Identification of Targets from LRRK2 Rescue Phenotypes.

Parkinson's disease (PD) is an age-dependent neurodegenerative condition. Leucine-rich repeat kinase 2 (LRRK2) mutations are the most frequent cause of sporadic and autosomal dominant PD. The exact role of LRRK2 protective variants (R1398H, N551K) together with a pathogenic mutant (G2019S) in aging and neurodegeneration is unknown. We generated the following myc-tagged UAS-LRRK2 transgenic Drosophila: LRRK2 (WT), N551K, R1398H, G2019S single allele, and double-mutants (N551K/G2019S or R1398H/G2019S). The protective variants alone were able to suppress the phenotypic effects caused by the pathogenic LRRK2 mutation. Next, we conducted RNA-sequencing using mRNA isolated from dopaminergic neurons of these different groups of transgenic Drosophila. Using pathway enrichment analysis, we identified the top 10 modules (p < 0.05), with "LRRK2 in neurons in Parkinson's disease" among the candidates. Further dissection of this pathway identified the most significantly modulated gene nodes such as eEF1A2, ACTB, eEF1A, and actin cytoskeleton reorganization. The induction of the pathway was successfully restored by the R1398H protective variant and R1398H-G2019S or N551K-G2019S rescue experiments. The oxidoreductase family of genes was also active in the pathogenic mutant and restored in protective and rescue variants. In summary, we provide in vivo evidence supporting the neuroprotective effects of LRRK2 variants. RNA sequencing of dopaminergic neurons identified upregulation of specific gene pathways in the Drosophila carrying the pathogenic variant, and this was restored in the rescue phenotypes. Using protective gene variants, our study identifies potential new targets and provides proof of principle of a new therapeutic approach that will further our understanding of aging and neurodegeneration in PD.

Chetomin rescues pathogenic phenotype of LRRK2 mutation in drosophila.

Leucine-rich repeat kinase 2 (LRRK2) is a complex protein kinase involved in a diverse set of functions. Mutations in LRRK2 are a common cause of autosomal dominant familial Parkinson's disease. Peroxiredoxin 2 (PRDX2) belongs to a family of anti-oxidants that protect cells from oxidative stress. Importantly, PRDX2 is a cytoplasmic protein, similar to Leucine-rich repeat kinase 2, which localizes predominantly in the cytosol. Here, we demonstrated that Leurice-rich repeat kinase 2 phosphorylates PRDX2 in Drosophila, leading to a loss of dopaminergic neurons, climbing ability and shortened lifespan. These pathogenic phenotypes in the LRRK2 Drosophila were rescued with transgenic expression of PRDX2. Chetomin, a PRDX2 mimic, belongs to a class of epidithio-diketopiperazine fungal secondary metabolites (containing a dithiol group that has hydrogen peroxide-reducing activity). As proof of principle, we demonstrated that Chetomin recapitulated the rescue in these mutant Drosophila. Our findings suggest that Chetomin can be a potential therapeutic compound in LRRK2 linked Parkinson's disease.

Medical social work positions: BSW or MSW?

Acute care social work positions face budgetary scrutiny in the current climate of fiscal restraint in Canadian health care. Managers may be faced with the question of whether a new or vacant medical social work position should be filled by a BSW social worker or an MSW social worker. This question is further complicated when experienced and less costly BSW social workers are available while MSW social workers with medical or hospital experience may be limited in supply. This paper reviews the literature relevant to medical social work practice and hiring. A small scale survey was conducted with inter-professional managers responsible for the hiring of medical social workers. The purpose of this research was to examine the current hiring practices and considerations for hospital medical social workers.

In vivo evidence of pathogenicity of VPS35 mutations in the Drosophila.

Mutations of VPS35, a component of the retromer complex have been associated with late onset familial Parkinson's disease. The D620N mutation in VPS35 appears to be most prevalent, however, P316S was found in two cases within the same family and a control, whereas L774M was identified in 6 cases and 1 control. In vivo evidence of their pathogenicity is lacking. Here we investigated the in vivo effects of P316S, D620N and L774M using Drosophila as a model. We generated transgenic human VPS35-expressing mutations and demonstrated that VPS35 D620N transgenic flies led to late-onset loss of TH-positive DA neurons, poor mobility, shortened lifespans and increased sensitivity to rotenone, a PD-linked environmental toxin, with some of these phenotypes observed for P316S but not in L774M transgenic flies. We conclude that D620N and to a smaller extent P316S are associated with pathogenicity in PD.

Asymmetric cell division and Notch signaling specify dopaminergic neurons in Drosophila.

In Drosophila, dopaminergic (DA) neurons can be found from mid embryonic stages of development till adulthood. Despite their functional involvement in learning and memory, not much is known about the developmental as well as molecular mechanisms involved in the events of DA neuronal specification, differentiation and maturation. In this report we demonstrate that most larval DA neurons are generated during embryonic development. Furthermore, we show that loss of function (l-o-f) mutations of genes of the apical complex proteins in the asymmetric cell division (ACD) machinery, such as inscuteable and bazooka result in supernumerary DA neurons, whereas l-o-f mutations of genes of the basal complex proteins such as numb result in loss or reduction of DA neurons. In addition, when Notch signaling is reduced or abolished, additional DA neurons are formed and conversely, when Notch signaling is activated, less DA neurons are generated. Our data demonstrate that both ACD and Notch signaling are crucial mechanisms for DA neuronal specification. We propose a model in which ACD results in differential Notch activation in direct siblings and in this context Notch acts as a repressor for DA neuronal specification in the sibling that receives active Notch signaling. Our study provides the first link of ACD and Notch signaling in the specification of a neurotransmitter phenotype in Drosophila. Given the high degree of conservation between Drosophila and vertebrate systems, this study could be of significance to mechanisms of DA neuronal differentiation not limited to flies.

On the roles of Notch, Delta, kuzbanian, and inscuteable during the development of Drosophila embryonic neuroblast lineages.

The generation of cellular diversity in the nervous system involves the mechanism of asymmetric cell division. Besides an array of molecules, including the Par protein cassette, a heterotrimeric G protein signalling complex, Inscuteable plays a major role in controlling asymmetric cell division, which ultimately leads to differential activation of the Notch signalling pathway and correct specification of the two daughter cells. In this context, Notch is required to be active in one sibling and inactive in the other. Here, we investigated the requirement of genes previously known to play key roles in sibling cell fate specification such as members of the Notch signalling pathway, e.g., Notch (N), Delta (Dl), and kuzbanian (kuz) and a crucial regulator of asymmetric cell division, inscuteable (insc) throughout lineage progression of 4 neuroblasts (NB1-1, MP2, NB4-2, and NB7-1). Notch-mediated cell fate specification defects were cell-autonomous and were observed in all neuroblast lineages even in cells born from late ganglion mother cells (GMC) within the lineages. We also show that Dl functions non-autonomously during NB lineage progression and clonal cells do not require Dl from within the clone. This suggests that within a NB lineage Dl is dispensable for sibling cell fate specification. Furthermore, we provide evidence that kuz is involved in sibling cell fate specification in the central nervous system. It is cell-autonomously required in the same postmitotic cells which also depend on Notch function. This indicates that KUZ is required to facilitate a functional Notch signal in the Notch-dependent cell for correct cell fate specification. Finally, we show that three neuroblast lineages (NB1-1, NB4-2, and NB7-1) require insc function for sibling cell fate specification in cells born from early GMCs whereas insc is not required in cells born from later GMCs of the same lineages. Thus, there is differential requirement for insc for cell fate specification depending on the stage of lineage progression of NBs.