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Home / Equine Research Bank / Equine Vet J / Whole-genome sequencing identifies missense mutation in GRM6...
Equine veterinary journal2020; 53(2); 316-323; doi: 10.1111/evj.13318

Whole-genome sequencing identifies missense mutation in GRM6 as the likely cause of congenital stationary night blindness in a Tennessee Walking Horse.

Abstract: The only known genetic cause of congenital stationary night blindness (CSNB) in horses is a 1378 bp insertion in TRPM1. However, an affected Tennessee Walking Horse was found to have no copies of this variant. Objective: To identify the genetic cause for CSNB in an affected Tennessee Walking Horse. Methods: Case report detailing a whole-genome sequencing (WGS) approach to identify a causal variant. Methods: A complete ophthalmic exam, including an electroretinogram (ERG), was performed on suspected CSNB-affected horse. WGS data were generated from the case and compared with data from seven other breeds (n = 29). One hundred candidate genes were evaluated for coding variants homozygous in the case and absent in all other horses. Protein modelling was used to assess the functional effects of the identified variant. A random cohort of 90 unrelated Tennessee Walking Horses and 273 horses from additional breeds were screened to estimate allele frequency of the GRM6 variant. Results: ERG results were consistent with CSNB. WGS analysis identified a missense mutation in metabotropic glutamate receptor 6 (GRM6) (c.533C>T p.Thr178Met). This single nucleotide polymorphism (SNP) is predicted to be deleterious and protein modelling supports impaired binding of the neurotransmitter glutamate. This variant was not detected in 273 horses from three additional breeds. The estimated allele frequency in Tennessee Walking Horses is 10%. Conclusions: Limited phenotype information for controls and no additional cases with which to replicate this finding. Conclusions: We identified a likely causal recessive missense variant in GRM6. Based on protein modelling, this variant alters GRM6 binding, and thus signalling from the retinal rod cell to the ON-bipolar cell, impairing vision in low light conditions. Given the 10% population allele frequency, it is likely that additional affected horses exist in this breed and further work is needed to identify and examine these animals.
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Publication Date: 2020-08-03 PubMed ID: 32654228DOI: 10.1111/evj.13318Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research study describes how whole-genome sequencing helped identify a likely genetic cause, a missense mutation in GRM6, of congenital stationary night blindness in a Tennessee Walking Horse. This was different from the previously known genetic cause associated with a 1378 bp insertion in TRPM1.

Methodology:

The research used a methodical approach with the following steps:

  • A complete ophthalmic exam, inclusive of an electroretinogram (ERG), was performed on the supposedly CSNB-affected horse. The ERG results confirmed the condition of CSNB.
  • Whole-Genome Sequencing (WGS) was performed on the affected horse. The resultant data were contrasted with data from other horses encompassing seven different breeds.
  • From this analysis, potentially significant genes which may carry the causal variant were evaluated. Here, the researchers focused on coding variants that were homozygous in the affected horse and absent from all the other horses.
  • Protein modelling was undertaken to examine the potential functional effects of the identified variant.
  • The identified GRM6 variant was screened in a sizable cohort of 90 unrelated Tennessee Walking Horses and 273 horses from additional breeds. This helped to estimate the allele frequency of the GRM6 variant.

Findings:

The findings of the research unfolded as such:

  • The WGS and ERG analyses identified a missense mutation in the metabotropic glutamate receptor 6 (GRM6) (c.533C>T p.Thr178Met) as the likely cause of CSNB in the affected horse.
  • This specific SNP was suggested to be damaging, as protein modelling indicated that this mutation hampers the binding of the neurotransmitter glutamate.
  • The estimated frequency of the GRM6 allele was found to be 10% specifically within the Tennessee Walking Horses, and it was unseen in 273 horses from three unrelated breeds.

Conclusion:

The conclusion of the study centered around the following points:

  • The research highlighted a likely causal recessive missense variant in GRM6 as the cause of CSNB.
  • This variant is believed to disrupt GRM6 binding and subsequently the signalling from the retinal rod cell to the ON-bipolar cell, which then worsens vision in low light conditions.
  • Considering the 10% population allele frequency, the researchers suggested that additional affected horses likely exist in this breed.
  • However, it was also noted that limited phenotype information for controls and no additional cases with which to replicate this finding were present, hence further research is required to identify and examine these animals.

