Comparative analysis of immature neuronal populations in the paralaminar nucleus of the amygdala and the ventricular-subventricular zone across postnatal mammalian species

• Autores: Lucía Inés Torrijos Saiz
• Directores de la Tesis: Vicente Herranz Pérez (dir. tes.), Jose Manuel García Verdugo (codir. tes.)
• Lectura: En la Universitat de València ( España ) en 2025
• Idioma: inglés
• Número de páginas: 166
• Tribunal Calificador de la Tesis: Enrique Lanuza Navarro (presid.), Vivian Capilla González (secret.), Naoko Kaneko (voc.)
• Programa de doctorado: Programa de Doctorado en Neurociencias por la Universitat de València (Estudi General)
• Menciones:
  • Internacional
• Calificación: Sobresaliente Cum Laude
• Materias:
  • Ciencias de la vida
    • Biología celular
• Enlaces
  • Tesis en acceso abierto en:  TESEO  RODERIC 
• Resumen

  • Immature neurons in the postnatal brain have been proposed as an alternative form of neural plasticity in mammals with limited adult neurogenesis. In addition to the canonical neurogenic niches, the ventricular-subventricular zone (V-SVZ) and the dentate gyrus of the hippocampus, immature neurons have been identified in other brain regions, including the piriform cortex and the paralaminar nucleus (PL) of the amygdala. The PL is a relatively understudied subregion of the ventral amygdala, characterized by a population of cells that retain immature features into well postnatal development. Although the PL has been mostly studied in humans and non-human primates due to its prominence in these species, understanding its delayed maturation requires accessible and versatile animal models. In this study, we examined the PL in four mammalian species (mouse, ferret, marmoset, and swine) with the aim of characterizing the molecular identity, ultrastructural features, and postnatal maturation of immature neurons. We also investigated their migratory dynamics and determined their time of origin using birth dating approaches. To this end, we employed diaminobenzidine immunohistochemistry and immunofluorescence for specific molecular markers, combined with transmission electron microscopy and pre-embedding immunogold labeling. Our results in mice indicated that the PL contains Dcx-expressing immature neurons, whose number declines with age, coinciding with a progressive increase in NeuN expression, thus reflecting neuronal maturation. Three maturation states (immature, intermediate, and mature) were identified in mouse PL neurons based on ultrastructural characteristics and a subset of them migrate ventrally to adjacent regions. In ferrets, the PL remains rich in markers for immature neurons throughout juvenile and adult stages, unlike in rodents where these populations decline markedly after early postnatal life. Embryonic BrdU labeling in ferrets showed that PL neurons were generated during prenatal development, but the generation of Dcx+ cells continued briefly after birth declining rapidly during the first postnatal weeks, pointing to a delayed maturation process rather than adult neurogenesis. In adult marmosets, PL neurons also continued to express immature markers during adulthood, suggesting that neuronal maturation might be more protracted or arrested, perhaps contributing to long-lasting plasticity in primates. Finally, in the juvenile swine, the PL showed a robust population of Dcx+ neurons, many forming long chains extending into the endopiriform cortex, consistent with active postnatal migration and circuit integration. Moreover, swine PL neurons co-express excitatory markers, supporting their classification as immature glutamatergic neurons, and suggesting functional homology with PL neurons in primates. These findings demonstrate that the PL is a conserved structure across distant mammalian lineages, and its size and position appear to be species-specific rather than linked to cortical expansion or folding. Although the functional role and maturation triggers remain unclear, our results establish novel animal models for future mechanistic studies. We also characterized the juvenile swine V-SVZ, a well-established neurogenic niche, using the same molecular and ultrastructural approaches. We described a previously unrecognized four-layered cytoarchitecture, identified distinct cell types, including neuroblasts, and tracked their migratory trajectories along the rostral migratory stream. Some neuroblasts deviated from this path, forming chains that extended toward cortical regions such as the anterior olfactory nucleus, revealing broader migratory potential in the swine brain. Together, our findings support the use of the juvenile swine as a valuable model for studying postnatal neurogenesis in large-brained mammals. The cellular organization and migration patterns observed in the swine V-SVZ reinforce structural and functional parallels with primate neurogenic niches, while also highlighting species-specific features. By redefining the layered architecture of the porcine V-SVZ and detailing the spatial distribution of its cellular components, this work provides a foundation for comparative analyses and future molecular and lineage-tracing studies. These will be crucial to delineate conserved and divergent aspects of postnatal neurogenesis and to evaluate the translational relevance of these models in regenerative neuroscience. Overall, these findings highlight the presence of conserved populations of immature neurons across diverse mammalian species, revealing species-specific patterns of maturation, migration, and persistence in the paralaminar nucleus and the ventricular-subventricular region that may contribute to prolonged plasticity in the postnatal and adult brain.