Progressive photoreceptor degeneration, outer segment dysplasia, and rhodopsin mislocalization in mice with targeted disruption of the retinitis pigmentosa-1 (Rp1) gene

doi:10.1073/pnas.042122399

Progressive photoreceptor degeneration, outer segment dysplasia, and rhodopsin mislocalization in mice with targeted disruption of the retinitis pigmentosa-1 (Rp1) gene

^*Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, TN 38105; ^‡Department of Anatomy and Neurobiology, University of Tennessee, Memphis, TN 38163; ^§Jules Stein Eye Institute, University of California School of Medicine, Los Angeles, CA 90095-7000; ^¶F. M. Kirby Center for Molecular Ophthalmology, Scheie Eye Institute, Philadelphia, PA 19104; and ^‖Human Genetics Center, School of Public Health, and Department of Ophthalmology and Visual Science, University of Texas-Houston Health Science Center, Houston, TX 77030

Communicated by Richard L. Sidman, Harvard Medical School, Boston, MA (received for review January 8, 2002)

Abstract

Retinitis pigmentosa (RP), a common group of human retinopathic diseases, is characterized by late-onset night blindness, loss of peripheral vision, and diminished or absent electroretinogram (ERG) responses. Mutations in the photoreceptor-specific gene RP1 account for 5–10% of cases of autosomal dominant RP. We generated a mouse model of the RP1 form of RP by targeted disruption of the mouse ortholog (Rp1) of human RP1. In Rp1 ^−/− mice, the number of rod photoreceptors decreased progressively over a period of 1 year, whereas that of cone photoreceptors did not change for at least 10 months. Light and electron microscopic analysis revealed that outer segments of Rp1 ^−/− rods and cones were morphologically abnormal and became progressively shorter in length. Before photoreceptor cell death, rhodopsin was mislocalized in inner segments and cell bodies of Rp1 ^−/− rods. Rod ERG amplitudes of Rp1 ^−/− mice were significantly smaller than those of Rp1 ^+/+ mice over a period of 12 months, whereas those of Rp1 ^+/− mice were intermediate. The decreases in cone ERG amplitudes were slower and less severe than those in rods. These findings demonstrate that Rp1 is required for normal morphogenesis of photoreceptor outer segments and also may play a role in rhodopsin transport to the outer segments. The phenotype of Rp1 mutant mice resembles the human RP1 disease. Thus, these mice provide a useful model for studies of RP1 function, disease pathology, and therapeutic interventions.

Footnotes

↵ † J.G. and K.C. contributed equally to this work.
↵ ** S.P.D, D.B.F., J.R.H., E.A.P, L.S.S., and J.Z. are members of the RP1 Consortium.
↵ ‡‡ To whom reprint requests should be addressed. E-mail: jian.zuo{at}stjude.org.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF291754).
Abbreviations:

RP,

retinitis pigmentosa;

ERG,

electroretinogram/electroretinography;

DCX,

human doublecortin;

OS,

outer segment;

Rho,

rhodopsin;

P,

postnatal day;

TEM,

transmission electron microscopy;

ONL,

outer nuclear layer;

TUNEL,

terminal deoxynucleotidyltransferase-mediated UTP end labeling;

Prph2,

peripherin