Vittorio Sebastiano lab
Germ cells, preimplantation embryos and pluripotent stem cells at first glance seem to have nothing in common. A more careful look, though, reveals that they are very closely linked to each other. The zygote originates from the fusion of two highly specialized germ cells (the sperm and the oocyte) and in a few days develops into a blastocyst with a pluripotent cell population (the inner cell mass). These cells diverge from the extraembryonic cells of the trophoectoderm and can give rise to embryonic stem cells, in which a perpetual pluripotent and undifferentiated state is maintained.
The thread of Ariadne that connects germ cells, preimplatation development and pluripotent stem cells is the focus of my research, with a specific interest in human development. My long-term goals are several fold: 1. Understanding the biology of germ cells and and their ability to sustain early phases of preimplantation development; 2. Understanding the mechanisms that regulate very early cell fate decisions in human embryos; 3. Understanding the biology of Pluripotent Stem Cells and the mechanisms that lead to their formation also in the context of iPSCs derivation.
A Comprehensive TALEN-Based Knockout Library for Generating Human Induced Pluripotent Stem Cell-Based Models for Cardiovascular Diseases.
Targeted genetic engineering using programmable nucleases such as transcription activator-like effector nucleases (TALENs) is a valuable tool for precise, site-specific genetic modification in the human genome.The emergence of novel technologies such as human induced pluripotent stem cells (iPSCs) and nuclease-mediated genome editing represent a unique opportunity for studying cardiovascular diseases in vitro.By incorporating extensive literature and database searches, we designed a collection of TALEN constructs to knockout 88 human genes that are associated with cardiomyopathies and congenital heart diseases. The TALEN pairs were designed to induce double-strand DNA break near the starting codon of each gene that either disrupted the start codon or introduced a frameshift mutation in the early coding region, ensuring faithful gene knockout. We observed that all the constructs were active and disrupted the target locus at high frequencies. To illustrate the utility of the TALEN-mediated knockout technique, 6 individual genes (TNNT2, LMNA/C, TBX5, MYH7, ANKRD1, and NKX2.5) were knocked out with high efficiency and specificity in human iPSCs. By selectively targeting a pathogenic mutation (TNNT2 p.R173W) in patient-specific iPSC-derived cardiac myocytes, we demonstrated that the knockout strategy ameliorates the dilated cardiomyopathy phenotype in vitro. In addition, we modeled the Holt-Oram syndrome in iPSC-cardiac myocytes in vitro and uncovered novel pathways regulated by TBX5 in human cardiac myocyte development.Collectively, our study illustrates the powerful combination of iPSCs and genome editing technologies for understanding the biological function of genes, and the pathological significance of genetic variants in human cardiovascular diseases. The methods, strategies, constructs, and iPSC lines developed in this study provide a validated, readily available resource for cardiovascular research.
View details for DOI 10.1161/CIRCRESAHA.116.309948
View details for PubMedID 28246128
View details for PubMedCentralID PMC5429194
Spatiotemporal Reconstruction of the Human Blastocyst by Single-Cell Gene-Expression Analysis Informs Induction of Naive Pluripotency
2016; 38 (1): 100-115
Human preimplantation embryo development involves complex cellular and molecular events that lead to the establishment of three cell lineages in the blastocyst: trophectoderm, primitive endoderm, and epiblast. Owing to limited resources of biological specimens, our understanding of how the earliest lineage commitments are regulated remains narrow. Here, we examined gene expression in 241 individual cells from early and late human blastocysts to delineate dynamic gene-expression changes. We distinguished all three lineages and further developed a 3D model of the inner cell mass and trophectoderm in which individual cells were mapped into distinct expression domains. We identified in silico precursors of the epiblast and primitive endoderm lineages and revealed a role for MCRS1, TET1, and THAP11 in epiblast formation and their ability to induce naive pluripotency in vitro. Our results highlight the potential of single-cell gene-expression analysis in human preimplantation development to instruct human stem cell biology.
View details for DOI 10.1016/j.devcel.2016.06.014
View details for Web of Science ID 000380073400013
View details for PubMedID 27404362
YAP Induces Human Naive Pluripotency.
2016; 14 (10): 2301-2312
The human naive pluripotent stem cell (PSC) state, corresponding to a pre-implantation stage of development, has been difficult to capture and sustain in vitro. We report that the Hippo pathway effector YAP is nuclearly localized in the inner cell mass of human blastocysts. Overexpression of YAP in human embryonic stem cells (ESCs) and induced PSCs (iPSCs) promotes the generation of naive PSCs. Lysophosphatidic acid (LPA) can partially substitute for YAP to generate transgene-free human naive PSCs. YAP- or LPA-induced naive PSCs have a rapid clonal growth rate, a normal karyotype, the ability to form teratomas, transcriptional similarities to human pre-implantation embryos, reduced heterochromatin levels, and other hallmarks of the naive state. YAP/LPA act in part by suppressing differentiation-inducing effects of GSK3 inhibition. CRISPR/Cas9-generated YAP(-/-) cells have an impaired ability to form colonies in naive but not primed conditions. These results uncover an unexpected role for YAP in the human naive state, with implications for early human embryology.
View details for DOI 10.1016/j.celrep.2016.02.036
View details for PubMedID 26947063
View details for PubMedCentralID PMC4807727
The primate-specific noncoding RNA HPAT5 regulates pluripotency during human preimplantation development and nuclear reprogramming.
2016; 48 (1): 44-52
Long intergenic noncoding RNAs (lincRNAs) are derived from thousands of loci in mammalian genomes and are frequently enriched in transposable elements (TEs). Although families of TE-derived lincRNAs have recently been implicated in the regulation of pluripotency, little is known of the specific functions of individual family members. Here we characterize three new individual TE-derived human lincRNAs, human pluripotency-associated transcripts 2, 3 and 5 (HPAT2, HPAT3 and HPAT5). Loss-of-function experiments indicate that HPAT2, HPAT3 and HPAT5 function in preimplantation embryo development to modulate the acquisition of pluripotency and the formation of the inner cell mass. CRISPR-mediated disruption of the genes for these lincRNAs in pluripotent stem cells, followed by whole-transcriptome analysis, identifies HPAT5 as a key component of the pluripotency network. Protein binding and reporter-based assays further demonstrate that HPAT5 interacts with the let-7 microRNA family. Our results indicate that unique individual members of large primate-specific lincRNA families modulate gene expression during development and differentiation to reinforce cell fate.
View details for DOI 10.1038/ng.3449
View details for PubMedID 26595768
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