Drosophila imaginal disc growth factor 2 is a trophic factor involved in energy balance, detoxification, and innate immunity.

Drosophila imaginal disc growth factor 2 (IDGF2) is a member of chitinase-like protein family (CLPs) able to induce the proliferation of imaginal disc cells in vitro. In this study we characterized physiological concentrations and expression of IDGF2 in vivo as well as its impact on the viability and transcriptional profile of Drosophila cells in vitro. We show that IDGF2 is independent of insulin and protects cells from death caused by serum deprivation, toxicity of xenobiotics or high concentrations of extracellular adenosine (Ado) and deoxyadenosine (dAdo). Transcriptional profiling suggested that such cytoprotection is connected with the induction of genes involved in energy metabolism, detoxification and innate immunity. We also show that IDGF2 is an abundant haemolymph component, which is further induced by injury in larval stages. The highest IDGF2 accumulation was found at garland and pericardial nephrocytes supporting its role in organismal defence and detoxification. Our findings provide evidence that IDGF2 is an important trophic factor promoting cellular and organismal survival.

Characterization of the Drosophila adenosine receptor: the effect of adenosine analogs on cAMP signaling in Drosophila cells and their utility for in vivo experiments.

Adenosine receptors (AR) belonging to the G protein-coupled receptor family influence a wide range of physiological processes. Recent elucidation of the structure of human A2AR revealed the conserved amino acids necessary for contact with the Ado moiety. However, the selectivity of Ado analogs for AR subtypes is still not well understood. We have shown previously that the Drosophila adenosine receptor (DmAdoR) evokes an increase in cAMP and calcium concentration in heterologous cells. In this study, we have characterized the second-messenger stimulation by endogenous DmAdoR in a Drosophila neuroblast cell line and examined a number of Ado analogs for their ability to interact with DmAdoR. We show that Ado can stimulate cAMP but not calcium levels in Drosophila cells. We found one full and four partial DmAdoR agonists, as well as four antagonists. The employment of the full agonist, 2-chloroadenosine, in flies mimicked in vivo the phenotype of DmAdoR over-expression, whereas the antagonist, SCH58261, rescued the flies from the lethality caused by DmAdoR over-expression. Differences in pharmacological effect of the tested analogs between DmAdoR and human A2AR can be partially explained by the dissimilarity of specific key amino acid residues disclosed by the alignment of these receptors.

Differential response of Drosophila cell lines to extracellular adenosine.

Adenosine (Ado) is a crucial metabolite that affects a wide range of physiological processes. Key proteins regulating Ado signaling, transport and metabolism are conserved among vertebrates and invertebrates. It is well known that Ado influences proliferation of several vertebrate and invertebrate cells. Here we show that Ado negatively influences viability, changes morphology and mitochondrial polarity of the Drosophila imaginal disc cell line (Cl.8+) via a mechanism exclusively dependent on cellular Ado uptake. High transport of Ado is followed by phosphorylation and ATP production as a part of Ado salvation, which at higher concentrations may interfere with cellular homeostasis. In contrast, hematopoietic cell line Mbn2, which grows well in high Ado concentration, preferentially uses adenosine deaminase as a part of the purine catabolic pathway. Our results show that different types of Drosophila cell lines use different pathways for Ado conversion and suggest that such differences may be an important part of complex mechanisms maintaining energy homeostasis in the body.

Mouse models of tooth abnormalities.

Tooth number is abnormal in about 20% of the human population. The most common defect is agenesis of the third molars, followed by loss of the lateral incisors and loss of the second premolars. Tooth loss appears as both a feature of multi-organ syndromes and as a non-syndromic isolated character. Apart from tooth number, abnormalities are also observed in tooth size, shape, and structure. Many of the genes that underlie dental defects have been identified, and several mouse models have been created to allow functional studies to understand, in greater detail, the role of particular genes in tooth development. The ability to manipulate the mouse embryo using explant culture and genome targeting provides a wealth of information that ultimately may pave the way for better diagnostics, treatment or even cures for human dental disorders. This review aims to summarize recent knowledge obtained in mouse models, which can be used to gain a better understanding of the molecular basis of human dental abnormalities.