Defective neuroepithelial cell cohesion affects tangential branchiomotor neuron migration in the zebrafish neural tube

Identifying key m6A-methylated lncRNAs and genes associated with neural tube defects via integrative MeRIP and RNA sequencing analyses

Objective: N6-methyladenosine (m6A) is a common post-transcriptional modification of messenger RNAs (mRNAs) and long non-coding RNAs (lncRNAs). However, m6A-modified lncRNAs are still largely unexplored. This study aimed to investigate differentially m6A-modified lncRNAs and genes involved in neural tube defect (NTD) development. Methods: Pregnant Kunming mice (9-10 weeks of age) were treated with retinoic acid to construct NTD models. m6A levels and methyltransferase-like 3 (METTL3) expression were evaluated in brain tissues of the NTD models. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were performed on the NovaSeq platform and Illumina HiSeq 2,500 platform, respectively. Differentially m6A-methylated differentially expressed lncRNAs (DElncRNAs) and differentially expressed genes (DEGs) were identified, followed by GO biological process and KEGG pathway functional enrichment analyses. Expression levels of several DElncRNAs and DEGs were evaluated by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) for validation. Results: m6A levels and METTL3 expression levels were significantly lower in the brain tissues of the NTD mouse model than in controls. By integrating MeRIP-seq and RNA-seq data, 13 differentially m6A-methylated DElncRNAs and 170 differentially m6A-methylated DEGs were identified. They were significantly enriched in the Hippo signaling pathway and mannose-type O-glycan biosynthesis. The qRT-PCR results confirmed the decreased expression levels of lncRNAs, such as Mir100hg, Gm19265, Gm10544, and Malat1, and genes, such as Zfp236, Erc2, and Hmg20a, in the NTD group. Conclusion: METTL3-mediated m6A modifications may be involved in NTD development. In particular, decreased expression levels of Mir100hg, Gm19265, Gm10544, Malat1, Zfp236, Erc2, and Hmg20a may contribute to the development of NTD.

High-throughput transcriptome sequencing reveals the key stages of cardiovascular development in zebrafish embryos

BACKGROUND

The cardiovascular developmental process is a tightly regulated network involving multiple genes. The current understanding of the molecular mechanism behind cardiovascular development is insufficient and requires further research.

RESULTS

Transcriptome sequencing of three developmental stages in zebrafish embryos was performed and revealed three key cardiovascular developmental stages. Then, the differentially expressed genes (DEGs) involved in cardiovascular development were screened out. The three developmental stages were 18 (T1), 24 (T2), and 42 h post fertilization (hpf) (T3), and the three stages were confirmed by detecting differences in expression between cardiomyocyte and endothelial marker genes (cmlc2, fli1) using in situ hybridization, which represents the characteristics of cardiovascular development. Thousands of DEGs were identified using transcriptome analysis. Of them, 2605 DEGs were in T1-vs-T2, including 2003 up-regulated and 602 down-regulated genes, 6446 DEGs were in T1-vs-T3, consisting of 4608 up-regulated and 1838 down-regulated genes, and 3275 DEGs were in T2-vs-T3, including 2420 up-regulated and 855 down-regulated genes. There were 644 common DEGs and 167 common five-fold higher differentially expressed genes (HDEGs) identified, and Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the Database for Annotation, Visualization and Integrated Discovery (DAVID). Significant differences was observed in the levels of gene expression among different developmental stages in multiple GO terms and KEGG pathways, such as cell migration to the midline involved in heart development, cardiovascular system development, circulatory system process for biological processes of GO terms; and cardiac muscle contraction, adrenergic signaling in cardiomyocytes for KEGG pathways. These results demonstrated that these three stages were important period for the development of the cardiovascular system. Lastly, we used quantitative real-time PCR (qPCR) to validate the reliability of RNA-sequencing by selecting 21 DEGs.

CONCLUSIONS

These results demonstrated that these three stages represented the important periods for cardiovascular system development of zebrafish and some candidate genes was obtained and provided a solid foundation for additional functional studies of the DEGs.

