We read with great interest and pleasure Mackey’s article [1] concerning the vast opportunities of leveraging broad genetic and epigenetic concepts, which are essential to genetically literate ophthalmologists, by teaching the subjects of eye colour and colour perception.
Additionally, the author demonstrated the gene-environment interaction in colour blindness mainly by twin study on the #TheDress photograph [2]. A recent retrospective study of Israeli Jewish adolescents further supports this notion and illuminates the intricate relationship between genetics and environmental factors affecting colour blindness [3]. The unique composition of the population enabled to investigate the association of congenital colour blindness prevalence with both ethnicity (place of origin, representing the genetic component) and place of birth (representing environmental factors and habits), and the interplay between them. It provided three main lines of evidence: (I) The prevalence of congenital colour blindness differed among subpopulations of different ethnic background and among subpopulations of different place of birth; (II) differences in the prevalence of congenital colour blindness were obtained among subjects of the same origin, who were born in Israel compared to those who were born elsewhere; and (III) both variables - place of origin (p < 0.01) and place of birth (p < 0.05) were associated with the prevalence of congenital colour blindness in a multivariable regression model. Thus, congenital colour blindness may be associated with both genetics and environmental factors.
Colour blindness pertains to the cone photoreceptors in the retina. Preservation of cone photoreceptors was shown to be affected by the environment [4]. Epigenetic mechanisms may underly environmental contribution to the pathogenesis of colour blindness, in a similar manner to other congenital anomalies [5]. We anticipate and hope that this evidence may pave the way to future research exploring if and to what extent epigenetic mechanisms are implicated in the aetiology of colour blindness. This may provide novel insights into the consequences of environmental driven in utero modifications of the human genome regulatory architecture on the pathogenesis of colour blindness, which is considered as primarily genetic in origin. This in turn, should be integrated into the genetic education programme of every ophthalmologist, as proposed by Professor David A. Mackey.
References
Mackey DA. What colour are your eyes? Teaching the genetics of eye colour & colour vision. Edridge Green Lecture RCOphth Annual Congress Glasgow May 2019. Eye. 2021. https://doi.org/10.1038/s41433-021-01749-x
Mahroo OA, Williams KM, Hossain IT, Yonova-Doing E, Kozareva D, Yusuf A, et al. Do twins share the same dress code? Quantifying relative genetic and environmental contributions to subjective perceptions of “the dress” in a classical twin study. J Vis. 2017;17:29 https://doi.org/10.1167/17.1.29
Machluf Y, Allon G, Sebbag A, Chaiter Y, Mezer E. A large population study reveals a novel association between congenital color vision deficiency and environmental factors. Graefes Arch Clin Exp Ophthalmol. 2021. https://doi.org/10.1007/s00417-021-05417-4
Barone I, Novelli E, Strettoi E. Long-term preservation of cone photoreceptors and visual acuity in rd10 mutant mice exposed to continuous environmental enrichment. Mol Vis. 2014;20:1545–56.
Barbosa M, Joshi RS, Garg P, Martin-Trujillo A, Patel N, Jadhav B, et al. Identification of rare de novo epigenetic variations in congenital disorders. Nat Commun. 2018;9:2064 https://doi.org/10.1038/s41467-018-04540-x
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EM, YM and YC conceived the idea of this correspondence. All authors carefully and critically read the original articles by Mackey [1], and collaboratively designed the outline of this article. YM wrote the paper with inputs from all the co-authors.
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Machluf, Y., Chaiter, Y., Allon, G. et al. Comment on: ‘What colour are your eyes? Teaching the genetics of eye colour & colour vision. Edridge Green Lecture RCOphth Annual Congress Glasgow May 2019’. Eye 36, 1144 (2022). https://doi.org/10.1038/s41433-022-01975-x
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DOI: https://doi.org/10.1038/s41433-022-01975-x