Transitions in development – an interview with Kate McDole

Kate McDole is a Group Leader at the MRC Laboratory of Molecular Biology (LMB) in Cambridge, UK. Using the mouse embryo as a model, Kate's research group studies how mechanical forces can shape complex three-dimensional structures out of simple populations of cells. We met with Kate to find out more about her career, the challenges of setting up a lab during the pandemic, and her thoughts on mentorship and transitioning to a group leader position.

Pre-implantation mouse embryo movement under hormonally altered conditions

Precise regulation of embryo movement is crucial to successful implantation, but the role of ovarian hormones in this process is not understood. We ascertain the effects of altered hormonal environment on embryo movement using two delayed implantation models: Natural lactational Diapause (ND), a naturally occurring alternate model of pregnancy, and Artificially induced Diapause (AD), a laboratory version of ND. Our previous work suggests that embryos in a natural pregnancy (NP) first display unidirectional clustered embryo movement, followed by bidirectional scattering and spacing movement. In contrast, in the ND model, embryos are present as clusters near the oviductal-uterine junction for ~24-hours longer than NP, followed by locations consistent with a unidirectional scattering and spacing movement. Intriguingly, the AD model closely resembles embryo location in NP and not ND. Further, unlike the popular paradigm of reduced estrogen (E2) levels in diapause E2 levels are comparable across NP, ND, and AD, while progesterone (P4) levels are reduced in ND and highly increased in AD when compared to NP. Exogenous administration of E2 or P4 modifies the unidirectional clustered embryo movement, while E2 treatment causes a reduction in P4 and affects the bidirectional phase of embryo movement. Taken together, our data suggest embryo movement can be modulated by both P4 and E2. Understanding natural hormonal adaptation in diapause provides an opportunity to determine key players regulating embryo movement and implantation success. This knowledge can be leveraged to understand pregnancy survival and implantation success in hormonally altered conditions in the clinic.

Advances in live imaging early mouse development: exploring the researcher's interdisciplinary toolkit

ABSTRACT Live imaging is an important part of the developmental biologist's armoury of methods. In the case of the mouse embryo, recent advances in several disciplines including embryo culture, microscopy hardware and computational analysis have all contributed to our ability to probe dynamic events during early development. Together, these advances have provided us with a versatile and powerful ‘toolkit’, enabling us not only to image events during mouse embryogenesis, but also to intervene with them. In this short Spotlight article, we summarise advances and challenges in using live imaging specifically for understanding early mouse embryogenesis.

Two ISREs cooperatively regulate ISG expression in West Nile virus infected IFNAR -/- MEFs.

We previously identified a subset of interferon stimulated genes (ISGs) upregulated by West Nile virus (WNV) infection in wildtype mouse embryo fibroblasts (MEFs) after viral proteins had inhibited type 1 interferon (IFN)-mediated JAK-STAT signaling and also in WNV-infected RIG-I -/- , MDA5 -/- , STAT1 -/- , STAT2 -/- , IFNAR -/- , IRF3 -/- , IRF7 -/- , and IRF3/7 -/- MEFs. In this study, ISG upregulation by WNV infection in IFNAR -/- MEFs was confirmed by RNA-seq. ISG upregulation by WNV infection was inhibited in RIG-I -/- /MDA5 -/- MEFs. ISGs were upregulated in IRF1 -/- and IRF5 -/- MEFs but only minimally upregulated in IRF3/5/7 -/- MEFs, suggesting redundant IRF involvement. We previously showed that a single proximal interferon stimulated response element (ISRE) in the Oas1a and Oas1b promoters bound the ISGF3 complex after type 1 IFN treatment. In this study, we used wild-type and mutant promoter luciferase reporter constructs to identify critical regions in the Oas1b and Ifit1 promoters for gene activation in infected IFNAR -/- MEFs. Two ISREs were required in both promoters. Mutation of these ISREs in an Ifit1 promoter DNA probe reduced in vitro complex formation with infected nuclear extracts. An NF-κB inhibitor decreased Ifit1 promoter activity in cells and in vitro complex formation. IRF3 and p50 promoter binding were detected by ChIP for upregulated ISGs with two proximal ISREs. The data indicate that ISREs function cooperatively to upregulate the expression of some ISGs when type 1 IFN-signaling is absent with the binding complex consisting of IRF3, 5, and/or 7 and an NF-κB component(s) as well as other as yet unknown factors. AUTHOR SUMMARY Type 1 IFN signaling in mammalian cells induces formation of the ISGF3 transcription factor complex, which binds to interferon stimulated response elements (ISREs) in the promoters of interferon stimulated genes (ISGs) in the cell nucleus. Flavivirus proteins counteract type 1 IFN signaling by preventing either the formation or nuclear localization of ISGF3. A subset of ISRE-regulated ISGs was still induced in West Nile virus (WNV)-infected mouse embryo fibroblasts (MEFs) indicating that cells have an alternative mechanism for activating these ISGs. In this study, cellular components involved in this ISG upregulation mechanism were identified using gene-knockout MEFs and ChIP and critical promoter regions for gene activation were mapped using reporter assays. The data indicate cooperative function between two ISREs and required binding of IRF3, 5, and/or 7 and an NF-κB component(s). Moreover, type 1 IFN signaling-independent ISG activation requires different additional promoter activation regions than type 1 IFN-dependent activation.