Dyslexia associated gene KIAA0319 regulates cell cycle during human neuroepithelial cell development

Dyslexia, also known as reading disability, is defined as difficulty processing written language in individuals with normal intellectual capacity and educational opportunity. The prevalence of dyslexia is between 5 and 17%, and the heritability ranges from 44 to 75%. Genetic linkage analysis and association studies have identified several genes and regulatory elements linked to dyslexia and reading ability. However, their functions and molecular mechanisms are not well understood. Prominent among these is KIAA0319, encoded in the DYX2 locus of human chromosome 6p22. The association of KIAA0319 with reading performance has been replicated in independent studies and different languages. Rodent models suggest that kiaa0319 is involved in neuronal migration, but its role throughout the cortical development is largely unknown. In order to define the function of KIAA0319 in human cortical development, we applied the neural developmental model of a human embryonic stem cell. We knocked down KIAA0319 expression in hESCs and performed the cortical neuroectodermal differentiation. We found that neuroepithelial cell differentiation is one of the first stages of hESC differentiation that are affected by KIAA0319 knocked down could affect radial migration and thus differentiation into diverse neural populations at the cortical layers.

Development and migration of the zebrafish rhombencephalic octavolateral efferent neurons

In vertebrate animals, motor and sensory efferent neurons carry information from the central nervous system (CNS) to peripheral targets. These two types of efferent systems sometimes bear a close resemblance, sharing common segmental organization, axon pathways, and chemical messengers. Here, we focus on the development of the octavolateral efferent neurons (OENs) and their interactions with the closely-related facial branchiomotor neurons (FBMNs) in zebrafish. Using live-imaging approaches, we investigate the birth, migration, and projection patterns of OENs. We find that OENs are born in two distinct groups: a group of rostral efferent neurons (RENs) that arises in the fourth segment, or rhombomere (r4), of the hindbrain and a group of caudal efferent neurons (CENs) that arises in r5. Both RENs and CENs then migrate posteriorly through the hindbrain between 18 and 48 hrs postfertilization, alongside the r4-derived FBMNs. Like the FBMNs, migration of the r4-derived RENs depends on function of the segmental identity gene hoxb1a; unlike the FBMNs, however, both OEN populations move independently of prickle1b. Further, we investigate whether the previously described "pioneer" neuron that leads FBMN migration through the hindbrain is an r4-derived FBMN/REN or an r5-derived CEN. Our experiments verify that the pioneer is an r4-derived neuron and reaffirm its role in leading FBMN migration across the r4/5 border. In contrast, the r5-derived CENs migrate independently of the pioneer. Together, these results indicate that the mechanisms OENs use to navigate the hindbrain differ significantly from those employed by FBMNs.

Robo1 and 2 Repellent Receptors Cooperate to Guide Facial Neuron Cell Migration and Axon Projections in the Embryonic Mouse Hindbrain

The facial nerve is necessary for our ability to eat, speak, and make facial expressions. Both the axons and cell bodies of the facial nerve undergo a complex embryonic developmental pattern involving migration of the cell bodies caudally and tangentially through rhombomeres, and simultaneously the axons projecting to exit the hindbrain to form the facial nerve. Our goal in this study was to test the functions of the chemorepulsive receptors Robo1 and Robo2 in facial neuron migration and axon projection by analyzing genetically marked motor neurons in double-mutant mouse embryos through the migration time course, E10.0-E13.5. In Robo1/2 double mutants, axon projection and cell body migration errors were more severe than in single mutants. Most axons did not make it to their motor exit point, and instead projected into and longitudinally within the floor plate. Surprisingly, some facial neurons had multiple axons exiting and projecting into the floor plate. At the same time, a subset of mutant facial cell bodies failed to migrate caudally, and instead either streamed dorsally toward the exit point or shifted into the floor plate. We conclude that Robo1 and Robo2 have redundant functions to guide multiple aspects of the complex cell migration of the facial nucleus, as well as regulating axon trajectories and suppressing formation of ectopic axons.

Distinct roles for the cell adhesion molecule Contactin2 in the development and function of neural circuits in zebrafish

