Guiqun Cao

Lanosterol reverses protein aggregation in cataracts

The human lens is comprised largely of crystallin proteins assembled into a highly ordered, interactive macro-structure essential for lens transparency and refractive index. Any disruption of intra- or inter-protein interactions will alter this delicate structure, exposing hydrophobic surfaces, with consequent protein aggregation and cataract formation. Cataracts are the most common cause of blindness worldwide, affecting tens of millions of people, and currently the only treatment is surgical removal of cataractous lenses. The precise mechanisms by which lens proteins both prevent aggregation and maintain lens transparency are largely unknown. Lanosterol is an amphipathic molecule enriched in the lens. It is synthesized by lanosterol synthase (LSS) in a key cyclization reaction of a cholesterol synthesis pathway. Here we identify two distinct homozygous LSS missense mutations (W581R and G588S) in two families with extensive congenital cataracts. Both of these mutations affect highly conserved amino acid residues and impair key catalytic functions of LSS. Engineered expression of wild-type, but not mutant, LSS prevents intracellular protein aggregation of various cataract-causing mutant crystallins. Treatment by lanosterol, but not cholesterol, significantly decreased preformed protein aggregates both in vitro and in cell-transfection experiments. We further show that lanosterol treatment could reduce cataract severity and increase transparency in dissected rabbit cataractous lenses in vitro and cataract severity in vivo in dogs. Our study identifies lanosterol as a key molecule in the prevention of lens protein aggregation and points to a novel strategy for cataract prevention and treatment.

WNT7A and PAX6 define corneal epithelium homeostasis and pathogenesis

The surface of the cornea consists of a unique type of non-keratinized epithelial cells arranged in an orderly fashion, and this is essential for vision by maintaining transparency for light transmission. Cornea epithelial cells (CECs) undergo continuous renewal from limbal stem or progenitor cells (LSCs), and deficiency in LSCs or corneal epithelium—which turns cornea into a non-transparent, keratinized skin-like epithelium—causes corneal surface disease that leads to blindness in millions of people worldwide. How LSCs are maintained and differentiated into corneal epithelium in healthy individuals and which key molecular events are defective in patients have been largely unknown. Here we report establishment of an in vitro feeder-cell-free LSC expansion and three-dimensional corneal differentiation protocol in which we found that the transcription factors p63 (tumour protein 63) and PAX6 (paired box protein PAX6) act together to specify LSCs, and WNT7A controls corneal epithelium differentiation through PAX6. Loss of WNT7A or PAX6 induces LSCs into skin-like epithelium, a critical defect tightly linked to common human corneal diseases. Notably, transduction of PAX6 in skin epithelial stem cells is sufficient to convert them to LSC-like cells, and upon transplantation onto eyes in a rabbit corneal injury model, these reprogrammed cells are able to replenish CECs and repair damaged corneal surface. These findings suggest a central role of the WNT7A–PAX6 axis in corneal epithelial cell fate determination, and point to a new strategy for treating corneal surface diseases.

Lens regeneration using endogenous stem cells with gain of visual function

The repair and regeneration of tissues using endogenous stem cells represents an ultimate goal in regenerative medicine. To our knowledge, human lens regeneration has not yet been demonstrated. Currently, the only treatment for cataracts, the leading cause of blindness worldwide, is to extract the cataractous lens and implant an artificial intraocular lens. However, this procedure poses notable risks of complications. Here we isolate lens epithelial stem/progenitor cells (LECs) in mammals and show that Pax6 and Bmi1 are required for LEC renewal. We design a surgical method of cataract removal that preserves endogenous LECs and achieves functional lens regeneration in rabbits and macaques, as well as in human infants with cataracts. Our method differs conceptually from current practice, as it preserves endogenous LECs and their natural environment maximally, and regenerates lenses with visual function. Our approach demonstrates a novel treatment strategy for cataracts and provides a new paradigm for tissue regeneration using endogenous stem cells.

