Wednesday, October 14, 2020

Drosophila as a "3Rs" (Replace, Reduce and Refine) model system is emphasized in a study with potential relevance to neurodegenerative disease

Gonçalves-Pimentel C, Mazaud D, Kottler B, Proelss S, Hirth F, Fanto M. A miRNA screen procedure identifies garz as an essential factor in adult glia functions and validates Drosophila as a beneficial 3Rs model to study glial functions and GBF1 biology. F1000Res. 2020 May 1;9:317. doi:
10.12688/f1000research.23154.2. PMID: 32595956; PMCID: PMC7309417.



"Invertebrate glia performs most of the key functions controlled by mammalian glia in the nervous system and provides an ideal model for genetic studies of glial functions. To study the influence of adult glial cells in ageing we have performed a genetic screen in Drosophila using a collection of transgenic lines providing conditional expression of micro-RNAs (miRNAs). Here, we describe a methodological algorithm to identify and rank genes that are candidate to be targeted by miRNAs that shorten lifespan when expressed in adult glia. We have used four different databases for miRNA target prediction in Drosophila but find little agreement between them, overall. However, top candidate gene analysis shows potential to identify essential genes involved in adult glial functions. One example from our top candidates' analysis is gartenzwerg ( garz). We establish that garz is necessary in many glial cell types, that it affects motor behaviour and, at the sub-cellular level, is responsible for defects in cellular membranes, autophagy and mitochondria quality control. We also verify the remarkable conservation of functions between garz and its mammalian orthologue, GBF1, validating the use of Drosophila as an alternative 3Rs-beneficial model to knock-out mice for studying the biology of GBF1, potentially involved in human neurodegenerative diseases."

Establishment of a "multi-species high-throughput platform" to evaluate candidate congential heart disease genes

Theis JL, Vogler G, Missinato MA, Li X, Nielsen T, Zeng XI, Martinez- Fernandez A, Walls SM, Kervadec A, Kezos JN, Birker K, Evans JM, O'Byrne MM, Fogarty ZC, Terzic A, Grossfeld P, Ocorr K, Nelson TJ, Olson TM, Colas AR, Bodmer R. Patient-specific genomics and cross-species functional analysis implicate LRP2 in hypoplastic left heart syndrome. Elife. 2020 Oct 2;9:e59554.
doi: 10.7554/eLife.59554. Epub ahead of print. PMID: 33006316.


From the abstract:

"Congenital heart diseases (CHDs) ... are genetically complex and poorly understood. Here, a multi-disciplinary platform was established to functionally evaluate novel CHD gene candidates, based on whole genome and iPSC RNA sequencing of a HLHS family-trio. ... siRNA/RNAi-mediated knockdown in generic human iPSC-derived cardiomyocytes (hiPSC-CM) and in developing Drosophila and zebrafish hearts revealed that LDL receptor-related protein LRP2 is required for cardiomyocyte proliferation and differentiation. ... Collectively, we have established a multi-species high-throughput platform to rapidly evaluate candidate genes and their interactions during heart development, which are crucial first steps towards deciphering oligogenic underpinnings of CHDs, including maladaptive left hearts."

Tuesday, October 13, 2020

Article discusses potential use of Drosophila in COVID-19 / SARS-CoV-2 related studies

Front Pharmacol. 2020; 11: 588561.

Potential Application of Drosophila melanogaster as a Model Organism in COVID-19-Related Research
Firzan Nainu, Dini Rahmatika, Talha Bin Emran, and Harapan Harapan

Published online 2020 Sep 4. doi: 10.3389/fphar.2020.588561

[No abstract]

PMCID: PMC7500409
PMID: 33013425

Click here to access the article at PubMed Central.

Monday, October 12, 2020

'Humanized' Drosophila Model of Meier-Gorlin Syndrome

Humanized Drosophila Model of the Meier-Gorlin Syndrome Reveals Conserved and Divergent Features of the Orc6 Protein

Maxim Balasov, Katarina Akhmetova and Igor Chesnokov
Genetics Early online October 9, 2020


Meier-Gorlin syndrome (MGS) is a rare autosomal recessive disorder characterized by microtia, primordial dwarfism, small ears and skeletal abnormalities. Patients with MGS often carry mutations in genes encoding the subunits of the Origin Recognition Complex (ORC), components of the pre-replicative complex (pre-RC) and replication machinery. Orc6 is an important component of ORC and has functions in both DNA replication and cytokinesis. A mutation in the conserved C-terminal motif of Orc6 associated with MGS impedes the interaction of Orc6 with core ORC. Recently, a new mutation in Orc6 was also identified however, it is localized in the N-terminal domain of the protein. In order to study the functions of Orc6 we used the human gene to rescue the orc6 deletion in Drosophila. Using this "humanized" Orc6-based Drosophila model of the Meier-Gorlin syndrome we discovered that unlike the previous Y225S MGS mutation in Orc6, the K23E substitution in the N-terminal TFIIB-like domain of Orc6 disrupts the protein ability to bind DNA. Our studies revealed the importance of evolutionarily conserved and variable domains of Orc6 protein and allowed the studies of human protein functions and the analysis of the critical amino acids in live animal heterologous system as well as provided novel insights into the mechanisms underlying MGS pathology.

