Biology subjects

Tiana, M.

Publications and source records attributed to Tiana, M..

4 recordsLinked to original sources

bioRxiv2026

DNA replication is dispensable for developmental progression, but required for heterochromatin organization at mouse zygotic genome activation

Early mammalian development progresses through a small number of cleavage divisions with extensive transcriptional and epigenetic reprogramming that result in the very first lineage decisions, leading to blastocyst formation. Although classical embryological studies suggested that developmental progression can occur independently of normal cell division, the extent to which DNA replication contributes to these processes remains unclear. In particular, whether replication is required simply for proliferation or also for establishing the cellular states that regulate stage-specific gene expression is unknown. Here we show that mouse preimplantation development can proceed without DNA replication, but it is required to maintain proper heterochromatin organization at the 2-cell stage, the time of zygotic genome activation. The inhibition of DNA replication with aphidicolin blocked cleavage divisions without preventing zygotic genome activation, embryo morphogenesis, activation of lineage-specification factors, or the establishment of stage-specific transcriptional programs. However, replication arrest selectively altered the expression of developmental genes associated with late-replicating, Polycomb-enriched chromatin domains, and also reduced global levels of H3K27me3 and H3K9me3. These findings indicate that developmental timing in the early embryo is largely uncoupled from DNA replication and cell-cycle progression. Instead, DNA replication contributes to transcriptional fidelity by establishing or maintaining repressive chromatin states during the extensive genome reprogramming that accompanies zygotic genome activation.

developmental biology↗

bioRxiv2025

NR6A1 is essential for neural crest cell specification, formation and survival

Neural crest cells (NCC) are a migratory progenitor cell population considered unique to vertebrates. Derived from the neuroepithelium during early embryogenesis, NCC contribute to nearly every tissue and organ system throughout the body, and disruptions in NCC development can result in congenital disorders, termed neurocristopathies. Despite decades of research, we have a poor understanding of the cellular mechanisms and signals that govern mammalian NCC formation. We discovered nuclear receptor superfamily 6 group member 1 (NR6A1/GCNF/RTR), is a novel, critical regulator of mammalian NCC specification, formation and survival. Nr6a1 is expressed throughout the neuroepithelium in mouse embryos from E8.0 to E9.5 and briefly in newly delaminated NCC. Nr6a1 loss-of-function perturbs anterior cranial NCC formation and survival, and results in the complete agenesis of migratory NCC caudal to the first pharyngeal arch. Using mouse ESC and human iPSC differentiation into NCC, chromatin immunoprecipitation, and multiomic approaches, we demonstrate that these phenotypes are associated with perturbation of NCC specification (Foxd3, Sox9, Sox10) and epithelial-mesenchymal transition (EMT; Snail1, Zeb2), in concert with persistent expression of pluripotency-associated factors (Oct4 and Nanog) in the neuroepithelium. Conditional deletion revealed that Nr6a1 is required during mid-late gastrulation, demonstrating that murine NCC specification occurs earlier than previously thought. Consistent with these observations, in vivo overexpression of Oct4 in gastrulating mouse embryos disrupts NCC specification and formation. Therefore, Nr6a1 is essential for mammalian NCC formation and moreover, may function as a bimodal switch repressing pluripotency-associated factors in the neuroepithelium, while concomitantly activating NCC specifiers and regulators of EMT.

developmental biology↗

bioRxiv2021

Establishment of 3D chromatin structure after fertilization and the metabolic switch at the morula-to-blastocyst transition require CTCF

The eukaryotic genome is tightly packed inside the nucleus, where it is organized in 3D at different scales. This structure is driven and maintained by different chromatin states and by architectural factors that bind DNA, such as the multi-zinc finger protein CTCF. Zygotic genome structure is established de novo after fertilization, but the impact of such structure on genome function during the first stages of mammalian development is still unclear. Here, we show that deletion of the Ctcf gene in mouse embryos impairs the correct establishment of chromatin structure, but initial lineage decisions take place and embryos are viable until the late blastocyst stage. Furthermore, we observe that maternal CTCF is not necessary for development. Transcriptomic analyses of mutant embryos show that the changes in metabolic and protein homeostasis programs that occur during the progression from the morula to the blastocyst depend on CTCF. Yet, these changes in gene expression do not correlate with disruption of chromatin structure, but mainly with proximal binding of CTCF to the promoter region of genes downregulated in mutants. Our results show that CTCF regulates both 3D genome organization and transcription during mouse preimplantation development, but mostly as independent processes.

developmental biology↗

bioRxiv2019

Pluripotency factors regulate the onset of Hox cluster activation in the early embryo

Pluripotent cells are a transient population present in the early mammalian embryo dependent on transcription factors, such as OCT4 and NANOG, which maintain pluripotency while simultaneously suppressing lineage specification. Interestingly, these factors are not exclusive to uncommitted cells, but are also expressed during early phases of differentiation. However, their role in the transition from pluripotency to lineage specification is largely unknown. Using genetic models for controlled Oct4 or Nanog expression during postimplantation stages, we found that pluripotency factors play a dual role in regulating key lineage specifiers, initially repressing their expression and later being required for their proper activation. We show that the HoxB cluster is coordinately regulated in this way by OCT4 binding sites located at the 3 end of the cluster. Our results show that core pluripotency factors are not limited to maintaining the pre-committed epiblast, but are also necessary for the proper deployment of subsequent developmental programs.

developmental biology↗