Spatial transcriptomics reveals novel genes during the remodelling of the embryonic human arterial valves

Abnormalities of the arterial valves, including bicuspid aortic valve (BAV) are amongst the most common congenital defects and are a significant cause of morbidity as well as predisposition to disease in later life. Despite this, and compounded by their small size and relative inaccessibility, there is still much to understand about how the arterial valves form and remodel during embryogenesis, both at the morphological and genetic level. Here we set out to address this in human embryos, using Spatial Transcriptomics (ST). We show that ST can be used to investigate the transcriptome of the developing arterial valves, circumventing the problems of accurately dissecting out these tiny structures from the developing embryo. We show that the transcriptome of CS16 and CS19 arterial valves overlap considerably, despite being several days apart in terms of human gestation, and that expression data confirm that the great majority of the most differentially expressed genes are valve-specific. Moreover, we show that the transcriptome of the human arterial valves overlaps with that of mouse atrioventricular valves from a range of gestations, validating our dataset but also highlighting novel genes, including four that are not found in the mouse genome and have not previously been linked to valve development. Importantly, our data suggests that valve transcriptomes are under-represented when using commonly used databases to filter for genes important in cardiac development; this means that causative variants in valve-related genes may be excluded during filtering for genomic data analyses for, for example, BAV. Finally, we highlight "novel" pathways that likely play important roles in arterial valve development, showing that mouse knockouts of RBP1 have arterial valve defects. Thus, this study has confirmed the utility of ST for studies of the developing heart valves and broadens our knowledge of the genes and signalling pathways important in human valve development.

A Roadmap for the Human Gut Cell Atlas

The number of studies investigating the human gastrointestinal tract using various single-cell profiling methods has increased substantially in the past few years. Although this increase provides a unique opportunity for the generation of the first comprehensive Human Gut Cell Atlas (HGCA), there remains a range of major challenges ahead. Above all, the ultimate success will largely depend on a structured and coordinated approach that aligns global efforts undertaken by a large number of research groups. In this Roadmap, we discuss a comprehensive forward-thinking direction for the generation of the HGCA on behalf of the Gut Biological Network of the Human Cell Atlas. Based on the consensus opinion of experts from across the globe, we outline the main requirements for the first complete HGCA by summarizing existing data sets and highlighting anatomical regions and/or tissues with limited coverage. We provide recommendations for future studies and discuss key methodologies and the importance of integrating the healthy gut atlas with related diseases and gut organoids. Importantly, we critically overview the computational tools available and provide recommendations to overcome key challenges.

The 'straight mouse': defining anatomical axes in 3D embryo models

A primary objective of the eMouseAtlas Project is to enable 3D spatial mapping of whole embryo gene expression data to capture complex 3D patterns for indexing, visualization, cross-comparison and analysis. For this we have developed a spatio-temporal framework based on 3D models of embryos at different stages of development coupled with an anatomical ontology. Here we introduce a method of defining coordinate axes that correspond to the anatomical or biologically relevant anterior–posterior (A–P), dorsal–ventral (D–V) and left–right (L–R) directions. These enable more sophisticated query and analysis of the data with biologically relevant associations, and provide novel data visualizations that can reveal patterns that are otherwise difficult to detect in the standard 3D coordinate space. These anatomical coordinates are defined using the concept of a ‘straight mouse-embryo’ within which the anatomical coordinates are Cartesian. The straight embryo model has been mapped via a complex non-linear transform onto the standard embryo model. We explore the utility of this anatomical coordinate system in elucidating the spatial relationship of spatially mapped embryonic ‘Fibroblast growth factor’ gene expression patterns, and we discuss the importance of this technology in summarizing complex multimodal mouse embryo image data from gene expression and anatomy studies.

Database URL:www.emouseatlas.org

PhenoImageShare: an image annotation and query infrastructure

Background

High throughput imaging is now available to many groups and it is possible to generate a large quantity of high quality images quickly. Managing this data, consistently annotating it, or making it available to the community are all challenges that come with these methods.

Results

PhenoImageShare provides an ontology-enabled lightweight image data query, annotation service and a single point of access backed by a Solr server for programmatic access to an integrated image collection enabling improved community access. PhenoImageShare also provides an easy to use online image annotation tool with functionality to draw regions of interest on images and to annotate them with terms from an autosuggest-enabled ontology-lookup widget. The provenance of each image, and annotation, is kept and links to original resources are provided. The semantic and intuitive search interface is species and imaging technology neutral. PhenoImageShare now provides access to annotation for over 100,000 images for 2 species.

Conclusion

The PhenoImageShare platform provides underlying infrastructure for both programmatic access and user-facing tools for biologists enabling the query and annotation of federated images. PhenoImageShare is accessible online at http://www.phenoimageshare.org.