Contactin2 (Cntn2)/Transient Axonal Glycoprotein 1 (Tag1), a neural cell adhesion molecule, has established roles in neuronal migration and axon fasciculation in chick and mouse. In zebrafish, antisense morpholino-based studies have indicated roles for cntn2 in the migration of facial branchiomotor (FBM) neurons, the guidance of the axons of the nucleus of the medial longitudinal fascicle (nucMLF), and the outgrowth of Rohon-Beard (RB) central axons. To study functions of Cntn2 in later stages of neuronal development, we generated cntn2 mutant zebrafish using CRISPR-Cas9. Using a null mutant allele, we detected genetic interactions between cntn2 and the planar cell polarity gene vangl2, as shown previously with cntn2 morphants, demonstrating a function for cntn2 during FBM neuron migration in a sensitized background of reduced planar cell polarity signaling. In addition, maternal-zygotic (MZ) cntn2 mutant larvae exhibited aberrant touch responses and swimming, suggestive of defects in sensorimotor circuits, consistent with studies in mice. However, the nucMLF axon convergence, FBM neuron migration, and RB outgrowth defects seen in morphants were not seen in the mutants, and we show here that they are likely off-target effects of morpholinos. However, MLF axons exhibited local defasciculation in MZcntn2 mutants, consistent with a role for Cntn2 in axon fasciculation. These data demonstrate distinct roles for zebrafish cntn2 in neuronal migration and axon fasciculation, and in the function of sensorimotor circuits.

Actin-Based Adhesion Modules Mediate Cell Interactions with the Extracellular Matrix and Neighboring Cells

Cell adhesions link cells to the extracellular matrix (ECM) and to each other and depend on interactions with the actin cytoskeleton. Both cell-ECM and cell-cell adhesion sites contain discrete, yet overlapping, functional modules. These modules establish physical associations with the actin cytoskeleton, locally modulate actin organization and dynamics, and trigger intracellular signaling pathways. Interplay between these modules generates distinct actin architectures that underlie different stages, types, and functions of cell-ECM and cell-cell adhesions. Actomyosin contractility is required to generate mature, stable adhesions, as well as to sense and translate the mechanical properties of the cellular environment into changes in cell organization and behavior. Here, we review the organization and function of different adhesion modules and how they interact with the actin cytoskeleton. We highlight the molecular mechanisms of mechanotransduction in adhesions and how adhesion molecules mediate cross talk between cell-ECM and cell-cell adhesion sites.

Cadherin-2 Is Required Cell Autonomously for Collective Migration of Facial Branchiomotor Neurons

Collective migration depends on cell-cell interactions between neighbors that contribute to their overall directionality, yet the mechanisms that control the coordinated migration of neurons remains to be elucidated. During hindbrain development, facial branchiomotor neurons (FBMNs) undergo a stereotypic tangential caudal migration from their place of birth in rhombomere (r)4 to their final location in r6/7. FBMNs engage in collective cell migration that depends on neuron-to-neuron interactions to facilitate caudal directionality. Here, we demonstrate that Cadherin-2-mediated neuron-to-neuron adhesion is necessary for directional and collective migration of FBMNs. We generated stable transgenic zebrafish expressing dominant-negative Cadherin-2 (Cdh2ΔEC) driven by the islet1 promoter. Cell-autonomous inactivation of Cadherin-2 function led to non-directional migration of FBMNs and a defect in caudal tangential migration. Additionally, mosaic analysis revealed that Cdh2ΔEC-expressing FBMNs are not influenced to migrate caudally by neighboring wild-type FBMNs due to a defect in collective cell migration. Taken together, our data suggest that Cadherin-2 plays an essential cell-autonomous role in mediating the collective migration of FBMNs.

2- and 6-O-sulfated proteoglycans have distinct and complementary roles in cranial axon guidance and motor neuron migration

The correct migration and axon extension of neurons in the developing nervous system is essential for the appropriate wiring and function of neural networks. Here, we report that O-sulfotransferases, a class of enzymes that modify heparan sulfate proteoglycans (HSPGs), are essential to regulate neuronal migration and axon development. We show that the 6-O-sulfotransferases HS6ST1 and HS6ST2 are essential for cranial axon patterning, whilst the 2-O-sulfotransferase HS2ST (also known as HS2ST1) is important to regulate the migration of facial branchiomotor (FBM) neurons in the hindbrain. We have also investigated how HS2ST interacts with other signals in the hindbrain and show that fibroblast growth factor (FGF) signalling regulates FBM neuron migration in an HS2ST-dependent manner.

Summary: 2-O-sulfated proteoglycans are essential for cranial motor neuron migration, whereas 6-O-sulfated proteoglycans regulate cranial axon guidance.

