An analysis of a CP49 missense mutation in 129–based mouse strains

Abstract

Abstract: : Purpose: To determine the effect of a CP49 missense mutation upon lens properties in 129–based mouse strains. Methods:In the process of generating the CP49 targeted knockout, we discovered that some mouse strains contained a missense mutation that deleted the acceptor site of exon 2 in the CP49 gene. This results in exon 1 being erroneously spliced to exon 3 causing a frameshift in the reading frame and the introduction of a stop codon at position 2 of exon 3 in the Bfsp2 transcript. The mutation was found in the 129X1, S1, 2, and 4 as well as CBA and would appear to be a naturally occurring CP49 knockout. Slit lamp analyses were followed by confocal immunofluorescence light microscopy and immunoelectron microscopy of lens sections and blotting of subcellular fractions using antibodies to cytoskeletal and cytoskeletal associated proteins and their regulators. Results: As expected, this mutation in CP49 altered the lens fibre cell cytoskeleton morphology and it also changed the stability of its assembly partner, filensin. Beaded filament morphology was also changed and became very similar to the residual cytoskeleton of the targeted CP49 knockout. We have also analysed the effect of this mutation upon lens cell polarity, protein expression patterns and lens optical properties using membrane markers. Conclusions: The missense mutation in CP49 produces lens effects similar to those found in the targeted CP49 knockout. Less fibre cell organisation is disrupted by the presence of the missense mutation. These data show that the beaded filament cytoskeleton is an important determinant in lens function.

Keywords: cytoskeleton • gene/expression • mutations