Lateral plate mesoderm cell-based organoid system for NK cell regeneration from human pluripotent stem cells

ABSTRACTHuman pluripotent stem cell (hPSC)-induced NK (iNK) cells are a promising “off-the-shelf” cell product for universal immune therapy. Conventional methods for iNK cell regeneration from hPSCs include embryonic body-formation and feeder-based expansion steps, which bring instability, time-consuming, and high costs for manufacture. In this study, we develop an embryonic body-free, organoid aggregate method for NK cell regeneration from hPSCs. In a short time window of 27-day induction, millions of hPSC input can produce over billions of iNK cells without the necessity of NK cell-expansion feeders. The iNK cells highly express classical toxic granule proteins, apoptosis-inducing ligands, as well as abundant activating and inhibitory receptors. Functionally, the iNK cells eradicate human tumor cells by mechanisms of direct cytotoxity, apoptosis, and antibody-dependent cellular cytotoxicity. This study provides a reliable scale-up method for regenerating human NK cells from hPSCs, which promotes the universal availability of NK cell products for immune therapy.

osr1 couples intermediate mesoderm cell fate with temporal dynamics of vessel progenitor cell differentiation

Transcriptional regulatory networks refine gene expression boundaries to define the dimensions of organ progenitor territories. Kidney progenitors originate within the intermediate mesoderm (IM), but the pathways that establish the boundary between the IM and neighboring vessel progenitors are poorly understood. Here, we delineate roles for the zinc finger transcription factor Osr1 in kidney and vessel progenitor development. Zebrafish osr1 mutants display decreased IM formation and premature emergence of lateral vessel progenitors (LVPs). These phenotypes contrast with the increased IM and absent LVPs observed with loss of the bHLH transcription factor Hand2, and loss of hand2 partially suppresses osr1 mutant phenotypes. hand2 and osr1 are expressed together in the posterior mesoderm, but osr1 expression decreases dramatically prior to LVP emergence. Overexpressing osr1 during this timeframe inhibits LVP development while enhancing IM formation and can rescue the osr1 mutant phenotype. Together, our data demonstrate that osr1 modulates the extent of IM formation and the temporal dynamics of LVP development, suggesting that a balance between levels of osr1 and hand2 expression is essential to demarcate the kidney and vessel progenitor territories.

osr1 couples intermediate mesoderm cell fate with temporal dynamics of vessel progenitor cell differentiation

ABSTRACTTranscriptional regulatory networks refine gene expression boundaries throughout embryonic development to define the precise dimensions of organ progenitor territories. Kidney progenitors originate within the intermediate mesoderm (IM), but the pathways that establish the boundary between the IM and its neighboring vessel progenitors are poorly understood. Here, we delineate new roles for the zinc finger transcription factor Osr1 in kidney and vessel progenitor development. Zebrafish osr1 mutants display decreased IM formation and premature emergence of neighboring lateral vessel progenitors (LVPs). These phenotypes contrast with the increased IM and absent LVPs observed with loss of the bHLH transcription factor Hand2, and loss of hand2 partially suppresses the osr1 mutant phenotypes. hand2 and osr1 are both expressed in the posterior lateral mesoderm, but osr1 expression decreases dramatically prior to LVP emergence. Overexpressing osr1 inhibits LVP development while enhancing IM formation. Together, our data demonstrate that osr1 modulates both the extent of IM formation and the temporal dynamics of LVP development, suggesting that a balance between levels of osr1 and hand2 expression is essential to demarcate the dimensions of kidney and vessel progenitor territories.SUMMARY STATEMENTAnalysis of the osr1 mutant phenotype reveals roles in determining the extent of intermediate mesoderm formation while inhibiting premature differentiation of neighboring vessel progenitors.

Transcriptome profiling of the branchial arches reveals cell type composition and a conserved signature of neural crest cell invasion

ABSTRACTThe vertebrate branchial arches that give rise to structures of the head, neck, and heart form with very dynamic tissue growth and well-choreographed neural crest, ectoderm, and mesoderm cell dynamics. Although this morphogenesis has been studied by marker expression and fate-mapping, the mechanisms that control the collective migration and diversity of the neural crest and surrounding tissues remain unclear, in part due to the effects of averaging and need for cell isolation in conventional transcriptome analysis experiments of multiple cell populations. We used label free single cell RNA sequencing on 95,000 individual cells at 2 developmental stages encompassing formation of the first four chick branchial arches to measure the transcriptional states that define the cellular hierarchy and invasion signature of the migrating neural crest. The results confirmed basic features of cell type diversity and led to the discovery of many novel markers that discriminate between axial level and distal-to-proximal cell populations within the branchial arches and neural crest streams. We identified the transcriptional signature of the most invasive neural crest that is conserved within each branchial arch stream and elucidated a set of genes common to other cell invasion signatures in types in cancer, wound healing and development. These data robustly delineate molecularly distinct cell types within the branchial arches and identify important molecular transitions within the migrating neural crest during development.

STRIP1, a core component of STRIPAK complexes, is essential for normal mesoderm migration in the mouse embryo

Regulated mesoderm migration is necessary for the proper morphogenesis and organ formation during embryonic development. Cell migration and its dependence on the cytoskeleton and signaling machines have been studied extensively in cultured cells; in contrast, remarkably little is known about the mechanisms that regulate mesoderm cell migration in vivo. Here, we report the identification and characterization of a mouse mutation in striatin-interacting protein 1 (Strip1) that disrupts migration of the mesoderm after the gastrulation epithelial-to-mesenchymal transition (EMT). STRIP1 is a core component of the biochemically defined mammalian striatin-interacting phosphatases and kinase (STRIPAK) complexes that appear to act through regulation of protein phosphatase 2A (PP2A), but their functions in mammals in vivo have not been examined. Strip1-null mutants arrest development at midgestation with profound disruptions in the organization of the mesoderm and its derivatives, including a complete failure of the anterior extension of axial mesoderm. Analysis of cultured mesoderm explants and mouse embryonic fibroblasts from null mutants shows that the mesoderm migration defect is correlated with decreased cell spreading, abnormal focal adhesions, changes in the organization of the actin cytoskeleton, and decreased velocity of cell migration. The results show that STRIPAK complexes are essential for cell migration and tissue morphogenesis in vivo.