We investigate mutations in trβ2, a splice variant of thrb, identifying changes in function, structure, and behavior in larval and adult zebrafish retinas. Two N-terminus CRISPR mutants were identified. The first is a 6BP+1 insertion deletion frameshift resulting in a truncated protein. The second is a 3BP in frame deletion with intact binding domains. ERG recordings of isolated cone signals showed that the 6BP+1 mutants did not respond to red wavelengths of light while the 3BP mutants did respond. 6BP+1 mutants lacked optomotor and optokinetic responses to red/black and green/black contrasts. Both larval and adult 6BP+1 mutants exhibit a loss of red-cone contribution to the ERG and an increase in UV-cone contribution. Transgenic reporters show loss of cone trβ2 activation in the 6BP+1 mutant but increase in the density of cones with active blue, green, and UV opsin genes. Antibody reactivity for red-cone LWS1 and LWS2 opsin was absent in the 6BP+1 mutant, as was reactivity for arrestin3a. Our results confirm a critical role for trβ2 in long-wavelength cone development.

我们调查了thrb的一个剪接变体trβ2中的突变，确定了幼虫和成年斑马鱼视网膜中功能，结构和行为的变化。鉴定了两个N末端CRISPR突变体。第一个是6BP + 1插入缺失移码，导致蛋白质被截断。第二个是具有完整结合域的3BP框架缺失。隔离的视锥细胞信号的ERG记录显示6BP + 1突变体对红色波长的光没有反应，而3BP突变体却有反应。6BP + 1突变体缺乏对红色/黑色和绿色/黑色对比度的光动力和光动力学响应。幼虫和成年6BP + 1突变体表现出红色锥体对ERG的损失和紫外线锥体的增加。转基因报道基因显示6BP + 1突变体中视锥细胞trβ2的激活丧失，但具有活跃的蓝色，绿色和紫外线视蛋白基因的视锥细胞密度增加。红锥LWS1和LWS2视蛋白的抗体反应性在6BP + 1突变体中不存在，而在restagein3a中则没有。我们的结果证实了trβ2在长波锥发展中的关键作用。