Deletion of the Parkin co-regulated gene causes defects in ependymal ciliary motility and hydrocephalus in the quakingviable mutant mouse
Bruce Lefroy Centre for Genetic Health Research, Murdoch Childrens Research Institute, Parkville 3052, Australia. Human Molecular Genetics
(Impact Factor: 6.39).
04/2010; 19(8):1593-602. DOI: 10.1093/hmg/ddq031
The quakingviable mouse (qkv) is a spontaneous recessive mouse mutant with a deletion of ~ 1.1 Mb in the proximal region of chromosome 17. The deletion affects the expression of three genes; quaking (Qk), Parkin-coregulated gene (Pacrg) and parkin (Park2). The resulting phenotype, which includes dysmyelination of the central nervous system and male sterility, is due to reduced expression of Qk and a complete lack of Pacrg expression, respectively. Pacrg is required for correct development of the spermatozoan flagella, a specialized type of motile cilia. In vertebrates, motile cilia are required for multiple functions related to cellular movement or movement of media over a stationary cell surface. To investigate the potential role of PACRG in motile cilia we analysed qkv mutant mice for evidence of cilial dysfunction. Histological and magnetic resonance imaging analyses demonstrated that qkv mutant mice were affected by acquired, communicating hydrocephalus (HC). Structural analysis of ependymal cilia demonstrated that the 9 + 2 arrangement of axonemal microtubules was intact and that both the density of ciliated cells and cilia length was similar to wild-type littermates. Cilia function studies showed a reduction in ependymal cilial beat frequency and cilial mediated flow in qkv mutant mice compared with wild-type littermate controls. Moreover, transgenic expression of Pacrg was necessary and sufficient to correct this deficit and rescue the HC phenotype in the qkv mutant. This study provides novel in vivo evidence that Pacrg is required for motile cilia function and may be involved in the pathogenesis of human ciliopathies, such as HC, asthenospermia and primary ciliary dyskinesia. © The Author 2010. Published by Oxford University Press. All rights reserved. For Permissions, please email: [email protected]
Available from: Bryan P. Bollman
- "Deletion of a genomic segment encompassing the human FOXC1 gene has been associated with hydrocephalus in four human patients (Kume et al., 1998). Abnormal development of the subcommissural organ, overproduction of CSF by the choroid plexus, ependymal denudation or disorganization, and defects in ependymal cilia have also been shown to cause hydrocephalus in mouse and rat models (Banizs et al., 2005; Batiz et al., 2006; Blackshear et al., 2003; Davy and Robinson, 2003; Feng et al., 2009; Ibanez-Tallon et al., 2004; Jones and Bucknall, 1988; Krebs et al., 2004; Lechtreck et al., 2008; Lindeman et al., 1998; Sapiro et al., 2002; Tullio et al., 2001; Wilson et al., 2010). Enhancer trapping, the random integration of a minimal promoterreporter transgene, can localize genes active in specific tissues or at specific times during development (Allen et al., 1988). "
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ABSTRACT: Congenital hydrocephalus, the accumulation of excess cerebrospinal fluid (CSF) in the ventricles of the brain, affects one of every 1,000 children born today, making it one of the most common human developmental disorders. Genetic causes of hydrocephalus are poorly understood in humans, but animal models suggest a broad genetic program underlying the regulation of CSF balance. In this study, the random integration of a transgene into the mouse genome led to the development of an early onset and rapidly progressive hydrocephalus. Juvenile hydrocephalus transgenic mice (Jhy(lacZ)) inherit communicating hydrocephalus in an autosomal recessive fashion with dilation of the lateral ventricles observed as early as postnatal day 1.5. Ventricular dilation increases in severity over time, becoming fatal at 4-8 weeks of age. The ependymal cilia lining the lateral ventricles are morphologically abnormal and reduced in number in Jhy(lacZ/lacZ) brains, and ultrastructural analysis revealed disorganization of the expected 9+2 microtubule pattern. Rather, the majority of Jhy(lacZ/lacZ) cilia develop axonemes with 9+0 or 8+2 microtubule structures. Disruption of an unstudied gene, 4931429I11Rik (now named Jhy) appears to underlie the hydrocephalus of Jhy(lacZ/lacZ) mice, and the Jhy transcript and protein are decreased in Jhy(lacZ/lacZ) mice. Partial phenotypic rescue was achieved in Jhy(lacZ/lacZ) mice by the introduction of a bacterial artificial chromosome (BAC) carrying 60-70% of the JHY protein coding sequence. Jhy is evolutionarily conserved from humans to basal vertebrates, but the predicted JHY protein lacks identifiable functional domains. Ongoing studies are directed at uncovering the physiological function of JHY and its role in CSF homeostasis.
