Abstract
Purpose:
Mutations in CEP290 cause over 20% of Leber congenital amaurosis (LCA) and are associated with syndromic ciliopathies that include retinal degeneration. We have previously characterized rd16 and rd16/Nrl-/- mice as models of LCA.
Methods:
To elucidate the role of CEP290 in cilia biogenesis, we generated Cep290ko/ko mice by replacing exons 1-4 of Cep290 with a beta-Galactosidase-Neomycin cassette. Using high resolution MRI, we evaluated the effect of the Cep290 gene ko on brain compartments and CSF volume. Eight Cep290ko/ko and four control C57BL/6 mice were imaged. The contrast medium Gd-DTPA (0.2%), in 4% paraformaldehyde was injected intracardially in anesthetized mice. The fixed brain submerged in Fomblin oil for magnetic susceptibility matching was placed in a NMR tube and transferred to the transmit/receive radiofrequency coil of the vertical bore of 14 Tesla Bruker Avance scanner. 3D volume of whole brain was specified using scout scans. T1-weighted 3D gradient-echo images were acquired for 12 hours with an isotropic resolution of 50 µm. Series of axial, coronal and sagittal slices (~90 each), interleaved at 250 µm, were specified from the 3D images. The volumes of cerebrum, cerebellum and CSF were calculated using Bruker image display and analysis software by the summation of sliced volumes.
Results:
Summary of brain and CSF volumetry (mm3) data is as follows: Control (4): Cerebrum: 170±19, Cerebellum: 40±15, CSF: 20±12 Cep290ko/ko (8): Cerebrum: 238±17, Cerebellum: 38±10, CSF: 75±55 CSF volume was significantly higher in Cep290 ko than WT mice. In ko mice with hydrocephalus, more than half of the brain volume is occupied by CSF. In spite of CSF buildup, cerebral volume in the knockout was also greater. Cerebellar volume, however, was unaffected.
Conclusions:
Pathology of hydrocephalus is thought to be due to loss of coordinated beating of primary cilia of ependymal cells in cerebral ventricles, resulting in the loss of cilia-mediated laminar CSF flow and thus loss of its drainage into blood and its resorption from the subarachnoid space. Resulting buildup of CSF leads to moderate communicating hydrocephalus. High-resolution MRI is a useful tool for evaluating the status of CSF buildup and CNS abnormalities in ko mice.
Keywords: 611 neuro-ophthalmology: cortical function/rehabilitation •
552 imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) •
549 image processing