Distribution and fate of DCX/PSA-NCAM expressing cells in the adult mammalian cortex: A local reservoir for adult cortical neuroplasticity?

Abstract

The expression of early developmental markers such as doublecortin (DCX) and the polysialylated-neural cell adhesion molecule (PSA-NCAM) has been used to identify immature neurons within canonical neurogenic niches. Additionally, DCX/PSA-NCAM + immature neurons reside in cortical layer II of the paleocortex and in the paleo-and entorhinal cortex of mice and rats, respectively. These cells are also found in the neocortex of guinea pigs, rabbits, some afrotherian mammals, cats, dogs, non-human primates, and humans. The population of cortical DCX/PSA-NCAM + immature neurons is generated prenatally as conclusively demonstrated in mice, rats, and guinea pigs. Thus, the majority of these cells do not appear to be the product of adult proliferative events. The immature neurons in cortical layer II are most abundant in the cortices of young individuals, while very few DCX/PSA-NCAM + cortical neurons can be detected in aged mammals. Maturation of DCX/PSA-NCAM + cells into glutamatergic and GABAergic neurons has been proposed as an explanation for the age-dependent reduction in their population over time. In this review, we compile the recent information regarding the age-related decrease in the number of cortical DCX/PSA-NCAM + neurons. We compare the distribution and fates of DCX/PSA-NCAM + neurons among mammalian species and speculate their impact on cognitive function. To respond to the diversity of adult neurogenesis research produced over the last number of decades, we close this review by discussing the use and precision of the term "adult non-canonical neurogenesis."

Non-proliferative neurogenesis in human periodontal ligament stem cells

“…In addition, it is important to note that almost none of these labeled new born neurons show mitotic chromosomes or mitotic spindle to really confirm that adult neurogenesis occurs progressively through sequential phases of proliferation 43,[47][48][49][50][51][52][53] . Importantly, the existence of non-proliferative neuronal precursors in several brain areas has also been observed 76,77 . Moreover, the self-renewal and multipotent properties demonstrated by NSC in vitro 78 have not been clearly demonstrated in vivo 54,67,79 .…”

Non-Newly Generated, “Immature” Neurons in the Sheep Brain Are Not Restricted to Cerebral Cortex

“…The cytoskeletal protein DCX is associated with neuronal maturation and cell shape global remodeling and thus is involved in structural plasticity (Nacher et al, 2001;Brown et al, 2003). For decades, much attention was drawn to adult neurogenesis as a striking process of plasticity involving the production of new neurons that affect learning and memory, also opening possibilities for brain repair (Martino et al, 2011;Peretto and Bonfanti, 2014;Berninger and Jessberger, 2016).…”

“…These exceptions span from formation/elimination of synapses in preexisting neurons (synaptic plasticity; Bonfanti-and Theodosis, 2009;Bailey et al, 2015) to addition/replacement of new neurons (adult neurogenesis; Bonfanti-and Peretto, 2011; Aimone et al, 2014). The occurrence, amount, type, and location of neural structural plasticity, as well as its reparative capacity, vary greatly in the animal world (Bonfanti-and Peretto, 2011;Grandel and Brand, 2013) and, to a lesser extent, among mammals (Feliciano et al, 2015;Lipp and Bonfanti, 2016). The cytoskeletal protein doublecortin (DCX) is an excellent marker for cells that retain high potential for structural plasticity in the CNS (Gleeson et al, 1999;Nacher et al, 2001).…”

“…The occurrence, amount, type, and location of neural structural plasticity, as well as its reparative capacity, vary greatly in the animal world (Bonfanti-and Peretto, 2011;Grandel and Brand, 2013) and, to a lesser extent, among mammals (Feliciano et al, 2015;Lipp and Bonfanti, 2016). The cytoskeletal protein doublecortin (DCX) is an excellent marker for cells that retain high potential for structural plasticity in the CNS (Gleeson et al, 1999;Nacher et al, 2001). Due to its heavy expression in newly generated neuroblasts and during the early phases of their migration/differentiation, DCX is commonly used as a marker for adult neurogenesis (Brown et al, 2003).…”

Adult Hippocampal Neurogenesis in Mammals (and Humans): The Death of a Central Dogma in Neuroscience and its Replacement by a New Dogma

“…There is, in fact, recent evidence from a variety of relatively long‐lived, large‐brained mammals, that cortical neurons generated early in life (via developmental, non‐adult neurogenesis) may provide cohorts of immature but excitable “stand‐by” neurons that mediate adult plasticity in response to environmental events. These cells express markers selective for immature, post‐mitotic neurons and are found in non‐human primates and humans and are suggested to complete maturation during adulthood in response to experience‐related signals (Penz et al , ; Konig et al , ; Palazzo et al , ; Parolisi et al , ).…”