Elucidating the role of manganese in brain physiology and disease

i) Background

Manganese (Mn) is an essential trace metal in our diet that is required for normal brain function. However, exposure to high Mn concentrations causes brain damage and a debilitating movement disorder similar to Parkinson's disease. Mn toxicity, also known as manganism, occurs in children and adults upon environmental and occupational overexposure due to contaminated drinking water and drug formulations, industrial fumes or intravenous nutrition, and in patients with liver damage. The recent identification of inherited disorders of Mn transport due to abnormalities in the genes SLC30A10, SLC39A14 and SLC39A8 has further highlighted the important influence Mn has on brain physiology. These disorders lead to impaired control of the body's Mn load, resulting in Mn overload or deficiency, and are associated with detrimental neurodevelopmental disorders of childhood. There is increasing evidence that Mn imbalance is also a feature of common neurodegenerative disorders including Parkinson, Alzheimer and Huntington disease.

Our understanding of how Mn imbalance leads to disease is poor and treatments to alleviate neurological symptoms for the above conditions remain unsatisfactory. Currently available therapies to lower Mn levels are extremely burdensome due to frequent intravenous administration requiring life-long, monthly hospital admissions, venous access related complications and medication side effects. Therefore, there is a great need for research in this field.

ii) Aims of my research

This fellowship intends to establish the role of Mn in normal brain function and to understand how Mn imbalance disturbs the physiological processes within nerve cells. Thereby, my work aims to identify novel therapeutic targets and improve treatments for Mn related disease. This will be accomplished through the study of established and validated genetically modified zebrafish as models for the human Mn transporter disorders. Zebrafish are ideally suited for the study of neurological processes as their nervous system is structurally and chemically similar to that of humans whilst also transparent allowing brain imaging while alive.

First, I will determine which nerve cells are affected by Mn overload and deficiency through analysis of brain activity, anatomy and neuronal function. To better understand the effects of Mn imbalance I will generate cell culture models of the specific neuronal cells targeted by Mn. This will allow me to study the effect of Mn on energy metabolism, free radicals and cellular stress with a view to identifying the key events caused by Mn imbalance.

My previous work has identified a novel Mn binding drug that effectively lowers Mn levels and normalises swimming activity in a zebrafish model of Mn toxicity. This and other compounds will be tested biochemically and in a mouse model of Mn overload in order to develop a suitable paediatric formulation for further preclinical studies beyond this fellowship.

The project will be carried out by myself, a scientist with extensive expertise in Mn and zebrafish research, as well as a postdoctoral researcher with significant experience in mouse laboratory skills. A unique set of collaborators will share world-class expertise on zebrafish and mouse neuroscience, cell biology, paediatric drug development and chemistry ensuring translational relevance.

iii) Expected benefit

This fellowship will provide a better understanding of how Mn imbalance is involved in the disease processes underlying inherited and acquired disorders associated with Mn associated brain damage. This will allow the development of effective treatments to halt disease progression and reduce disability and mortality in children and adults suffering from these disorders. Identification of the role of Mn in neurodegenerative disease processes may also shed new light on the disease mechanisms underlying common neurodegenerative disorders such as Parkinson's disease.

Aim:

My work aims to establish the role of manganese (Mn) in neuronal physiology and disease with the view to identify novel therapeutic targets and treatments for Mn related disorders.

Objectives:

1. Determine how Mn dyshomeostasis impairs brain activity and identify the neuronal subtypes affected by Mn imbalance.
2. Identify key molecular targets underlying Mn dyshomeostasis and elucidate hierarchical interactions between them.
3. Develop a Mn specific chelator with oral bioavailability that can reverse Mn neurotoxicity.

Methodologies:

1. Study of Mn transporter mutant zebrafish (slc39a14-/- and slc39a8-/-) as models of Mn overload and deficiency: Whole-brain neuronal activity, neuroanatomy and neurochemistry mapping, in vivo calcium imaging, retinal immunohistochemistry, LA-ICP-MS, single-cell RNA sequencing and CRISPR/Cas9 genome editing.

2. Subtype-specific neuronal cultures from mutant zebrafish using FAC sorting of transgenic lines: study of the effect of Mn on cell biology (neuronal morphology, cytotoxicity, Mn distribution, Ca2+ homeostasis, oxidative stress, mitochondrial physiology, bulk RNA sequencing). Complementary in vivo analysis of mutant zebrafish using fluorescent probes, transgenic lines, and pathway inhibitors to assess their effect on the locomotor phenotype.

3. Preformulation studies of Mn chelators and prodrugs to design clinically relevant formulations. Neuropathological and behavioural characterisation of Slc30a10-/- mice to develop phenotypic readouts of Mn neurotoxicity and assessing the effects of compounds with suitable physiochemical and biopharmaceutical properties on neurological markers.

Scientific and medical opportunities:

This work will provide a clear understanding of the effects of Mn dyshomeostasis on key neuronal functions and its role in disease processes. The data on novel Mn ligands will be essential for the translation into preclinical studies and clinical trials.