Fly genetic study related to fatal infantile cardioencephalomyopathy, Leigh syndrome, and Charcot-Marie-Tooth disease,

Sci Rep. 2021 Oct 27;11(1):21207. doi: 10.1038/s41598-021-00663-2.

The function of Scox in glial cells is essential for locomotive ability in Drosophila.

Kowada R, Kodani A, Ida H, Yamaguchi M, Lee IS, Okada Y, Yoshida H

Abstract:

Synthesis of cytochrome c oxidase (Scox) is a Drosophila homolog of human SCO2 encoding a metallochaperone that transports copper to cytochrome c, and is an essential protein for the assembly of cytochrome c oxidase in the mitochondrial respiratory chain complex. SCO2 is highly conserved in a wide variety of species across prokaryotes and eukaryotes, and mutations in SCO2 are known to cause mitochondrial diseases such as fatal infantile cardioencephalomyopathy, Leigh syndrome, and Charcot-Marie-Tooth disease, a neurodegenerative disorder. These diseases have a common symptom of locomotive dysfunction. However, the mechanisms of their pathogenesis remain unknown, and no fundamental medications or therapies have been established for these diseases. In this study, we demonstrated that the glial cell-specific knockdown of Scox perturbs the mitochondrial morphology and function, and locomotive behavior in Drosophila. In addition, the morphology and function of synapses were impaired in the glial cell-specific Scox knockdown. Furthermore, Scox knockdown in ensheathing glia, one type of glial cell in Drosophila, resulted in larval and adult locomotive dysfunction. This study suggests that the impairment of Scox in glial cells in the Drosophila CNS mimics the pathological phenotypes observed by mutations in the SCO2 gene in humans.

DOI: 10.1038/s41598-021-00663-2
PMID: 34707123

Fly model related to FIG-4 associated neurological disorders uncovers potential link to epigenetic regulation

Neuroreport. 2021 May 5;32(7):562-568. doi: 10.1097/WNR.0000000000001636.

Identification of Rpd3 as a novel epigenetic regulator of Drosophila FIG 4, a
Charcot-Marie-Tooth disease-causing gene.

Muraoka Y, Nikaido A, Kowada R, Kimura H, Yamaguchi M, Yoshida H

Abstract:

Mutations in the factor-induced-gene 4 (FIG 4) gene are associated with multiple disorders, including Charcot-Marie-Tooth disease (CMT), epilepsy with polymicrogyria, Yunis-Varón syndrome and amyotrophic lateral sclerosis. The wide spectrum of disorders associated with FIG 4 may be related to the dysregulated epigenetics. Using Gene Expression Omnibus, we found that HDAC1 binds to the FIG 4 gene locus in the genome of human CD4+ T cells. Rpd3 is a well-known Drosophila homolog of human HDAC1. We previously established Drosophila models targeting Drosophila FIG 4 (dFIG 4) that exhibited defective locomotive ability, abnormal synapse morphology at neuromuscular junctions, enlarged vacuoles in the fat body and aberrant compound eye morphology. Genetic crossing experiments followed by physiological and immunocytochemical analyses revealed that Rpd3 mutations suppressed these defects induced by dFIG 4 knockdown. This demonstrated Rpd3 to be an important epigenetic regulator of dFIG 4, suggesting that the inhibition of HDAC1 represses the pathogenesis of FIG 4-associated disorders, including CMT. Defects in epigenetic regulators, such as HDAC1, may also explain the diverse symptoms of FIG 4-associated disorders.

Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.

DOI: 10.1097/WNR.0000000000001636
PMID: 33850086

Review: Drosophila models of neurological diseases including ALS, CMT and Sotos syndrome

Exp Cell Res. 2021 Mar 31:112584. doi: 10.1016/j.yexcr.2021.112584. Online ahead
of print.

