Morphology, topology and dimensions of the heart and arteries of genetically normal and mutant mouse embryos at stages S21–S23

Abstract

Accurate identification of abnormalities in the mouse embryo depends not only on comparisons with appropriate, developmental stage‐matched controls, but also on an appreciation of the range of anatomical variation that can be expected during normal development. Here we present a morphological, topological and metric analysis of the heart and arteries of mouse embryos harvested on embryonic day (E)14.5, based on digital volume data of whole embryos analysed by high‐resolution episcopic microscopy (HREM). By comparing data from 206 genetically normal embryos, we have analysed the range and frequency of normal anatomical variations in the heart and major arteries across Theiler stages S21–S23. Using this, we have identified abnormalities in these structures among 298 embryos from mutant mouse lines carrying embryonic lethal gene mutations produced for the Deciphering the Mechanisms of Developmental Disorders (DMDD) programme. We present examples of both commonly occurring abnormal phenotypes and novel pathologies that most likely alter haemodynamics in these genetically altered mouse embryos. Our findings offer a reference baseline for identifying accurately abnormalities of the heart and arteries in embryos that have largely completed organogenesis.

Visualising the Cardiovascular System of Embryos of Biomedical Model Organisms with High Resolution Episcopic Microscopy (HREM)

“…HREM data of nearly 700 embryos of 87 knock out lines producing embryonically lethal offspring have been produced and thoroughly analysed in this program. Due to the unmatched spatial resolution and image quality of HREM and the availability of newly created reference data precisely defining normal cardiovascular morphology in the substages of E14.5 [93] vascular variations, large and small heart defects, but also entirely new and potentially life-threatening cardiovascular abnormalities were diagnosed and annotated [72] (Figure 4).…”

Standardised imaging pipeline for phenotyping mouse laterality defects and associated heart malformations, at multiple scales and multiple stages

“…It is relevant to morphometric analyses, as well as quantification of trabeculation or myofibre orientation (Garcia-Canadilla et al, 2018; Paun et al, 2018). HREM was used here for the heart, but could be extended to other explanted organs, or the whole fetus (Geyer et al, 2017).…”

“…With a higher imaging depth and wider field of view, micro-CT was selected for routine screening of mouse mutants (Wong et al, 2014). Finally, histological based approaches such as Episcopic Fluorescence Image Capture (EFIC) or High Resolution Episcopic Microscopy (HREM) (Mohun and Weninger, 2012) reach very high spatial resolution, able to resolve subtle anatomical variations, as exemplified in the heart (Geyer et al, 2017). A challenge to fully describe laterality defects, is to combine images at multiple scales, to resolve the situs of all visceral organs together with fine anatomical left/right features, and at multiple stages of development, to understand the origin of the defects.…”

High-Resolution Episcopic Microscopy (HREM): Looking Back on 13 Years of Successful Generation of Digital Volume Data of Organic Material for 3D Visualisation and 3D Display

“…In the scope of DMDD [37], which was linked with the International Mouse Phenotyping Consortium (IMPC), HREM was employed to build a virtual resource of fully annotated phenotype data of over 200 normal and over 500 mutant mouse embryos harvested at E14.5 stemming from 87 individual single knock-out or knock-down lines producing lethal or subvital homozygous offspring. In the scope of this program, a standardised and ergonomic protocol for the comprehensive scoring of the morphologic phenotype of E14.5 embryos [38], a novel system for defining developmental substages of E14.5 mouse embryos [39], and reference data for the correct interpretation of phenotype abnormalities and for distinguishing variations from abnormalities [40] were created. Approximately 200 novel mouse phenotype (MP) terms were added to the MP ontology list as a result of HREM allowing for the detection of details that could not be detected with alternative imaging techniques.…”

“…Approximately 200 novel mouse phenotype (MP) terms were added to the MP ontology list as a result of HREM allowing for the detection of details that could not be detected with alternative imaging techniques. Numerous publications in highly ranked journals were produced based on HREM data generated in DMDD [38][39][40][41][42][43][44][45][46][47][48].…”