Laura Lázaro-Carot

Neural stem cells (NSCs) sustain neurogenesis within specialized niches, yet how adhesion-dependent mechanisms during development control lifelong behavior remains unclear. Here, we identify Afadin, a core adherens junction protein, as a regulator. Dorsal loss of Afadin during development drives formation of a stable, ventricular-independent ectopic germinal zone in the neocortex, populated by self-renewing, multipotent NSCs sustaining neurogenesis into adulthood. This ectopic niche emerges within a disorganized cortical environment reminiscent of subcortical band heterotopia, a malformation linked to human neurodevelopmental disorders. Concomitantly, the canonical ventricular-subventricular zone (V-SVZ) is disrupted, with persistent NSC activation, altered ependymal specification, ventricular disorganization, and increased neurogenesis. Transcriptomic profiling of the V-SVZ reveals a shift from adhesion- and quiescence-associated programs toward proliferative and neurogenic states through cell-autonomous and non-cell-autonomous mechanisms. Mosaic postnatal or adult deletion confirms a cell-intrinsic role of Afadin in NSC activation. Together, these findings reveal flexibility and plasticity of NSCs across the lifespan.

Stem cells are generally thought to depend on specialized niches that provide signals for their long-term maintenance. Whether stem-cell competence is intrinsically constrained by anatomical organization remains unclear. Here, we show that neural stem cells can establish and sustain functional persistent stem-cell populations outside their normal anatomical context. Using developmental deletion of the cell-adhesion regulator Afadin as a tool to disrupt cortical tissue organization, we find that neural progenitors are displaced from the ventricular surface and establish an ectopic germinal zone (EGZ) into advanced adulthood. EGZ stem-cell populations retain self-renewal and multilineage differentiation capacity throughout this period. In parallel, the ventricular-subventricular zone (V-SVZ) undergoes persistent reorganization of tissue architecture, cellular composition, molecular state, and stem-cell activity. Together, these findings reveal unexpected plasticity in the relationship between stem cells and their tissue environment, suggesting that canonical niche anatomy may constrain where stem cells normally reside without defining the limits of functional stem-cell competence.

Ten-eleven translocation (TET) enzymes are key regulators of active DNA demethylation, converting 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC) and thereby shaping the epigenetic landscape and cellular identity. While their roles have been characterized in pluripotent and some multipotent stem cells, their function in adult neural stem cells (NSCs) of the subventricular zone (SVZ) remains poorly understood. Here, we show that TET2 is critical for the maintenance and differentiation of adult NSCs, orchestrating locus-specific 5hmC deposition across promoters, gene bodies, and enhancers. Importantly, 5hmC remodeling segregates into two functionally distinct programs: promoter-associated gains of 5hmC are strongly TET2-dependent and drive transcription of genes controlling neural differentiation and calcium signaling, whereas gene body- and enhancer-associated 5hmC gains partially depend on TET2 and sustain proliferative and metabolic pathways, thereby maintaining stemness. Loss of TET2 disrupts these 5hmC programs, downregulates key differentiation- and calcium-related genes, and impairs the normal differentiation-associated increase in intracellular calcium, revealing a functional consequence of altered epigenetic regulation. Together, our findings uncover a pivotal role for TET2 in coordinating complementary epigenetic and transcriptional programs that balance stemness and differentiation in adult NSCs.

Genomic imprinting is an epigenetic mechanism that drives monoallelic gene expression depending on parental origin. Loss of imprinting (LOI) is associated with human imprinting disorders, fetal development, and cancer progression. Imprinted genes, organized in clusters, are regulated by methylation at imprint control regions (ICRs), differentially methylated regions (DMRs) between parental chromosomes. Somatic cell reprogramming into induced pluripotent stem cells (iPSCs) is a valuable tool for studying pluripotency and holds promise for patient-specific therapies. Discerning whether genomic imprinting changes during reprogramming represent epigenetic abnormalities or essential adaptations linked to pluripotency is crucial. Here, we perform RNA-seq and MeDIP-seq analysis on mouse iPSCs derived from neural stem cells (NSCs). Our findings reveal that ICRs undergo DNA hypomethylation, confirming widespread LOI in pluripotent cells. However, the IG-DMR within the Dlk1-Dio3 imprinted cluster resists hypomethylation, a hallmark of successful pluripotency acquisition. We also identify a non-canonical role of TET3 in IG-DMR methylation protection through transcriptional regulation of Oct4 and Trim28 . These findings highlight genomic imprinting as a key mechanism of gene dosage control in pluripotency acquisition and maintenance.

Genomic imprinting is an epigenetic mechanism that causes monoallelic expression of genes depending on their parental origin. Loss of imprinting (LOI) is associated with cancer progression and human imprinting disorders (IDs), impacting foetal development, metabolism and cognition. Imprinted genes, organized in clusters, rely on methylation at imprint control regions (ICRs), which are differentially methylated regions (DMRs) on both parental chromosomes. Somatic cell reprogramming into induced pluripotent stem cells (iPSCs) is a valuable tool to understand the mechanisms associated with pluripotency and holds promise for generating patient-specific stem cells for therapeutical applications to treat different pathologies such as IDs. Here, we conduct genome-wide RNA-seq and MeDIP-seq analysis on mouse iPSCs derived from adult neural stem cells (NSCs). Our findings reveal a comprehensive alteration in iPSCs transcriptome profile, aligning with DNA hypomethylation. This correlation is pivotal in discerning which modifications in genomic imprinting during the reprogramming process represent undesirable epigenetic abnormalities that could compromiise the quality of iPSCs. Simultaneously, it helps identify genuine epigenetic modifications that are inherently linked to pluripotency, thus ensuring a clearer understanding of the factors influencing iPSC quality and pluripotent potential.