Biology subjects

Espin-Palazon, R.

Publications and source records attributed to Espin-Palazon, R..

3 recordsLinked to original sources

bioRxiv2026

Tracing developmental and adult hematopoiesis with an endogenous zebrafish runx1-2A-CreERT2 CRISPR knock-in

Zebrafish combines the power of genetics and unparalleled in vivo imaging to investigate the dynamics of vertebrate hematopoietic development. The conserved transcription factor Runx1 is essential for definitive hematopoiesis. We generated an endogenous zebrafish runx1-2A-creERT2 CRISPR knock-in for tamoxifen-regulated Runx1 lineage tracing and characterized its activity using recombinase-dependent fluorescence reporters, live imaging and flow cytometry. Tamoxifen induction of Cre in the early embryo labeled all expected Runx1 lineages, including neuroectodermal olfactory placode and Rohan-Beard neurons, primitive hematopoietic blood cells, and emerging definitive hematopoietic stem and progenitor cells (HSPCs) in the dorsal aorta. Short windows of tamoxifen treatment allowed separation of Runx1 primitive from definitive hematopoiesis and visualization of HSPC colonization of the larval caudal hematopoietic tissue, thymus and kidney. Runx1 HSPCs labeled during development persisted into adulthood and contributed to hematopoietic precursors, myeloid, lymphoid, and peripheral blood lineages. Labeling of all blood lineages was also effective by tamoxifen treatment of 5-month-old adults. The runx1-2A-creERT2 knock-in line provides a novel genetic tool for inducible spatial and temporal analysis of Runx1 progenitor mechanisms in developmental and adult hematopoiesis.

developmental biology↗

bioRxiv2024

Developmental regulation of endothelial-to-hematopoietic transition from induced pluripotent stem cells

Hematopoietic stem cells (HSCs) arise in embryogenesis from a specialized hemogenic endothelium (HE). In this process, HE cells undergo a unique fate change termed endothelial-to-hematopoietic transition, or EHT. While induced pluripotent stem cells (iPSCs) give rise to HE with robust hemogenic potential, the generation of bona fide HSCs from iPSCs remains a challenge. Here, we map single cell dynamics of EHT during embryoid body differentiation from iPSCs and integrate it with human embryo datasets to identify key transcriptional differences between in vitro and in vivo cell states. We further map ligand-receptor interactions associated with differential expression of developmental programs in the iPSC system. We found that the expression of endothelial genes was incompletely repressed during iPSC EHT. Elevated FGF signaling by FGF23, an endothelial pathway ligand, was associated with differential gene expression between in vitro and in vivo EHT. Chemical inhibition of FGF signaling during EHT increased HSPC generation in the zebrafish, while an FGF agonist had the opposite effect. Consistently, chemical inhibition of FGF signaling increased hematopoietic output from iPSCs. In summary, we map the dynamics of EHT from iPSCs at single cell resolution and identify ligand-receptor interactions that can be modulated to improve iPSC differentiation protocols. We show, as proof of principle, that chemical inhibition of FGF signaling during EHT improves hematopoietic output in zebrafish and the iPSC system.

developmental biology↗

bioRxiv2019

In vivo lineage conversion of vertebrate muscle into early endoderm-like cells

The extent to which differentiated cells, while remaining in their native microenvironment, can be reprogrammed to assume a different identity will reveal fundamental insight into cellular plasticity and impact regenerative medicine. To investigate in vivo cell lineage potential, we leveraged the zebrafish as a practical vertebrate platform to determine factors and mechanisms necessary to induce differentiated cells of one germ layer to adopt the lineage of another. We discovered that ectopic co-expression of Sox32 and Oct4 in several non-endoderm lineages, including skeletal muscle, can specifically trigger an early endoderm genetic program in a cell-autonomous manner. Gene expression, live imaging, and functional studies reveal that the endoderm-induced muscle cells lose muscle gene expression and morphology, while specifically gaining endoderm organogenesis markers, such as the pancreatic specification genes, hhex and ptf1a, via a mechanism resembling normal development. Endoderm induction by a pluripotent defective form of Oct4, endoderm markers appearing prior to loss of muscle cell morphology, a lack of dependence on cell division, and a lack of mesoderm, ectoderm, dedifferentiation, and pluripotency gene activation, together, suggests that reprogramming is endoderm specific and occurs via direct lineage conversion. Our work demonstrates that within a vertebrate animal, stably differentiated cells can be induced to directly adopt the identity of a completely unrelated cell lineage, while remaining in a distinct microenvironment, suggesting that differentiated cells in vivo may be more amenable to lineage conversion than previously appreciated. This discovery of possibly unlimited lineage potential of differentiated cells in vivo challenges our understanding of cell lineage restriction and may pave the way towards a vast new in vivo supply of replacement cells for degenerative diseases such as diabetes.

developmental biology↗