title: mRNA Transcriptomics of Galectins Unveils Heterogeneous Organization in Mouse and Human Brain.
abstract: Background:Galectins, a family of non-classically secreted, β-galactoside binding proteins is involved in several brain disorders; however, no systematic knowledge on the normal neuroanatomical distribution and functions of galectins exits. Hence, the major purpose of this study was to understand spatial distribution and predict functions of galectins in brain and also compare the degree of conservationvs.divergence between mouse and human species. The latter objective was required to determine the relevance and appropriateness of studying galectins in mouse brain which may ultimately enable us to extrapolate the findings to human brain physiology and pathologies.Results:In order to fill this crucial gap in our understanding of brain galectins, we analyzed thein situ hybridizationand microarray data of adult mouse and human brain respectively, from the Allen Brain Atlas, to resolve each galectin-subtype's spatial distribution across brain distinct cytoarchitecture. Next, transcription factors (TFs) that may regulate galectins were identified using TRANSFAC software and the list obtained was further curated to sort TFs on their confirmed transcript expression in the adult brain. Galectin-TF cluster analysis, gene-ontology annotations and co-expression networks were then extrapolated to predict distinct functional relevance of each galectin in the neuronal processes. Data shows that galectins have highly heterogeneous expression within and across brain sub-structures and are predicted to be the crucial targets of brain enriched TFs.Lgals9had maximal spatial distribution across mouse brain with inferred predominant roles in neurogenesis whileLGALS1was ubiquitously expressed in human. Limbic region associated with learning, memory and emotions and substantia nigra associated with motor movements showed strikingly high expression ofLGALS1andLGALS8in humanvs.mouse brain. The overall expression profile of galectin-8 was most preserved across both these species, however, galectin-9 showed maximal preservation only in the cerebral cortex.Conclusion:It is for the first time that a comprehensive description of galectins' mRNA expression profile in brain is presented. Results suggests that spatial transcriptome changes in galectins may contribute to differential brain functions and evolution across species that highlights galectins as novel signatures of brain heterogeneity and functions, which if disturbed, can promote several brain disorders.
authors.affiliation: Disease Biology Program, Department of Neurobiology and Genetics, Rajiv Gandhi Centre for Biotechnology Thiruvananthapuram, India.
authors.forename: Sebastian
authors.initials: S
authors.lastname: John
authors.affiliation: Disease Biology Program, Department of Neurobiology and Genetics, Rajiv Gandhi Centre for Biotechnology Thiruvananthapuram, India.
authors.forename: Rashmi
authors.initials: R
authors.lastname: Mishra
keywords: Allen Brain Atlas; TRANSFAC; brain heterogeneity; galectin; molecular neuroanatomy; neural stem cell (NSC); neurogenesis; transcriptomics