Loss of Dishevelleds Disrupts Planar Polarity in Ependymal Motile Cilia and Results in Hydrocephalus

Defects in ependymal (E) cells, which line the ventricle and generate cerebrospinal fluid flow through ciliary beating, can cause hydrocephalus. Dishevelled genes (Dvls) are essential for Wnt signaling and Dvl2 has been shown to localize to the rootlet of motile cilia. Using the hGFAP-Cre;Dvl1−/−;2flox/flox;3+/− mouse, we show that compound genetic ablation of Dvls causes hydrocephalus. In hGFAP-Cre;Dvl1−/−;2flox/flox;3+/− mutants, E cells differentiated normally, but the intracellular and intercellular rotational alignments of ependymal motile cilia were disrupted. As a consequence, the fluid flow generated by the hGFAP-Cre;Dvl1−/−;2flox/flox;3+/− E cells was significantly slower than that observed in control mice. Dvls were also required for the proper positioning of motile cilia on the apical surface. Tamoxifen-induced conditional removal of Dvls in adult mice also resulted in defects in intracellular rotational alignment and positioning of ependymal motile cilia. These results suggest that Dvls are continuously required for E cell planar polarity and may prevent hydrocephalus

Longitudinal zonation pattern in Arabidopsis root tip defined by a multiple structural change algorithm

Background and Aims The Arabidopsis thaliana root is a key experimental system in developmental biology. Despite its importance, we are still lacking an objective and broadly applicable approach for identification of number and position of developmental domains or zones along the longitudinal axis of the root apex or boundaries between them, which is essential for understanding the mechanisms underlying cell proliferation, elongation and differentiation dynamics during root development. Methods We used a statistics approach, the multiple structural change algorithm (MSC), for estimating the number and position of developmental transitions in the growing portion of the root apex. Once the positions of the transitions between domains and zones were determined, linear models were used to estimate the critical size of dividing cells (L(critD)) and other parameters. Key Results The MSC approach enabled identification of three discrete regions in the growing parts of the root that correspond to the proliferation domain (PD), the transition domain (TD) and the elongation zone (EZ). Simultaneous application of the MSC approach and G2-to-M transition (CycB1;1DB:GFP) and endoreduplication (pCCS52A1:GUS) molecular markers confirmed the presence and position of the TD. We also found that the MADS-box gene XAANTAL1 (XAL1) is required for the wild-type (wt) PD increase in length during the first 2 weeks of growth. Contrary to wt, in the xal1 loss-of-function mutant the increase and acceleration of root growth were not detected. We also found alterations in L(critD) in xal1 compared with wt, which was associated with longer cell cycle duration in the mutant. Conclusions The MSC approach is a useful, objective and versatile tool for identification of the PD, TD and EZ and boundaries between them in the root apices and can be used for the phenotyping of different genetic backgrounds, experimental treatments or developmental changes within a genotype. The tool is publicly available at www.ibiologia.com.mx/MSC_analysis

Mechanosensory Genes Pkd1 and Pkd2 Contribute to the Planar Polarization of Brain Ventricular Epithelium.

UNLABELLED: Directional beating of ependymal (E) cells cilia in the walls of the ventricles in the brain is essential for proper CSF flow. E cells display two forms of planar cell polarity (PCP): rotational polarity of individual cilium and translational polarity (asymmetric positioning of cilia in the apical area). The orientation of individual E cells varies according to their location in the ventricular wall (location-specific PCP). It has been hypothesized that hydrodynamic forces on the apical surface of radial glia cells (RGCs), the embryonic precursors of E cells, could guide location-specific PCP in the ventricular epithelium. However, the detection mechanisms for these hydrodynamic forces have not been identified. Here, we show that the mechanosensory proteins polycystic kidney disease 1 (Pkd1) and Pkd2 are present in primary cilia of RGCs. Ablation of Pkd1 or Pkd2 in Nestin-Cre;Pkd1(flox/flox) or Nestin-Cre;Pkd2(flox/flox) mice, affected PCP development in RGCs and E cells. Early shear forces on the ventricular epithelium may activate Pkd1 and Pkd2 in primary cilia of RGCs to properly polarize RGCs and E cells. Consistently, Pkd1, Pkd2, or primary cilia on RGCs were required for the proper asymmetric localization of the PCP protein Vangl2 in E cells apical area. Analyses of single- and double-heterozygous mutants for Pkd1 and/or Vangl2 suggest that these genes function in the same pathway to establish E cells PCP. We conclude that Pkd1 and Pkd2 mechanosensory proteins contribute to the development of brain PCP and prevention of hydrocephalus. SIGNIFICANCE STATEMENT: This study identifies key molecules in the development of planar cell polarity (PCP) in the brain and prevention of hydrocephalus. Multiciliated ependymal (E) cells within the brain ventricular epithelium generate CSF flow through ciliary beating. E cells display location-specific PCP in the orientation and asymmetric positioning of their cilia. Defects in this PCP can result in hydrocephalus. Hydrodynamic forces on radial glial cells (RGCs), the embryonic progenitors of E cells, have been suggested to guide PCP. We show that the mechanosensory proteins Pkd1 and Pkd2 localize to primary cilia in RGCs, and their ablation disrupts the development of PCP in E cells. Early shear forces on RGCs may activate Pkd1 and Pkd2 in RGCs primary cilia to properly orient E cells. This study identifies key molecules in the development of brain PCP and prevention of hydrocephalus