The atlas of mouse development eHistology resource

The Atlas of Mouse Development by Professor Mathew Kaufman is an essential text for understanding mouse developmental anatomy. This definitive and authoritative atlas is still in production and is essential for any biologist working with the mouse embryo, although the last revision dates back to 1994. Here, we announce the eHistology online resource that provides free access to high-resolution colour images digitized from the original histological sections (www.emouseatlas.org/emap/eHistology/index.php) used by Kaufman for the Atlas. The images are provided with the original annotations and plate numbering of the paper atlas and enable viewing the material to cellular resolution.

The atlas of mouse development eHistology resource

There was an error published in Development 142, 1909-1911. Author Yogmatee Roochun was omitted. The corrected author list appears above. The authors apologise to readers for this mistake.

Deducing the stage of origin of Wilms' tumours from a developmental series of Wt1-mutant mice

Wilms' tumours, paediatric kidney cancers, are the archetypal example of tumours caused through the disruption of normal development. The genetically best-defined subgroup of Wilms' tumours is the group caused by biallelic loss of the WT1 tumour suppressor gene. Here, we describe a developmental series of mouse models with conditional loss of Wt1 in different stages of nephron development before and after the mesenchymal-to-epithelial transition (MET). We demonstrate that Wt1 is essential for normal development at all kidney developmental stages under study. Comparison of genome-wide expression data from the mutant mouse models with human tumour material of mutant or wild-type WT1 datasets identified the stage of origin of human WT1-mutant tumours, and emphasizes fundamental differences between the two human tumour groups due to different developmental stages of origin.

Summary: The comparison of different nephron-specific Wt1-knockout mouse models identifies the stage of origin of human WT1-mutant Wilms' tumours.

The BioMart community portal: an innovative alternative to large, centralized data repositories

The BioMart Community Portal (www.biomart.org) is a community-driven effort to provide a unified interface to biomedical databases that are distributed worldwide. The portal provides access to numerous database projects supported by 30 scientific organizations. It includes over 800 different biological datasets spanning genomics, proteomics, model organisms, cancer data, ontology information and more. All resources available through the portal are independently administered and funded by their host organizations. The BioMart data federation technology provides a unified interface to all the available data. The latest version of the portal comes with many new databases that have been created by our ever-growing community. It also comes with better support and extensibility for data analysis and visualization tools. A new addition to our toolbox, the enrichment analysis tool is now accessible through graphical and web service interface. The BioMart community portal averages over one million requests per day. Building on this level of service and the wealth of information that has become available, the BioMart Community Portal has introduced a new, more scalable and cheaper alternative to the large data stores maintained by specialized organizations.

Pleiotropic effects of Sox2 during the development of the zebrafish epithalamus

The zebrafish epithalamus is part of the diencephalon and encompasses three major components: the pineal, the parapineal and the habenular nuclei. Using sox2 knockdown, we show here that this key transcriptional regulator has pleiotropic effects during the development of these structures. Sox2 negatively regulates pineal neurogenesis. Also, Sox2 is identified as the unknown factor responsible for pineal photoreceptor prepatterning and performs this function independently of the BMP signaling. The correct levels of sox2 are critical for the functionally important asymmetrical positioning of the parapineal organ and for the migration of parapineal cells as a coherent structure. Deviations from this strict control result in defects associated with abnormal habenular laterality, which we have documented and quantified in sox2 morphants.

Functional tissue units and their primary tissue motifs in multi-scale physiology

Background

Histology information management relies on complex knowledge derived from morphological tissue analyses. These approaches have not significantly facilitated the general integration of tissue- and molecular-level knowledge across the board in support of a systematic classification of tissue function, as well as the coherent multi-scale study of physiology. Our work aims to support directly these integrative goals.

Results

We describe, for the first time, the precise biophysical and topological characteristics of functional units of tissue. Such a unit consists of a three-dimensional block of cells centred around a capillary, such that each cell in this block is within diffusion distance from any other cell in the same block. We refer to this block as a functional tissue unit. As a means of simplifying the knowledge representation of this unit, and rendering this knowledge more amenable to automated reasoning and classification, we developed a simple descriptor of its cellular content and anatomical location, which we refer to as a primary tissue motif. In particular, a primary motif captures the set of cellular participants of diffusion-mediated interactions brokered by secreted products to create a tissue-level molecular network.