Cite This Article

APA
Hack YL, Crabtree EE, Avila F, Sutton RB, Grahn R, Oh A, Gilger B, Bellone RR. (2020). Whole-genome sequencing identifies missense mutation in GRM6 as the likely cause of congenital stationary night blindness in a Tennessee Walking Horse. Equine Vet J, 53(2), 316-323. https://doi.org/10.1111/evj.13318

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 53
Issue: 2
Pages: 316-323

Researcher Affiliations

Hack, Yael L
  • Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA.
Crabtree, Elizabeth E
  • College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
Avila, Felipe
  • Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA.
Sutton, Roger B
  • Cell Physiology and Molecular Biophysics, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, Texas, USA.
Grahn, Robert
  • Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA.
Oh, Annie
  • College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
Gilger, Brian
  • College of Veterinary Medicine, North Carolina State University, Raleigh, North Carolina, USA.
Bellone, Rebecca R
  • Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis, California, USA.
  • Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA.

MeSH Terms

  • Animals
  • Eye Diseases, Hereditary / genetics
  • Eye Diseases, Hereditary / veterinary
  • Genetic Diseases, X-Linked
  • Horse Diseases / genetics
  • Horses
  • Mutation, Missense
  • Myopia
  • Night Blindness / genetics
  • Night Blindness / veterinary
  • Receptors, Glutamate / genetics
  • Tennessee

Grant Funding

  • 16-12 / UC Davis Center for Equine Health
  • North Carolina State University's College of Veterinary Medicine
  • School of Veterinary Medicine at the University of California, Davis

