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  • Title: Thyroid hormone action is required for normal cone opsin expression during mouse retinal development.
    Author: Pessôa CN, Santiago LA, Santiago DA, Machado DS, Rocha FA, Ventura DF, Hokoç JN, Pazos-Moura CC, Wondisford FE, Gardino PF, Ortiga-Carvalho TM.
    Journal: Invest Ophthalmol Vis Sci; 2008 May; 49(5):2039-45. PubMed ID: 18436838.
    Abstract:
    PURPOSE: The expression of S- and M-opsins in the murine retina is altered in different transgenic mouse models with mutations in the thyroid hormone receptor (TR)-beta gene, demonstrating an important role of thyroid hormone (TH) in retinal development. METHODS: The spatial expression of S- and M-opsin was compared in congenital hypothyroidism and in two different TR mutant mouse models. One mouse model contains a ligand-binding mutation that abolishes TH binding and results in constitutive binding to nuclear corepressors. The second model contains a mutation that blocks binding of coactivators to the AF-2 domain without affecting TH binding. RESULTS: Hypothyroid newborn mice showed an increase in S-opsin expression that was completely independent of the genotype. Concerning M-opsin expression, hypothyroidism caused a significant decrease (P < 0.01) only in wild-type animals. When TRbeta1 and -beta2 were T3-binding defective, the pattern of opsin expression was similar to TRbeta ablation, showing increased S-opsin expression in the dorsal retina and no expression of M-opsin in the entire retina. In an unexpected finding, immunostaining for both opsins was detected when both subtypes of TRbeta were mutated in the helix 12 AF-2 domain. CONCLUSIONS: The results show, for the first time, that the expression of S- and M-opsin is dependent on normal thyroid hormone levels during development.
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