Conclusions

Multi-organ communication, therefore, may be interpreted in terms of interactions between molecular networks housed by interconnected functional tissue units. By extension, a functional picture of an organ, or its tissue components, may be rationally assembled using a collection of these functional tissue units as building blocks. In our work, we outline the biophysical rationale for a rigorous definition of a unit of functional tissue organization, and demonstrate the application of primary motifs in tissue classification. In so doing, we acknowledge (i) the fundamental role of capillaries in directing and radically informing tissue architecture, as well as (ii) the importance of taking into full account the critical influence of neighbouring cellular environments when studying complex developmental and pathological phenomena.

Bloomsbury report on mouse embryo phenotyping: recommendations from the IMPC workshop on embryonic lethal screening

Identifying genes that are important for embryo development is a crucial first step towards understanding their many functions in driving the ordered growth, differentiation and organogenesis of embryos. It can also shed light on the origins of developmental disease and congenital abnormalities. Current international efforts to examine gene function in the mouse provide a unique opportunity to pinpoint genes that are involved in embryogenesis, owing to the emergence of embryonic lethal knockout mutants. Through internationally coordinated efforts, the International Knockout Mouse Consortium (IKMC) has generated a public resource of mouse knockout strains and, in April 2012, the International Mouse Phenotyping Consortium (IMPC), supported by the EU InfraCoMP programme, convened a workshop to discuss developing a phenotyping pipeline for the investigation of embryonic lethal knockout lines. This workshop brought together over 100 scientists, from 13 countries, who are working in the academic and commercial research sectors, including experts and opinion leaders in the fields of embryology, animal imaging, data capture, quality control and annotation, high-throughput mouse production, phenotyping, and reporter gene analysis. This article summarises the outcome of the workshop, including (1) the vital scientific importance of phenotyping embryonic lethal mouse strains for basic and translational research; (2) a common framework to harmonise international efforts within this context; (3) the types of phenotyping that are likely to be most appropriate for systematic use, with a focus on 3D embryo imaging; (4) the importance of centralising data in a standardised form to facilitate data mining; and (5) the development of online tools to allow open access to and dissemination of the phenotyping data.

Deciphering the Mechanisms of Developmental Disorders (DMDD): a new programme for phenotyping embryonic lethal mice

International efforts to test gene function in the mouse by the systematic knockout of each gene are creating many lines in which embryonic development is compromised. These homozygous lethal mutants represent a potential treasure trove for the biomedical community. Developmental biologists could exploit them in their studies of tissue differentiation and organogenesis; for clinical researchers they offer a powerful resource for investigating the origins of developmental diseases that affect newborns. Here, we outline a new programme of research in the UK aiming to kick-start research with embryonic lethal mouse lines. The ‘Deciphering the Mechanisms of Developmental Disorders’ (DMDD) programme has the ambitious goal of identifying all embryonic lethal knockout lines made in the UK over the next 5 years, and will use a combination of comprehensive imaging and transcriptomics to identify abnormalities in embryo structure and development. All data will be made freely available, enabling individual researchers to identify lines relevant to their research. The DMDD programme will coordinate its work with similar international efforts through the umbrella of the International Mouse Phenotyping Consortium [see accompanying Special Article (Adams et al., 2013)] and, together, these programmes will provide a novel database for embryonic development, linking gene identity with molecular profiles and morphology phenotypes.

eMouseAtlas, EMAGE, and the spatial dimension of the transcriptome

eMouseAtlas (www.emouseatlas.org) is a comprehensive online resource to visualise mouse development and investigate gene expression in the mouse embryo. We have recently deployed a completely redesigned Mouse Anatomy Atlas website (www.emouseatlas.org/emap/ema) that allows users to view 3D embryo reconstructions, delineated anatomy, and high-resolution histological sections. A new feature of the website is the IIP3D web tool that allows a user to view arbitrary sections of 3D embryo reconstructions using a web browser. This feature provides interactive access to very high-volume 3D images via a tiled pan-and-zoom style interface and circumvents the need to download large image files for visualisation. eMouseAtlas additionally includes EMAGE (Edinburgh Mouse Atlas of Gene Expression) (www.emouseatlas.org/emage), a freely available, curated online database of in situ gene expression patterns, where gene expression domains extracted from raw data images are spatially mapped into atlas embryo models. In this way, EMAGE introduces a spatial dimension to transcriptome data and allows exploration of the spatial similarity between gene expression patterns. New features of the EMAGE interface allow complex queries to be built, and users can view and compare multiple gene expression patterns. EMAGE now includes mapping of 3D gene expression domains captured using the imaging technique optical projection tomography. 3D mapping uses WlzWarp, an open-source software tool developed by eMouseAtlas.

