iScience (Jun 2020)

Retinal Degeneration Caused by Rod-Specific Dhdds Ablation Occurs without Concomitant Inhibition of Protein N-Glycosylation

  • Sriganesh Ramachandra Rao,
  • Lara A. Skelton,
  • Fuguo Wu,
  • Agnieszka Onysk,
  • Grzegorz Spolnik,
  • Witold Danikiewicz,
  • Mark C. Butler,
  • Delores A. Stacks,
  • Liliana Surmacz,
  • Xiuqian Mu,
  • Ewa Swiezewska,
  • Steven J. Pittler,
  • Steven J. Fliesler

Journal volume & issue
Vol. 23, no. 6
p. 101198

Abstract

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Summary: Dehydrodolichyl diphosphate synthase (DHDDS) catalyzes the committed step in dolichol synthesis. Recessive mutations in DHDDS cause retinitis pigmentosa (RP59), resulting in blindness. We hypothesized that rod photoreceptor-specific ablation of Dhdds would cause retinal degeneration due to diminished dolichol-dependent protein N-glycosylation. Dhddsflx/flx mice were crossed with rod-specific Cre recombinase-expressing (Rho-iCre75) mice to generate rod-specific Dhdds knockout mice (Dhddsflx/flx iCre+). In vivo morphological and electrophysiological evaluation of Dhddsflx/flx iCre+ retinas revealed mild retinal dysfunction at postnatal (PN) 4 weeks, compared with age-matched controls; however, rapid photoreceptor degeneration ensued, resulting in almost complete loss of rods and cones by PN 6 weeks. Retina dolichol levels were markedly decreased by PN 4 weeks in Dhddsflx/flx iCre+ mice, relative to controls; despite this, N-glycosylation of retinal proteins, including opsin (the dominant rod-specific glycoprotein), persisted in Dhddsflx/flx iCre+ mice. These findings challenge the conventional mechanistic view of RP59 as a congenital disorder of glycosylation.

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