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Soma Dash, Christine Dang, David C Beebe, Salil Anil Lachke; Investigation of Caprin2 (RNG140 RNA granule protein 140) function in mouse lens. Invest. Ophthalmol. Vis. Sci. 2014;55(13):736.
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© ARVO (1962-2015); The Authors (2016-present)
We recently identified two post-transcriptional regulatory proteins (Tdrd7 and Celf1) that are essential for vertebrate lens development as demonstrated by the severe lens defects caused by their deficiency in multiple animal models. Here, we explore the function of a third conserved lens-expressed protein Caprin2 (RNG140, Eeg1, C1qdc1) that has multiple conserved domains, including the coiled-coil and RGG domains (for RNA binding) as well as the C1q domain, found in TNF super-family of proteins, that mediates protein-protein interactions.
iSyTE predicted Caprin2 as a candidate with high lens-enriched expression and potential function in lens development and/or homeostasis. In situ hybridization, qRT-PCR, western blotting and immunofluorescence were used to detect Caprin2 RNA and protein expression in the lens. To test Caprin2 function in the lens, we obtained mice carrying Caprin2 conditional mutant allele from EUCOMM (Caprin2tm2a(EUCOMM)Wtsi) and crossed them with an established lens deleter mouse line Pax6GFPCre to generate lens-specific Caprin2 null mutants (hereafter referred to as Caprin2 cKO).
Caprin2 expression has been previously shown to be responsive to induction by FGF8 in chicken lens fiber cells, indicating a potential role in the lens (Loren et al. 2009 Differentiation. 77:386-94). These findings, together with its high rank in iSyTE expression datasets and its association with RNA granules in neurons, encouraged us to investigate Caprin2 function in the lens. We confirmed previous findings that Caprin2 exhibits enriched expression in mouse lens from E10.5 onwards and is expressed in postnatal lens. We recently generated Caprin2 cKO mutants and have initiated the phenotypic characterization of lens defects in these animals. Although there is no overt opacity in young adult Caprin2 cKO mutant lenses, initial microscopic analyses suggest a mild but consistent abnormality in the central part of the lens. Compound mouse mutants carrying combinations of Caprin2, Tdrd7 or Celf1 null alleles are being characterized for further insight into its function in the lens.
We have investigated the function of Caprin2 in the lens, and demonstrate that its nullizygosity in mouse mutants causes mild lens defects. In sum, Caprin2 represents a new regulatory protein that, along with Tdrd7 and Celf1, may function in a conserved post-transcriptional regulatory network in the lens.
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