Combining Cep290 and Mkks ciliopathy alleles in mice rescues sensory defects and restores ciliogenesis
Rivka A. Rachel, … , Matthew W. Kelley, Anand Swaroop
Rivka A. Rachel, … , Matthew W. Kelley, Anand Swaroop
Published March 26, 2012
Citation Information: J Clin Invest. 2012;122(4):1233-1245. https://doi.org/10.1172/JCI60981.
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Research Article

Combining Cep290 and Mkks ciliopathy alleles in mice rescues sensory defects and restores ciliogenesis

Abstract

Cilia are highly specialized microtubule-based organelles that have pivotal roles in numerous biological processes, including transducing sensory signals. Defects in cilia biogenesis and transport cause pleiotropic human ciliopathies. Mutations in over 30 different genes can lead to cilia defects, and complex interactions exist among ciliopathy-associated proteins. Mutations of the centrosomal protein 290 kDa (CEP290) lead to distinct clinical manifestations, including Leber congenital amaurosis (LCA), a hereditary cause of blindness due to photoreceptor degeneration. Mice homozygous for a mutant Cep290 allele (Cep290rd16 mice) exhibit LCA-like early-onset retinal degeneration that is caused by an in-frame deletion in the CEP290 protein. Here, we show that the domain deleted in the protein encoded by the Cep290rd16 allele directly interacts with another ciliopathy protein, MKKS. MKKS mutations identified in patients with the ciliopathy Bardet-Biedl syndrome disrupted this interaction. In zebrafish embryos, combined subminimal knockdown of mkks and cep290 produced sensory defects in the eye and inner ear. Intriguingly, combinations of Cep290rd16 and Mkksko alleles in mice led to improved ciliogenesis and sensory functions compared with those of either mutant alone. We propose that altered association of CEP290 and MKKS affects the integrity of multiprotein complexes at the cilia transition zone and basal body. Amelioration of the sensory phenotypes caused by specific mutations in one protein by removal of an interacting domain/protein suggests a possible novel approach for treating human ciliopathies.

Authors

Rivka A. Rachel, Helen L. May-Simera, Shobi Veleri, Norimoto Gotoh, Byung Yoon Choi, Carlos Murga-Zamalloa, Jeremy C. McIntyre, Jonah Marek, Irma Lopez, Alice N. Hackett, Matthew Brooks, Anneke I. den Hollander, Philip L. Beales, Tiansen Li, Samuel G. Jacobson, Raman Sood, Jeffrey R. Martens, Paul Liu, Thomas B. Friedman, Hemant Khanna, Robert K. Koenekoop, Matthew W. Kelley, Anand Swaroop

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Figure 4

Triallelic loss of Mkks and/or the Cep290-DSD domain ameliorate cilia phenotypes in photoreceptors.

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Triallelic loss of Mkks and/or the Cep290-DSD domain ameliorate cilia ph...
(A) Cross sections through the P18 retina in different combinations of Cep290rd16 and Mkksko alleles, as indicated. Note the short, abnormal OSs in Cep290rd16/rd16 or Mkksko/ko genotypes and the more normal OS in the triallelic Cep290rd16/+;Mkksko/ko genotype. Here, the Cep290rd16/rd16;Mkksko/ko genotype looks similar to Cep290rd16/rd16. The white arrows indicate comparison between 2 similar genotypes that are improved by combining alleles of Cep290 and Mkks. Original magnification, ×40. (B) Quantitation of outer nuclear layer thickness at P18 in the genotypes indicated. Higher variability is noted in double-homozygous mutants (see error bars on Cep290rd16/rd16 versus Cep290rd16/rd16;Mkksko/ko). Error bars are SD; n = 6 (WT), n = 4 (Cep290rd16/+;Mkksko/ko), n = 3 (Mkksko/ko), n = 14 (Cep290rd16/rd16;Mkksko/ko), n = 8 (Cep290rd16/rd16). (C) Scotopic ERG b-wave amplitudes in the indicated mouse genotypes (at P20). Removing one WT Mkks allele on a Cep290rd16/rd16 background results in improved responses, as does adding one Cep290rd16 allele on a Mkksko/ko background. Note that single homozygous or double-homozygous genotypes have essentially no ERG b-wave response. Error bars are SD; n = 3 (WT), n = 3 (Cep290rd16/rd16), n = 6 (Cep290rd16/rd16;Mkksko/+), n = 4 (Mkksko/ko), n = 3 (Cep290rd16/+;Mkksko/ko), and n = 3 (Cep290rd16/rd16;Mkksko/ko). (D) Longitudinal EM sections through the OS, connecting cilia, and inner segments in P14 retina show that OS morphology is disrupted in the indicated mutant genotypes. Original magnification, ×3,000. (E) Higher-magnification images (original magnification, ×30,000) of OSs in P14 retina confirm improved OS morphology in Cep290rd16/+;Mkksko/ko and Cep290rd16/rd16;Mkksko/+ triallelic genotypes. OSs of triallelic mice form concentric stacks of discs (parallel orange lines), more similar to WT. The white arrows indicate comparison between 2 similar genotypes that are improved by combining alleles of Cep290 and Mkks. RPE, retinal pigment epithelium; CC, connecting cilia; IS, inner segment; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; ONH, optic nerve head.