The BioMart interface to the eMouseAtlas gene expression database EMAGE

Here, we describe the BioMart interface to the eMouseAtlas gene expression database EMAGE. EMAGE is a spatiotemporal database of in situ gene expression patterns in the developing mouse embryo. BioMart provides a generic web query interface and programmable access using web services. The BioMart interface extends access to EMAGE via a powerful method of structuring complex queries and one with which users may already be familiar with from other BioMart implementations. The interface is structured into several data sets providing the user with comprehensive query access to the EMAGE data. The federated nature of BioMart allows scope for integration and cross querying of EMAGE with other similar BioMarts.

Database URL:http://biomart.emouseatlas.org

BioMart Central Portal: an open database network for the biological community

BioMart Central Portal is a first of its kind, community-driven effort to provide unified access to dozens of biological databases spanning genomics, proteomics, model organisms, cancer data, ontology information and more. Anybody can contribute an independently maintained resource to the Central Portal, allowing it to be exposed to and shared with the research community, and linking it with the other resources in the portal. Users can take advantage of the common interface to quickly utilize different sources without learning a new system for each. The system also simplifies cross-database searches that might otherwise require several complicated steps. Several integrated tools streamline common tasks, such as converting between ID formats and retrieving sequences. The combination of a wide variety of databases, an easy-to-use interface, robust programmatic access and the array of tools make Central Portal a one-stop shop for biological data querying. Here, we describe the structure of Central Portal and show example queries to demonstrate its capabilities.

The HUDSEN Atlas: a three-dimensional (3D) spatial framework for studying gene expression in the developing human brain

We are developing a three-dimensional (3D) atlas of the human embryonic brain using anatomical landmarks and gene expression data to define major subdivisions through 12 stages of development [Carnegie Stages (CS) 12-23; approximately 26-56 days post conception (dpc)]. Virtual 3D anatomical models are generated from intact specimens using optical projection tomography (OPT). Using MAPAINT software, selected gene expression data, gathered using standard methods of in situ hybridization and immunohistochemistry, are mapped to a representative 3D model for each chosen Carnegie stage. In these models, anatomical domains, defined on the basis of morphological landmarks and comparative knowledge of expression patterns in vertebrates, are linked to a developmental neuroanatomic ontology. Human gene expression patterns for genes with characteristic expression in different vertebrates (e.g. PAX6, GAD65 and OLIG2) are being used to confirm and/or refine the human anatomical domain boundaries. We have also developed interpolation software that digitally generates a full domain from partial data. Currently, the 3D models and a preliminary set of anatomical domains and ontology are available on the atlas pages along with gene expression data from approximately 100 genes in the HUDSEN Human Spatial Gene Expression Database (http://www.hudsen.org). The aim is that full 3D data will be generated from expression data used to define a more detailed set of anatomical domains linked to a more advanced anatomy ontology and all of these will be available online, contributing to the long-term goal of the atlas, which is to help maximize the effective use and dissemination of data wherever it is generated.

The IKMC web portal: a central point of entry to data and resources from the International Knockout Mouse Consortium

The International Knockout Mouse Consortium (IKMC) aims to mutate all protein-coding genes in the mouse using a combination of gene targeting and gene trapping in mouse embryonic stem (ES) cells and to make the generated resources readily available to the research community. The IKMC database and web portal (www.knockoutmouse.org) serves as the central public web site for IKMC data and facilitates the coordination and prioritization of work within the consortium. Researchers can access up-to-date information on IKMC knockout vectors, ES cells and mice for specific genes, and follow links to the respective repositories from which corresponding IKMC products can be ordered. Researchers can also use the web site to nominate genes for targeting, or to indicate that targeting of a gene should receive high priority. The IKMC database provides data to, and features extensive interconnections with, other community databases.

Identification of genes downstream of the Shh signalling in the developing chick wing and syn-expressed with Hoxd13 using microarray and 3D computational analysis

Sonic hedgehog (Shh) signalling by the polarizing region at the posterior margin of the chick wing bud is pivotal in patterning the digits but apart from a few key downstream genes, such as Hoxd13, which is expressed in the posterior region of the wing that gives rise to the digits, the genes that mediate the response to Shh signalling are not known. To find genes that are co-expressed with Hoxd13 in the posterior of chick wing buds and regulated in the same way, we used microarrays to compare gene expression between anterior and posterior thirds of wing buds from normal chick embryos and from polydactylous talpid³ mutant chick embryos, which have defective Shh signalling due to lack of primary cilia. We identified 1070 differentially expressed gene transcripts, which were then clustered. Two clusters contained genes predominantly expressed in posterior thirds of normal wing buds; in one cluster, genes including Hoxd13, were expressed at high levels in anterior and posterior thirds in talpid³ wing buds, in the other cluster, genes including Ptc1, were expressed at low levels in anterior and posterior thirds in talpid³ wing buds. Expression patterns of genes in these two clusters were validated in normal and talpid³ mutant wing buds by in situ hybridisation and demonstrated to be responsive to application of Shh. Expression of several genes in the Hoxd13 cluster was also shown to be responsive to manipulation of protein kinase A (PKA) activity, thus demonstrating regulation by Gli repression. Genes in the Hoxd13 cluster were then sub-clustered by computational comparison of 3D expression patterns in normal wing buds to produce syn-expression groups. Hoxd13 and Sall1 are syn-expressed in the posterior region of early chick wing buds together with 6 novel genes which are likely to be functionally related and represent secondary targets of Shh signalling. Other groups of syn-expressed genes were also identified, including a group of genes involved in vascularisation.

