Multiscale analysis of single and double maternal-zygotic Myh9 and Myh10 mutants during mouse preimplantation development

Abstract

During the first days of mammalian development, the embryo forms the blastocyst, the structure responsible for implanting the mammalian embryo. Consisting of an epithelium enveloping the pluripotent inner cell mass and a fluid-filled lumen, the blastocyst results from a series of cleavages divisions, morphogenetic movements and lineage specification. Recent studies identified the essential role of actomyosin contractility in driving the cytokinesis, morphogenesis and fate specification leading to the formation of the blastocyst. However, the preimplantation development of contractility mutants has not been characterized. Here, we generated single and double maternal-zygotic mutants of non-muscle myosin II heavy chains (NMHC) to characterize them with multiscale imaging. We find that Myh9 (NMHC II-A) is the major NMHC during preimplantation development as its maternal-zygotic loss causes failed cytokinesis, increased duration of the cell cycle, weaker embryo compaction and reduced differentiation, whereas Myh10 (NMHC II-B) maternal-zygotic loss is much less severe. Double maternal-zygotic mutants for Myh9 and Myh10 show a much stronger phenotype, failing most attempts of cytokinesis. We find that morphogenesis and fate specification are affected but nevertheless carry on in a timely fashion, regardless of the impact of the mutations on cell number. Strikingly, even when all cell divisions fail, the resulting single-celled embryo can initiate trophectoderm differentiation and lumen formation by accumulating fluid in increasingly large vacuoles. Therefore, contractility mutants reveal that fluid accumulation is a cell-autonomous process and that the preimplantation program carries on independently of successful cell division.

Ferroptosis Related Genes in Ischemic and Idiopathic Cardiomyopathy: Screening for Potential Pharmacological Targets

“…PLIN2 (Perilipin 2) is associated with the lipid globule surface membrane material that may be involved in adipose tissue development and maintenance ( Bildirici et al, 2018 ). Mutations in MYH10 (Myosin Heavy Chain 10) have been associated with May-Hegglin anomaly and developmental defects in brain and heart ( Schliffka et al, 2021 ). Ten hub genes: YWHAZ, EIF4A1, FASN, HSPB1, ATF4, HSP90B1, MYC, MAP1LC3B, PLIN2, SNCA, and were identified for ferroptosis in idiopathic cardiomyopathy by Cytoscape ( Figure 4B ).…”

Cortical softening elicits zygotic contractility during mouse preimplantation development

“…GenomONE-CF FZ SeV-E cell fusion kit (Cosmo Bio, Tokyo, Japan, ISK-CF-001-EX) is used to fuse blastomeres [ 40 ]. HVJ envelope is resuspended following manufacturer’s instructions and diluted in FHM for use.…”

“…As previously [ 22 , 40 ], PIVlab 2.02 running on MATLAB [ 67 , 68 ] is used to process approximately 10 minutes long time lapses with images taken every 5 seconds using 2 successive passes through interrogation windows of 20/10 μm resulting in approximately 180 vectors per embryo.…”

“…However, little is known about what initiates and regulates PeCoWaCo. The analysis of maternal zygotic mutants suggests that PeCoWaCo in mouse blastomeres result primarily from the action of the nonmuscle myosin heavy chain IIA (encoded by Myh9 ) rather than IIB (encoded by Myh10 ) [ 40 ]. Dissociation of mouse blastomeres shows that PeCoWaCo are cell autonomous since they persist in single cells [ 22 ].…”

Does the Actin Network Architecture Leverage Myosin-I Functions?

“…Class 2 myosins (Myh genes in humans) dimerize and slide antiparallel actin filaments against each other. In muscle, these activities lead to muscle contraction, whereas in other cells, non-muscle myosin-II a/b (Myh9 and Myh10 in humans) crosslinks actin to (i) produce the actin retrograde flow [ 3 ], (ii) regulate cell cortex tension [ 4 , 5 , 6 ], or (iii) pull on adhesive structures [ 7 ]. In addition to myosin-II, some other myosins, such as myosin-V (Myo5) and -XVIII (Myo18), act as dimers that interact through their C-terminal coiled-coils.…”