Resisting the effects of aging: a function for the fiber cell beaded filament.

Purpose: The beaded filament is a cytoskeletal structure that has been found only in the lens fiber cell. It includes phakosin and filensin, two divergent members of the intermediate filament family of proteins that are also unique to the fiber cell. The authors sought to determine what function the beaded filament fulfills in the lens.

Structural specializations emerging late in mouse lens fiber cell differentiation.

Purpose: To describe a previously uncharacterized structural specialization in the mouse lens fiber cell and to delineate its emergence relative to lens development and fiber cell differentiation.

Methods: Lens fixation efficiency was explored using (14)C-formaldehyde and autoradiography. Lens fiber cell architecture was examined by scanning electron microscopy and by DiI labeling of methacrylate sections in lenses ranging from 2 weeks to 8 months.

Characterization of a mutation in the lens-specific CP49 in the 129 strain of mouse.

Purpose: The 129 strain of mouse carries a mutation in the gene for CP49 (phakinin), an intermediate filament protein thus far demonstrated only in the lens fiber cell. As such, these mice represent naturally occurring mutants of interest in the study of the lens cytoskeleton. However, this strain of mouse is also widely used as a source of embryonic stem cells in gene-targeting studies.

Targeted deletion of the lens fiber cell-specific intermediate filament protein filensin.

Purpose: To determine the function of the lens fiber cell-specific cytoskeletal protein, filensin, in lens biology.

Methods: Targeted genomic deletion was used to delete exon 1 and the transcriptional start site of the filensin gene. Resultant chimeric animals were bred to homozygosity for the mutant allele.

Analysis of non-crystallin lens fiber cell gene expression in c-Maf -/- mice.

Purpose: To examine the role of the c-Maf transcription factor in the regulation of non-crystallin lens fiber cell specific gene expression.

Methods: Expression of lens fiber cell genes in c-Maf null mice was analyzed by immunohistochemical and RT-PCR methods. In addition, the effect of c-Maf on fiber cell gene promoter fragments was examined in co-transfection experiments.

Targeted genomic deletion of the lens-specific intermediate filament protein CP49.

Purpose: To deduce the function of the lens-specific cytoskeletal structure, the beaded filament, by blocking expression of the fiber cell-specific beaded filament protein CP49.

Methods: The first exon of the mouse CP49 gene was deleted by using targeted genomic deletion techniques. Gene deletion was assessed through Southern blot analysis and PCR.