Biology subjects

Guerra, M. C.

Publications and source records attributed to Guerra, M. C..

4 recordsLinked to original sources

bioRxiv2026

Co-option of ILF2/3 in primates restrains Alu hyper-editing to enable cell fate transitions

Understanding human specific mechanisms of cell fate control is essential for advancing developmental biology and regenerative medicine. Here, we identify the ILF2/3 complex as a critical regulator of primate cell fate transitions. Using genetically and epigenetically engineered gastruloids and adult stem cells, we show that ILF2/3 is required for gastrulation in primates but not mice, and for differentiation of adult progenitor cells. Mechanistically, ILF2/3 directly binds Alu elements in chromatin-associated RNAs and shields them from ADAR1-mediated adenosine-to-inosine (A-to-I) editing. Acute ILF2/3 degradation increases A-to-I editing at Alu elements, but not murine retrotransposons, leading to aberrant splicing and nonsense-mediated decay of transcripts encoding key chromatin regulators in primate cells. This in turn destabilizes the epigenetic landscape and blocks lineage commitment across all three germ layers. Re-expression of correctly spliced chromatin regulators rescues differentiation defects in ILF2/3-deficient cells, functionally linking Alu editing control to chromatin regulation and cell fate. These findings define an evolutionary mechanism that restrains retrotransposon-associated RNA editing to preserve proteome integrity and enable primate-specific developmental programs.

genetics↗

bioRxiv2025

Juxtaposition of human pluripotent stem cells with amnion-like cells is sufficient to trigger primitive streak formation

Studies in the mouse have established that communication between the trophectoderm and the epiblast is crucial for initiating gastrulation. In the primate embryo, the amnion rather than the trophectoderm is directly juxtaposed to the epiblast and may play this role. To model the interactions between the amnion and epiblast, we differentiated human pluripotent stem cells (hPSCs) to amnion-like cells (AMLCs) and juxtaposed them in a controlled manner with undifferentiated hPSCs, which represent the epiblast. We found that juxtaposition between these cell types is sufficient to initiate a range of cell behaviors associated with gastrulation including organized differentiation to primitive streak and downstream mesendodermal cell fates and directed cell migration out of the primitive streak region. Performing knockout experiments specifically in either the epiblast or amnion compartment revealed intricate crosstalk that is required to properly initiate gastrulation. In particularly, using knockouts of NODAL we show that Nodal signaling in both the amnion and epiblast is required for gastrulation patterning. Finally, we show that inductive ability is a transient property acquired during amnion differentiation, and that cells that differentiate from this inductive state acquire an extraembryonic mesenchyme identity. This study establishes a system to study epiblast-amnion communication and shows that this communication is sufficient to initiate gastrulation in the epiblast.

developmental biology↗

bioRxiv2021

Nodal is a short-range morphogen with activity that spreads through a relay mechanism in human gastruloids

Morphogens are signaling molecules that convey positional information and dictate cell fates during development. Little is known about how morphogen gradients are created and interpreted during mammalian embryogenesis. Here we take advantage of a human gastruloid model to visualize endogenous Nodal protein in living cells. We show that Nodal is extremely short range so that Nodal protein is limited to the immediate neighborhood of source cells. Nodal activity spreads through a relay mechanism in which Nodal production induces neighboring cells to transcribe Nodal. We further show that the Nodal inhibitor Lefty, while biochemically capable of long-range diffusion, also acts locally to control the timing of Nodal spread and therefore of mesoderm differentiation during patterning. Our study establishes a novel paradigm for tissue patterning by an activator-inhibitor pair.

developmental biology↗

bioRxiv2017

Morphogen dynamics control patterning in a stem cell model of the human embryo

During embryonic development, diffusible signaling molecules called morphogens are thought to determine cell fates in a concentration-dependent manner1-4, and protocols for directed stem cell differentiation are based on this picture5-8. However, in the mammalian embryo, morphogen concentrations change rapidly compared to the time for making cell fate decisions9-12. It is unknown how changing ligand levels are interpreted, and whether the precise timecourse of ligand exposure plays a role in cell fate decisions. Nodal and BMP4 are morphogens crucial for gastrulation in vertebrates13. Each pathway has distinct receptor complexes that phosphorylate specific signal transducers, known as receptor-Smads, which then complex with the shared cofactor Smad4 to activate target genes14. Here we show in human embryonic stem cells (hESCs) that the response to BMP4 signaling indeed is determined by the ligand concentration, but that unexpectedly, the expression of many mesodermal targets of Activin/Nodal depends on rate of concentration increase. In addition, we use live imaging of hESCs with GFP integrated at the endogenous SMAD4 locus to show that a stem cell model for the human embryo15 generates a wave of Nodal signaling. Cells experience rapidly increasing Nodal specifically in the region of mesendoderm differentiation. We also demonstrate that pulsatile stimulation with Activin induces repeated strong signaling and enhances mesoderm differentiation. Our results break with the paradigm of concentration-dependent differentiation and demonstrate an important role for morphogen dynamics in the cell fate decisions associated with mammalian gastrulation. They suggest a highly dynamic picture of embryonic patterning where some cell fates depend on rapid concentration increase rather than absolute levels, and point to ligand dynamics as a new dimension to optimize protocols for directed stem cell differentiation.

developmental biology↗