Early-onset macular degeneration with drusen in a cynomolgus monkey (Macaca fascicularis) pedigree: exclusion of 13 candidate genes and loci.
OBJECTIVE
To describe hereditary macular degeneration observed in the cynomolgus monkey (Macaca fascicularis), which shares phenotypic features with age-related macular degeneration in humans, and to test the involvement of candidate gene loci by mutation screening and linkage analysis.


METHODS
Ophthalmic examinations with fundus photography, fluorescein angiography (FA), indocyanine green angiography (IA), electroretinography (ERG), and histologic studies were performed on both affected and unaffected monkeys in the pedigree. The monkey orthologues of the human ABCA4, VMD2, EFEMP1, TIMP3, and ELOVL4 genes were cloned and screened for mutations by single-strand conformation polymorphism (SSCP) analysis or denaturing high-performance liquid chromatography (DHPLC) and direct sequencing in six affected and five unaffected monkeys from the pedigree and in six unrelated, unaffected monkeys. Subsequently, 13 human macular degeneration loci including these five genes were analyzed to test for linkage with the disease. Nineteen affected and seven unaffected monkeys in the pedigree were analyzed by using human microsatellite markers linked to the 13 loci.


RESULTS
Yellowish white spots were observed in the macula and fovea centralis, and in some cases the spots scattered to the peripheral retina along the blood vessels. FA showed hyperfluorescence corresponding to the dots except in the foveola. No anomalies were found by IA and ERG. Histologic studies demonstrated that the spots were drusen. Mutation analysis of the ABCA4, VMD2, EFEMP1, TIMP3, and ELOVL4 genes identified a few sequence variants, but none of them segregated with the disease. Linkage analysis with markers linked to these five genes and an additional eight human macular degeneration loci failed to establish linkage. Haplotype analysis excluded the involvement of the 13 candidate loci for harboring the gene associated with macular degeneration in the monkeys.


CONCLUSIONS
Significant homology was identified between monkey and human orthologues of the five macular degeneration genes. Thirteen loci associated with macular degeneration in humans or harboring macular degeneration genes were excluded as causal of early-onset macular degeneration in the monkeys. It is likely that none of these loci, but rather a novel gene, is involved in causing the observed phenotype in this monkey pedigree.
Umeda
Shinsuke
S
National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo 152-8902, Japan.
Ayyagari
Radha
R
Allikmets
Rando
R
Suzuki
Michihiro T
MT
Karoukis
Athancios J
AJ
Ambasudhan
Rajesh
R
Zernant
Jana
J
Okamoto
Haru
H
Ono
Fumiko
F
Terao
Keiji
K
Mizota
Atsushi
A
Yoshikawa
Yasuhiro
Y
Tanaka
Yasuhiko
Y
Iwata
Takeshi
T
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000818:Animals; D000075002:Bestrophins; D018118:Chloride Channels; D004252:DNA Mutational Analysis; D017931:DNA Primers / Q000737:chemistry; D004596:Electroretinography; D016326:Extracellular Matrix Proteins / Q000235:genetics; D005136:Eye Proteins / Q000235:genetics; D005260:Female; D005451:Fluorescein Angiography; D005654:Fundus Oculi; D008040:Genetic Linkage; D007208:Indocyanine Green; D008252:Macaca fascicularis / Q000235:genetics*; D008268:Macular Degeneration / Q000235:genetics*; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D010375:Pedigree; D018807:Polymorphism, Single-Stranded Conformational; D015593:Retinal Drusen / Q000235:genetics*; D019717:Tissue Inhibitor of Metalloproteinase-3; D019714:Tissue Inhibitor of Metalloproteinases / Q000235:genetics
D018528:ATP-Binding Cassette Transporters; C113133:BEST1 protein, human; D000075002:Bestrophins; D018118:Chloride Channels; D017931:DNA Primers; C119630:EFEMP1 protein, human; D016326:Extracellular Matrix Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; C088390:TIMP3 protein, human; D019717:Tissue Inhibitor of Metalloproteinase-3; D019714:Tissue Inhibitor of Metalloproteinases; D007208:Indocyanine Green