723
  9.  Mackay DS, Henderson RH, Sergouniotis PI, et al. Novel mutations in MERTK associated with childhood onset rod-cone dystrophy. Mol Vis. 2010;16:369-377
  10.  Ksantini M, Lafont E, Bocquet B, Meunier I, Hamel CP. Homozygous mutation in MERTK causes severe autosomal recessive retinitis pigmentosa. Eur J Ophthalmol. 2012;22(4):647-653
  11.  Jonsson F, Burstedt M, Kellgren TG, Golovleva I. Non-homologous recombination between Alu and LINE-1 repeats results in a 91 kb deletion in MERTK causing severe retinitis pigmentosa. Mol Vis. 2018;24:667-678

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Updated on November 30, 2020
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