A new mutation in BFSP2 (G1091A) causes autosomal dominant congenital lamellar cataracts.
OBJECTIVE
We sought to identify the genetic defect in a four-generation Chinese family with autosomal dominant congenital lamellar cataracts and demonstrate the functional analysis with biosoftware of a candidate gene in the family.


METHODS
Family history data were recorded. Clinical and ophthalmologic examinations were performed on family members. All the members were genotyped with microsatellite markers at loci considered to be associated with cataracts. Two-point LOD scores were calculated by using the Linkage Software after genotyping. A mutation was detected by using gene-specific primers in direct sequencing. Wild type and mutant proteins were analyzed with Online Bio-Software.


RESULTS
Affected members of this family had lamellar cataracts. Linkage analysis was obtained at markers D3S2322 (LOD score [Z]=7.22, recombination fraction [theta]=0.0) and D3S1541 (Z=5.42, theta=0.0). Haplotype analysis indicated that the cataract gene was closely linked to these two markers. Sequencing the beaded filament structural protein 2 (BFSP2) gene revealed a G>A transversion in exon 5, which caused a conservative substitution of Arg to His at codon 339 (P.R339H). This mutation cosegregated with the disease phenotype in all affected individuals and was not observed in the unaffected family members or in 100 normal, unrelated individuals. Bioinformatic analyses showed that a highly conserved region was located around Arg339. Data generated with Online Bio-Software revealed that the mutation altered the protein's hydrophobicity, hydrophobic moment, and chaperone and regulation activities.


CONCLUSIONS
This is the first reported case of a congenital lamellar cataract phenotype associated with the mutation of Arg339His (P.R339H) in BFSP2. It highlights the physiologic importance of the beaded filament protein and demonstrates a possible mechanism of action for the mutant gene.
Ma
Xu
X
Graduate School, Peking Union Medical College, Beijing, China.
Li
Fei-Feng
FF
Wang
Shu-Zhen
SZ
Gao
Chang
C
Zhang
Meng
M
Zhu
Si-Quan
SQ
D000409:Alanine / Q000235:genetics; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D002386:Cataract / Q000151:congenital* / Q000235:genetics*; D002648:Child; D002851:Chromatography, High Pressure Liquid; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D004252:DNA Mutational Analysis; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics*; D005260:Female; D005799:Genes, Dominant; D008040:Genetic Linkage; D005998:Glycine / Q000235:genetics; D006239:Haplotypes; D006801:Humans; D007381:Intermediate Filament Proteins / Q000737:chemistry / Q000235:genetics*; D008126:Lod Score; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D010375:Pedigree; D011489:Protein Denaturation; D016415:Sequence Alignment
D005136:Eye Proteins; D007381:Intermediate Filament Proteins; C084808:phakinin; D000409:Alanine; D005998:Glycine