Transcription Factor PAX6 (Paired Box 6) Controls Limbal Stem Cell Lineage in Development and Disease

Background: PAX6 is a master regulatory gene involved in eye development. Results: PAX6 is expressed in the primitive eye cup and later in corneal tissue progenitors in early embryonic development. Conclusion: PAX6 plays a critical role in limbal stem cell and corneal epithelial fate determination. Significance: These findings provide important insight into corneal homeostasis and disease. PAX6 is a master regulatory gene involved in neuronal cell fate specification. It also plays a critical role in early eye field and subsequent limbal stem cell (LSC) determination during eye development. Defects in Pax6 cause aniridia and LSC deficiency in humans and the Sey (Small eye) phenotype in mice (Massé, K., Bhamra, S., Eason, R., Dale, N., and Jones, E. A. (2007) Nature 449, 1058–1062). However, how PAX6 specifies LSC and corneal fates during eye development is not well understood. Here, we show that PAX6 is expressed in the primitive eye cup and later in corneal tissue progenitors in early embryonic development. In contrast, p63 expression commences after that of PAX6 in ocular adnexal and skin tissue progenitors and later in LSCs. Using an in vitro feeder-free culture system, we show that PAX6 knockdown in LSCs led to up-regulation of skin epidermis-specific keratins concomitant with differentiation to a skin fate. Using gene expression analysis, we identified the involvement of Notch, Wnt, and TGF-β signaling pathways in LSC fate determination. Thus, loss of PAX6 converts LSCs to epidermal stem cells, as demonstrated by a switch in the keratin gene expression profile and by the appearance of congenital dermoid tissue.

CETP Gene may be Associated with Advanced Age-related Macular Degeneration in the Chinese Population

Abstract Objectives: This study aims to investigate whether variations in LIPC, CETP, ABCA1 and LPL, which are involved in high-density lipoprotein (HDL) metabolism, are associated with advanced age-related macular degeneration (AMD) in the Chinese population. Design and Methods: A total of 119 Chinese patients with advanced AMD and 99 control individuals were recruited. Genomic DNA was extracted from peripheral blood leukocytes. Genotypes of seven single nucleotide polymorphisms (SNPs) including rs1061170 and rs1410996 in CFH, rs10490924 in HTRA1, rs10468017 in LIPC, rs3764261 in CETP, rs1883025 in ABCA1 and rs12678919 near LPL were determined by polymerase chain reaction (PCR) followed by allele-specific restriction enzyme digestion or SNaPshot. Unconditional logistic regression analyses were performed to generate a risk predictive model. Results: We observed the frequency of allele A of rs3764261 in CETP to be significantly lower in advanced AMD after Bonferroni correction (15.5% in patients with AMD and 20.7% in controls; OR = 0.49, 95% CI: 0.29–0.85; p = 0.011). Furthermore, we found that it was also associated with reduced risk of both unilateral AMD (OR = 0.52, 95% CI: 0.28–0.98; p = 0.043) and bilateral AMD (OR = 0.45, 95% CI: 0.22–0.91; p = 0.026). Rs10468017 in LIPC, rs12678919 near LPL and rs1883025 in ABCA1 were not found to be associated with advanced AMD (all p > 0.05). Conclusion: Our data suggested that the allele A in rs3764261 in CETP gene may be associated with a decreased risk of advanced AMD in Chinese population.

Salidroside protects retinal endothelial cells against hydrogen peroxide-induced injury via modulating oxidative status and apoptosis

Oxidative stress can cause injury in retinal endothelial cells. Salidroside is a strong antioxidative and cytoprotective supplement in Chinese traditional medicine. In this study, we investigated the effects of salidroside on H2O2-induced primary retinal endothelial cells injury. Salidroside decreased H2O2-induced cell death, and efficiently suppressed cellular ROS production, malondialdehyde generation, and cell apoptosis induced by H2O2 treatment. Salidroside induced the intracellular mRNA expression, protein expression, and enzymatic activities of catalase and Mn-SOD and increased the ratio of Bcl2/Bax. Our results demonstrated that salidroside protected retinal endothelial cells against oxidative injury through increasing the Bcl2/Bax signaling pathway and activation of endogenous antioxidant enzymes. This finding presents salidroside as an attractive agent with potential to attenuate retinopathic diseases. Salidroside protected primary-cultured retinal endothelial cells against H2O2-induced apoptosis and oxidation.

