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9317854 
Journal Article 
Developmental changes of cone opsin expression but not retinal morphology in the hypothyroid Pax8 knockout mouse 
Cottrill, PB; Davies, WL; Semo, M; Bowmaker, JK; Hunt, DM; Jeffery, G; , 
2009 
Yes 
BMC Developmental Biology
ISSN: 1471-213X
EISSN: 1471213X 
BMC 
LONDON 
English 
20025774 
WOS:000273819900002 
The effects of postnatal hypothyroidism on retinal development and spatial patterning of cone opsin expression were studied in Pax8-deficient mice. Pax8(-/-) mice are incapable of synthesizing thyroxine and serve as a model for congenital hypothyroidism.Pax8(-/-), Pax8(+/-), and Pax8(+/+) littermates were studied. Serum thyroid hormone levels, body weight, and eye size were measured. Retinal cell-type-specific antibodies were used on frozen sections to examine the postnatal development of the major retinal cell classes and of retinal structure. The expression of short-wavelength-sensitive (S) and middle-to-long-wavelength-sensitive (M) cone opsins was assessed with opsin antibodies on retinal sections and whole retinas. The pattern of S opsin mRNA was assessed by in situ hybridization.In Pax8(-/-) mice, S opsin was upregulated in all cones, whereas M opsin was downregulated throughout the retina, the wild-type dorsoventral gradients of S and M opsin expression were absent. Otherwise, Pax8(-/-) mice showed no overt mutant phenotype in eye size, gross retinal anatomy, and the time-course of structural differentiation of retinal photoreceptors, horizontal cells, bipolars, amacrines, ganglion cells, and Müller glia cells.Pax8(-/-) mice show a pattern of cone opsin expression that differs substantially from the wild-type pattern, but exhibit no apparent alterations in general retinal development. The finding that a postnatal decrease in serum thyroid hormone yields changes in postnatal cone opsin expression is consistent with a ligand-dependent role of thyroid hormone receptor beta2 in S opsin repression and M opsin activation.