PubMed · 11256358
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A Singh, H Krema, A D Singh. 2001. Looking through a cataract.. https://doi.org/10.1016/s0886-3350(00)00853-1
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PURPOSE: Traumatic cataract is a common blinding eye disease after ocular trauma, and its pathogenesis is closely related to lens epithelial cell dysfunction, while the definite molecular regulatory mechanism between upstream transcription factor and downstream target gene remains poorly clarified. This study aimed to clarify the role and molecular mechanism of the krüppel-like factor 5 (KLF5)/ thrombosponin 1 (THBS1) axis in regulating proliferation, migration, epithelial-mesenchymal transition and autophagy of lens epithelial cells in traumatic cataract, and to explore its potential clinical therapeutic value. METHODS: The GSE295383 dataset in the gene expression omnibus (GEO) database was downloaded, and the differentially expressed genes (DEGs) were screened by linear models for microarray data (limma) package of R language. Combined with Weighted gene co-expression network analysis (WGCNA), the gene co-expression network was constructed and the key modules were screened. Gene ontology (GO), kyoto encyclopedia of genes and genomes (KEGG) and gene set enrichment analysis (GSEA) combined with human transcription factor target (hTFtarget) and JASPAR databases were used to predict the upstream transcription factors of THBS1. Subsequently, SRA01/04 cells were induced with transforming growth factor-beta 2 (TGF-β2) to construct a cataract cell model. RESULTS: THBS1 and KLF5 were highly expressed in LECs exposed to TGF-β2. KLF5 could activate THBS1 transcription by binding to THBS1 promoter - 174 to -165 sites. Knockdown of THBS1 inhibited TGF-β2-induced viability, proliferation, migration, and altered the expression of epithelial-mesenchymal transition (EMT)- and autophagy-related markers in LECs. Knockdown of KLF5 downregulated THBS1 expression and produced a similar inhibitory effect, while overexpression of THBS1 reversed the effect of KLF5 knockdown. CONCLUSIONS: This study demonstrated that KLF5 promoted the proliferation, migration, and EMT‑associated molecular changes of LECs in traumatic cataract through transcriptional activation of THBS1, and regulated the expression of autophagy‑related markers in LECs, suggesting that KLF5/THBS1 axis might be a potential target for the treatment of traumatic cataract.
BACKGROUND: An isolated form of congenital cataract associated with macular hypoplasia and a generally hypopigmented fundus in infancy was observed in a German family. To test the hypothesis that a de-novo mutation had occurred in one of the parental germ lines, a functional candidate gene approach was applied. METHODS: The family was carefully examined by a senior paediatric ophthalmologist according to routine procedures (slit lamp, funduscopy, ERG). Blood was taken from the proband and his parents, genomic DNA was isolated and some candidate genes for cataract (CRYAA, CRYBB2, GJA8) or macular hypoplasia (OA1, P) or both (PAX6) were analyzed. RESULTS: The proband showed bilateral cataracts at the age of 4 months; the fundus appeared pale, the optic disc grayish, and macular reflexes were absent. After cataract surgery, the nystagmus persisted, and a control ERG at age 9 years showed essentially normal scotopic and photopic wave forms. An infectious aetiology as well as galactosemia were excluded. However, a heterozygous mutation was found in the proband in exon 1 of CRYAA (62 C-->T), which leads to an exchange from Arg to Leu at amino acid position 21 (R21L). This sequence alteration was not found in the parents and in 96 randomly selected DNA samples from ophthalmologically normal individuals of the KORA S4 study population. In addition, two heterozygous mutations in P were identified (R419Q and A481T); one of both was present in each of the unaffected parents. CONCLUSION: Based upon the unique finding of the mutation and the expression of CRYAA in the lens, this R21L mutation in the CRYAA is considered to be causative for the dominant cataract phenotype. Moreover, the macular hypoplasia has to be considered a concerted interaction with compound heterozygous mutations in the P gene manifesting a mild form of oculocutaneous albinism. Nevertheless, this combination is rare and future studies will focus on identifying similar phenotypes.
The T5P mutation in human gamma C-crystallin produces a lens cataract. Here, we have investigated the effects of the T5P mutation upon the aggregation of gamma C-crystallin in vitro and in transfected cells. By sedimentation assay and sucrose gradient centrifugation, the mutation significantly increased the aggregation of the protein and reduced dramatically its solubility in vitro. Similar effects were seen when T5P gamma C-crystallin was transfected into tissue culture cells, resulting in the formation of cytoplasmic aggregates of T5P gamma C-crystallin. Interestingly, the major lenticular protein chaperones, alpha A- and alpha B-crystallin, increased the solubility of the T5P gamma C-crystallin both in vitro and in transfected cells. More importantly, the size of the T5P gamma C-crystallin aggregates were also significantly reduced in the presence of the lenticular chaperones. These data therefore suggest a dual role for these chaperones in maintaining transparency in the lens. The first is that these protein chaperones increase the proportion of the soluble T5P gamma C-crystallin and the second is that they also reduce light scatter by reducing the aggregate size of T5P gamma C-crystallin. Both activities could modify the cataract phenotype and help explain the observed variability reported for identical gamma-crystallin mutations, which identify cataract as a polygenic disease.