PUM 2: THE PROTEIN OF INTELLECTUAL ABILITY

At the beginning of the last decade some researchers identified in the drosophila melanogaster the existence of two proteins, Nanos and Pumilio (Pum), important for dendrite morphogenesis, the excitability of neurons, and the correlated functions such as learning and memory (Schweers et al., 2002; Dabnau et al., 2003; Ye et al., 2004; Mee et al., 2004; Menon et al., 2004).

Today an international study group, led by John Vessey of the Center for Research on the Brain of the Faculty of Medicine at the University of Vienna, identified a homolgue of Pum named Pum 2, that is found in the somato-dendrites of the hippocampal neurons of mammals. Among the researches responsible for the discovery are the Italians Paolo Macchi and Francesca di Leva, of the Interdepartmental Center for Integrated Biology of the University of Trento, and Ettore Luzi, of the Laboratory of Molecular Genetics of the Center on Endocrine Tumors of the Faculty of Medicine of the University of Florence.

In the study it was observed that Pum 2 has an important role in the development and the maturation of neurons, mediated from the capacity of interference with the actions of RNA.

In immature neurons the absence of Pum 2 is associated with an increase in the growth and arborization of dentrites. In mature neurons the induction of a reduction in the concentration of Pum 2 is instead followed by a significant reduction of dendritic spines and an increase of elongated dendritic filopodia and excitatory synapses.

In neurons that lack Pum 2 electrofisiological analysis of the synaptic functionhas pointed out an increment of the postsynaptic excitatory current. This increment can be determined from the action of elF4E and Scn1a, two verifiable molecules from Pum 2 and in degree of respective condition the transcription of mRNA and the activation of voltage-gated sodium channels.

Pum 2 is a protein synthesized in the nervous tissue already in the first stages of the construction of the central nervous system. It seems that its task is to regulate the development of neurons in way that they can carry out in the best way their principle function to receive and transmit information. If they are produced in excess or in defect, Pum 2 seems to cause morpho-functional changes of the nervous tissue that results in the degeneration of principle cognitive functions, and therefore serious forms of mental retardation

The development of intelligence is controlled from the combination of biological, psychological and socio-environmental factors. Between the biological factors, those of genetic type, that refer to the information contained in our DNA, have a predominant role. The code of the double helix of DNA comes is translated in protein as a result of the work of a mediator known as messenger-RNA (m-RNA). In the central nervous system, some of the proteins produced, like Pum 2, can serve to regulate the flow of genetic information backwards in the action of development and regulation of intellectual function that is also expressed in the creation of new cellular ramifications and new conjunctions between cells.