Naive pluripotent stem cells have the highest developmental potential but their in vivo existence in the blastocyst is transient. Here we report a blastocyst motif substrate for the in vitro reversion of mouse and human pluripotent stem cells to a naive state. The substrate features randomly varied microstructures, which we call motifs, mimicking the geometry of the blastocyst. Motifs representing mouse-blastocyst-scaled curvature ranging between 15 and 62 mm-1 were the most efficient in promoting reversion to naivety, as determined by time-resolved correlative analysis. In these substrates, apical constriction enhances E-cadherin/RAC1 signalling and activates the mechanosensitive nuclear transducer YAP, promoting the histone modification of pluripotency genes. This results in enhanced levels of pluripotency transcription factor NANOG, which persist even after cells are removed from the substrate. Pluripotent stem cells cultured in blastocyst motif substrates display a higher development potential in generating embryoid bodies and teratomas. These findings shed light on naivety-promoting substrate design and their large-scale implementation.
© 2024. The Author(s).

Germline SAMD9 mutations are one of the most common alterations that predispose to pediatric myelodysplastic syndrome (MDS), a clonal disorder characterized by ineffective hematopoiesis, increasing the risk of developing acute myeloid leukemia (AML). Up to date, a disease model to study the role of SAMD9 mutation in MDS is still lacking. Here, we have generated a human induced pluripotent stem cell (hiPSC) line carrying SAMD9mut (p.I1567M), taking advantage of CRISPR/Cas9 system. As a result, the genetic engineered hiPSC line represent a new in vitro disease model to understand the impact of SAMD9 mutation at molecular and cellular level during hematopoiesis.
Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.

Germline heterozygous GATA2 mutations underlie a complex disorder characterized by bone marrow failure, immunodeficiency and high risk to develop myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Our understanding about GATA2 deficiency is limited due to the lack of relevant disease models. Here we generated high quality human induced pluripotent stem cell (iPSC) lines carrying two of the most recurrent germline GATA2 mutations (R389W and R396Q) associated with MDS, using CRISPR/Cas9. These hiPSCs represent an in vitro model to study the molecular and cellular mechanisms underlying GATA2 deficiency, when differentiated into blood progenitors.
Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.

The histone H3 lysine 79 (H3K79) methyltransferase DOT1L is a key chromatin-based barrier to somatic cell reprogramming. However, the mechanisms by which DOT1L safeguards cell identity and somatic-specific transcriptional programs remain unknown.
We employed a proteomic approach using proximity-based labeling to identify DOT1L-interacting proteins and investigated their effects on reprogramming. Among DOT1L interactors, suppression of AF10 (MLLT10) via RNA interference or CRISPR/Cas9, significantly increases reprogramming efficiency. In somatic cells and induced pluripotent stem cells (iPSCs) higher order H3K79 methylation is dependent on AF10 expression. In AF10 knock-out cells, re-expression wild-type AF10, but not a DOT1L binding-impaired mutant, rescues overall H3K79 methylation and reduces reprogramming efficiency. Transcriptomic analyses during reprogramming show that AF10 suppression results in downregulation of fibroblast-specific genes and accelerates the activation of pluripotency-associated genes.
Our findings establish AF10 as a novel barrier to reprogramming by regulating H3K79 methylation and thereby sheds light on the mechanism by which cell identity is maintained in somatic cells.

Human induced pluripotent stem cells (iPSCs) have emerged as an invaluable resource for basic research, disease modeling, and drug discovery over recent years. Given the numerous advantages of iPSCs over alternative models-including their human origin, their ability to be differentiated into almost any cell type, and the therapeutic potential of patient-specific iPSCs in personalized medicine-many labs are now considering iPSC models for their studies. As the quality of the starting population of iPSCs is a key determinant in the success of any one of these applications, it is crucial to adhere to best practices in iPSC culture. In the following protocol, we offer a comprehensive guide to the culture, cryopreservation, and quality control methods required for the establishment and maintenance of high-quality iPSC cultures.
© 2021. Springer Science+Business Media, LLC.