GLI3 Is Required for OLIG2+ Progeny Production in Adult Dorsal Neural Stem Cells

The ventricular–subventricular zone (V-SVZ) is a postnatal germinal niche. It holds a large population of neural stem cells (NSCs) that generate neurons and oligodendrocytes for the olfactory bulb and (primarily) the corpus callosum, respectively. These NSCs are heterogeneous and generate different types of neurons depending on their location. Positional identity among NSCs is thought to be controlled in part by intrinsic pathways. However, extrinsic cell signaling through the secreted ligand Sonic hedgehog (Shh) is essential for neurogenesis in both the dorsal and ventral V-SVZ. Here we used a genetic approach to investigate the role of the transcription factors GLI2 and GLI3 in the proliferation and cell fate of dorsal and ventral V-SVZ NSCs. We find that while GLI3 is expressed in stem cell cultures from both dorsal and ventral V-SVZ, the repressor form of GLI3 is more abundant in dorsal V-SVZ. Despite this high dorsal expression and the requirement for other Shh pathway members, GLI3 loss affects the generation of ventrally-, but not dorsally-derived olfactory interneurons in vivo and does not affect trilineage differentiation in vitro. However, loss of GLI3 in the adult dorsal V-SVZ in vivo results in decreased numbers of OLIG2-expressing progeny, indicating a role in gliogenesis

Single-cell analysis of the ventricular-subventricular zone reveals signatures of dorsal and ventral adult neurogenesis.

The ventricular-subventricular zone (V-SVZ), on the walls of the lateral ventricles, harbors the largest neurogenic niche in the adult mouse brain. Previous work has shown that neural stem/progenitor cells (NSPCs) in different locations within the V-SVZ produce different subtypes of new neurons for the olfactory bulb. The molecular signatures that underlie this regional heterogeneity remain largely unknown. Here, we present a single-cell RNA-sequencing dataset of the adult mouse V-SVZ revealing two populations of NSPCs that reside in largely non-overlapping domains in either the dorsal or ventral V-SVZ. These regional differences in gene expression were further validated using a single-nucleus RNA-sequencing reference dataset of regionally microdissected domains of the V-SVZ and by immunocytochemistry and RNAscope localization. We also identify two subpopulations of young neurons that have gene expression profiles consistent with a dorsal or ventral origin. Interestingly, a subset of genes are dynamically expressed, but maintained, in the ventral or dorsal lineages. The study provides novel markers and territories to understand the region-specific regulation of adult neurogenesis

[Álbum de la Srta. Josefina Pérez de Ayala] [Manuscrito]

Contiene: Introito / Amancio Díaz [¿Amancio Díaz del Riego?]. [Marinero] [Material gráfico] / Álvarez Sala. ¡Ese portero! / Alfredo Alonso. Fuenterrabía [Material gráfico] / T. Gª Sampedro. Con permiso-- / Pepín Quevedo. Naveces [Material gráfico] / Julio del Val. [Retrato de Josefina Pérez de Ayala] [Material gráfico] / J. Robles [José Robles (1843-1911)]. ¡Quién supiera escribir! / J. Robles. Un dezir y dos layes en loa a Josefina, en la mejor edad de su belleza / Ramón Pérez de Ayala. ¡Ay, quián fose poeta! / Marcos del Torniello. A Josefina / Joaquín González Pastor. [Poema sin título] / Rubén Darío. [Descendimiento] [Material gráfico] / F. Granda Buylla. A Josefina / Vital Aza. San Esteban [Material gráfico] / C. Arregui. A Josefina P. Ayala / Bernardo Acevedo. [Cabeza de mujer] [Material gráfico] / A. SordoAutógrafo firmadoVarias hojas y páginas en blancoCopia digital : Biblioteca de Asturias "Ramón Pérez de Ayala", 2014Adquirido por la Biblioteca de Asturias a Finarte España en 199

Sonic hedgehog signaling in the postnatal brain

Sonic hedgehog (Shh) is a pleiotropic factor in the developing central nervous system (CNS), driving proliferation, specification, and axonal targeting in multiple sites within the forebrain, hindbrain, and spinal cord. Studies in embryonic CNS have shown how gradients of this morphogen are translated by neuroepithelial precursors to determine the types of neurons and glial cells they produce [1, 2]. Shh also has a well-characterized role as a mitogen for specific progenitor cell types in neural development [3, 4]. As we begin to appreciate that Shh continues to act in the adult brain, a central question is what functional role this ligand plays when major morphogenetic and proliferative processes are no longer in operation. A second fundamental question is whether similar signaling mechanisms operate in embryonic and adult CNS. In the two major germinal zones of the adult brain, Shh signaling modulates the self-renewal and specification of astrocyte-like primary progenitors, frequently referred to as neural stem cells (NSCs). It also may regulate the response of the mature brain to injury, as Shh signaling has been variously proposed to enhance or inhibit the development of a reactive astrocyte phenotype. The identity of cells producing the Shh ligand, and the conditions that trigger its release, are also areas of growing interest; both germinal zones in the adult brain contain Shh-responsive cells but do not autonomously produce this ligand. Here, we review recent findings revealing the function of this fascinating pathway in the postnatal and adult brain, and highlight ongoing areas of investigation into its actions long past the time when it shapes the developing brain