Drosophila models to study causative genes for human rare intractable
neurological diseases

Yamaguchi M, Lee IS, Jantrapirom S, Suda K, Yoshida H

Abstract

Drosophila is emerging as a convenient model for investigating human diseases. Functional homologues of almost 75% of human disease-related genes are found in Drosophila. Amyotrophic lateral sclerosis (ALS) is a severe neurodegenerative disease that causes defects in motoneurons. Charcot-Marie-Tooth disease (CMT) is one of the most commonly found inherited neuropathies affecting both motor and  sensory neurons. No effective therapy has been established for either of these diseases. In this review, after overviewing ALS, Drosophila models targeting several ALS-causing genes, including TDP-43, FUS and Ubiquilin2, are described with their genetic interactants. Then, after overviewing CMT, examples of
Drosophila models targeting several CMT-causing genes, including mitochondria-related genes and FIG 4, are also described with their genetic interactants. In addition, we introduce Sotos syndrome caused by mutations in the epigenetic regulator gene NSD1. Lastly, several genes and pathways that commonly interact with ALS- and/or CMT-causing genes are described. In the case of ALS and CMT that have many causative genes, it may be not practical to perform gene therapy for each of the many disease-causing genes. The possible uses of the common genes and pathways as novel diagnosis markers and effective  therapeutic targets are discussed.

Copyright © 2021. Published by Elsevier Inc.

DOI: 10.1016/j.yexcr.2021.112584
PMID: 33812867

Fly studies help provide insights into molecular mechanisms related to Charcot-Marie-Tooth and related disorders

Suda K, Muraoka Y, Ortega-Yáñez A, Yoshida H, Kizu F, Hochin T, Kimura H, Yamaguchi M. Reduction of Rpd3 suppresses defects in locomotive ability and neuronal morphology induced by the knockdown of Drosophila SLC25A46 via an epigenetic pathway. Exp Cell Res. 2019 Dec 15;385(2):111673. PubMed PMID: 31614134.

Abstract: "Mitochondrial dysfunction causes various diseases. Mutations in the SLC25A46 gene have been identified in mitochondrial diseases that are sometimes classified as Charcot-Marie-Tooth disease type 2, optic atrophy, and Leigh syndrome. A homolog of SLC25A46 was identified in Drosophila and designated as dSLC25A46 (CG5755). We previously established mitochondrial disease model targeting of dSLC25A46, which causes locomotive dysfunction and morphological defects at neuromuscular junctions, such as reduced synaptic branch lengths and decreased numbers of boutons. The diverse symptoms of mitochondrial diseases carrying mutations in SLC25A46 may be associated with the dysregulation of some epigenetic regulators. To investigate the involvement of epigenetic regulators in mitochondrial diseases, we examined candidate epigenetic regulators that interact with human SLC25A46 by searching Gene Expression Omnibus (GEO). We discovered that HDAC1 binds to several SLC25A46 genomic regions in human cultured CD4 (+) cells, and attempted to prove this in an in vivo Drosophila model. By demonstrating that Rpd3, Drosophila HDAC1, regulates the histone H4K8 acetylation state in dSLC25A46 genomic regions, we confirmed that Rpd3 is a novel epigenetic regulator modifying the phenotypes observed with the mitochondrial disease model targeting of dSLC25A46. The functional reduction of Rpd3 rescued the deficient locomotive ability and aberrant morphology of motoneurons at presynaptic terminals induced by the dSLC25A46 knockdown. The present results suggest that the inhibition of HDAC1 suppresses the pathogenic processes that lead to the degeneration of motoneurons in mitochondrial diseases."

Flies, folic acid, CMT2A -- and a video abstract

Garrido-Maraver J, Celardo I, Costa AC, Lehmann S, Loh SHY, Martins LM. Enhancing folic acid metabolism suppresses defects associated with loss of Drosophila mitofusin. Cell Death Dis. 2019 Mar 25;10(4):288. PMID: 30911005; PMCID: PMC6433915.