Cell segregation in the vertebrate hindbrain: a matter of boundaries

Segregating cells into compartments during embryonic development is essential for growth and pattern formation. In the developing hindbrain, boundaries separate molecularly, physically and neuroanatomically distinct segments called rhombomeres. After rhombomeric cells have acquired their identity, interhombomeric boundaries restrict cell intermingling between adjacent rhombomeres and act as signaling centers to pattern the surrounding tissue. Several works have stressed the relevance of Eph/ephrin signaling in rhombomeric cell sorting. Recent data have unveiled the role of this pathway in the assembly of actomyosin cables as an important mechanism for keeping cells from different rhombomeres segregated. In this Review, we will provide a short summary of recent evidences gathered in different systems suggesting that physical actomyosin barriers can be a general mechanism for tissue separation. We will discuss current evidences supporting a model where cell-cell signaling pathways, such as Eph/ephrin, govern compartmental cell sorting through modulation of the actomyosin cytoskeleton and cell adhesive properties to prevent cell intermingling.

Dual pipette aspiration: a unique tool for studying intercellular adhesion

The dual pipette aspiration (DPA) assay is a highly versatile tool that enables the micromanipulation of cells and the precise measurement of a range of biophysical parameters in combination with concurrent high-resolution imaging. DPA permits the juxtaposition of cells, their manipulation using pressure and the controlled formation or separation of cell-cell contacts. The DPA set-up can thus readily be used to probe the dynamics and mechanics of cell-cell adhesion, notably adhesion strength and adhesion energy. In particular, the DPA set-up has been used to measure a wide range of separation forces between pairs of cells. Here, we describe how to build and use the DPA set-up in order to measure the separation force of cell doublets. We first describe how to prepare adequate pipettes, then how to assemble and calibrate the pipettes and pressure control devices, followed by how to manipulate cells in order to calculate separation forces. Finally, we give recommendations on how to use the DPA set-up and compare it to other methods used to study cell-cell contacts and adhesion strength in particular.

Proper migration and axon outgrowth of zebrafish cranial motoneuron subpopulations require the cell adhesion molecule MDGA2A

The formation of functional neuronal circuits relies on accurate migration and proper axonal outgrowth of neuronal precursors. On the route to their targets migrating cells and growing axons depend on both, directional information from neurotropic cues and adhesive interactions mediated via extracellular matrix molecules or neighbouring cells. The inactivation of guidance cues or the interference with cell adhesion can cause severe defects in neuronal migration and axon guidance. In this study we have analyzed the function of the MAM domain containing glycosylphosphatidylinositol anchor 2A (MDGA2A) protein in zebrafish cranial motoneuron development. MDGA2A is prominently expressed in distinct clusters of cranial motoneurons, especially in the ones of the trigeminal and facial nerves. Analyses of MDGA2A knockdown embryos by light sheet and confocal microscopy revealed impaired migration and aberrant axonal outgrowth of these neurons; suggesting that adhesive interactions mediated by MDGA2A are required for the proper arrangement and outgrowth of cranial motoneuron subtypes.

Mouse hindbrain ex vivo culture to study facial branchiomotor neuron migration

Embryonic neurons are born in the ventricular zone of the brain, but subsequently migrate to new destinations to reach appropriate targets. Deciphering the molecular signals that cooperatively guide neuronal migration in the embryonic brain is therefore important to understand how the complex neural networks form which later support postnatal life. Facial branchiomotor (FBM) neurons in the mouse embryo hindbrain migrate from rhombomere (r) 4 caudally to form the paired facial nuclei in the r6-derived region of the hindbrain. Here we provide a detailed protocol for wholemount ex vivo culture of mouse embryo hindbrains suitable to investigate the signaling pathways that regulate FBM migration. In this method, hindbrains of E11.5 mouse embryos are dissected and cultured in an open book preparation on cell culture inserts for 24 hr. During this time, FBM neurons migrate caudally towards r6 and can be exposed to function-blocking antibodies and small molecules in the culture media or heparin beads loaded with recombinant proteins to examine roles for signaling pathways implicated in guiding neuronal migration.

Three functions of cadherins in cell adhesion

Cadherins are transmembrane proteins that mediate cell-cell adhesion in animals. By regulating contact formation and stability, cadherins play a crucial role in tissue morphogenesis and homeostasis. Here, we review the three major functions of cadherins in cell-cell contact formation and stability. Two of those functions lead to a decrease in interfacial tension at the forming cell-cell contact, thereby promoting contact expansion--first, by providing adhesion tension that lowers interfacial tension at the cell-cell contact, and second, by signaling to the actomyosin cytoskeleton in order to reduce cortex tension and thus interfacial tension at the contact. The third function of cadherins in cell-cell contact formation is to stabilize the contact by resisting mechanical forces that pull on the contact.

