Vascular changes in the cerebellum of Norrin /Ndph knockout mice correlate with high expression of Norrin and Frizzled-4.
X-linked Norrie disease, familial exudative vitreoretinopathy (FEVR), Coat's disease and retinopathy of prematurity are severe human eye diseases and can all be caused by mutations in the Norrie disease pseudoglioma gene. They all show vascular defects and characteristic features of retinal hypoxia. Only Norrie disease displays additional neurological symptoms, which are sensorineural hearing loss and mental retardation. In the present study, we analysed transcript levels of the ligand Norrin (Ndph) and its two receptors Frizzled-4 (Fzd4) and LDL-related protein receptor 5 (Lrp5) in six different brain regions (cerebellum, cortex, hippocampus, olfactory bulb, pituitary and brain stem) of 6- to 8-month-old wild-type and Ndph knockout mice by quantitative real-time PCR. No effect of the Ndph knockout allele on Fzd4 or Lrp5 receptor expression was found. Furthermore, no alterations of the transcript levels of three hypoxia-regulated angiogenic factors (Vegfa, Itgrb3 and Tie1) were observed in the absence of Norrin. Interestingly, we identified significant differences in Ndph, Fzd4 and Lrp5 transcript levels in brain regions of wild-type mice and observed highest expression of Norrin and frizzled-4 in cerebellum. Transcript analyses were correlated with morphological data obtained from cerebellum and immunohistochemical studies of blood vessels in different brain regions. Vessel density was reduced in the cerebellum of Ndph knockout mice but the number of Purkinje and granular cells was not altered. This provides the first description of a brain phenotype in Ndph knockout mice, which will help to elucidate the role of Norrin in the brain.
Division of Medical Molecular Genetics & Gene Diagnostics, Institute of Medical Genetics, University of Zurich, Schorenstrasse 16, CH-8603 Schwerzenbach, Switzerland.
Ulrich F O
UF
Luhmann
John
J
Neidhardt
Barbara
B
Kloeckener-Gruissem
Nikolaus F
NF
Schäfer
Esther
E
Glaus
Silke
S
Feil
Wolfgang
W
Berger
D043924:Angiogenesis Modulating Agents; D042501:Angiogenic Proteins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002531:Cerebellum / Q000002:abnormalities* / Q000098:blood supply* / Q000378:metabolism; D002536:Cerebral Arteries / Q000002:abnormalities* / Q000378:metabolism; D005136:Eye Proteins / Q000235:genetics*; D005260:Female; D051157:Frizzled Receptors / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D026502:LDL-Receptor Related Proteins / Q000235:genetics*; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics*; D011689:Purkinje Cells / Q000166:cytology / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics*
D043924:Angiogenesis Modulating Agents; D042501:Angiogenic Proteins; D005136:Eye Proteins; D051157:Frizzled Receptors; C498581:Fzd4 protein, mouse; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; C555483:Lrp5 protein, mouse; C489916:Ndph protein, mouse; D009419:Nerve Tissue Proteins; D043562:Receptors, G-Protein-Coupled