Fly studies relevant to myopathies

Jean S, Cox S, Schmidt EJ, Robinson FL, Kiger A. Sbf/MTMR13 coordinates PI(3)P and Rab21 regulation in endocytic control of cellular remodeling. Mol Biol Cell. 2012 Jul;23(14):2723-40. doi: 10.1091/mbc.E12-05-0375. PubMed PMID: 22648168; PubMed Central PMCID: PMC3395661.

Updated in 2019 to include this 2011 study from the same group:

Ribeiro I, Yuan L, Tanentzapf G, Dowling JJ, Kiger A. Phosphoinositide regulation of integrin trafficking required for muscle attachment and maintenance. PLoS Genet. 2011 Feb 10;7(2):e1001295. PMID: 21347281; PMCID: PMC3037412.

From the abstract: "Muscles must maintain cell compartmentalization when remodeled during development and use. How spatially restricted adhesions are regulated with muscle remodeling is largely unexplored. We show that the myotubularin (mtm) phosphoinositide phosphatase is required for integrin-mediated myofiber attachments in Drosophila melanogaster, and that mtm-depleted myofibers exhibit hallmarks of human XLMTM myopathy. ... Importantly, similar integrin localization defects found in human XLMTM myofibers signify conserved MTM1 function in muscle membrane trafficking. Our results indicate that regulation of distinct phosphoinositide pools plays a central role in maintaining cell compartmentalization and attachments during muscle remodeling, and they suggest involvement of Class II PI3-kinase in MTM-related disease.

Results from a fly genetic screen implicate a long non-coding RNA in Charcot-Marie-Tooth disease

Muraoka Y, Nakamura A, Tanaka R, Suda K, Azuma Y, Kushimura Y, Piccolo LL, Yoshida H, Mizuta I, Tokuda T, Mizuno T, Nakagawa M, Yamaguchi M. Genetic screening of the genes interacting with Drosophila FIG4 identified a novel link between CMT-causing gene and long noncoding RNAs. Exp Neurol. 2018 Aug 27. pii: S0014-4886(18)30377-7. PMID: 30165075.

From the abstract: "Neuron-specific knockdown of the dFIG4 gene, a Drosophila homologue of human FIG4 and one of the causative genes for Charcot-Marie-Tooth disease (CMT), reduces the locomotive abilities of adult flies, as well as causing defects at neuromuscular junctions ... By genetic screening, we detected 9 and 15 chromosomal regions whose deletions either suppressed or enhanced the rough eye phenotype induced by the dFIG4 knockdown. By further genetic screening ... we identified the gene CR18854 that suppressed the rough eye phenotype and the loss-of-cone cell phenotype. The CR18854 gene encodes a long non-coding RNA (lncRNA) consisting of 2566 bases. ... We also obtained data indicating genetic interaction between CR18854 and Cabeza, a Drosophila homologue of human FUS, which is one of the causing genes for amyotrophic lateral sclerosis (ALS). These results suggest that lncRNAs such as CR18854 and hsrω are involved in a common pathway in CMT and ALS pathogenesis."

New fly model of mitochondrial disease associated with disruption of SLC25A46

1: Suda K, Ueoka I, Azuma Y, Muraoka Y, Yoshida H, Yamaguchi M. Novel Drosophila model for mitochondrial diseases by targeting of a solute carrier protein SLC25A46. Brain Res. 2018 Mar 28. pii: S0006-8993(18)30163-X. PMID: 29604258.

From the abstract: "Mutations in SLC25A46 gene have been identified in mitochondrial diseases that are sometimes classified as Charcot-Marie-Tooth disease type 2, optic atrophy and Leigh syndrome. Human SLC25A46 functions as a transporter across the outer mitochondrial membrane. However, it is still unknown how the neurodegeneration occurring in these diseases relates to the loss of SLC25A46 function. Drosophila has CG5755 (dSLC25A46) as a single human SLC25A46 homolog. Here we established pan-neuron specific dSLC25A46 knockdown flies, and examined their phenotypes. ... The dSLC25A46 knockdown fly ... recapitulates most of the phenotypes in mitochondrial disease patients, providing a useful tool to study these diseases."