Identify the signature genes for diagnose of uveal melanoma by weight gene co-expression network analysis

AIM To identify and understand the relationship between co-expression pattern and clinic traits in uveal melanoma, weighted gene co-expression network analysis (WGCNA) is applied to investigate the gene expression levels and patient clinic features. Uveal melanoma is the most common primary eye tumor in adults. Although many studies have identified some important genes and pathways that were relevant to progress of uveal melanoma, the relationship between co-expression and clinic traits in systems level of uveal melanoma is unclear yet. We employ WGCNA to investigate the relationship underlying molecular and phenotype in this study. METHODS Gene expression profile of uveal melanoma and patient clinic traits were collected from the Gene Expression Omnibus (GEO) database. The gene co-expression is calculated by WGCNA that is the R package software. The package is used to analyze the correlation between pairs of expression levels of genes. The function of the genes were annotated by gene ontology (GO). RESULTS In this study, we identified four co-expression modules significantly correlated with clinic traits. Module blue positively correlated with radiotherapy treatment. Module purple positively correlates with tumor location (sclera) and negatively correlates with patient age. Module red positively correlates with sclera and negatively correlates with thickness of tumor. Module black positively correlates with the largest tumor diameter (LTD). Additionally, we identified the hug gene (top connectivity with other genes) in each module. The hub gene RPS15A, PTGDS, CD53 and MSI2 might play a vital role in progress of uveal melanoma. CONCLUSION From WGCNA analysis and hub gene calculation, we identified RPS15A, PTGDS, CD53 and MSI2 might be target or diagnosis for uveal melanoma.

RAD51 gene is associated with advanced age-related macular degeneration in Chinese population

OBJECTIVES This study aims to investigate whether variations in RAD51, B3GALTL, TNFRSF10A and REST-C4ORF14-POLR2B-IGFBP7 are associated with advanced forms of age-related macular degeneration (AMD) in Chinese population. DESIGN AND METHODS A total of 119 Chinese patients with AMD and 99 control individuals were recruited. Genomic DNA was extracted from peripheral blood leukocytes. Seven single nucleotide polymorphisms (SNPs) from CFH, HTRA1, RAD51, B3GALTL, TNFRSF10A and REST-C4ORF14-POLR2B-IGFBP7 were genotyped by polymerase chain reaction (PCR) followed by allele-specific restriction enzyme digestion or SNaPshot. RESULTS Rs10483810 in RAD51 was significantly associated with advanced AMD (P=0.045). Compared with the wild-type genotype GG, the odds ratio for the risk of advanced AMD was 4.92 (95% confidence interval: 1.04-23.36) for the heterozygous TG genotype. Moreover, the GT genotype at rs10483810 confers significantly increased risk of bilateral AMD compared to unilateral AMD (OR=12.04, 95% CI: 2.50-57.69, P=0.002). Rs13278062 in TNFRSF10A, rs1713985 in REST-C4ORF14-POLR2B-IGFBP7 and rs9542236 in B3GALTL were not found to be associated with AMD (all P>0.05). CONCLUSION Our data suggested that the risk allele T of rs10483810 in RAD51 gene is associated with an increased risk of advanced AMD, especially bilateral AMD, in Chinese population.

Malattia leventinese/Doyne honeycomb retinal dystrophy in a chinese family with mutation of the EFEMP1 gene.

Purpose: To characterize the clinical features and molecular genetic findings in a Chinese pedigree with Malattia leventinese/Doyne honeycomb retinal dystrophy. Methods: All patients underwent ophthalmologic examinations, including Snellen best-corrected visual acuity, fundus photography, fundus autofluorescence imaging, fundus fluorescein angiography, and optical coherence tomography. Genomic DNA was isolated from blood samples. All exons of EFEMP1 were amplified by polymerase chain reaction and sequenced. Possible structural and functional impacts of the protein because of amino acid substitution were predicted by bioinformatics analysis. Results: A heterozygous missense mutation comprising C > T in exon 10 of EFEMP1 was identified in all patients of the pedigree; this resulted in an amino acid substitution at position 345 (Arg345Trp, R345W). Clinically, six patients from the Chinese family were ascertained with varying degrees of early onset drusen. Besides the drusen, choroidal neovascularization and retinal pigment epithelium changes were noted in some patients. Increased autofluorescence corresponding to the drusen was detected in the R345W mutation patients. Intrafamilial patients with Malattia leventinese/Doyne honeycomb retinal dystrophy seem to be phenotypically variable in visual loss, ophthalmoscopic findings, autofluorescence imaging, and optical coherence tomography changes. The amino acid change may have an effect on protein structure and function through bioinformatics analysis. Conclusion: The R345W mutation in EFEMP1 caused Malattia leventinese/Doyne honeycomb retinal dystrophy in a Chinese family. This is the first report, as per our knowledge, of the R345W mutation in EFEMP1 in a Chinese pedigree of this disease.

Corrigendum: Lanosterol reverses protein aggregation in cataracts

This corrects the article DOI: 10.1038/nature14650