Exploring the elephant: histopathology in high-throughput phenotyping of mutant mice

Abstract

Recent advances in gene knockout techniques and the in vivo analysis of mutant mice, together with the advent of large-scale projects for systematic mouse mutagenesis and genome-wide phenotyping, have allowed the creation of platforms for the most complete and systematic analysis of gene function ever undertaken in a vertebrate. The development of high-throughput phenotyping pipelines for these and other large-scale projects allows investigators to search and integrate large amounts of directly comparable phenotype data from many mutants, on a genomic scale, to help develop and test new hypotheses about the origins of disease and the normal functions of genes in the organism. Histopathology has a venerable history in the understanding of the pathobiology of human and animal disease, and presents complementary advantages and challenges to in vivo phenotyping. In this review, we present evidence for the unique contribution that histopathology can make to a large-scale phenotyping effort, using examples from past and current programmes at Lexicon Pharmaceuticals and The Jackson Laboratory, and critically assess the role of histopathology analysis in high-throughput phenotyping pipelines.

Amelogenesis Imperfecta and Other Biomineralization Defects in Fam20a and Fam20c Null Mice

“…Future studies to measure fetuin-A responses to administration of FAM20A protein will be needed to confirm this hypothesis, but finding very similar pathology phenotypes in two different lines of knockout mice commonly indicates that they have homologous functions, are in the same gene family, or are active in the same metabolic pathway. 81 The partial resolution of ectopic mineralization in the muscular arteries and lungs as the mice matured indicates that age-related factors must also be involved in the pathogenesis of these lesions in Fam20a -/-mice. We also observed that male Fam20a -/-mice are more susceptible than females to ectopic mineralization.…”

Nephronophthisis and Retinal Degeneration inTmem218–/–Mice

“…In our experience, the appearance of very similar phenotypes (phenocopies) in either mice or humans with mutations in different genes often indicates that the proteins encoded by these mutant genes involve different steps in a common metabolic pathway or affect the same process or structure. 86,[106][107][108][109] It is often instructive to consider what is known about the underlying pathogenic mechanisms in phenocopies (whether in humans or in animal models) when attempting to understand the pathogenesis of lesions in a novel line of knockout mice. We believe that the simultaneous development of NPHP and retinal degeneration in Tmem218 -/-mice is highly suggestive of an underlying defect in the structure/function of the sensory primary cilium of renal epithelium and the connecting cilium of retinal photoreceptors, respectively.…”

“…Many other pathologic phenotypes resulted from abnormal development of structurally complex tissues/organs (eg, eyes, teeth, sperm). 2,86 Over time, it also became clear that numerous pathologic phenotypes in knockout mice were associated with the inactivation of genes involved in the biogenesis and/or function of the extremely complex multifunctional organelles known as cilia. 22 Recognition that polycystin 1, polycystin 2, and nephrocystin proteins could all be localized to the primary cilium/ basal body/centrosome indicated the involvement of dysfunctional primary cilia in the pathogenesis of polycystic kidney disease (PKD) and nephronophthisis (NPHP).…”

Practical approaches to reviewing and recording pathology data

“…variation and common spontaneous pathology (Taylor 2011). It is important that these background changes are recognized and understood so that they are not misinterpreted as experimental or treatment-related changes (Schofield et al 2012) particularly when encountered for the first time by scientists. Systematic recording of these background changes is also important to build up background data on the normal extent of variation within a strain or colony and to ensure that mouse phenotypes that result in alterations in the nature or incidence or severity of these changes are recognized.…”