Essential and synergistic roles of RP1 and RP1L1 in rod photoreceptor axoneme and retinitis pigmentosa.
Retinitis pigmentosa 1 (RP1) is a common inherited retinopathy with variable onset and severity. The RP1 gene encodes a photoreceptor-specific, microtubule-associated ciliary protein containing the doublecortin (DCX) domain. Here we show that another photoreceptor-specific Rp1-like protein (Rp1L1) in mice is also localized to the axoneme of outer segments (OSs) and connecting cilia in rod photoreceptors, overlapping with Rp1. Rp1L1-/- mice display scattered OS disorganization, reduced electroretinogram amplitudes, and progressive photoreceptor degeneration, less severe and slower than in Rp1-/- mice. In single rods of Rp1L1-/-, photosensitivity is reduced, similar to that of Rp1-/-. While individual heterozygotes are normal, double heterozygotes of Rp1 and Rp1L1 exhibit abnormal OS morphology and reduced single rod photosensitivity and dark currents. The electroretinogram amplitudes of double heterozygotes are more reduced than those of individual heterozygotes combined. In support, Rp1L1 interacts with Rp1 in transfected cells and in retina pull-down experiments. Interestingly, phototransduction kinetics are normal in single rods and whole retinas of individual or double Rp1 and Rp1L1 mutant mice. Together, Rp1 and Rp1L1 play essential and synergistic roles in affecting photosensitivity and OS morphogenesis of rod photoreceptors. Our findings suggest that mutations in RP1L1 could underlie retinopathy or modify RP1 disease expression in humans.
Yamashita
Tetsuji
T
Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
Liu
Jiewu
J
Gao
Jiangang
J
LeNoue
Sean
S
Wang
Changguan
C
Kaminoh
Jack
J
Bowne
Sara J
SJ
Sullivan
Lori S
LS
Daiger
Stephen P
SP
Zhang
Kang
K
Fitzgerald
Malinda E C
ME
Kefalov
Vladimir J
VJ
Zuo
Jian
J
D000818:Animals; D054468:Axoneme / Q000378:metabolism*; D000089662:Doublecortin Protein; D004596:Electroretinography; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D005838:Genotype; D007700:Kinetics; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D010775:Photic Stimulation; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012160:Retina / Q000378:metabolism / Q000502:physiology / Q000648:ultrastructure; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism* / Q000502:physiology / Q000648:ultrastructure; D012174:Retinitis Pigmentosa / Q000150:complications / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism; D015398:Signal Transduction; D014785:Vision, Ocular / Q000502:physiology
C000714847:Dcx protein, mouse; D000089662:Doublecortin Protein; D005136:Eye Proteins; D008869:Microtubule-Associated Proteins; D012333:RNA, Messenger; C497821:RP1 protein, mouse; C543007:Rp1L1 protein, mouse; D012243:Rhodopsin