References

This article includes 42 references
  1. Nunnery C, Pickett JP, Zimmerman KL. Congenital stationary night blindness in a Thoroughbred and a Paso Fino.. Vet Ophthalmol 2005;8:415-419.
  2. Aguirre GD, Baldwin V, Pearce-Kelling S, Narfström K, Ray K, Acland GM. Congenital stationary night blindness in the dog: common mutation in the RPE65 gene indicates founder effect.. Mol Vision 1998;4:23-29.
  3. Das G, Miyadera K, Santana E, Aguirre GD, Kondo M. Molecular and immunohistochemical characterization of a canine model of complete congenital stationary night blindness (CSNB).. Investig Ophthalmol Visual Sci 2014;55:3288.
  4. Riggs LA. Electroretinography in cases of night blindness.. Am J Ophthalmol 1954;38:70-78.
  5. Langrová H, Gamer D, Friedburg C, Besch D, Zrenner E, Apfelstedt-Sylla E. Abnormalities of the long flash ERG in congenital stationary night blindness of the Schubert-Bornschein type.. Vision Res 2002;42:1475-1483.
  6. Neuillé M, Shamieh SE, Orhan E, Michiels C, Antonio A, Lancelot M-E. Lrit3 Deficient Mouse (nob6): a novel model of Complete Congenital Stationary Night Blindness (cCSNB).. PLoS ONE 2014;9:e90342.
  7. Sandmeyer LS, Breaux CB, Archer S, Grahn BH. Clinical and electroretinographic characteristics of congenital stationary night blindness in the Appaloosa and the association with the leopard complex.. Vet Ophthalmol 2007;10:368-375.
  8. Witzel DA, Smith EL, Wilson RD, Aguirre GD. Congenital stationary night blindness: an animal model.. Investig Ophthalmol Visual Sci 1978;17:788-795.
  9. Bellone R, Brooks S, Sandmeyer L, Murphy B, Forsyth G, Archer S. Differential gene expression of TRPM1, the potential cause of congenital stationary night blindness and coat spotting patterns (LP) in the Appaloosa horse (Equus caballus).. Genetics 2008;179:1861-1870.
  10. Bellone RR, Holl H, Setaluri V, Devi S, Maddodi N, Archer S. Evidence for a retroviral insertion in TRPM1 as the cause of congenital stationary night blindness and leopard complex spotting in the horse.. PLoS ONE 2013;8:e78280.
  11. Morgans CW, Brown RL, Duvoisin RM. TRPM1: the endpoint of the mGluR6 signal transduction cascade in retinal ON-bipolar cells.. BioEssays 2010;32:609-614.
  12. Shen Y, Heimel JA, Kamermans M, Peachey NS, Gregg RG, Nawy S. A transient receptor potential-like channel mediates synaptic transmission in rod bipolar cells.. J Neurosci 2009;29:6088-6093.
  13. Sandmeyer LS, Bellone RR, Archer S, Bauer BS, Nelson J, Forsyth G. Congenital stationary night blindness is associated with the leopard complex in the miniature horse.. Vet Ophthalmol 2012;15:18-22.
  14. Bellone RR, Liu J, Petersen JL, Mack M, Singer-Berk M, Drögemüller C. A missense mutation in damage-specific DNA binding protein 2 is a genetic risk factor for limbal squamous cell carcinoma in horses.. Int J Cancer 2017;141:342-353.
  15. Locke MM, Penedo MCT, Bricker SJ, Millon LV, Murray JD. Linkage of the grey coat colour locus to microsatellites on horse chromosome 25.. Anim Genet 2002;33:329-337.
  16. HTStream. https://github.com/ibest/HTStream
  17. Li H, Durbin R. Fast and accurate short read alignment with Burrows-Wheeler transform.. Bioinformatics 2009;25:1754-1760.
  18. Garrison E, Marth G. Haplotype-based variant detection from short-read sequencing.. ArXiv 2012.
  19. Li H*, Handsaker B*, Wysoker A, Fennell T, Ruan J, Homer N. The Sequence alignment/map (SAM) format and SAMtools.. Bioinformatics 2009;25:2078-2079.
  20. Cingolani P, Platts A, Wang LL, Coon M, Nguyen T, Wang L. A program for annotating and predicting the effects of single nucleotide polymorphisms, SnpEff: SNPs in the genome of Drosophila melanogaster strain w1118; iso-2; iso-3.. Fly 2012;6:80-92.
  21. Online Mendelian Inheritance in Man. OMIM®. McKusick-Nathans Institute of Genetic Medicine, John Hopkins University (Baltimore, MD). https://omim.org/
  22. Online Mendelian Inheritance in Animals. OMIA. Sydney School of Veterinary Science. http://omia.org/
  23. Zerbino DR, Achuthan P, Akanni W, Amode MR, Barrell D, Bhai J. Ensembl 2018.. Nucleic Acids Res 2017;46:D754-D761.
  24. NCBI Resource Coordinators. Database resources of the National Center for Biotechnology Information.. Nucleic Acids Res 2016;44:D7-D19.
  25. Ye J, Coulouris G, Zaretskaya I, Cutcutache I, Rozen S, Madden TL. Primer-BLAST: a tool to design target-specific primers for polymerase chain reaction.. BMC Bioinformatics 2012;13:134.
  26. Bendl J, Stourac J, Salanda O, Pavelka A, Wieben ED, Zendulka J. PredictSNP: Robust and Accurate Consensus Classifier for Prediction of Disease-Related Mutations (PredictSNP: Robust Consensus Classifier).. PLoS Comput Biol 2014;10:e1003440.
    doi: 10.1371/journal.pcbi.1003440google scholar: lookup
  27. Kent WJ, Sugnet CW, Furey TS, Roskin KM, Pringle TH, Zahler AM. The human genome browser at UCSC.. Genome Res 2002;12:996-1006.
  28. Webb B, Sali A. Comparative protein structure modeling using modeller.. Curr Protoc Bioinformatics 2016;54:5.6.1-5.6.37.
  29. Schkeryantz JM, Chen Q, Ho JD, Atwell S, Zhang A, Vargas MC. Determination of L-AP4-bound human mGlu8 receptor amino terminal domain structure and the molecular basis for L-AP4’s group III mGlu receptor functional potency and selectivity.. Bioorg Med Chem Lett 2018;28:612-617.
  30. Muto T, Tsuchiya D, Morikawa K, Jingami H. Structures of the extracellular regions of the group II/III metabotropic glutamate receptors.. Proc Natl Acad Sci USA 2007;104:3759-3764.
  31. Koes DR, Baumgartner MP, Camacho CJ. Lessons learned in empirical scoring with smina from the CSAR 2011 benchmarking exercise.. J Chem Inform Model 2013;53:1893-1904.
  32. Combs SA, Deluca SL, Deluca SH, Lemmon GH, Nannemann DP, Nguyen ED. Small-molecule ligand docking into comparative models with Rosetta.. Nat Protoc 2013;8:1277-1298.
  33. The PyMOL Molecular Graphics System, Version 2.0 Schrödinger, LLC. https://pymol.org/2/
  34. Zeitz C, Forster U, Neidhardt J, Feil S, Kälin S, Leifert D. Night blindness-associated mutations in the ligand-binding, cysteine-rich, and intracellular domains of the metabotropic glutamate receptor 6 abolish protein trafficking.. Hum Mutat 2007;28:771-780.
  35. Niswender CM, Conn PJ. Metabotropic glutamate receptors: physiology, pharmacology, and disease.. Annu Rev Pharmacol Toxicol 2010;50:295-322.
  36. Morgans CW. Neurotransmitter release at ribbon synapses in the retina.. Immunol Cell Biol 2000;78:442-6.
  37. Dhingra A, Lyubarsky A, Jiang M, Pugh EN, Birnbaumer L, Sterling P. The light response of ON bipolar neurons requires Gαo.. J Neurosci 2000;20:9053-9058.
  38. Kondo M, Das G, Imai R, Santana E, Nakashita T, Imawaka M. A naturally occurring canine model of autosomal recessive congenital stationary night blindness.. Plos One 2015;10.
  39. Koike C, Obara T, Uriu Y, Numata T, Sanuki R, Miyata K. TRPM1 is a component of the retinal ON bipolar cell transduction channel in the mGluR6 cascade.. Proc Natl Acad Sci USA 2010;107:332-337.
  40. Dryja TP, Mcgee TL, Berson EL, Fishman GA, Sandberg MA, Alexander KR. Night blindness and abnormal cone electroretinogram ON responses in patients with mutations in the GRM6 gene encoding mGluR6.. Proc Natl Acad Sci USA 2005;102(13):4884-4889.
  41. Zeitz C, Genderen MV, Neidhardt J, Luhmann UFO, Hoeben F, Forster U. Mutations in GRM6 cause autosomal recessive congenital stationary night blindness with a distinctive scotopic 15-Hz flicker electroretinogram.. Investig Ophthalmol Visual Sci 2005;46:4328-4335.
  42. O’Connor E, Allen LE, Bradshaw K, Boylan J, Moore AT, Trump D. Congenital stationary night blindness associated with mutations in GRM6 encoding glutamate receptor MGluR6.. Br J Ophthalmol 2006;90:653-654.

