6533b7d8fe1ef96bd1269587

RESEARCH PRODUCT

Estudio de la función de los factores de transcripción PBX en la diferenciación a neurona dopaminérgica del bulbo olfatorio de ratón

subject

description

[EN] Dopamine signalling regulates a variety of complex behaviours and defects in dopaminergic neuron function or survival result in severe human pathologies such as Parkinson´s disease. All dopaminergic neurons are characterized by the expression of a battery of genes that code for a set of proteins required for the synthesis, release and re-uptake of dopamine and all together are called the DA pathway genes. Therefore, understanding how this set of genes are transcriptionally activated in a coordinated manner is the first step to discover the clues of dopaminergic terminal differentiation. The dopamine pathway genes are highly conserved throughout evolution. Studies in the nematode C.elegans have shown that three transcription factors, CEH-20 (PBX transcription factor family), AST-1 (ETS transcription factor family) and CEH-43 (Homeodomain transcription factor family) are necessary for the terminal differentiation of DA neurons. These factors act in a coordinated manner to bind the regulatory regions and activate the expression not only of the DA pathway but of most of the mature dopaminergic neuron transcriptome. The dopaminergic system in mammals is distributed in nuclei of the mesencephalon, diencephalon and olfactory bulb. However, in this project we have focused on the olfactory bulb dopaminergic neurons since it is the most ancestral population and also because it requires AST-1 and CEH -43 orthologs (ER81 and DLX2 respectively) for their correct differentiation. Our main interest in this PhD project has therefore been to study whether homologues of CEH-20, the third known factor in the worm, directly participates in the dopaminergic specification of the bulb in higher organisms such as the mouse. In mammals, there are four members in the PBX family: PBX1, PBX2, PBX3 and PBX4. The study of its expression in the bulb, by double immunostaining against tyrosine hydroxylase (DA marker) and PBX factors, determined that both PBX1 (isoform 1a but not 1b) and PBX2 are expressed in neonatal and adult olfactory bulb DA neurons. The same study also revealed that the expression of PBX1a and PBX2 is not exclusive to dopaminergic neurons and other cells of the periglomerular layer as well as in the granular layer (the most internal layer) of the olfactory bulb and other neurons of the brain also express them. Expression analysis of Tyrosine hydroxylase, the rate limiting enzyme for dopamine synthesis, in Pbx1 specific conditional mutants of the dopaminergic lineage, null mutants for Pbx2 and double mutants demonstrate that Pbx1 but not Pbx2 is necessary for the differentiation to dopaminergic neuron of the bulb, both those generated at embryonic stages as well as at adult stages.