The Drosophila neural lineages: a model system to study brain development and circuitry

In Drosophila, neurons of the central nervous system are grouped into units called lineages. Each lineage contains cells derived from a single neuroblast. Due to its clonal nature, the Drosophila brain is a valuable model system to study neuron development and circuit formation. To better understand the mechanisms underlying brain development, genetic manipulation tools can be utilized within lineages to visualize, knock down, or over-express proteins. Here, we will introduce the formation and development of lineages, discuss how one can utilize this model system, offer a comprehensive list of known lineages and their respective markers, and then briefly review studies that have utilized Drosophila neural lineages with a look at how this model system can benefit future endeavors

Ubiquitin Ligase HUWE1 Regulates Axon Branching through the Wnt/beta-Catenin Pathway in a Drosophila Model for Intellectual Disability

Contains fulltext : 126190.pdf (publisher's version ) (Open Access)We recently reported that duplication of the E3 ubiquitin ligase HUWE1 results in intellectual disability (ID) in male patients. However, the underlying molecular mechanism remains unknown. We used Drosophila melanogaster as a model to investigate the effect of increased HUWE1 levels on the developing nervous system. Similar to the observed levels in patients we overexpressed the HUWE1 mRNA about 2-fold in the fly. The development of the mushroom body and neuromuscular junctions were not altered, and basal neurotransmission was unaffected. These data are in agreement with normal learning and memory in the courtship conditioning paradigm. However, a disturbed branching phenotype at the axon terminals of the dorsal cluster neurons (DCN) was detected. Interestingly, overexpression of HUWE1 was found to decrease the protein levels of dishevelled (dsh) by 50%. As dsh as well as Fz2 mutant flies showed the same disturbed DCN branching phenotype, and the constitutive active homolog of beta-catenin, armadillo, could partially rescue this phenotype, our data strongly suggest that increased dosage of HUWE1 compromises the Wnt/beta-catenin pathway possibly by enhancing the degradation of dsh

HUWE1 affects DCN axon branching.

<p>(A-C’) Axon projections of the DCN in the optic lobe, visualized via staining against mCD8-GFP. Lo = lobula, Me = Medulla. (A) Representative image of a control brain: w;UAS-mCD8-GFP/+;control^VK31/atoGal4-14a,UAS-LacZ. (A’) Magnification of the branching area in the white square shown in panel A. (B,C) Overexpression of HUWE1 in w;UAS-HUWE1^VK37/UAS-mCD8-GFP;atoGal4-14a,UAS-LacZ/+ and w;UAs-mCD8-GFP/+;UAS-HUWE1^VK31/atoGal4-14a,UAS-LacZ flies does not affect axon number in the medulla, but leads to increased axon branching at the 3^rd branching point. (B’,C’) Magnification of the branching area in the white squares shown in panels B and C. </p

NF-κB is involved in the regulation of CD154 (CD40 ligand) expression in primary human T cells

Cognate interactions between CD154 (CD40 ligand, CD40L) on activated T cells and its receptor CD40 on various antigen-presenting cells are involved in thymus-dependent humoral immune responses and multiple other cell-mediated immune responses. We have studied the regulation of CD154 expression in human T cells after activation with anti-CD3 and anti-CD28 antibodies or after pharmacological activation of protein kinase C with phorbol 12-myristate 13-acetate, and the calcium ionophore ionomycin. Under these conditions, transcription of the CD154 gene was rapidly induced without requiring de novo protein synthesis. Pharmacological inhibitors of NF-κB activation down-regulated CD154 mRNA and protein levels. Cyclosporin A, an inhibitor of NF-AT activation, acted similarly, and the effects of both inhibitors were additive. A potential NF-κB binding site is present within the CD154 promoter at positions −1190 to −1181. In electrophoretic mobility shift assays, this sequence was specifically bound by NF-κB present in nuclear extracts from activated T cells. Furthermore, in transient co-transfection of Jurkat T cells, p65 activated the transcription of a reporter construct containing a multimer of this NF-κB binding site. These observations demonstrate a role of NF-κB transcription factors in the regulation of CD40L expression in activated primary human T cells

The Wnt/β-catenin pathway is involved in the disturbed DCN branching.

<p>(A,B) Reduced dsh levels in w;UAS-dsh-RNAi/UAS-mCD8-GFP;atoGal4-14a,UAS-LacZ/+ and heterozygous null mutant dsh⁶/+;UAS-mCD8-GFP/+;atoGal4-14a,UAS-LacZ/+ animals also led to an increased axon branching at the 3^rd branching point. (C) DCN axon branching is normal in dsh¹;UAS-mCD8-GFP/+;atoGal4-14a,UAS-LacZ/+ males, which are only mutant in the DEP domain responsible for activation of the non-canonical pathway. (D) DCN axon branching is equally affected in dominant negative Fz2;UAS-dn-Fz2/UAS-mCD8-GFP;atoGal4-14a,UAS-LacZ/+ flies. (E) Combined expression of HUWE1 and <i>Arm</i>^<i>ACT</i> in w;UAS-Arm^ACT/UAS-mCD8-GFP;UAS-HUWE1^VK31/atoGal4-14a,UAS-LacZ flies partially rescues the branching phenotype, although the number of branches is not completely reverted to wild-type levels. (F) Expression of a constitutively active <i>Arm</i> mutant in w;UAS-Arm^ACT/UAS-mCD8-GFP;atoGal4-14a,UAS-LacZ/+ animals results in a reduced branching phenotype. (G) Model showing the association of HUWE1 with the Wnt/β-catenin pathway and its effect on axon branching and/or pruning, as evidenced by our data. (H,I) Quantitation of the axon branching levels at the 3^rd branching point of the DCNs in the medulla. We evaluated 20-25 neurons from at least 5 different brains per genotype. Error bars represent standard error of the mean (SEM) (*** p<0.001, ** p<0.01). </p