From spatial-data to 3D models of the developing human brain

Visualisation and interpretation of gene expression data have been crucial to advances in our understanding of mechanisms underlying early brain development. As most developmental processes involve complex changes in size, shape and structure, spatial-data can most readily provide information at multiple levels (cell type, cell location in relation to tissue organisation or body axes, etc.), that can be related to these complex changes. Although three-dimensional (3D) spatial-data are ideal, the restricted availability of suitable tissues makes it difficult to generate these for genes expressed at early human fetal stages. Mapping gene expression data to representative 3D models facilitates combinatorial analysis of multiple expression patterns but does not overcome the problems of sparsely sampled data in time and space. Here we describe software that allows 3D domains to be reconstructed by interpolating between sparse 2D gene expression patterns that have been mapped to 3D representative models of corresponding human developmental stages. A set of procedures are proposed to infer expression domains in these gaps. The procedures, which are connected in a serial way, include components clustering, components tracking, shape matching and points interpolation. Each procedure consists of a graphical user interface and a set of algorithms. Results on exemplar gene data are provided.

The Mouse Limb Anatomy Atlas: an interactive 3D tool for studying embryonic limb patterning

Background

The developing mouse limb is widely used as a model system for studying tissue patterning. Despite this, few references are available that can be used for the correct identification of developing limb structures, such as muscles and tendons. Existing textual references consist of two-dimensional (2D) illustrations of the adult rat or mouse limb that can be difficult to apply when attempting to describe the complex three-dimensional (3D) relationship between tissues.

Results

To improve the resources available in the mouse model, we have generated a free, web-based, interactive reference of limb muscle, tendon, and skeletal structures at embryonic day (E) 14.5 . The Atlas was generated using mouse forelimb and hindlimb specimens stained using immunohistochemistry to detect muscle and tendon. Limbs were scanned using Optical Projection Tomography (OPT), reconstructed to make 3D models and annotated using computer-assisted segmentation tools in Amira 3D Visualisation software. The annotated dataset is visualised using Java, JAtlasView software. Users click on the names of structures and view their shape, position and relationship with other structures within the 3D model and also in 2D virtual sections.

Conclusion

The Mouse Limb Anatomy Atlas provides a novel and valuable tool for researchers studying limb development and can be applied to a range of research areas, including the identification of abnormal limb patterning in transgenic lines and studies of models of congenital limb abnormalities. By using the Atlas for "virtual" dissection, this resource offers an alternative to animal dissection. The techniques we have developed and employed are also applicable to many other model systems and anatomical structures.

Data integration in eHealth: a domain/disease specific roadmap

The paper documents a series of data integration workshops held in 2006 at the UK National e-Science Centre, summarizing a range of the problem/solution scenarios in multi-site and multi-scale data integration with six HealthGrid projects using schizophrenia as a domain-specific test case. It outlines emerging strategies, recommendations and objectives for collaboration on shared ontology-building and harmonization of data for multi-site trials in this domain.

Anatomical and gene expression mapping of the ventral pallium in a three-dimensional model of developing human brain

