Identification of two novel LRP5 mutations in families with familial exudative vitreoretinopathy.
OBJECTIVE
To investigate the clinical features and disease-causing mutations in two Chinese families with familial exudative vitreoretinopathy (FEVR).


METHODS
Clinical data and genomic DNA were collected for patients with FEVR. The coding exons and adjacent intronic regions of FZD4, LRP5, TSPAN12, and NDP were amplified with PCR, and the resulting amplicons were analyzed with Sanger sequencing. Wild-type and mutant LRP5 proteins were assayed for the Norrin/β-catenin pathway by luciferase reporter assays.


RESULTS
Two novel heterozygous mutations in the LRP5 gene were identified in two relatives--p.A422T and p.L540P. Typical FEVR fundus change and mild reduced bone mineral density (BMD) was found in the two patients and the affected parent. In the luciferase studies, both p.A422T and p.L540P mutants displayed a significant reduction of the luciferase activity in SuperTopFlash (STF) cells in response to Norrin (87% reduction for p.A422T and 97% reduction for p.L540P). Both patients had an additional LRP5 sequence change (p.Q816P in Patient 1 from the unaffected mother and p.T852M in Patient 2 verified as a new mutation). Luciferase assay showed no reduction for p.Q816P and 94.9% reduction for the new mutation p.T852M, suggesting that p.Q816P may be not pathogenic and p.T852M may be pathogenic.


CONCLUSIONS
Our findings demonstrated two new novel LRP5 mutations in Chinese patients with FEVR and mild reduced BMD. They emphasize the complexity of FEVR mutations and phenotypes.
Department of Ophthalmology, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Ping
P
Fei
Department of Ophthalmology, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Qi
Q
Zhang
Sichuan Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, School of Medicine, University of Science and Technology of China & Sichuan Provincial People's Hospital & Sichuan Provincial People's Hospital, Sichuan, China.
Luling
L
Huang
Department of Ophthalmology, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Yu
Y
Xu
Sichuan Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, School of Medicine, University of Science and Technology of China & Sichuan Provincial People's Hospital & Sichuan Provincial People's Hospital, Sichuan, China.
Xiong
X
Zhu
Sichuan Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, School of Medicine, University of Science and Technology of China & Sichuan Provincial People's Hospital & Sichuan Provincial People's Hospital, Sichuan, China.
Zhengfu
Z
Tai
Sichuan Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, School of Medicine, University of Science and Technology of China & Sichuan Provincial People's Hospital & Sichuan Provincial People's Hospital, Sichuan, China.
Bo
B
Gong
Sichuan Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, School of Medicine, University of Science and Technology of China & Sichuan Provincial People's Hospital & Sichuan Provincial People's Hospital, Sichuan, China.
Shi
S
Ma
West high school, Salt Lake City, UT.
Quanyao
Q
Yao
Department of Ophthalmology, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Jing
J
Li
Department of Ophthalmology, Xin Hua Hospital affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China.
Peiquan
P
Zhao
Sichuan Key Laboratory for Human Disease Gene Study, Institute of Laboratory Medicine, School of Medicine, University of Science and Technology of China & Sichuan Provincial People's Hospital & Sichuan Provincial People's Hospital, Sichuan, China.
Zhenglin
Z
Yang
D000595:Amino Acid Sequence; D001483:Base Sequence; D002648:Child; D005190:Family; D005260:Female; D005654:Fundus Oculi; D005799:Genes, Dominant; D017930:Genes, Reporter; D006579:Heterozygote; D006801:Humans; D007223:Infant; D060492:Low Density Lipoprotein Receptor-Related Protein-5 / Q000737:chemistry / Q000235:genetics*; D008156:Luciferases / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D010375:Pedigree; D016415:Sequence Alignment; D015398:Signal Transduction / Q000235:genetics; D018630:Vitreoretinopathy, Proliferative / Q000235:genetics*
C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D050505:Mutant Proteins; D008156:Luciferases