Disease relevance of Bfsp2

• In mice, targeted genomic deletion of the proteins CP49 (a lens-specific filament) or Six5 (a model for myotonic dystrophy) resulted in subtle cataracts that were easily recorded and quantified using this instrumentation [1].

High impact information on Bfsp2

• It is well established that vertebrate lens fiber cells normally express a modified intermediate filament network consisting of the proteins filensin and CP49, and it was recently reported that the mouse strain 129 harbors mutations in CP49 that have the potential to confound the interpretation of gene knockout studies of the lens [2].
• The demonstration that FVB/N mice lack CP49 protein in the lens suggests that it may be necessary to reevaluate the mechanisms underlying lens phenotypes obtained as a result of transgenic manipulation of this strain [2].
• PURPOSE: CP49 is a fiber cell-specific type I cytokeratin, but its function as part of the fiber cell-beaded filament remains unknown [3].
• However, CP49 is not essential for the assumption or maintenance of overall fiber cell shape or long-range order of fiber cells [4].
• Filensin and phakinin are two lens-specific members of the intermediate filament (IF) superfamily of proteins [5].

Biological context of Bfsp2

• 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 [6].
• The co-transfection of a c-Maf expression construct with reporter constructs containing the proximal promoters of the CP49 and CP115 genes, the structural components of the lens fiber cell beaded filament, did not result in activation of reporter gene expression, as was observed with a crystallin promoter [7].
• The results confirm previously reported phosphorylations of actin, phakinin, alphaA- and alphaB-crystallin, demonstrate previously unrecognized phosphorylations of filensin and betaB1-crystallin, and provide unequivocal evidence for phosphorylation of alphaA-crystallin at serine-148 [8].
• Although present in relatively low abundance, the mRNA for a unique splice variant of CP49, CP49(INS), was also detected early in embryonic development and into adulthood [9].
• Eye lens proteomics: from global approach to detailed information about phakinin and gamma E and F crystallin genes [10].

Anatomical context of Bfsp2

• The CP49 knockout mouse is therefore an important model to study the functional link between lens transparency, the cytoskeleton and plasma membrane organisation [11].
• The early embryonic development and expression patterns of the eye lens specific cytoskeletal proteins, CP49 and CP95, were determined for the chick and were found to be similar in both human and mouse [9].

Regulatory relationships of Bfsp2

• Bfsp2 mutation found in mouse 129 strains causes the loss of CP49 and induces vimentin-dependent changes in the lens fibre cell cytoskeleton [12].

Other interactions of Bfsp2

• Like the knockout of Bfsp2 reported recently, filensin protein levels and its proteolytic processing were altered also in the 129S1/SvImJ and 129S4/SvJae strains compared to C57BL/6J [12].
• Vimentin was a key component of this residual material as shown by immunoelectron microscopy and by the generation of a CP49/vimentin double knockout mouse [6].
• The organization of the phakinin gene exon/intron boundaries provides evidence that this partner may be sharing a common origin with type I cytokeratin genes [5].

Analytical, diagnostic and therapeutic context of Bfsp2

• Immunofluorescence demonstrated that FVB/N mice do not have detectable CP49 or filensin protein in the lens, whereas C57BL/6 mice have the expected protein distribution [2].
• METHODS: PCR analysis of genomic DNA was used to evaluate the status of the CP49 gene in FVB/N mice procured from the four major US distributors of these animals-Harlan Laboratories, Taconic Farms, Jackson Laboratory, and the NIH/NCI/DCT production facility run by Charles River Laboratories [2].
• Electron microscopy of the lens cytoskeleton from 129S2/SvPas revealed similar morphological changes in the cytoskeleton as compared to the CP49 knockout, with beaded and intermediate filaments being apparently replaced by poorly defined filament-like material [6].
• Two proteins, with molecular weights of 49 (CP49) and 115 kDa (CP115) as judged by SDS PAGE, have been shown by immunocytochemistry to be components of the beaded filament, a cytoskeletal structure thus far demonstrated only in the lens fiber cell [13].
• Translation and protein expression were characterized by Northern and Western blot analysis of both CP49 and its assembly partner filensin [4].

References