Wednesday, August 5, 2020

CRISPR editing used to introduce human disease-associated mutation into equivalent gene in flies -- new Friedreich Ataxia fly model

Russi M, Martin E, D'Autréaux B, Tixier L, Tricoire H, Monnier V. A Drosophila model of Friedreich Ataxia with CRISPR/Cas9 insertion of GAA repeats in the frataxin gene reveals in vivo protection by N-acetyl cysteine. Hum Mol Genet. 2020 Aug 3:ddaa170. doi: 10.1093/hmg/ddaa170. Epub ahead of print. PMID: 32744307.

From the abstract:

"Friedreich Ataxia (FA) is caused by GAA repeat expansions in the first intron of FXN, the gene encoding frataxin, which results in decreased gene expression. ... Drosophila melanogaster fruitfly appears as an adequate animal model to study this disease ... Here, we generated a Drosophila model of FA with CRISPR/Cas9 insertion of approximately 200 GAA in the intron of the fly frataxin gene fh. ... We were able to by-pass preadult lethality ... These frataxin-deficient adults are short-lived and present strong locomotor defects. RNA-Seq analysis identified deregulation of genes involved in amino-acid metabolism and transcriptomic signatures of oxidative stress. In particular, we observed a progressive increase of Tspo expression, fully rescued by adult frataxin expression. Thus, Tspo expression constitutes a molecular marker of the disease progression in our fly model and might be of interest in other animal models or in patients. Finally, in a candidate drug screening, we observed that N-acetyl cysteine improved the survival, locomotor function, resistance to oxidative stress and aconitase activity of frataxin-deficient flies. ..."

Tuesday, August 4, 2020

Detailed genetic characterization of a Drosophila fragile X model

Kennedy T, Rinker D, Broadie K. Genetic background mutations drive neural circuit hyperconnectivity in a fragile X syndrome model. BMC Biol. 2020 Jul 30;18(1):94. doi: 10.1186/s12915-020-00817-0. PMID: 32731855.


Background: Neural circuits are initially assembled during development when neurons synapse with potential partners and later refined as appropriate connections stabilize into mature synapses while inappropriate contacts are eliminated. Disruptions to this synaptogenic process impair connectivity optimization and can cause neurodevelopmental disorders. Intellectual disability (ID) and autism spectrum disorder (ASD) are often characterized by synaptic overgrowth, with the maintenance of immature or inappropriate synapses. Such synaptogenic defects can occur through mutation of a single gene, such as fragile X mental retardation protein (FMRP) loss causing the neurodevelopmental disorder fragile X syndrome (FXS). FXS represents the leading heritable cause of ID and ASD, but many other genes that play roles in ID and ASD have yet to be identified.

Results: In a Drosophila FXS disease model, one dfmr150M null mutant stock exhibits previously unreported axonal overgrowths at developmental and mature stages in the giant fiber (GF) escape circuit. These excess axon projections contain both chemical and electrical synapse markers, indicating mixed synaptic connections. Extensive analyses show these supernumerary synapses connect known GF circuit neurons, rather than new, inappropriate partners, indicating hyperconnectivity within the circuit. Despite the striking similarities to well-characterized FXS synaptic defects, this new GF circuit hyperconnectivity phenotype is driven by genetic background mutations in this dfmr150M stock. Similar GF circuit synaptic overgrowth is not observed in independent dfmr1 null alleles. Bulked segregant analysis (BSA) was combined with whole genome sequencing (WGS) to identify the quantitative trait loci (QTL) linked to neural circuit hyperconnectivity. The results reveal 8 QTL associated with inappropriate synapse formation and maintenance in the dfmr150M mutant background.

Conclusions: Synaptogenesis is a complex, precisely orchestrated neurodevelopmental process with a large cohort of gene products coordinating the connectivity, synaptic strength, and excitatory/inhibitory balance between neuronal partners. This work identifies a number of genetic regions that contain mutations disrupting proper synaptogenesis within a particularly well-mapped neural circuit. These QTL regions contain potential new genes involved in synapse formation and refinement. Given the similarity of the synaptic overgrowth phenotype to known ID and ASD inherited conditions, identifying these genes should increase our understanding of these devastating neurodevelopmental disease states.

Results using a fly model of Parkinsons Disease suggests Skp1 is a potential therapeutic target for neurodegenerative diseases

iScience. 2020 Jul 16;23(8):101375. doi: 10.1016/j.isci.2020.101375. Online
ahead of print.

Drosophila Skp1 Homologue SkpA Plays a Neuroprotective Role in Adult Brain.

Dabool L, Hakim-Mishnaevski K, Juravlev L, Flint-Brodsly N, Mandel
S, Kurant E.


Skp1, a component of the ubiquitin E3 ligases, was found to be decreased in the brains of sporadic Parkinson's disease (PD) patients, and its overexpression prevented death of murine neurons in culture. Here we expose the neuroprotective role of the Drosophila skp1 homolog, skpA, in the adult brain. Neuronal knockdown of skpA leads to accumulation of ubiquitinated protein aggregates and loss of dopaminergic neurons accompanied by motor dysfunction and reduced lifespan. Conversely, neuronal overexpression of skpA reduces aggregate load, improves age-related motor decline, and prolongs lifespan. Moreover, SkpA rescues neurodegeneration in a Drosophila model of PD. We also show that a Drosophila homolog of FBXO7, the F Box protein, Nutcracker (Ntc), works in the same pathway with SkpA. However, skpA overexpression rescues ntc knockdown phenotype, suggesting that SkpA interacts with additional F box proteins in the adult brain neurons. Collectively, our study discloses Skp1/SkpA as a potential therapeutic target in neurodegenerative diseases.

DOI: 10.1016/j.isci.2020.101375
PMID: 32739834