Mutations in ARL2BP, Encoding ADP-Ribosylation-Factor-Like 2 Binding Protein, Cause Autosomal-Recessive Retinitis Pigmentosa

UCL Institute of Ophthalmology, London EC1V 9EL, UK.
The American Journal of Human Genetics (Impact Factor: 10.93). 07/2013; 93(2). DOI: 10.1016/j.ajhg.2013.06.003
Source: PubMed


Retinitis pigmentosa (RP) is a genetically heterogeneous retinal degeneration characterized by photoreceptor death, which results in visual failure. Here, we used a combination of homozygosity mapping and exome sequencing to identify mutations in ARL2BP, which encodes an effector protein of the small GTPases ARL2 and ARL3, as causative for autosomal-recessive RP (RP66). In a family affected by RP and situs inversus, a homozygous, splice-acceptor mutation, c.101-1G>C, which alters pre-mRNA splicing of ARLBP2 in blood RNA, was identified. In another family, a homozygous c.134T>G (p.Met45Arg) mutation was identified. In the mouse retina, ARL2BP localized to the basal body and cilium-associated centriole of photoreceptors and the periciliary extension of the inner segment. Depletion of ARL2BP caused cilia shortening. Moreover, depletion of ARL2, but not ARL3, caused displacement of ARL2BP from the basal body, suggesting that ARL2 is vital for recruiting or anchoring ARL2BP at the base of the cilium. This hypothesis is supported by the finding that the p.Met45Arg amino acid substitution reduced binding to ARL2 and caused the loss of ARL2BP localization at the basal body in ciliated nasal epithelial cells. These data demonstrate a role for ARL2BP and ARL2 in primary cilia function and that this role is essential for normal photoreceptor maintenance and function.

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    • "Previous case reports described onset in childhood, flat ERG by 18 years, macular involvement before 20 years, or even total blindness before 20 [46-53]. Macular involvement is found earlier in RP due to cilia-associated genes, such as Bardet–Biedl syndrome genes and the recently described ARL2BP gene [54]. Conversely, PDE6A and PDE6B phenotypes show great variation in the severity of disease and frequent macular edema [55]. "
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