Various types of LRP5 mutations in four patients with osteoporosis-pseudoglioma syndrome: identification of a 7.2-kb microdeletion using oligonucleotide tiling microarray.
Osteoporosis-pseudoglioma syndrome (OPS; OMIM 259770) is an autosomal-recessive genetic disorder characterized by severe osteoporosis and visual disturbance from childhood. Biallelic mutations in the low-density lipoprotein receptor-related protein 5 gene (LRP5) have been frequently detected, while a subset of patients had only one or no detectable mutation. We report on the clinical and molecular findings of four unrelated Japanese patients with the syndrome. The four patients had typical skeletal and ocular phenotypes of OPS, namely severe juvenile osteoporosis and early-onset visual disturbance, with or without mental retardation. We undertook standard PCR-based sequencing for LRP5 and found four missense mutations (p.L145F, p.T244M, p.P382L, and p.T552M), one nonsense mutation (p.R1534X), and one splice site mutation (c.1584+1G>A) among four OPS patients. Although three patients had two heterozygous mutations, one had only one heterozygous splice site mutation. In this patient, RT-PCR from lymphocytic RNA demonstrated splice error resulting in 63-bp insertion between exons 7 and 8. Furthermore, the patient was found to have only mutated RT-PCR fragment, implying that a seemingly normal allele did not express LRP5 mRNA. We then conducted custom- designed oligonucleotide tiling microarray analyses targeted to a 600-kb genome region harboring LRP5 and discovered a 7.2-kb microdeletion encompassing exons 22 and 23 of LRP5. We found various types of LRP5 mutations, including an exon-level deletion that is undetectable by standard PCR-based mutation screening. Oligonucleotide tiling microarray seems to be a powerful tool in identifying cryptic structural mutations.
Narumi
Satoshi
S
Department of Pediatrics, Keio University School of Medicine, Tokyo, Japan.
Numakura
Chikahiko
C
Shiihara
Takashi
T
Seiwa
Chizuru
C
Nozaki
Yasuyuki
Y
Yamagata
Takanori
T
Momoi
Mariko Y
MY
Watanabe
Yoriko
Y
Yoshino
Makoto
M
Matsuishi
Toyojiro
T
Nishi
Eriko
E
Kawame
Hiroshi
H
Akahane
Tsutomu
T
Nishimura
Gen
G
Emi
Mitsuru
M
Hasegawa
Tomonobu
T
D000293:Adolescent; D000328:Adult; D001483:Base Sequence; D002648:Child; D017931:DNA Primers; D005260:Female; D005910:Glioma / Q000235:genetics*; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000235:genetics*; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D008297:Male; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010024:Osteoporosis / Q000235:genetics*; D010375:Pedigree; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D013577:Syndrome
D017931:DNA Primers; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5