Combining gene expression data with morphological information has revolutionized developmental neuroanatomy in the last decade. Visualization and interpretation of complex images have been crucial to these advances in our understanding of mechanisms underlying early brain development, as most developmental processes are spatially oriented, in topologically invariant patterns that become overtly distorted during brain morphogenesis. It has also become clear that more powerful methodologies are needed to accommodate the increasing volume of data available and the increasingly sophisticated analyses that are required, for example analyzing anatomy and multiple gene expression patterns at individual developmental stages, or identifying and analyzing homologous structures through time and/or between species. Three-dimensional models have long been recognized as a valuable way of providing a visual interpretation and overview of complex morphological data. We have used a recently developed method, optical projection tomography, to generate digital three-dimensional models of early human brain development. These models can be used both as frameworks, onto which normal or experimental gene expression data can be mapped, and as objects, within which topological morphological relationships can be investigated in silico. Gene expression patterns and selected morphological structures or boundaries can then be visualized individually or in different combinations in order to study their respective morphogenetic significance. Here, we review briefly the optical projection tomography method, placing it in the context of other methods used to generate developmental three dimensional models, and show the definition of some CNS anatomical domains within a Carnegie stage 19 human model. We also map the telencephalic EMX1 and PAX6 gene expression patterns to this model, corroborating for the first time the existence of a ventral pallium primordium in the telencephalon of human embryos, a distinct claustroamygdaloid histogenetic area comparable to the recently defined mouse primordium given that name [Puelles L, Kuwana E, Puelles E, Bulfone A, Shimamura K, Keleher J, Smiga S, Rubenstein JLR (2000) Pallial and subpallial derivatives in the embryonic chick and mouse telencephalon, traced by the expression of the genes Dlx-2, Emx-1, Nkx-2.1, Pax-6, and Tbr-1. J Comp Neurol 424:409-438; Puelles L, Martínez S, Martínez-de-la-Torre M, Rubenstein JLR (2004) Gene maps and related histogenetic domains in the forebrain and midbrain. In: The rat nervous system, 3rd ed (Paxinos G, ed), pp 3-25. San Diego: Academic Press].

3D modelling, gene expression mapping and post-mapping image analysis in the developing human brain

As human brain development proceeds, there are complex changes in size and shape, most notably in the developing forebrain. Molecular technologies enable us to characterise the gene expression patterns that underlie these changes. To interpret these patterns the location of expression must be identified and, often, gene expression patterns compared for several genes or across several developmental stages. To facilitate interpretation we have generated a set of three-dimensional models using a recently developed technique, optical projection tomography. The models act as a framework onto which gene expression patterns are mapped and anatomical domains identified using custom-designed software, MAPaint. Here, we demonstrate their use to compare forebrain development at two embryonic stages (Carnegie stages 18 and 21; 44 and 52 days post conception, respectively) and as a means of recording, storing and visualising gene expression data for three example genes EMX1, EMX2 and OTX2. Anatomical domains were also mapped to the models and the comparison of gene expression and anatomical data is demonstrated at Carnegie stage 21. The three-dimensional models and sophisticated software facilitate the analysis and visualisation of morphological changes and gene expression patterns during early brain development and can be applied to the development of other complex structures.

A criticality-based framework for task composition in multi-agent bioinformatics integration systems

MOTIVATION

During task composition, such as can be found in distributed query processing, workflow systems and AI planning, decisions have to be made by the system and possibly by users with respect to how a given problem should be solved. Although there is often more than one correct way of solving a given problem, these multiple solutions do not necessarily lead to the same result. Some researchers are addressing this problem by providing data provenance information. Others use expert advice encoded in a supporting knowledge-base. In this paper, we propose an approach that assesses the importance of such decisions with respect to the overall result. We present a way of measuring decision criticality and describe its potential use.

RESULTS

A multi-agent bioinformatics integration system is used as the basis of a framework that facilitates such functionality. We propose an agent architecture, and a concrete bioinformatics example (prototype) is used to show how certain decisions may not be critical in the context of more complex tasks.

Anatomical ontologies: names and places in biology

Recently, ideas from the field of ontology have been picked up by computer scientists as a basis for encoding knowledge and with the hope of achieving interoperability and intelligent system behavior. The use of anatomy ontologies to represent space in biological organisms, specifically mouse and human are reviewed here.

Ontology has long been the preserve of philosophers and logicians. Recently, ideas from this field have been picked up by computer scientists as a basis for encoding knowledge and with the hope of achieving interoperability and intelligent system behavior. In bioinformatics, ontologies might allow hitherto impossible query and data-mining activities. We review the use of anatomy ontologies to represent space in biological organisms, specifically mouse and human.

Integrating partonomic hierarchies in anatomy ontologies

BACKGROUND

Anatomy ontologies play an increasingly important role in developing integrated bioinformatics applications. One of the primary relationships between anatomical tissues represented in such ontologies is part-of. As there are a number of ways to divide up the anatomical structure of an organism, each may be represented by more than one valid partonomic (part-of) hierarchy. This raises the issue of how to represent and integrate multiple such hierarchies.

RESULTS

In this paper we describe a solution that is based on our work on an anatomy ontology for mouse embryo development, which is part of the Edinburgh Mouse Atlas Project (EMAP). The paper describes the basic conceptual aspects of our approach and discusses strengths and limitations of the proposed solution. A prototype was implemented in Prolog for evaluation purposes.

CONCLUSION

With the proposed name set approach, rather than having to standardise hierarchies, it is sufficient to agree on a suitable set of basic tissue terms and their meaning in order to facilitate the integration of multiple partonomic hierarchies.