Report of a "true ortholog" in flies of the human Charcot-Marie-Tooth disease-related gene GDAP1

López Del Amo V, Seco-Cervera M, García-Giménez JL, Whitworth AJ, Pallardó FV, Galindo MI. Mitochondrial defects and neuromuscular degeneration caused by altered expression of Drosophila Gdap1: implications for the Charcot-Marie-Tooth neuropathy. Hum Mol Genet. 2015 Jan 1;24(1):21-36. PMID: 25122658.

From the abstract: "One of the genes involved in Charcot-Marie-Tooth (CMT) disease, an inherited peripheral neuropathy, is GDAP1. In this work, we show that there is a true ortholog of this gene in Drosophila, which we have named Gdap1. By up- and down-regulation of Gdap1 in a tissue-specific manner, we show that altering its levels of expression produces changes in mitochondrial size, morphology and distribution, and neuronal and muscular degeneration. ... Our results contribute to a better understanding of the role of mitochondria in CMT disease and pave the way to generate clinically relevant disease models to study the relationship between mitochondrial dynamics and peripheral neurodegeneration."

Fly studies contribute to study focused on centronuclear myopathy

Chin YH, Lee A, Kan HW, Laiman J, Chuang MC, Hsieh ST, Liu YW. Dynamin-2 mutations associated with centronuclear myopathy are hypermorphic and lead to T-tubule fragmentation. Hum Mol Genet. 2015 Oct 1;24(19):5542-54. PMID: 26199319.

From the abstract: "Skeletal muscle requires adequate membrane trafficking and remodeling to maintain its normal structure and functions. Consequently, many human myopathies are caused by mutations in membrane trafficking machinery. The large GTPase dynamin-2 (Dyn2) is best known for catalyzing membrane fission during clathrin-mediated endocytosis (CME), which is critical for cell signaling and survival. Despite its ubiquitous expression, mutations of Dyn2 are associated with two tissue-specific congenital disorders: centronuclear myopathy (CNM) and Charcot-Marie-Tooth (CMT) neuropathy. Several disease models for CNM-Dyn2 have been established ... . ... we found that the expression of CNM-Dyn2 mutants does not impair CME in myoblast, but leads to T-tubule fragmentation in both C2C12-derived myotubes and Drosophila body wall muscle. Our results demonstrate that CNM-Dyn2 mutants are gain-of-function mutations, and their primary effect in muscle is T-tubule disorganization, which explains the susceptibility of muscle to Dyn2 hyperactivity."

New fly models of FIG4-related diseases including Charcot-Marie-Tooth

Bharadwaj R, Cunningham KM, Zhang K, Lloyd TE. FIG4 regulates lysosome membrane homeostasis independent of phosphatase function. Hum Mol Genet. 2015 Dec 11. pii: ddv505. PMID: 26662798.

From the abstract: "FIG4 is a phosphoinositide phosphatase that is mutated in several diseases including Charcot-Marie-Tooth Disease 4J (CMT4J) and Yunis-Varon syndrome (YVS). To investigate the mechanism of disease pathogenesis, we generated Drosophila models of FIG4-related diseases. Fig4 null mutant animals are viable but exhibit marked enlargement of the lysosomal compartment in muscle cells and neurons, accompanied by an age-related decline in flight ability. Transgenic animals expressing Drosophila Fig4 missense mutations corresponding to human pathogenic mutations can partially rescue lysosomal expansion phenotypes, consistent with these mutations causing decreased FIG4 function. Interestingly, Fig4 mutations predicted to inactivate FIG4 phosphatase activity rescue lysosome expansion phenotypes, and mutations in the phosphoinositide (3) phosphate kinase Fab1 that performs the reverse enzymatic reaction also causes a lysosome expansion phenotype. ... These data show that FIG4 plays a critical noncatalytic function in maintaining lysosomal membrane homeostasis, and that this function is disrupted by mutations that cause CMT4J and YVS."