Citations

This article has been cited 3 times.
  1. Tozaki T, Ohnuma A, Nakamura K, Hano K, Takasu M, Takahashi Y, Tamura N, Sato F, Shimizu K, Kikuchi M, Ishige T, Kakoi H, Hirota KI, Hamilton NA, Nagata SI. Detection of Indiscriminate Genetic Manipulation in Thoroughbred Racehorses by Targeted Resequencing for Gene-Doping Control.. Genes (Basel) 2022 Sep 4;13(9).
    doi: 10.3390/genes13091589pubmed: 36140757google scholar: lookup
  2. Peng S, Petersen JL, Bellone RR, Kalbfleisch T, Kingsley NB, Barber AM, Cappelletti E, Giulotto E, Finno CJ. Decoding the Equine Genome: Lessons from ENCODE.. Genes (Basel) 2021 Oct 27;12(11).
    doi: 10.3390/genes12111707pubmed: 34828313google scholar: lookup
  3. Orhan E, Neuillé M, de Sousa Dias M, Pugliese T, Michiels C, Condroyer C, Antonio A, Sahel JA, Audo I, Zeitz C. A New Mouse Model for Complete Congenital Stationary Night Blindness Due to Gpr179 Deficiency.. Int J Mol Sci 2021 Apr 23;22(9).
    doi: 10.3390/ijms22094424pubmed: 33922602google scholar: lookup
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