quantifying-drosophila-melanogaster-eye-phenotypes-computational

Quantifying <i>Drosophila melanogaster</i> Eye Phenotypes: A Computational Approach Integrating ilastik and Flynotyper

The Drosophila melanogaster compound eye is a well-structured and comprehensive array of around 800 ommatidia, exhibiting a symmetrical and hexagonal ...

University of Minnesota

Neuronal function depends on the retrograde relay of growth and survival signals from the synaptic terminal, where the neuron interacts with its targets, to the nucleus, where gene transcription is regulated. Activation of the Bone Morphogenetic Protein (BMP) pathway at the Drosophila larval neuromuscular junction results in nuclear accumulation of the phosphorylated form of the transcription factor Mad in the motoneuron nucleus. This in turn regulates transcription of genes that control synaptic growth. How BMP signaling at the synaptic terminal is relayed to the cell body and nucleus of the motoneuron to regulate transcription is unknown. We show that the BMP receptors are endocytosed at the synaptic terminal and transported retrogradely along the axon. Furthermore, this transport is dependent on BMP pathway activity, as it decreases in the absence of ligand or receptors. We further demonstrate that receptor traffic is severely impaired when Dynein motors are inhibited, a condition that has previously been shown to block BMP pathway activation. In contrast to these results, we find no evidence for transport of phosphorylated Mad along the axons, and axonal traffic of Mad is not affected in mutants defective in BMP signaling or retrograde transport. These data support a model in which complexes of activated BMP receptors are actively transported along the axon towards the cell body to relay the synaptogenic signal, and that phosphorylated Mad at the synaptic terminal and cell body represent two distinct molecular populations.

Relay of retrograde synaptogenic signals through axonal transport of BMP receptors.

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10 (CHCHD10) can cause amyotrophic lateral sclerosis and frontotemporal dementia (ALS-FTD). However, the underlying mechanisms are unclear. Here, we generate CHCH10-mutant Drosophila melanogaster and HeLa cell lines to model CHCHD10-associated ALS-FTD. The CHCHD10 mutation results in cell toxicity in several tissues and mitochondrial defects. CHCHD10 independently affects the TDP-43 and PINK1 pathways. CHCHD10 expression increases TDP-43 insolubility and mitochondrial translocation. Blocking TDP-43 mitochondrial translocation with a peptide inhibitor reduced CHCHD10-mediated toxicity. While genetic and pharmacological modulation of PINK1 expression and activity of its substrates rescues and mitigates the CHCHD10-induced phenotypes and mitochondrial defects, respectively, in both Drosophila and HeLa cells. Our findings suggest that CHCHD10-induced TDP-43 mitochondrial translocation and chronic activation of PINK1-mediated pathways result in dominant toxicity, providing a mechanistic insight into the CHCHD10 mutations associated with ALS-FTD.

TDP-43 and PINK1 mediate CHCHD10 mutation-induced defects in Drosophila and in vitro.

Author Correction: TDP-43 and PINK1 mediate CHCHD10 mutation-induced defects in Drosophila and in vitro.

In 2012, Liu et al. reported that miR-34 is an age-related miRNA regulating age-associated events and long-term brain integrity in Drosophila. They demonstrated that modulating miR-34 and its downstream target, Eip74EF, showed beneficial effects on an age-related disease using a Drosophila model of Spinocerebellar ataxia type 3 expressing SCA3trQ78. These results imply that miR-34 could be a general genetic modifier and therapeutic candidate for age-related diseases. Thus, the goal of this study was to examine the effect of miR-34 and Eip47EF on another age-related Drosophila disease model.

Eip74EF is a dominant modifier for ALS-FTD-linked VCP phenotypes in the Drosophila eye model.

Author Correction: Selective modulation of the androgen receptor AF2 domain rescues degeneration in spinal bulbar muscular atrophy.

One of the greatest strengths of Drosophila genetics is its easily observable and selectable phenotypic markers. The mini-white marker has been widely used as a transgenic marker for Drosophila transgenesis. Flies carrying a mini-white construct can exhibit various eye colors ranging from pale orange to intense red, depending on the insertion site and gene dosage. Because the two copies of the mini-white marker show a stronger orange color, this is often used for selecting progenies carrying two transgenes together in a single chromosome after chromosomal recombination. However, some GAL4 lines available in the fly community originally have very strong red eyes. Without employing another marker, such as GFP, generating a recombinant chromosome with the strong red-eyed GAL4 and a desired UAS-transgene construct may be difficult. Therefore, we decided to change the red eyes of GAL4 lines to orange color. To change the eye color of the fly, we tested the CRISPR/Cas9 method with a guide RNA targeting the white gene with OK371-GAL4 and elav-GAL4. After a simple screening, we have successfully obtained multiple lines of orange-eyed OK371-GAL4 and elav-GAL4 that still maintain their original expression patterns. All of these simple experiments were performed by undergraduate students, allowing them to learn about a variety of different genetic experiments and genome editing while contributing to the fly research community by creating fruit fly lines that will be used in real-world research.

Orange maker: a CRISPR/Cas9-mediated genome editing and screening project to generate orange-eyed DarkJedi GAL4 lines by undergraduate students.

Mutations in coiled-coil-helix-coiled-coil-helix domain containing 10 () have been identified as a genetic cause of amyotrophic lateral sclerosis and/or frontotemporal dementia(ALS-FTD). In our previous studies using in vivo  model expressing CHCHD10, and human cell models expressing CHCHD10, we have identified that the PINK1/Parkin pathway is activated and causes cellular toxicity. Furthermore, we demonstrated that pseudo-substrate inhibitors for PINK1 and mitofusin2 agonists mitigated the cellular toxicity of CHCHD10. Evidences using  genetic, and chemical tools indicate that inhibiting PINK1 would be the most promising treatment for CHCHD10-induced diseases.

Article	Year
Relay of retrograde synaptogenic signals through axonal transport of BMP receptors. Journal of cell science\| PubMed ID: 22573823	2012
TDP-43 and PINK1 mediate CHCHD10 mutation-induced defects in Drosophila and in vitro. Nature communications\| PubMed ID: 33772006	2021
Author Correction: TDP-43 and PINK1 mediate CHCHD10 mutation-induced defects in Drosophila and in vitro. Nature communications\| PubMed ID: 34016983	2021
Eip74EF is a dominant modifier for ALS-FTD-linked VCP phenotypes in the Drosophila eye model. BMC research notes\| PubMed ID: 36879317	2023
Author Correction: Selective modulation of the androgen receptor AF2 domain rescues degeneration in spinal bulbar muscular atrophy. Nature medicine\| PubMed ID: 38191617	2024
Orange maker: a CRISPR/Cas9-mediated genome editing and screening project to generate orange-eyed DarkJedi GAL4 lines by undergraduate students. Scientific reports\| PubMed ID: 39138316	2024
FDA-approved PDE4 inhibitors alleviate the dominant toxicity of ALS-FTD-associated CHCHD10S59L by reducing the PINK1/Parkin pathway. Research square\| PubMed ID: 39315251	2024

Nam Chul Kim

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