Macroautophagy/autophagy is known to be important for intracellular quality control in the lens. GJA8 is a major gap junction protein in vertebrate lenses. Mutations in GJA8 cause cataracts in humans. The well-known cataractogenesis mechanism is that mutated GJA8 leads to abnormal assembly of gap junctions, resulting in defects in intercellular communication among lens cells. In this study, we observed that ablation of Gja8b (a homolog of mammalian GJA8) in zebrafish led to severe defects in organelle degradation, an important cause of cataractogenesis in developing lens. The role of autophagy in organelle degradation in lens remains disputable. Intriguingly, we also observed that ablation of Gja8b induced deficient autophagy in the lens. More importantly, in vivo treatment of zebrafish with rapamycin, an autophagy activator that inhibits MAPK/JNK and MTORC1 signaling, stimulated autophagy in the lens and relieved the defects in organelle degradation, resulting in the mitigation of cataracts in gja8b mutant zebrafish. Conversely, inhibition of autophagy by treatment with the chemical reagent 3-MA blocked these recovery effects, suggesting the important roles of autophagy in organelle degradation in the lens in gja8b mutant zebrafish. Further studies in HLE cells revealed that GJA8 interacted with ATG proteins. Overexpression of GJA8 stimulated autophagy in HLE cells. These data suggest an unrecognized cataractogenesis mechanism caused by ablation of Gja8b and a potential treatment for cataracts by stimulating autophagy in the lens.

As the primary indication for corneal transplantation, the pathogenesis of keratoconus remains elusive. Aiming to identify whether any mutation from extracellular-matrix (ecM)-related genes contributes to the patients with sporadic cases of keratoconus (Kc) from chinese Han population, one hundred and fifty-three participants in total were enrolled in our study, including fifty-three KC patients and one hundred healthy controls. Mutational analysis of three ecM-related genes (LOX, COL5A1 and TIMP3) with next-generation sequencing and Sanger sequencing was performed. To further confirm the function of three ecM-related genes in the pathogenesis of keratoconus, we performed Realtime Quantitative pcR in vitro. Results showed that three new sequence variants (c.95 G > A in LOX, c.1372 C > t in COL5A1 and c.476 C > t in TIMP3) were identified in aforementioned ECM-related genes in Kc patients without being detected among the healthy controls. According to the results of QpcR, we found that the expression levels of LOX and TIMP3 were decreased in the Kc patients, while COL5A1 showed no significant difference of expression. This is the first time to screen so many ECMrelated genes in Chinese keratoconus patients using next-generation sequencing. We find numerous underlying causal variants, enlarging lots of mutation spectrums and thus providing new sites for other investigators to replicate and for further research. Keratoconus (KC) is a progressive disorder characterized by central cornea thinning and ectasia in a cone-shape fashion, leading to myopia, irregular astigmatism and even vision loss 1,2. KC usually occurs from the second decade to the fourth decade of life, and affects both genders. The prevalence of KC ranges from 900 to 3300 per 100,000 in recent population-based studies 2. Clinically, corneal tomography is most frequently used for diagnosis of KC, while mild or subclinical KC can be diagnosed by posterior corneal elevation abnormalities 3. The treatments of KC often begin with verbal guidance such as not rubbing eyes and wearing contact lenses, with 10-20% of patients finally turning to corneal transplantation 3,4. Collagen cross-linking (CXL) is a novel intervention effective in the therapy of KC. However, the exact etiology and pathogenesis of KC remains unclear, in which genetic, environmental, biomechanical and biochemical factors may involve 3. Eye rubbing 5 , atopy 6,7 and sun exposure 2 are important environmental factors indicating a high risk of KC. In addition, there are increasing evidences suggesting a genetic predisposition in the pathogenesis of keratoconus, with lots of genomic loci and genes identified, including visual system homeobox 1 (VSX1) 8-10 , superoxide dismutase 1 (SOD1) 10,11 , transforming growth factor beta-induced (TGFβI) 12 and microRNA 184 (MIR184) 13,14. Nevertheless, it is to be further explored whether and how these genomic loci and genes participate in the progression of KC. As a major component of the cornea, the corneal stroma rich in extracellular matrix (ECM) plays...

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The gap junction protein alpha 8 (GJA8) gene has been widely studied in human congenital cataracts. However, little is known about its relationship with age-related cataract (ARC). In this study, three GJA8-tagged single nucleotide polymorphisms related to an increased ARC risk were identified: rs2132397 for general ARC under both dominant and additive models; rs7541950 for general ARC under both recessive and additive models; and rs6657114 for cortical cataract under the recessive model. To uncover the underlying mechanisms, this study also sought to explore whether GJA8 is involved in the autophagy process in human lens epithelial cells. The results showed that GJA8 may participate in autophagy to maintain the intracellular environment, which may be a novel mechanism for cataract formation induced by GJA8. In conclusion, this study identified the genetic susceptibility of GJA8 polymorphisms on ARC and provides new clues for fully understanding the pathological mechanism of GJA8 variants in affecting lens opacity.Electronic supplementary materialThe online version of this article (10.1007/s00439-018-1945-5) contains supplementary material, which is available to authorized users.

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