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Stephanie Padula, Elaine Sidler, Frank J Lovicu, Michael L Robinson; Pten Deletion Rescues Fiber Cell Differentiation in FGFR-Deficient Lens Epithelial Explants. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3303.
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© ARVO (1962-2015); The Authors (2016-present)
Murine lenses lacking Fibroblast Growth Factor Receptor 2 (Fgfr2) in early lens development undergo widespread apoptosis and some abnormalities pertaining to fiber cell differentiation. Our lab recently showed that simultaneous Fgfr2 and Pten deletion rescues many of these defects relative to those lenses only lacking Fgfr2. However, the specific role that FGFR signaling plays in lens fiber cell differentiation remains incomplete. FGFR activation, followed by AKT and ERK1/2 activation, is necessary and sufficient for fiber cell differentiation in wild-type rat lens epithelial explants. Fgfr1, Fgfr2, and Fgfr3 (Fgfr1-3)-deficient lens epithelial explants exhibit low levels of p-AKT and p-ERK1/2, and fail to undergo fiber cell differentiation in the presence of vitreous. We hypothesized that simultaneous Pten deletion would restore p-AKT and p-ERK1/2 levels in the presence of vitreous and rescue fiber cell differentiation.
We used control mice (FVB/N) and mice carrying null (Fgfr3) or floxed (Fgfr1, Fgfr2, and Pten) alleles to generate lens epithelial explants at 8 days after birth. After establishment of the explants, recombinant adenovirus carrying CRE recombinase facilitated the generation of explants deficient for Fgfr1-3, Pten or both Fgfr1-3 and Pten. Following CRE delivery, explants were treated with bovine vitreous. Five days after vitreous exposure, explants were tested for cytoskeletal organization, expression of β-crystallin and Aquaporin0, and p-AKT/p-ERK1/2 levels.
Lens epithelial explants lacking Pten express b-crystallin even in the absence of vitreous. Explants lacking Pten (with or without simultaneous Fgfr1-3 deletion) also increased p-Erk1/2 levels relative to control and Fgfr1-3-deleted explants. Fgfr1-3-deleted epithelial cells fail to undergo proliferation or fiber cell differentiation in the presence of vitreous, but simultaneous Pten deletion restores the ability for these cells to differentiate, as measured by b-crystallin and Aquaporin0 expression, and cytoskeletal rearrangement. We failed to detect any cell cycle alterations in Pten-deleted explants.
This study suggests that Pten deletion causes vitreous-induced fiber cell differentiation via an FGFR-independent mechanism. Elucidating which proteins PTEN interacts with in this alternative pathway will increase our understanding of key regulators of lens fiber cell differentiation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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