Phakinin (49 kDa cytoskeletal protein) (Beaded filament structural protein 2) (Lens fiber cell beaded filament protein CP 47) (CP47) (Lens fiber cell beaded filament protein CP 49) (CP49) (Lens intermediate filament-like light) (LIFL-L)

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Functions of the intermediate filament cytoskeleton in the eye lens.

Intermediate filaments (IFs) are a key component of the cytoskeleton in virtually all vertebrate cells, including those of the lens of the eye. IFs help integrate individual cells into their respective tissues. This Review focuses on the lens-specific IF proteins beaded filament structural proteins 1 and 2 (BFSP1 and BFSP2) and their role in lens physiology and disease. Evidence generated in studies in both mice and humans suggests a critical role for these proteins and their filamentous polymers in establishing the optical properties of the eye lens and in maintaining its transparency. For instance, mutations in both BFSP1 and BFSP2 cause cataract in humans. We also explore the potential role of BFSP1 and BFSP2 in aging processes in the lens.

MeSH Terms

  • Aging
  • Animals
  • Cataract
  • Eye Proteins
  • Humans
  • Intermediate Filament Proteins
  • Intermediate Filaments
  • Lens, Crystalline
  • Mice
  • Mutation
  • Vimentin
  • alpha-Crystallin B Chain


The E233del mutation in BFSP2 causes a progressive autosomal dominant congenital cataract in a Chinese family.

Congenital cataract is a fundamental cause of blindness throughout the world. A large multi-generational family in northern China was investigated to determine the genetic cause of a progressive autosomal dominant congenital cataract. Slit-lamp photography was conducted to provide definite data for cataract diagnosis. A genome wide scan, linkage analysis, and haplotype analysis were performed to shield the linkage region on the chromosome. BFSP2 was investigated by direct sequencing and detection of fluorescent labeled polymerase chain reaction (PCR) products. Two-point linkage analysis mapped this autosomal dominant congenital cataract (ADCC) locus to D3S1292 in 3q22.1 with a LOD score Zmax=3.99 (theta=0.00). Haplotype analysis located the cosegregating region between marker D3S1551 and D3S3617. In this region, BFSP2 is a powerful candidate gene. Direct sequencing identified the cosegregating E233del mutation in exon 3 of BFSP2. This mutation was not detected in 100 unrelated controls. The E233del mutation in BFSP2 is the cause of the cataract phenotype in this pedigree. The progressive phenotype has provided more evidence for the heterogeneity of congenital cataract caused by BFSP2 mutations and for the important role BFSP2 plays in cataract formation.

MeSH Terms

  • Aged
  • Aging
  • Asian Continental Ancestry Group
  • Cataract
  • Child
  • Chromosome Mapping
  • Chromosome Segregation
  • Chromosomes, Human, Pair 3
  • Disease Progression
  • Exons
  • Eye Proteins
  • Female
  • Gene Deletion
  • Genes, Dominant
  • Haplotypes
  • Humans
  • Intermediate Filament Proteins
  • Lod Score
  • Male
  • Pedigree