The European dimension for the mouse genome mutagenesis program

The European Mouse Mutagenesis Consortium is the European initiative contributing to the international effort on functional annotation of the mouse genome. Its objectives are to establish and integrate mutagenesis platforms, gene expression resources, phenotyping units, storage and distribution centers and bioinformatics resources. The combined efforts will accelerate our understanding of gene function and of human health and disease.

A scalable mediator approach to process large biomedical 3-D images

The Edinburgh Mouse Atlas is a spatial-temporal framework to store and analyze biological data including three-dimensional (3-D) images that relate to mouse embryo development. The purpose of the system is the analysis and querying of complex spatial patterns, in particular the patterns of gene activity during embryo development. The framework holds large 3-D gray level images and is implemented in part as an object-oriented database. In this paper, we propose a dynamic layered architecture, based on the mediator approach, for the design of a transparent and scalable distributed system which can process objects that can exceed 1 GB in size. The system's data are distributed and/or declustered across a number of image servers and are processed by specialized mediators.

3 dimensional modelling of early human brain development using optical projection tomography

Background

As development proceeds the human embryo attains an ever more complex three dimensional (3D) structure. Analyzing the gene expression patterns that underlie these changes and interpreting their significance depends on identifying the anatomical structures to which they map and following these patterns in developing 3D structures over time. The difficulty of this task greatly increases as more gene expression patterns are added, particularly in organs with complex 3D structures such as the brain. Optical Projection Tomography (OPT) is a new technology which has been developed for rapidly generating digital 3D models of intact specimens. We have assessed the resolution of unstained neuronal structures within a Carnegie Stage (CS)17 OPT model and tested its use as a framework onto which anatomical structures can be defined and gene expression data mapped.

Results

Resolution of the OPT models was assessed by comparison of digital sections with physical sections stained, either with haematoxylin and eosin (H&E) or by immunocytochemistry for GAP43 or PAX6, to identify specific anatomical features. Despite the 3D models being of unstained tissue, peripheral nervous system structures from the trigeminal ganglion (~300 μm by ~150 μm) to the rootlets of cranial nerve XII (~20 μm in diameter) were clearly identifiable, as were structures in the developing neural tube such as the zona limitans intrathalamica (core is ~30 μm thick). Fourteen anatomical domains have been identified and visualised within the CS17 model. Two 3D gene expression domains, known to be defined by Pax6 expression in the mouse, were clearly visible when PAX6 data from 2D sections were mapped to the CS17 model. The feasibility of applying the OPT technology to all stages from CS12 to CS23, which encompasses the major period of organogenesis for the human developing central nervous system, was successfully demonstrated.

Conclusion

In the CS17 model considerable detail is visible within the developing nervous system at a minimum resolution of ~20 μm and 3D anatomical and gene expression domains can be defined and visualised successfully. The OPT models and accompanying technologies for manipulating them provide a powerful approach to visualising and analysing gene expression and morphology during early human brain development.

Formalization of mouse embryo anatomy

MOTIVATION

The Edinburgh Mouse Atlas and Gene Expression Database project has developed a digital atlas of mouse development to provide a spatio-temporal framework for spatially mapped data such as in situ gene expression and cell lineage. As part of this database, a mouse embryo anatomy ontology has been created. A formalization of this anatomy is required to document its precise semantics and how it is used in the context of the Mouse Atlas.

RESULTS

The paper describes the existing anatomy ontology and formalizes aspects of it using a predicate logic based approach. It therefore provides a guide for users of the current version of the ontology, as well as the basis for a description of the anatomy using an ontology language, such as OWL, thus enabling future work on reasoning about the Mouse Atlas in the context of an intelligent gene expression bioinformatics workflow system. The logic has been implemented in a Prolog prototype.

AVAILABILITY

The Mouse Atlas is available on-line at http://genex.hgu.mrc.ac.uk

Bioinformatics integration and agent technology

Vast amounts of life sciences data are scattered around the world in the form of a variety of heterogeneous data sources. The need to be able to co-relate relevant information is fundamental to increase the overall knowledge and understanding of a specific subject. Bioinformaticians aspire to find ways to integrate biological data sources for this purpose and system integration is a very important research topic. The purpose of this paper is to provide an overview of important integration issues that should be considered when designing a bioinformatics integration system. The currently prevailing approach for integration is presented with examples of bioinformatics information systems together with their main characteristics. Here, we introduce agent technology and we argue why it provides an appropriate solution for designing bioinformatics integration systems.

