Nyctalopin is a protein located on the surface of photoreceptor-to-ON bipolar cell synapse in the retina. It is composed of 481 amino acids.[1] and is encoded in human by the NYX gene.[2][3][4] This gene is found on the chromosome X[5] and has two exons.[1] This protein is a leucine-rich proteoglycan[6] which is expressed in the eye, spleen and brain in mice.[7] Mutations in this gene cause congenital stationary night blindness in humans (CSNB).[8] which is a stable retinal disorder.[2] The consequence of this mutation results in an abnormal night vision. Nyctalopin is critical due to the fact that it generates a depolarizing bipolar cell response due to the mutation on the NYX gene.[6] Most of the time, CSNB are associated to hygh myopia which is the result of a mutation on the same gene.[1] Several mutations can occur on the NYX gene resulting on many form of night blindness in humans.[1] Some studies show that these mutations are more present in Asian population than in Caucasian population.[1] A mouse strain called nob (no b-wave) carries a spontaneous mutation leading to a frameshift in this gene. These mice are used as an animal model for congenital stationary night blindness.[9]

NYX
Identifiers
AliasesNYX, CLRP, CSNB1, CSNB1A, CSNB4, NBM1, nyctalopin
External IDsOMIM: 300278 MGI: 2448607 HomoloGene: 11210 GeneCards: NYX
Orthologs
SpeciesHumanMouse
Entrez

60506

236690

Ensembl

ENSG00000188937

ENSMUSG00000051228

UniProt

Q9GZU5

P83503

RefSeq (mRNA)

NM_022567
NM_001378477

NM_173415

RefSeq (protein)

NP_072089
NP_001365406

NP_775591

Location (UCSC)Chr X: 41.45 – 41.48 MbChr X: 13.33 – 13.36 Mb
PubMed search[12][13]
Wikidata
View/Edit HumanView/Edit Mouse

Discovery

The first evidence of the existence of mutation in NYX gene, encoding the leucine-rich proteoglycan nyctalopin, cause X-linked complete congenital stationary night blindness was provided by Richard G. Weleber at the University of Alberta in 2000.[2]

Gene location

The NYX gene is located on the short arm (p) of chromosome X, from base pair 41,447,434 to base pair 41,475,710.[14]

Protein structure

Nyctalopin contains a N-terminal signal peptide and a C-terminal glycosylphosphatidylinositol (GPI) anchor.[15] Predicted signal sequence is likely to be processed by a co-translational mechanism.[16] Nyctalopin does not have two transmembrane domains and the only transmembrane domain is found to be between the amino acid 452 ad 472.[16] In the endoplasmic reticulum, the protein is oriented with the N-terminus in the lumen of the endoplasmic reticulum and the C-terminus is located in the cytoplasm.[16] The central part of the polypeptide encodes 11 consecutive leucines-rich repeats (LRRs).[3] These LRR are flanked by N-terminal and C-terminal rich LRRs[3] Tandem LRRs domains are folded into ß-sheets and α-helices, all joined by loops.[16] According to the cysteine pattern, nyctalopin is part of the class II small leucine-rich proteoglycans.[3] These proteins, are involved in several functions such as cell signalling, growth control, and formation of the extracellular matrix.[3] LRR domains are involved in the protein–protein interaction in small leucine rich repeat proteoglycan family members.[15] Also, LRR domains have a critical role in nyctalopin function. Congenital stationary night blindness in humans appears when a mutation in the LRR domains of nyctalopin occurs.

Mutations

The complete form of congenital stationary night blindness is due to the absence of nyctalopin.[16] This absence is due to a mutation involving an 85 base pair deletion.[17] In humans, more than 30 mutations are found in the NYX gene and most of them have an impact either on the tertiary structure of the LRR domains of nyctalopin or to truncate the protein.[15]

