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Dylan S. Audette, Melinda K. Duncan; The Function of Prox1 in Fiber Cell Differentiation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1038.
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The transcription factor Prox1 is known to be essential for primary fiber cell differentiation associated with a loss of cell cycle inhibitor expression in the posterior lens vesicle. However, the mechanisms by which Prox1 controls fiber cell differentiation remain poorly understood because Prox1 null embryos are difficult to study due to their numerous other defects leading to prenatal death. This work uses other approaches to investigate the involvement of Prox1 in lens fiber cell differentiation.
Mice homozygous for a floxed Prox1allele carrying the MLR10 Cre transgene were created to delete Prox1 from the lens vesicle. Immunofluorescence and PCR approaches were used to test deletion of the Prox1 gene as well as differential gene and protein expression in conditional null embryos.
PCR and immunofluorescence confirm that Prox1 is deleted from the lenses of Prox1 f/f MLR10 Cre mice by E13.5. These mice are microphthalmic and display the same failure of primary fiber cell extension as well as reduced cell cycle inhibitor expression as was reported in conventional nulls. Immunofluorescence analysis shows that the phenotype is cMAF independent as this transcription factor is retained in the conditional nulls. However, Aquaporin 0 expression is reduced indicating that there is a failure to robustly express fiber cell specific genes during development. Preliminary qRT-PCR results suggest also that βB1-crystallin expression is reduced in conditional nulls consistent with our prior report that Prox1 directly regulates this gene. We also see a loss of p-ERK1,2 activation in the posterior fiber cells indicating a possible failure in FGFR signaling. Prox 1 may be directly acting by regulating FGFR expression as FGFR2 and FGFR3 mRNA levels appear to decrease in Prox1nulls.
Prox1 is required for proper fiber cell differentiation in mice and this may be mediated through effects on FGF receptor expression.
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