Lack of cadherins Celsr2 and Celsr3 impairs ependymal ciliogenesis, leading to fatal hydrocephalus

Abstract

Cilia are organelles that protrude from the apical surface of most eukaryotic cells. According to their structure and motility, they are classified into three groups 1 . Primary monocilia, present in most cells, lack a central pair of microtubules (9+0 structure), and play several roles in mechanosensation and cell signaling. Nodal cilia have a 9+0 structure but, unlike primary cilia, they move and generate an asymmetric distribution of morphogenetic cues in the node, thereby contributing to laterality 2 . The third group is composed of motile 9+2 cilia that cover epithelial cells lining airways, reproductive tracts, and cerebral ventricles. Motile cilia play crucial functions in clearing mucus and debris in the airways and may assist the transit of sperm and eggs in genital tracts [3][4] . In the early postnatal mammalian brain, neuroepithelial cells that line the cerebral ventricles leave the cell cycle and differentiate into a monolayer of ependymal cells. At the end of maturation, the apical surface of ependymal cells bears dozens of cilia that beat in coordinate manner to facilitate the circulation of the cerebrospinal fluid (CSF), from sites of production in choroid plexuses to sites of absorption in subarachnoid spaces. In mice, mutations in genes involved in the assembly or structure of ependymal cilia, such as Mdnah5 5 , Ift88 (also known as Tg737 or Polaris) 6 , and Hy3 7-8 affect cilia genesis, CSF dynamics, and result in hydrocephalus. Thus far, however, little is known about the genetic factors that govern ependymal cilia polarization and the relationship between the polarity and the development and function of these organelles.Planar cell polarity (PCP), also known as tissue polarity, controls the polarization of epithelial cells in a plane perpendicular to their apicobasal axis. It was initially described in Drosophila, where it affects the stereotypic arrangement of cuticular hairs, sensory bristles, and Supplementary Fig. 1a, b). RT-PCR and (Supplementary Fig. 1c).Using the knocked-in beta-galactosidase reporter, we monitored the expression of Celsr2 in heterozygous mice. Consistent with published data [24][25][26] , Celsr2 expression was detected in all brain areas, from E11.5 to P5 (Fig. 1a-h). Celsr2 mutant mice develop progressive hydrocephalusCelsr2 mutant mice were viable and fertile, except for some females that had vaginal atresia. At birth, their brain did not display any flagrant morphological abnormality, suggesting that Celsr2 is not critical for cerebral embryonic development. However, a progressive ventricular dilation appeared between P5 and P10 with variable severity between animals, and became evident at P21 (Fig. 2a,b).The lateral ventricles were enlarged, and the septum had an abnormal triangular shape, due to 6 6 reduction of the dorsal part of the lateral septum. We did not observe any stenosis or constriction at the level of the foramen of Monro or of the aqueduct. The subcommissural organ (SCO), a structure thought to play a role in non-communicating hydrocephalus, was...

SNX27 Deletion Causes Hydrocephalus by Impairing Ependymal Cell Differentiation and Ciliogenesis

“…Genetic deficiency of genes such as Mdnah5 (Ibanez-Tallon et al, 2004), Tg737 (Banizs et al, 2005, Hy3 (Davy and Robinson, 2003), Celsr2/3 (Tissir et al, 2010), Foxj1 (Jacquet et al, 2009), Six3 (Lavado and Oliver, 2011), c-Myb (Malaterre et al, 2008, and Snx27 results in impaired ciliogenesis and hydrocephalus. Interestingly, we observed that Snx27 deletion results in deficiencies in proper ependymal cell differentiation to ependymal cell types with a compensatory increase in differentiation to nonciliated cells (Páez et al, 2007).…”

“…Inhibition of Notch signaling blocks Snx27 deletionassociated ependymal cell loss and partially rescues hydrocephalus in Snx27 ؊ / ؊ mice It has been reported that overexpression of the NICD leads to a reduced number of ciliated cells and, conversely, that repression of Notch signaling results in an increased number of precursor cells adopting a multiciliated cell fate (Deblandre et al, 1999;Tsao et al, 2009;Marcet et al, 2011). Although our previous findings indicate that SNX27 deficiency upregulates ␥-secretase cleavage of Notch and generation of NICD (Wang et al, 2014b), it was unclear how SNX27-mediated ␥-secretase suppression could influence pathophysiological brain development.…”

Planar cell polarity genes, Celsr1-3, in neural development

“…Celsr1 is expressed in FBM neuron precursors and the floor plate, but not in FBM neurons, which helps to specify the direction of FBM neuron migration in a noncell autonomous manner. In Celsr2-/-mutants, the initiation of FBM neuron migration is normal but these neurons This cooperative action is also found in the planar organization of ependymal cilia regulated by Celsr2 and Celsr3 [50] . Celsr2-deficient mice show defective cerebrospinal fluid dynamics and hydrocephalus, and the polarity of ependymal cilia is disrupted.…”

“…Single-Celsr knockout mice show different phenotypes, such as the failure of axonal projections in Celsr3-/- [38] , abnormal organization of ependymal cilia in Celsr2-/- [50] , and improper neuronal migration in Celsr1-/- [49] . However, …”

Multiple roles of Ulk4 in neurogenesis and brain function

“…23 Normal production and circulation of the CSF are known to be crucial for proper brain development. 24,25 For example, Wnt4 and Wnt modulator Tgm2 are regulated by Otx2, a master regulator of choroid plexus development which produces CSF. 24 We showed recently that Ulk4 is essential for ciliogenesis and CSF flow.…”