References

  1. 1 2 3 4 5 Yip SP, Li CC, Yiu WC, Hung WH, Lam WW, Lai MC, Ng PW, Fung WY, Chu PH, Jiang B, Chan HH, Yap MK (May 2013). "A novel missense mutation in the NYX gene associated with high myopia". Ophthalmic & Physiological Optics. 33 (3): 346–53. doi:10.1111/opo.12036. PMID 23406521. S2CID 8851666.
  2. 1 2 3 Bech-Hansen NT, Naylor MJ, Maybaum TA, Sparkes RL, Koop B, Birch DG, Bergen AA, Prinsen CF, Polomeno RC, Gal A, Drack AV, Musarella MA, Jacobson SG, Young RS, Weleber RG (November 2000). "Mutations in NYX, encoding the leucine-rich proteoglycan nyctalopin, cause X-linked complete congenital stationary night blindness". Nature Genetics. 26 (3): 319–23. doi:10.1038/81619. PMID 11062471. S2CID 10223880.
  3. 1 2 3 4 5 Pusch CM, Zeitz C, Brandau O, Pesch K, Achatz H, Feil S, Scharfe C, Maurer J, Jacobi FK, Pinckers A, Andreasson S, Hardcastle A, Wissinger B, Berger W, Meindl A (November 2000). "The complete form of X-linked congenital stationary night blindness is caused by mutations in a gene encoding a leucine-rich repeat protein". Nature Genetics. 26 (3): 324–7. doi:10.1038/81627. PMID 11062472. S2CID 42428370.
  4. ↑ "Entrez Gene: NYX nyctalopin".
  5. ↑ Jacobi FK, Andréasson S, Langrova H, Meindl A, Zrenner E, Apfelstedt-Sylla E, Pusch CM (October 2002). "Phenotypic expression of the complete type of X-linked congenital stationary night blindness in patients with different mutations in the NYX gene". Graefe's Archive for Clinical and Experimental Ophthalmology. 240 (10): 822–8. doi:10.1007/s00417-002-0562-z. PMID 12397430. S2CID 25140284.
  6. 1 2 Pearring JN, Bojang P, Shen Y, Koike C, Furukawa T, Nawy S, Gregg RG (July 2011). "A role for nyctalopin, a small leucine-rich repeat protein, in localizing the TRP melastatin 1 channel to retinal depolarizing bipolar cell dendrites". The Journal of Neuroscience. 31 (27): 10060–6. doi:10.1523/JNEUROSCI.1014-11.2011. PMC 3139999. PMID 21734298.
  7. ↑ Pesch K, Zeitz C, Fries JE, Münscher S, Pusch CM, Kohler K, Berger W, Wissinger B (May 2003). "Isolation of the mouse nyctalopin gene nyx and expression studies in mouse and rat retina". Investigative Ophthalmology & Visual Science. 44 (5): 2260–6. doi:10.1167/iovs.02-0115. PMID 12714669.
  8. ↑ Zhou L, Li T, Song X, Li Y, Li H, Dan H (2015). "NYX mutations in four families with high myopia with or without CSNB1". Molecular Vision. 21: 213–23. PMC 4357032. PMID 25802485.
  9. ↑ Pardue MT, McCall MA, LaVail MM, Gregg RG, Peachey NS (November 1998). "A naturally occurring mouse model of X-linked congenital stationary night blindness". Investigative Ophthalmology & Visual Science. 39 (12): 2443–9. PMID 9804152.
  10. 1 2 3 GRCh38: Ensembl release 89: ENSG00000188937 - Ensembl, May 2017
  11. 1 2 3 GRCm38: Ensembl release 89: ENSMUSG00000051228 - Ensembl, May 2017
  12. ↑ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  13. ↑ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  14. ↑ "NYX gene".
  15. 1 2 3 Gregg RG, Kamermans M, Klooster J, Lukasiewicz PD, Peachey NS, Vessey KA, McCall MA (November 2007). "Nyctalopin expression in retinal bipolar cells restores visual function in a mouse model of complete X-linked congenital stationary night blindness". Journal of Neurophysiology. 98 (5): 3023–33. doi:10.1152/jn.00608.2007. PMC 2933657. PMID 17881478.
  16. 1 2 3 4 5 Bojang P, Gregg RG (2012). "Topological analysis of small leucine-rich repeat proteoglycan nyctalopin". PLOS ONE. 7 (4): e33137. Bibcode:2012PLoSO...733137B. doi:10.1371/journal.pone.0033137. PMC 3317652. PMID 22485138.
  17. ↑ Gregg RG, Mukhopadhyay S, Candille SI, Ball SL, Pardue MT, McCall MA, Peachey NS (January 2003). "Identification of the gene and the mutation responsible for the mouse nob phenotype". Investigative Ophthalmology & Visual Science. 44 (1): 378–84. doi:10.1167/iovs.02-0501. PMID 12506099.

Further reading

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