Loss ofslc39a14causes simultaneous manganese deficiency and hypersensitivity in zebrafish

Abstract

21 Corresponding authors: 22 k.tuschl@ucl.ac.uk, https://orcid.org/0000-0001-8599-8516 23 emb81@cam.ac.uk, https://orcid.org/0000-0001-6450-744X 24 25 Abbreviated title: slc39a14 deficiency causes Mn dyshomeostasis 26 27 Abstract 30Mutations in SLC39A14, a manganese uptake transporter, lead to a neurodegenerative 31 disorder characterised by accumulation of manganese in the brain and rapidly progressive 32 dystonia-parkinsonism (Hypermanganesemia with Dystonia 2, HMNDYT2). Similar to the 33 human phenotype, zebrafish slc39a14 U801-/mutants show prominent brain manganese 34 accumulation and abnormal locomotor behaviour. In order to identify novel potential targets of 35 manganese neurotoxicity, we performed transcriptome analysis of individual homozygous 36 mutant and sibling slc39a14 U801 zebrafish at five days post fertilisation unexposed and 37 exposed to MnCl2. Anatomical gene enrichment analysis confirmed that differentially 38expressed genes map to the central nervous system and eye. Biological interpretation of 39differentially expressed genes suggests that calcium dyshomeostasis, activation of the 40 unfolded protein response, oxidative stress, mitochondrial dysfunction, lysosomal disruption, 41 apoptosis and autophagy, and interference with proteostasis are key events in manganese 42neurotoxicity. Differential expression of visual phototransduction genes also predicted visual 43 dysfunction in mutant larvae which was confirmed by the absence of visual background 44 adaptation and a diminished optokinetic reflex. Surprisingly, we found a group of differentially 45 expressed genes in mutant larvae that normalised upon MnCl2 treatment suggesting that, in 46 addition to neurotoxicity, manganese deficiency is present either subcellularly or in specific 47 cells or tissues. This may have important implications for treatment as manganese chelation 48 may aggravate neurological symptoms. Our analyses show that slc39a14 U801-/mutant 49 zebrafish present a powerful model to study the cellular and molecular mechanisms underlying 50 disrupted manganese homeostasis. 51 52 Significance statement 53 Manganese neurotoxicity leading to progressive dystonia-parkinsonism is a characteristic 54 feature of Hypermanganesemia with dystonia 2 (HMNDYT2) caused by mutations in 55 SLC39A14, a manganese uptake transporter. Transcriptional profiling in slc39a14 U801 loss-of-56 function zebrafish suggests that, in addition to manganese neurotoxicity, subcellular or cell 57 type specific manganese deficiency contributes to the disease phenotype. Both manganese 58 overload and deficiency appear to be associated with Ca 2+ dyshomeostasis. We further 59 demonstrate that activation of the unfolded protein response, oxidative stress, mitochondrial 60 dysfunction, apoptosis and autophagy, and disrupted proteostasis are likely downstream 61 events in manganese neurotoxicity. Our study shows that the zebrafish slc39a14 U801 loss-of-62 function mutant is a powerful model to elucidate the mechanistic basis of diseases affected by 63 manganese dy...

Molecular Targets of Manganese-Induced Neurotoxicity: A Five-Year Update

“…Microarray and subsequent cluster analysis demonstrated that 1057 differentially-expressed transcripts, being predominantly involved in regulation of neuronal differentiation and development, apoptosis, and synaptic transmission [ 53 ]. Correspondingly, using zebrafish slc39a14 U801-/- mutants exposed to Mn (50 µM for 72 h) for analysis of differentially-expressed genes demonstrated that the genes associated with Mn neurotoxicity are associated with mitochondrial dysfunction, oxidative stress, apoptosis, lysosomal dysfunction, altered proteostasis and unfolded protein response, Ca 2+ dyshomeostasis, as well as impaired visual phototransduction [ 54 ]. In parallel with the identified gene networks differentially expressed following acute Mn exposure (50 mM for 30 min), metal overload was also found to be associated with modulation of endoplasmic reticulum related genes and lipocalin-related (lpr) family members, thus indicating additional targets for Mn toxicity [ 55 ].…”

Proposal for a simplified classification of IMD based on a pathophysiological approach: A practical guide for clinicians

“…This group encompasses IMD of amino acid catabolism-like phenylketonuria, maple syrup urine disease, or homocystinuria-, urea cycle defects, organic aciduriaslike methylmalonic or glutaric aciduria type 1-, galactosemia, and metal accumulation-like Wilson disease, neuroferritinopathies and brain iron accumulation syndromes, or hypermanganesemia linked to SLC30A10 and SLC39A14 mutations. [15][16][17] Some small molecules accumulation may lead to visible crystals in diverse tissues like cystine in cystinosis (a lysosomal defect), oxalate in oxalosis (a peroxysomal defect) or homogentisic acid (ochronosis) in alkaptonuria.…”

Behavioral and Gene Regulatory Responses to Developmental Drug Exposures in Zebrafish

“…Even though this does not correlate with behavioral changes in the larvae, differential expression of these genes might interfere with other circadianregulated biological pathways during development, such as functioning of the reward and immune systems. It is important to note that differential expression of circadian rhythm genes is reported in other zebrafish RNA-seq experiments (156) and so could be a stress response rather than a drug-evoked response. Glucocorticoid release following stress is also found to induce Per2 expression and cause circadian phase delay (157).…”