Translation in fly models of CMT neuropathy

Niehues S, Bussmann J, Steffes G, Erdmann I, Köhrer C, Sun L, Wagner M, Schäfer K, Wang G, Koerdt SN, Stum M, RajBhandary UL, Thomas U, Aberle H, Burgess RW, Yang XL, Dieterich D, Storkebaum E. Impaired protein translation in Drosophila models for Charcot-Marie-Tooth neuropathy caused by mutant tRNA synthetases. Nat Commun. 2015 Jul 3;6:7520. PMID: 26138142.

Genetic modifiers of mutant tRNA synthetases--fly research relevant to Charcot-Marie-Tooth disease

Ermanoska B, Motley WW, Leitão-Gonçalves R, Asselbergh B, Lee LH, De Rijk P, Sleegers K, Ooms T, Godenschwege TA, Timmerman V, Fischbeck KH, Jordanova A. CMT-associated mutations in glycyl- and tyrosyl-tRNA synthetases exhibit similar pattern of toxicity and share common genetic modifiers in Drosophila. Neurobiol Dis. 2014 Aug;68:180-9. PMID: 24807208; PMCID: PMC4086162.

From the abstract: "Aminoacyl-tRNA synthetases are ubiquitously expressed proteins that charge tRNAs with their cognate amino acids. By ensuring the fidelity of protein synthesis, these enzymes are essential for the viability of every cell. Yet, mutations in six tRNA synthetases specifically affect the peripheral nerves and cause Charcot-Marie-Tooth (CMT) disease. ... Our study presents genetic evidence for common mutant-specific interactions between two CMT-associated aminoacyl-tRNA synthetases, lending support for a shared mechanism responsible for the synthetase-induced peripheral neuropathies. "

Human Rab7 mutations in fly

Janssens K, Goethals S, Atkinson D, Ermanoska B, Fransen E, Jordanova A, Auer-Grumbach M, Asselbergh B, Timmerman V. Human Rab7 mutation mimics features of Charcot-Marie-Tooth neuropathy type 2B in Drosophila. Neurobiol Dis. 2014 Feb 9. PMID: 24521780.

Charcot Marie Tooth Syndrome and Atypical Optic Atrophy. Recent report.

Eschenbacher WH, Song M, Chen Y, Bhandari P, Zhao P, Jowdy CC, Engelhard JT, Dorn GW 2nd. Two rare human mitofusin 2 mutations alter mitochondrial dynamics and induce retinal and cardiac pathology in Drosophila. PLoS One. 2012;7(9):e44296. PubMed PMID: 22957060

See also all posts on CMT.

Rab GTPase Gal4 Kit. Breaking Report.

The Gal4 expression 'kit' reported in this paper could be useful not only for studying Rab GTPases but also for Gal4-UAS mediated stage- or tissue-specific expression of other genes or reagents.

Jin EJ, Chan CC, Agi E, Cherry S, Hanacik E, Buszczak M, Hiesinger PR. Similarities of Drosophila rab GTPases Based on Expression Profiling: Completion and Analysis of the rab-Gal4 Kit. PLoS One. 2012;7(7):e40912. Epub 2012 Jul 23. PubMed PMID: 22844416.

According to the introduction of the paper, Rab GTPases or related factors have been implicated in at least the following: Griscelli Syndrome and Hermansky-Pudlak Syndrome, both of which are associated with albinism, as well as Charcot-Marie-Tooth Type 2B Disease, Warburg Micro Syndrome (also known by the abbreviation WARBM and as Warburg Sjo Fledelius Syndrome or simply Micro Syndrome), and X-linked mental retardation.

Related resource: UAS-Rab fly stocks at the BDSC. As described in Zhang J, Schulze KL, Hiesinger PR, Suyama K, Wang S, Fish M, Acar M, Hoskins RA, Bellen HJ, Scott MP. Thirty-one flavors of Drosophila rab proteins. Genetics. 2007 Jun;176(2):1307-22. Epub 2007 Apr 3. PubMed PMID: 17409086; PubMed Central PMCID: PMC1894592.