ToBio: Global Pathway Similarity Search Based on Topological and Biological Features

Heterogeneous information network and its application to human health and disease

The molecular components with the functional interdependencies in human cell form complicated biological network. Diseases are mostly caused by the perturbations of the composite of the interaction multi-biomolecules, rather than an abnormality of a single biomolecule. Furthermore, new biological functions and processes could be revealed by discovering novel biological entity relationships. Hence, more and more biologists focus on studying the complex biological system instead of the individual biological components. The emergence of heterogeneous information network (HIN) offers a promising way to systematically explore complicated and heterogeneous relationships between various molecules for apparently distinct phenotypes. In this review, we first present the basic definition of HIN and the biological system considered as a complex HIN. Then, we discuss the topological properties of HIN and how these can be applied to detect network motif and functional module. Afterwards, methodologies of discovering relationships between disease and biomolecule are presented. Useful insights on how HIN aids in drug development and explores human interactome are provided. Finally, we analyze the challenges and opportunities for uncovering combinatorial patterns among pharmacogenomics and cell-type detection based on single-cell genomic data.

TAMMiCol: Tool for analysis of the morphology of microbial colonies

Many microbes are studied by examining colony morphology via two-dimensional top-down images. The quantification of such images typically requires each pixel to be labelled as belonging to either the colony or background, producing a binary image. While this may be achieved manually for a single colony, this process is infeasible for large datasets containing thousands of images. The software Tool for Analysis of the Morphology of Microbial Colonies (TAMMiCol) has been developed to efficiently and automatically convert colony images to binary. TAMMiCol exploits the structure of the images to choose a thresholding tolerance and produce a binary image of the colony. The images produced are shown to compare favourably with images processed manually, while TAMMiCol is shown to outperform standard segmentation methods. Multiple images may be imported together for batch processing, while the binary data may be exported as a CSV or MATLAB MAT file for quantification, or analysed using statistics built into the software. Using the in-built statistics, it is found that images produced by TAMMiCol yield values close to those computed from binary images processed manually. Analysis of a new large dataset using TAMMiCol shows that colonies of Saccharomyces cerevisiae reach a maximum level of filamentous growth once the concentration of ammonium sulfate is reduced to 200 μM. TAMMiCol is accessed through a graphical user interface, making it easy to use for those without specialist knowledge of image processing, statistical methods or coding.

Many microbes are studied by examining the colony morphology via a two-dimensional top-down image. In order to quantify such images, we typically need to label each pixel as belonging either to the colony or the background, creating a binary image. This task is laborious when performed manually and proves infeasible for large datasets. To overcome this, we have developed the software Tool for Analysis of the Morphology of Microbial Colonies (TAMMiCol), which automatically and efficiently converts colony images to binary. Multiple images may be imported and processed simultaneously, and TAMMiCol exploits the structure of the images to identify an appropriate threshold for the binary conversion of each image. The images produced by TAMMiCol, which take around 20 seconds each to process, compare favourably with images processed manually, which take anywhere up to 15 minutes, while TAMMiCol outperforms several standard image segmentation methods. After processing, the images may be exported as a CSV or MATLAB MAT file for further analysis, or may be quantified by TAMMiCol using the in-built statistics. Using TAMMiCol, we have found that colonies of S. cerevisiae reach a maximum level of filamentous growth once the concentration of ammonium sulfate is reduced to 200 μM.

PathEmb: Random Walk Based Document Embedding for Global Pathway Similarity Search

Pathway analysis is a cornerstone of system biology. In particular, pathway similarity search plays a key role in establishing structural, functional, and evolutionary relationships between different biological entities. Given a query pathway as well as a database, a pathway similarity search aims to identify novel pathways that are homologous to the query pathway. Unfortunately, the pathway similarity search is computationally inefficient due to the NP-complete graph isomorphism problem. In this study, we introduce a novel algorithmic framework for pathway similarity search, named PathEmb (Pathway Embedding), which is analogous to the Skip-gram model where each pathway is represented as a "document." PathEmb exploits a second order random walk strategy to explore diverse pathway patterns. All signaling paths traversed from random walks are regarded as "sentences," which are constituted as a "document" afterwards. Then, the "document" pattern for the individual pathway is mapped into a low-dimensional feature space for downstream tasks. Furthermore, PathEmb is a topology-free pathway similarity search algorithm, which is feasible to handle any pathway with arbitrary structure. We have extensively evaluated PathEmb and other cutting-edge methods on three pathway datasets. The experimental results demonstrate that PathEmb outperforms the existing methods in terms of computational efficiency and search accuracy. The source code of PathEmb are freely available online https://github.com/zhangjiaobxy/PathEmb.