Facial motor neuron migration advances

During development, the migration of specific neuronal subtypes is required for the correct establishment of neural circuits. In mice and zebrafish, facial branchiomotor (FBM) neurons undergo a tangential migration from rhombomere 4 caudally through the hindbrain. Recent advances in the field have capitalized on genetic studies in zebrafish and mouse, and high-resolution time-lapse imaging in zebrafish. Planar cell polarity signaling has emerged as a critical conserved factor in FBM neuron migration, functioning both within the neurons and their environment. In zebrafish, migration depends on specialized 'pioneer' neurons to lead follower FBM neurons through the hindbrain, and on interactions with structural components including pre-laid axon tracts and the basement membrane. Despite fundamental conservation, species-specific differences in migration mechanisms are being uncovered.

Shaping the nervous system: role of the core planar cell polarity genes

Planar cell polarity (PCP) is complementary to the intrinsic polarization of single cells and refers to the global coordination of cell behaviour in the plane of a tissue and, by extension, to the signalling pathways that control it. PCP is most evident in cell sheets, and research into PCP was for years confined to studies in Drosophila melanogaster. However, PCP has more recently emerged as an important phenomenon in vertebrates, in which it regulates various developmental processes and is associated with multiple disorders. In particular, core PCP genes are crucial for the development and function of the nervous system. They are involved in neural tube closure, ependymal polarity, neuronal migration, dendritic growth and axon guidance.

Mechanosensitive systems at the cadherin-F-actin interface

Cells integrate biochemical and mechanical information to function within multicellular tissue. Within developing and remodeling tissues, mechanical forces contain instructive information that governs important cellular processes that include stem cell maintenance, differentiation and growth. Although the principles of signal transduction (protein phosphorylation, allosteric regulation of enzymatic activity and binding sites) are the same for biochemical and mechanical-induced signaling, the first step of mechanosensing, in which protein complexes under tension transduce changes in physical force into cellular signaling, is very different, and the molecular mechanisms are only beginning to be elucidated. In this Commentary, we focus on mechanotransduction at cell-cell junctions, aiming to comprehend the molecular mechanisms involved. We describe how different junction structures are associated with the actomyosin cytoskeleton and how this relates to the magnitude and direction of forces at cell-cell junctions. We discuss which cell-cell adhesion receptors have been shown to take part in mechanotransduction. Then we outline the force-induced molecular events that might occur within a key mechanosensitive system at cell-cell junctions; the cadherin-F-actin interface, at which α-catenin and vinculin form a central module. Mechanotransduction at cell-cell junctions emerges as an important signaling mechanism, and we present examples of its potential relevance for tissue development and disease.

α-Catenin and vinculin cooperate to promote high E-cadherin-based adhesion strength

Maintaining cell cohesiveness within tissues requires that intercellular adhesions develop sufficient strength to support traction forces applied by myosin motors and by neighboring cells. Cadherins are transmembrane receptors that mediate intercellular adhesion. The cadherin cytoplasmic domain recruits several partners, including catenins and vinculin, at sites of cell-cell adhesion. Our study used force measurements to address the role of αE-catenin and vinculin in the regulation of the strength of E-cadherin-based adhesion. αE-catenin-deficient cells display only weak aggregation and fail to strengthen intercellular adhesion over time, a process rescued by the expression of αE-catenin or chimeric E-cadherin·αE-catenins, including a chimera lacking the αE-catenin dimerization domain. Interestingly, an αE-catenin mutant lacking the modulation and actin-binding domains restores cadherin-dependent cell-cell contacts but cannot strengthen intercellular adhesion. The expression of αE-catenin mutated in its vinculin-binding site is defective in its ability to rescue cadherin-based adhesion strength in cells lacking αE-catenin. Vinculin depletion or the overexpression of the αE-catenin modulation domain strongly decreases E-cadherin-mediated adhesion strength. This supports the notion that both molecules are required for intercellular contact maturation. Furthermore, stretching of cell doublets increases vinculin recruitment and α18 anti-αE-catenin conformational epitope immunostaining at cell-cell contacts. Taken together, our results indicate that αE-catenin and vinculin cooperatively support intercellular adhesion strengthening, probably via a mechanoresponsive link between the E-cadherin·β-catenin complexes and the underlying actin cytoskeleton.

