Crognale M A, Teller D Y, Motulsky A G, Deeb S S
Department of Psychology, University of Washington, Seattle, 98195-1525, USA.
Vision Res. 1998 Nov;38(21):3377-85. doi: 10.1016/s0042-6989(97)00425-2.
Earlier research on phenotype/genotype relationships in color vision has shown imperfect predictability of color matching from the photopigment spectral sensitivities inferred from molecular genetic analysis. We previously observed that not all of the genes of the X-chromosome linked photopigment gene locus are expressed in the retina. Since sequence analysis of DNA does not necessarily reveal which of the genes are expressed into photopigments, we used ERG spectral sensitivities and adaptation measurements to assess expressed photopigment complement. Many deuteranomalous subjects had L, M, and L-M hybrid genes. The ERG results showed that M pigment is not present in measurable quantities in deutan subjects. Using these results to determine gene expression improved the correlations between inferred pigment separation and color matching. Furthermore, we found a subject who had normal L and M genes and normal proximal promoter sequences, yet he had a single photopigment (M) by ERG and tested as a protanope. These results demonstrate the utility of ERG measurements in studies of molecular genetics of color vision deficiencies, and further support the conclusion that not all genes are expressed in color deficient subjects. In particular, deuteranomaly requires a presently unknown mechanism of selective expression which excludes normal M genes and allows expression of L-M hybrid genes in one cone type, and the normal L in another.
早期关于色觉中表型/基因型关系的研究表明，从分子遗传学分析推断出的光色素光谱敏感性对颜色匹配的预测并不完美。我们之前观察到，并非所有X染色体连锁的光色素基因位点的基因都在视网膜中表达。由于DNA序列分析不一定能揭示哪些基因会表达为光色素，我们使用视网膜电图（ERG）光谱敏感性和适应性测量来评估表达出的光色素组成。许多绿色弱受试者拥有L、M和L-M杂合基因。ERG结果显示，绿色弱受试者体内不存在可测量量的M色素。利用这些结果来确定基因表达，改善了推断的色素分离与颜色匹配之间的相关性。此外，我们发现一名受试者拥有正常的L和M基因以及正常的近端启动子序列，但通过ERG检测他只有一种光色素（M），并被测试为红色盲。这些结果证明了ERG测量在色觉缺陷分子遗传学研究中的实用性，并进一步支持了并非所有基因都在色觉缺陷受试者中表达的结论。特别是，绿色弱需要一种目前未知的选择性表达机制，该机制排除正常的M基因，并允许L-M杂合基因在一种视锥细胞类型中表达，而正常的L基因在另一种视锥细胞类型中表达。
