Using neurons made from human stem cells to understand how THC affects the genes linked to neuropsychiatric disorders

Article: THC exposure of human iPSC neurons impacts genes associated with neuropsychiatric disorders

 

Translational Psychiatry volume 8, Article number: 89 (2018)
Doi: 10.1038/s41398-018-0137-3
https://www.nature.com/articles/s41398-018-0137-3?source=post_page

Authors:

Boris Guennewig 1,2,3, Maina Bitar 4, Ifeanyi Obiorah 5,6, James Hanks 5,7,8, Elizabeth A. O’Brien 4, Dominik C. Kaczorowski 3, Yasmin L. Hurd 5,9, Panos Roussos 5,7,8, Kristen J. Brennand 5,6 and Guy Barry 4

Affiliations:

1 Sydney Medical School, Brain and Mind Centre, The University of Sydney,
Camperdown, Sydney, NSW, Australia.
2 St. Vincent’s Clinical School and School of Biotechnology and Biomolecular Sciences, University of New South Wales, Kensington, NSW, Australia.
3 Garvan Institute of Medical Research, Darlinghurst, NSW, Australia.
4 QIMR Berghofer Medical Research Institute, Herston, QLD, Australia.
5 Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY, USA.
6 Department of Neuroscience and Friedman Brain Institute, New York, NY, USA.
7 Department of Genetics and Genomic Science and
Institute for Multiscale Biology, New York, NY, USA.
8 Mental Illness Research, Education, and Clinical Center (VISN 2), James J. Peters VA Medical Center, Bronx, NY, USA.
9 Fishberg Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA

Funders:

K.J.B. is a New York Stem Cell Foundation—Robertson Investigator. The Brennand Laboratory is partially supported by a Brain and Behavior Young Investigator Grant, National Institute of Health (NIH) grant R01 MH101454 and the New York Stem Cell Foundation. The Roussos Laboratory is partially supported by the National Institutes of Health (R01AG050986 Roussos and R01MH109677 Roussos), Brain Behavior Research Foundation (20540 Roussos), Alzheimer’s Association (NIRG- 340998 Roussos) and the Veterans Affairs (Merit grant BX002395 Roussos).

Aim:

THC is the main compound in cannabis that produces its effects. While there have been links between cannabis use and schizophrenia, the reasons behind this relationship are not fully clear.
Other studies which have imaged the brain show how frequent THC exposure can lead to changes in the brain’s neural circuits.
This study hopes to further examine how neurons respond to THC. These neurons have been produced from human induced pluripotent stem cells (hiPSCs).

Terminology:

THC: The psychoactive compound which produces the effects of cannabis
Human induced pluripotent stem cells (hiPSCs): Cells (eg blood or skin) which have had all of their programming removed and can turn into any cell type under specific conditions
Schizophrenia: A disorder that affects the brain and can lead to hallucinations, disorganised behaviour/speech and delusions
Mitochondria: A cellular organelle responsible for making energy
Glutamate: A neurotransmitter chemical that helps send signals between nerves and other cells
Neuron: The functional unit of the brain that helps send electrical signals around the body
Synapse: The space between two neurons which is filled with neurotransmitter by the previous neuron to pass messages forward

Method:

Human induced pluripotent stem cells (hiPSCs) were reprogrammed and produced neurons, followed by treatment with THC to simulate short exposure (1 uM of THC for 24 hours) or chronic exposure (50 nM THC; 5 treatments over 7 days).
How does ‘reprogramming’ work?
The organs/tissues in your body are made up of many cell types such as brain cells, heart cells, muscle cells… and many more. Reprogramming strips cells of their specific identities and reverts them back to a stem-cell-like state. These cells are called induced pluripotent stem cells. This process is similar to restoring your mobile phone to its factory settings and can be achieved in cells by adding transcription factors SOX2, OCT4, KLF-4, cMYC and LIN28 with a lentiviral vector. From here, cells are cultured in a soup of growth media that has ingredients to turn them into your cell type of choice. In this experiment, neurons.
Following this, neurons were then treated with THC. The genetic material (RNA) inside these neurons was then extracted and sequenced to look at gene expression under varying THC conditions. Groups of genes were analysed that have known roles in molecular and biological pathways.

Results:

Compared to controls, almost 500 genes were significantly altered in hiPSC neurons with short exposure to THC. In neurons under chronic THC exposure, roughly 800 genes were impacted. The genes affected in both short and chronic THC conditions were very similar. These genes have roles in neuron electrical signal transmission at synapses (glutamate pathways), ion channels and mitochondrial function.
Some epigenetic changes were also noted, which are accessory changes to the way that genes express without altering the genes themselves. These changes included gene methylation and in chronic THC scenarios, a reduction of histone-modification related proteins and methyl binding proteins.

Conclusion:

THC exposure is linked to gene expression changes within hiPSC neurons. These results are consistent with previous studies that have investigated gene expression from the induced neurons of schizophrenia patients. Additionally, the genes impacted are similar to those involved in other neurological disorders.

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