Axon tracts guide zebrafish facial branchiomotor neuron migration through the hindbrain

Appropriate localization of neurons within the brain is a crucial component of the establishment of neural circuitry. In the zebrafish hindbrain, the facial branchiomotor neurons (FBMNs) undergo a chain-like tangential migration from their birthplace in rhombomere (r) 4 to their final destination in r6/r7. Here, we report that ablation of either the cell body or the trailing axon of the leading FBMN, or 'pioneer' neuron, blocks the migration of follower FBMNs into r5. This demonstrates that the pioneer neuron and its axon are crucial to the early migration of FBMNs. Later migration from r5 to r6 is not dependent on pioneer neurons but on the medial longitudinal fasciculus (MLF), a bundle of axons lying ventral to the FBMNs. We find that MLF axons enter r5 only after the pioneer neuron has led several followers into this region; the MLF is then contacted by projections from the FBMNs. The interactions between FBMNs and the MLF are important for migration from r5 to r6, as blocking MLF axons from entering the hindbrain can stall FBMN migration in r5. Finally, we have found that the adhesion molecule Cdh2 (N-cadherin) is important for interactions between the MLF and FBMNs, as well as for interactions between the trailing axon of the pioneer neuron and follower FBMNs. Interestingly, migration of pioneer neurons is independent of both the MLF and Cdh2, suggesting pioneer migration relies on independent cues.

Regulation of cadherin expression in nervous system development

This review addresses our current understanding of the regulatory mechanisms for classical cadherin expression during development of the vertebrate nervous system. The complexity of the spatial and temporal expression patterns is linked to morphogenic and functional roles in the developing nervous system. While the regulatory networks controlling cadherin expression are not well understood, it is likely that the multiple signaling pathways active in the development of particular domains also regulate the specific cadherins expressed at that time and location. With the growing understanding of the broader roles of cadherins in cell-cell adhesion and non-adhesion processes, it is important to understand both the upstream regulation of cadherin expression and the downstream effects of specific cadherins within their cellular context.

Profiling, Bioinformatic, and Functional Data on the Developing Olfactory/GnRH System Reveal Cellular and Molecular Pathways Essential for This Process and Potentially Relevant for the Kallmann Syndrome

During embryonic development, immature neurons in the olfactory epithelium (OE) extend axons through the nasal mesenchyme, to contact projection neurons in the olfactory bulb. Axon navigation is accompanied by migration of the GnRH+ neurons, which enter the anterior forebrain and home in the septo-hypothalamic area. This process can be interrupted at various points and lead to the onset of the Kallmann syndrome (KS), a disorder characterized by anosmia and central hypogonadotropic hypogonadism. Several genes has been identified in human and mice that cause KS or a KS-like phenotype. In mice a set of transcription factors appears to be required for olfactory connectivity and GnRH neuron migration; thus we explored the transcriptional network underlying this developmental process by profiling the OE and the adjacent mesenchyme at three embryonic ages. We also profiled the OE from embryos null for Dlx5, a homeogene that causes a KS-like phenotype when deleted. We identified 20 interesting genes belonging to the following categories: (1) transmembrane adhesion/receptor, (2) axon-glia interaction, (3) scaffold/adapter for signaling, (4) synaptic proteins. We tested some of them in zebrafish embryos: the depletion of five (of six) Dlx5 targets affected axonal extension and targeting, while three (of three) affected GnRH neuron position and neurite organization. Thus, we confirmed the importance of cell-cell and cell-matrix interactions and identified new molecules needed for olfactory connection and GnRH neuron migration. Using available and newly generated data, we predicted/prioritized putative KS-disease genes, by building conserved co-expression networks with all known disease genes in human and mouse. The results show the overall validity of approaches based on high-throughput data and predictive bioinformatics to identify genes potentially relevant for the molecular pathogenesis of KS. A number of candidate will be discussed, that should be tested in future mutation screens.

Planar cell polarity in coordinated and directed movements

Planar cell polarity is a fundamental concept to understanding the coordination of cell movements in the plane of a tissue. Since the planar cell polarity pathway was discovered in mesenchymal tissues involving cell interaction during vertebrate gastrulation, there is an emerging evidence that a variety of mesenchymal and epithelial cells utilize this genetic pathway to mediate the coordination of cells in directed movements. In this review, we focus on how the planar cell polarity pathway is mediated by migrating cells to communicate with one another in different developmental processes.