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...

Short-read sequencing has enabled the de novo assembly of several individual human genomes, but with inherent limitations in characterizing repeat elements. Here we sequence a Chinese individual HX1 by single-molecule real-time (SMRT) long-read sequencing, construct a physical map by NanoChannel arrays and generate a de novo assembly of 2.93 Gb (contig N50: 8.3 Mb, scaffold N50: 22.0 Mb, including 39.3 Mb N-bases), together with 206 Mb of alternative haplotypes. The assembly fully or partially fills 274 (28.4%) N-gaps in the reference genome GRCh38. Comparison to GRCh38 reveals 12.8 Mb of HX1-specific sequences, including 4.1 Mb that are not present in previously reported Asian genomes. Furthermore, long-read sequencing of the transcriptome reveals novel spliced genes that are not annotated in GENCODE and are missed by short-read RNA-Seq. Our results imply that improved characterization of genome functional variation may require the use of a range of genomic technologies on diverse human populations.

Development of axonal tracts requires interactions between growth cones and the environment. Tracts such as the anterior commissure and internal capsule are defective in mice with null mutation of Celsr3. We generated a conditional Celsr3 allele, allowing regional inactivation. Inactivation in telencephalon, ventral forebrain, or cortex demonstrated essential roles for Celsr3 in neurons that project axons to the anterior commissure and subcerebral targets, as well as in cells that guide axons through the internal capsule. When Celsr3 was inactivated in cortex, subcerebral projections failed to grow, yet corticothalamic axons developed normally, indicating that besides guidepost cells, additional Celsr3-independent cues can assist their progression. These observations provide in vivo evidence that Celsr3-mediated interactions between axons and guidepost cells govern axonal tract formation in mammals.