Available from: Thomas Thumberger
- "Expression in the central nervous system was investigated in Xenopus whole-mount brain explants. The brain was interesting, because (1) adult qkv/qkv mice develop hydrocephalus, a phenotype related to impaired cilia function , and (2) PACRG mRNA and protein was described to be expressed in regional brain areas of newborn and adult mice such as the lateral ventricles, the third and fourth ventricle, the aqueduct of Sylvius and the choroid plexus [28,29]. Brain samples were analyzed in 3-day (stage 40, data not shown) and 5-day (stage 45) tadpoles with comparable results (Figure 2). "
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ABSTRACT: Park2-co-regulated gene (PACRG) is evolutionarily highly conserved from green algae to mammals. In Chlamydomonas and trypanosomes, the PACRG protein associates with flagella. Loss of PACRG results in shortened or absent flagella. In mouse the PACRG protein is required for spermatogenesis. The purpose of the present study was to analyze (1) the expression patterns of PACRG during vertebrate embryogenesis, and (2) whether the PACRG protein was required for left-right (LR) axis specification through cilia-driven leftward flow in Xenopus laevis.
PACRG cDNAs were cloned and expression was analyzed during early embryonic development of Xenopus, mouse, rabbit and zebrafish. Antisense morpholino oligonucleotide (MO) mediated gene knockdown was applied in Xenopus to investigate LR development at the level of tissue morphology, leftward flow and asymmetric marker gene expression, using timelapse videography, scanning electron microscopy (SEM) and whole-mount in situ hybridization. Results were statistically evaluated using Wilcoxon paired and χ2 tests.
PACRG mRNA expression was found in cells and tissues harboring cilia throughout the vertebrates. Highly localized expression was also detected in the brain. During early development, PACRG was specifically localized to epithelia where leftward flow arises, that is, the gastrocoel roof plate (GRP) in Xenopus, the posterior notochord (PNC) in mammals and Kupffer’s vesicle (KV) in zebrafish. Besides its association with ciliary axonemes, subcellular localization of PACRG protein was found around the nucleus and in a spotty pattern in the cytoplasm. A green fluorescent protein (GFP) fusion construct preferentially labeled cilia, rendering PACRG a versatile marker for live imaging. Loss-of-function in the frog resulted dose dependently in LR, neural tube closure and gastrulation defects, representing ciliary and non-ciliary functions of PACRG.
The PACRG protein is a novel essential factor of cilia in Xenopus.
Available from: Christina Gavino
- "Recently, we have shown that qkv/v
mice on a ptch1+/−background have a reduced
survival rate due to the development of fatal hydrocephalus18. A mild
hydrocephalic phenotype occurs in qkv mice due the loss of
PACRG expression in the ciliated ependymal cells lining the ventricular walls,
leading to cilia dysfunction16. Similarly,
ptch1+/−mice showed abnormal cilia
function, leading to accumulation of CSF in the ventricles and hydrocephalus18. "
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ABSTRACT: The qk(v) mutation is a one megabase deletion resulting in abnormal expression of the qkI gene. qk(v) mice exhibit hypomyelination of the central nervous system and display rapid tremors and seizures as adults. The qkI locus on 6q26-27 has also been implicated as a candidate tumor suppressor gene as the qkI locus maps to a region of genetic instability in Glioblastoma Multiforme (GBM), an aggressive brain tumor of astrocytic lineage. As GBM frequently harbors mutations affecting p53, we crossbred qk(v) and p53 mutant mice to examine whether qk(v) mice on a p53(-/-) background have an increased incidence of GBM. qk(v) (/v); p53(-/-) mice had a reduced survival rate compared to p53(-/-) littermates, and the cause of death of the majority of the mice remains unknown. In addition, immunohistochemistry revealed Purkinje cell degeneration in the cerebellum. These results suggest that p53 and qkI are genetically linked for neuronal maintenance and survival.
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