Unit:
Library of the School of Health SciencesΤομέας Βασικών Επιστημών
Dissertation committee:
Σταματάκης Αντώνιος, Αναπληρωτής Καθηγητής, Τμήμα Νοσηλευτικής, ΕΚΠΑ
Ζαγοραίου Λασκαρώ, Ερευνήτρια Γ, ΙΙΒΕΑΑ
Στυλιανοπούλου Φωτεινή, Καθηγήτρια, ΠΑΣΤΕΡ
Ευθυμιόπουλος Σπύρος, Καθηγητής, Τμήμα Βιολογίας, ΕΚΠΑ
Παπαζαφείρη Παναγιώτα, Αναπληρώτρια Καθηγήτρια, Τμήμα Βιολογίας, ΕΚΠΑ
Μάγκουρα Δήμητρα, Ερευνήτρια Α, ΙΙΒΕΑΑ
Πολίτης Παναγιώτης, Ερευνητής, ΙΙΒΕΑΑ
Original Title:
Ο ρόλος των ενδιάμεσων νευρώνων του νωτιαίου μυελού σε κινητικές λειτουργίες: Αναπτυξιακές και λειτουργικές προσεγγίσεις σε πειραματικά μοντέλα μυών
Translated title:
The role of spinal interneurons in locomotion: Developmental and functional approaches in the mouse experimental model
Summary:
One of the most striking features of the Vertebrate Central Nervous System (CNS) is the amazing diversity of its cell types. Identifying the responsible molecular mechanisms for neuronal diversity and understanding how they connect to each other, in order to produce accurate behaviors, still needs further investigation. The present study focused on one small interneuron population in the spinal cord, which is molecularly characterized by the expression of Pitx2 transcription factor. Although small, this population is further subdivided into two subsets: the cholinergic (V0c) and the glutamatergic (V0g). V0c interneurons comprise the source of C bouton synapses (a type of cholinergic synapse) on motor neurons. The primary objective of this work was to study the developmental events that lead to the differentiation of Pitx2+ interneurons from the parental V0 population. By using 5'-bromodeoxyuridine (BrdU) labeling, we determined that Pitx2+ neurons become post-mitotic over a wide period of time and not at a specific time window during the differentiation period of V0 neurons. We also attempted to study whether Notch signaling and Hox factors are involved in the acquisition process of Pitx2+ identity. Inactivation of the Notch signaling pathway was not found to affect the number of Pitx2+ differentiated neurons and probably is not actively involved in their differentiation process. In the experiments of this work, studying the involvement of Hox factors was not feasible. We couldn’t detect any Hox accessory factor in Pitx2+ neurons in order to deactivate it and stop the Hox signaling pathway, to study their role in the differentiation of Pitx2+ neurons.
The second and most important objective of this work was to examine whether Pitx2+ neurons express a second neurotransmitter, other than acetylcholine, in the synapse. Cart neuropeptide had been previously detected in the somata of almost all V0c interneurons (> 95%) and we detected it also in their C bouton synapses on motor neurons, therefore it was recognized as a second neurotransmitter of the V0c neurons. In animals in which cholinergic neurotransmission is inhibited exclusively in V0c neurons, C bouton synapse persists on motor neurons. This was initially surprising, because a non-functional synapse is not expected to survive. The detection of Cart neuropeptide in C boutons of these animals may explain why the synapse survived. Although it contains no acetylcholine, it still contains Cart. In addition, a detailed developmental and functional study of Cart expression was carried out in the C boutons of wild-type animals. The developmental analysis showed that Cart existence in the C bouton synapse is significantly higher during the earlier and later developmental stages analyzed compared to the intermediate ones. This finding points to a possible developmental association of Cart requirement. The functional analysis revealed significantly reduced performance of mice that do not express acetylcholine or Cart in the C bouton synapse in the hanging wire test, a test that measures strength and endurance parameters. In the future, it is important to further analyse the effect of Cart on motor neurons and thus on muscles and motor behavior. Furthermore, it is important to determine whether this effect is similar to the effect of acetylcholine or not.
Main subject category:
Health Sciences
Keywords:
Spinal cord, Interneuron, Locomotion, Acetylcholine, Cart
