A) Establishment of cellular fate
Neurogenesis in Drosophila takes place in two distinct developmental periods during embryonic and larval stages. Most neuronal cell lineages of the Central Nervous System (CNS) are produced via two asymmetric divisions. By the first division, each one of the Neuroblasts (NBs) [the Neuronal Stem Cells (NSCs) of Drosophila], generate a “renewed” NB and a short- lived precursor cell, the Ganglion Mother Cell (GMC). Upon the second division, the GMCs generate, primarily asymmetrically, two neurons of different fates or a neuron and a glia. In each of these two asymmetric divisions cell fate decisions are regulated by Delta-Notch dependent cell-cell signalling. In collaboration with Dr. Delidakis group, we have shown that the bHLH-O transcription factor HEY is a transcriptional target of Notch signalling and its effector molecule in GMC asymmetric cell divisions that establish an initial dichotomy in cellular fate within neuronal lineages (“A” type-Notch responsive- versus “B” type neurons). Ongoing research focuses on
a) The transcriptional and post-transcriptional regulation of Hey gene expression in Drosophila nervous system
b) The identification of HEY transcriptional targets
c) The elucidation of Hey expression and function in a non-neuronal Drosophila tissue, the developing and functional midgut
|Expression of Hey gene in developing CNS and midgut primordia||Expression of Hey (RED) in “A” type (vMP2) neurons of the MP2 neuronal lineage (GREEN)|
B) Development of neurochemical specificity
The neurochemical specificity defines a terminal property of each neuron in a mature nervous system. The development of this property relies on complex regulatory cascades and transcription factors (TFs) that establish the temporal and neuron-type specific expression of the key neuropeptides and chemical transmitter biosynthetic enzymes that characterise the terminally differentiated neurons. In relation to this topic, we center our research on the regulation of Tyramine-β hydroxylase (Tβh) gene expression that characterizes the neuronal populations producing the neurotransmitter–neurohormone Octopamine. TBH is a key enzyme in the biosynthesis of Octopamine and through our previous research based on the molecular genetics of Tβh gene we developed tools to manipulate Octopamine metabolism in insects and study the effects in specific physiological processes (i.e female insect reproductive activity, stress). Using bioinformatic tools and immunocytochemical analysis, we now analyse cis regulatory regions of Tβh locus that bear putative binding sites for particular TFs and we investigate their impact on Tbh expression pattern ( in the embryonic ventral nerve cord and in the adult abdominal ganglia neurons that innervate the female reproductive organs).
|TBH-expressing neurons in embryonic CNS midline||TBH-expressing neurons in larval CNS|
C) Exploring Octopamine Neurotransmitter System in insects
The biogenic amine Octopamine is an insect neurotransmitter and neurohormone that combines many of the roles that its functional analogue noradrenaline plays in vertebrate species. Molecular genetic analysis of Drosophila genes that are involved in Octopamine biosynthesis has revealed its requirement in different physiological processes of the fruitfly (appetitive olfactory learning, sleep, female fertility, stress reactivity and others). Our previous work with Octopamine deficient flies had established the absolute requirement of this neurotransmitter in Drosophila female fertility since Octopamine-deficient flies retain their mature eggs and become sterile due to an ovulation defect. We currently study the Octopamine system in insects of agricultural/medical interest (the medfly C. capitata and the malaria vector A. gambiae) and our efforts concentrate on employing modern methods to inactivate the Tβh gene. Our aim is to generate Οctopamine –less insects in order to study the effects of the deficit primarily in the reproductive process and to explore the potential of the system in pest management.