Biology subjects

Rito, T.

Publications and source records attributed to Rito, T..

3 recordsLinked to original sources

bioRxiv2025

Boundary constraints can determine pattern emergence

The robust patterning of cell fates during embryonic development requires precise coordination of signalling gradients within defined spatial constraints. Using a geometrically confined in vitro system derived from human embryonic stem cells, we demonstrate that patterning of neuromesodermal progenitors (NMPs) during axial elongation is driven by boundary-dependent mechanisms. Despite extensive work on radial fate patterning in confined 2D systems, the quantitative role of boundary conditions in shaping spatiotemporal dynamics remains unclear. Here, we show that a minimal reaction-diffusion model coupled with a simplified gene regulatory network accurately predicts spatial patterns across diverse geometries. Guided by its predictions, we identify Wnt signalling as a key component of the activator signal. Inhibition of Wnt secretion preserved initiation of patterning but disrupted subsequent morphogenesis, indicating distinct mechanisms govern pattern establishment versus maintenance. Our findings reveal how geometry encodes positional information that directs molecular patterning, providing insight into how spatial constraints and signalling dynamics guide robust tissue self-organisation during development.

systems biology↗

bioRxiv2024

An in vivo CRISPR screen in chick embryos reveals a role for MLLT3 in specification of neural cells from the caudal epiblast

Tissue development relies on the coordinated differentiation of stem cells in dynamically changing environments. The formation of the vertebrate neural tube from stem cells in the caudal lateral epiblast (CLE) is a well characterized example. Despite an understanding of the signalling pathways involved, the gene regulatory mechanisms remain poorly defined. To address this, we developed a multiplexed in vivo CRISPR screening approach in chick embryos targeting genes expressed in the caudal epiblast and neural tube. This revealed a role for MLLT3, a component of the super elongation complex, in the specification of neural fate. Perturbation of MLLT3 disrupted neural tube morphology and reduced neural fate acquisition. Mutant forms of Retinoic Acid Receptor A lacking the MLLT3 binding domain similarly reduced neural fate acquisition. Together, these findings validate an in vivo CRISPR screen strategy in chick embryos and identify a previously unreported role for MLLT3 in caudal neural tissue specification.

developmental biology↗

bioRxiv2023

Notochord and axial progenitor generation by timely BMP and NODAL inhibition during vertebrate trunk formation

The formation of the vertebrate body involves the coordinated and progressive production of trunk tissues from progenitors located in the posterior of the embryo. In vitro models based on pluripotent stem cells (PSCs) replicate aspects of this process, but they lack some tissue components normally present in the trunk. Most strikingly, the notochord, a hallmark of chordates and the source of midline signals that pattern surrounding tissues, is absent from current models of human trunk formation. To investigate how trunk tissue is formed, we performed single-cell transcriptomic analysis of chick embryos. This delineated molecularly discrete progenitor populations, which we spatially locate in the embryo, compare across species, and relate to signalling activity. Guided by this map, we determined how differentiating human PSCs develop a stereotypical spatial organization of tissue types. We found that LATS1/2 repression of YAP activity, in conjunction with FGF-mediated MAPK activation, induced the transcription factor Bra/TBXT and facilitated WNT signaling. In addition, inhibiting a WNT-induced NODAL and BMP signaling cascade at the appropriate time regulated the proportions of different tissue types produced, including notochordal cells. We used this information to create an integrated 3D model of human gastrulation undergoing morphogenetic movements to produce elongated structures with a notochord and spatially patterned neural tissue formation. Together the data provide insight into the mechanisms responsible for the formation of the tissues that comprise the vertebrate trunk and pave the way for future studies of patterning in a tissue-like environment.

developmental biology↗