CERKL gene knockout disturbs photoreceptor outer segment phagocytosis and causes rod-cone dystrophy in zebrafish

Shanshan Yu, Chang Li, Lincoln Biswas, Xuebin Hu, Fei Liu, James Reilly, Xiliang Liu, Ying Liu, Yuwen Huang, Zhaojing Lu, Shanshan Han, Lei Wang, Jing Yu Liu, Tao Jiang, Xinhua Shu, Fulton Wong, Zhaohui Tang, Mugen Liu

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In humans, CERKL mutations cause widespread retinal degeneration: early dysfunction and loss of rod and cone photoreceptors in the outer retina and, progressively, death of cells in the inner retina. Despite intensive efforts, the function of CERKL remains obscure and studies in animal models have failed to clarify the disease mechanism of CERKL mutations. To address this gap in knowledge, we have generated a stable CERKL knockout zebrafish model by TALEN technology and a 7bp deletion in CERKL cDNA that caused the premature termination of CERKL. These CERKL-/- animals showed progressive degeneration of photoreceptor outer segments (OSs) and increased apoptosis of retinal cells, including those in the outer and inner retinal layers. Additionally, we confirmed by immunofluorescence and western-blot that rod degeneration in CERKL-/- zebrafish occurred earlier and was more significant than that in cone cells. Accumulation of shed OSs in the interphotoreceptor matrix was observed by transmission election microscopy (TEM). This suggested that CERKL may regulate the phagocytosis of OSs by the retinal pigment epithelium (RPE). We further found that the phagocytosis-associated protein MERTK was significantly reduced in CERKL-/- zebrafish. Additionally, in ARPE-19 cell lines, knockdown of CERKL also decreased the mRNA and protein level of MERTK, as well as the ox-POS phagocytosis. We conclude that CERKL deficiency in zebrafish may cause rod-cone dystrophy, but not cone-rod dystrophy, while interfering with the phagocytosis function of RPE associated with down-regulation of the expression of MERTK.
Original languageEnglish
Pages (from-to)2335-2345
Number of pages11
JournalHuman Molecular Genetics
Issue number12
Early online date7 Apr 2017
Publication statusPublished - 15 Jun 2017


  • genetics
  • gene knockout
  • photoreceptor
  • zebrafish
  • retinal degeneration


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