Detailed characterizations of cranial nerve anatomy in E14.5 mouse embryos/fetuses and their use as reference for diagnosing subtle, but potentially lethal malformations in mutants

Abstract

Careful phenotype analysis of genetically altered mouse embryos/fetuses is vital for deciphering the function of pre- and perinatally lethal genes. Usually this involves comparing the anatomy of mutants with that of wild types of identical developmental stages. Detailed three dimensional information on regular cranial nerve (CN) anatomy of prenatal mice is very scarce. We therefore set out to provide such information to be used as reference data and selected mutants to demonstrate its potential for diagnosing CN abnormalities. Digital volume data of 152 wild type mice, harvested on embryonic day (E)14.5 and of 18 mutants of the Col4a2, Arid1b, Rpgrip1l and Cc2d2a null lines were examined. The volume data had been created with High Resolution Episcopic Microscopy (HREM) as part of the deciphering the mechanisms of developmental disorders (DMDD) program. Employing volume and surface models, oblique slicing and digital measuring tools, we provide highly detailed anatomic descriptions of the CNs and measurements of the diameter of selected segments. Specifics of the developmental stages of E14.5 mice and anatomic norm variations were acknowledged. Using the provided data as reference enabled us to objectively diagnose CN abnormalities, such as abnormal formation of CN3 (Col4a2), neuroma of the motor portion of CN5 (Arid1b), thinning of CN7 (Rpgrip1l) and abnormal topology of CN12 (Cc2d2a). Although, in a first glimpse perceived as unspectacular, defects of the motor CN5 or CN7, like enlargement or thinning can cause death of newborns, by hindering feeding. Furthermore, abnormal topology of CN12 was recently identified as a highly reliable marker for low penetrating, but potentially lethal defects of the central nervous system.

Effects of Tulp4 deficiency on murine embryonic development and adult phenotype

“…For this reason, highly elaborated and standardized phenotyping protocols exist to enable systematic interrogation of embryos for malformations and subsequent annotation of the detected phenotypes (Weninger et al, 2014). Moreover, detailed reference data for the developmental stages possibly present at E14.5 served for defining the “normal” morphology for each developmental stage actually observed at E14.5 (Geyer et al, 2022; Geyer, Reissig, Hüsemann, et al, 2017; Reissig et al, 2022).…”

Tissue-Targeted Transcriptomics Reveals SEMA3D Control of Hypoglossal Nerve Projection to Mouse Tongue Primordia

“…By embryonic day (E) 10.5, the hypoglossal nerve ventrally leaves the medulla oblongata and begins to emerge as multiple branches heading towards the tongue primordia. The branches fasciculate to form a nerve bundle that reaches its target tongue location at E14.5 under proper axon guidance [ 5 , 16 , 17 , 27 , 37 ]. Axon guidance factors are molecules that provide spatiotemporal cues to growth cones of the developing nerves by their specific localization during embryonic development [ 33 ].…”