An ontology of human developmental anatomy

Human developmental anatomy has been organized as structured lists of the major constituent tissues present during each of Carnegie stages 1-20 (E1-E50, approximately 8500 anatomically defined tissue items). For each of these stages, the tissues have been organized as a hierarchy in which an individual tissue is catalogued as part of a larger tissue. Such a formal representation of knowledge is known as an ontology and this anatomical ontology can be used in databases to store, organize and search for data associated with the tissues present at each developmental stage. The anatomical data for compiling these hierarchies comes from the literature, from observations on embryos in the Patten Collection (Ann Arbor, MI, USA) and from comparisons with mouse tissues at similar stages of development. The ontology is available in three versions. The first gives hierarchies of the named tissues present at each Carnegie stage (http://www.ana.ed.ac.uk/anatomy/database/humat/) and is intended to help analyse both normal and abnormal human embryos; it carries hyperlinked notes on some ambiguities in the literature that have been clarified through analysing sectioned material. The second contains many additional subsidiary tissue domains and is intended for handling tissue-associated data (e.g. gene-expression) in a database. This version is available at the humat site and at http://genex.hgu.mrc.ac.uk/Resources/intro.html/), and has been designed to be interoperable with the ontology for mouse developmental anatomy, also available at the genex site. The third gives the second version in GO ontology syntax (with standard IDs for each tissue) and can be downloaded from both the genex and the Open Biological Ontology sites (http://obo.sourceforge.net/).

Optical projection tomography as a tool for 3D microscopy and gene expression studies

Current techniques for three-dimensional (3D) optical microscopy (deconvolution, confocal microscopy, and optical coherence tomography) generate 3D data by "optically sectioning" the specimen. This places severe constraints on the maximum thickness of a specimen that can be imaged. We have developed a microscopy technique that uses optical projection tomography (OPT) to produce high-resolution 3D images of both fluorescent and nonfluorescent biological specimens with a thickness of up to 15 millimeters. OPT microscopy allows the rapid mapping of the tissue distribution of RNA and protein expression in intact embryos or organ systems and can therefore be instrumental in studies of developmental biology or gene function.

Bioinformatics beyond sequence: mapping gene function in the embryo

The spatio-temporal expression pattern of a gene during development is a valuable piece of information. But there is no way to compare precisely the patterns of expression of different genes, or the way the patterns are changed in a mutant. One way to solve this problem is to construct digital reference images of development (a bioinformatics framework), to which expression patterns can be mapped and stored, then compared. Such frameworks are under active development in several model systems. They will form the basis of powerful and integrated gene expression databases, which facilitate comparisons between genes, tissues and species.

The Edinburgh Mouse Atlas: using the CD

This paper provides a simple introduction to the reconstructions and data-handling tools stored on the Edinburgh Mouse Atlas CD, together with some of the ways in which the viewers and software can be used to understand mouse development and analyse data. The key aspect of the Mouse Atlas is that the underlying models are a complete representation of the histology, which has not been constrained to a particular interpretation. This means, for example, that the current anatomy domains can be further subdivided as required to any resolution up to the resolution of the models (2-7 microm). In the CD of the early embryos described here, virtually all tissues that can be usefully distinguished either by the histology or morphologically have been delineated.

The mouse atlas and graphical gene-expression database

The large amounts of gene-expression data on mouse development are now too extensive to be stored in any format other than that of a database. Furthermore, as this data is intrinsically graphical and as, in the early developmental stages at least, its boundaries do not map directly to those of anatomical tissues, the natural way to store it is in graphical format. We are therefore constructing a database able to handle such graphical gene-expression data by mapping it onto 3-D reconstructions of mouse embryos whose tissues have been delineated. This article reviews the progress that has been made in this project and describes its two major components, CD-ROMs of the 3-D reconstructions to be held on the user's computer and a gene-expression database that will be maintained at a host site, the two being linked over the internet by a complex Java-based interface for submitting data and querying the database.Copyright 1997 Academic Press Limited Copyright 1997Academic Press Limited

The Msh-like homeobox genes define domains in the developing vertebrate eye

The mouse Hox-7.1 gene has previously been shown to be related to the Drosophila Msh homeobox-containing gene. Here we report the isolation of a new member of this family which resides at an unlinked chromosomal location and has been designated Hox-8.1. Both Hox-7.1 and Hox-8.1 are expressed in the mouse embryo during the early stages of eye development in a distinct spatial and temporal relationship. Hox-8.1 is expressed in the surface ectoderm and in the optic vesicle before invagination occurs in regions corresponding to the prospective corneal epithelium and neural retina, respectively. Hox-7.1 is expressed after formation of the optic cup, marking the domain that will give rise to the ciliary body. The activity of these genes indicates that the inner layer of the optic cup is differentiated into three distinct compartments before overt cellular differentiation occurs. Our results suggest that these genes are involved in defining the region that gives rise to the inner layer of the optic cup and in patterning this tissue to define the iris, ciliary body and retina.