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N.M. Grzywacz, E. Lee, L.B. Mann, D.W. Rickman; Ectopic AII Amacrine Cells in the Developing and Adult Mouse Retinas . Invest. Ophthalmol. Vis. Sci. 2005;46(13):585.
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Purpose: Disabled 1 (Dab1) is an adapter molecule in a signaling pathway that controls cell positioning in the developing brain. This molecule has also been localized to AII amacrine cells in the mouse and guinea–pig retinas. In the present study, we set out to investigate AII amacrine cells in developing retinas of C57BL/6J black mice by using immunocytochemistry with specific antisera against Dab1. Methods: The retinas of C57BL/6J black mice at postnatal day (P) 10, 15, 21, and adult mice were immunostained with polyclonal antisera against Dab1 (1:1000; kindly provided by Dr. B. Howell, NIH). For double labeling, monoclonal antisera against calbindin (1:6000, Sigma) and glycine transporter 1 (1:10000; kindly provided by Dr. D. Pow). Results: As expected for AII amacrine cells, Dab1 immunoreactivity is present in cell bodies located in the INL adjacent to the IPL. These cells give rise to processes that ramify the entire depth of the IPL in all developmental stages. However, a distinct type of Dab1–immunoreactive cell was found in developing mouse retina from P10 onwards. The somata of this type of Dab1–immunoreactive cell were located in the outermost part of the INL, with processes extending toward the OPL. Double–labeling experiments demonstrated that these neurons were not horizontal cells. Rather, these Dab1 neurons had morphologies strongly reminiscent of AII amacrine cells. Moreover, as AII cells, Dab 1 neurons were immunoreactive to the glycine transporter Glyt–1. Surprisingly, close inspection revealed that similar kinds of Dab1 neurons appear in adult retinas. The density of these cells were low at all stages and their coverage factor was smaller than 1. Conclusions: The results suggest that there are AII amacrine cells in the mouse retina, which are displaced within the INL. Their low coverage suggests that their transmitter works at a distance through diffusion. Hence, if they have a role for vision, this role is of slow modulation, possibly for adaptation.
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