p73 is critical for the persistence of memory

p63 Regulates adult neural precursor and newly born neuron survival to control hippocampal-dependent Behavior

The molecular mechanisms that regulate adult neural precursor cell (NPC) survival, and thus maintain adult neurogenesis, are not well defined. Here, we investigate the role of p63, a p53 family member, in adult NPC function in mice. Conditional ablation of p63 in adult NPCs or p63 haploinsufficiency led to reduced numbers of NPCs and newborn neurons in the neurogenic zones of the hippocampus and lateral ventricles and in the olfactory bulb. These reductions were attributable to enhanced apoptosis of NPCs and newborn neurons and were rescued by inhibition of caspase activity, p53, or the p53 apoptotic effector PUMA (p53-upregulated modulator of apoptosis). Moreover, these cellular deficits were functionally important because they led to perturbations in hippocampus-dependent memory formation. These results indicate that p63 regulates the numbers of adult NPCs and adult-born neurons as well as neural stem cell-dependent cognitive functions, and that it does so, at least in part, by inhibiting p53-dependent cell death.

GLS2 is transcriptionally regulated by p73 and contributes to neuronal differentiation

The amino acid Glutamine is converted into Glutamate by a deamidation reaction catalyzed by the enzyme Glutaminase (GLS). Two isoforms of this enzyme have been described, and the GLS2 isoform is regulated by the tumor suppressor gene p53. Here, we show that the p53 family member TAp73 also drives the expression of GLS2. Specifically, we demonstrate that TAp73 regulates GLS2 during retinoic acid-induced terminal neuronal differentiation of neuroblastoma cells, and overexpression or inhibition of GLS2 modulates neuronal differentiation and intracellular levels of ATP. Moreover, inhibition of GLS activity, by removing Glutamine from the growth medium, impairs in vitro differentiation of cortical neurons. Finally, expression of GLS2 increases during mouse cerebellar development. Although, p73 is dispensable for the in vivo expression of GLS2, TAp73 loss affects GABA and Glutamate levels in cortical neurons. Together, these findings suggest a role for GLS2 acting, at least in part, downstream of p73 in neuronal differentiation and highlight a possible role of p73 in regulating neurotransmitter synthesis.

Embryonic stem cells and inducible pluripotent stem cells: two faces of the same coin?

Embryonic stem cells (ESCs) are derived from the inner cell mass of the blastocysts and are characterized by the ability to renew themselves (self-renewal) and the capability to generate all the cells within the human body. In contrast, inducible pluripotent stem cells (iPSCs) are generated by transfection of four transcription factors in somatic cells. Like embryonic stem cells, they are able to self-renew and differentiate. Because of these features, both ESCs and iPSCs, are under intense clinical investigation for cell-based therapy. In this review, we revisit stem cell biology and add a new layer of complexity. In particular, we will highlight some of the complexities of the system, but also where there may be therapeutic potential for modulation of intrinsic stem cells and where particular caution may be needed in terms of cell transplantation therapies.

P73 and age-related diseases: is there any link with Parkinson Disease?

P73 is a member of the p53 transcription factors family with a prominent role in neurobiology, affecting brain development as well as controlling neuronal survival. Accordingly, p73 has been identified as key player in many age-related neurodegenerative diseases, such as Alzheimer's disease, neuroAIDS and Niemann-Pick type C disease. Here we investigate possible correlations of p73 with Parkinson disease. Tyrosine hydroxylase is a crucial player in Parkinson disease being the enzyme necessary for dopamine synthesis. In this work we show that levels of tyrosine hydroxylase can be influenced by p73. We also demonstrate that p73 can protect against tyrosine hydroxylase depletion in an in vitro model of Parkinson disease.

Senescence and aging: the critical roles of p53

p53 functions as a transcription factor involved in cell-cycle control, DNA repair, apoptosis and cellular stress responses. However, besides inducing cell growth arrest and apoptosis, p53 activation also modulates cellular senescence and organismal aging. Senescence is an irreversible cell-cycle arrest that has a crucial role both in aging and as a robust physiological antitumor response, which counteracts oncogenic insults. Therefore, via the regulation of senescence, p53 contributes to tumor growth suppression, in a manner strictly dependent by its expression and cellular context. In this review, we focus on the recent advances on the contribution of p53 to cellular senescence and its implication for cancer therapy, and we will discuss p53's impact on animal lifespan. Moreover, we describe p53-mediated regulation of several physiological pathways that could mediate its role in both senescence and aging.

p63 steps into the limelight: crucial roles in the suppression of tumorigenesis and metastasis

The role of p63 in cancer has been an area of intense debate and controversy. Is TP63 (which encodes p63) a tumour suppressor gene or an oncogene? This debate is partly due to the complexity of the gene. There are several p63 isoforms - some with tumour suppressive functions and others with oncogenic functions. In this Opinion article, we focus on the recent advances in understanding p63 biology and its roles in cancer. In this regard, we discuss the role of p63 in multiple stem cell compartments, ageing, in the response to DNA damage and in DNA repair. Finally, we highlight the importance of understanding the interactions between all three p53 family members and the potential impact of this knowledge on cancer therapy and regenerative medicine.