SfN17: CRISPR and iPSCs – new techniques to study the brain

Written by Martha Powell

Research presented at Society for Neuroscience’s annual meeting, Neuroscience 2017 (11–15 November 2017, Washington DC, USA), has highlighted advances in genetic and cellular techniques that may help to identify novel therapeutic targets for disorders including schizophrenia, Zika infection and addiction.
One of the techniques explored was the gene-editing technology CRISPR-Cas9, which has been used by researchers to investigate the epigenetic mechanisms underlying cocaine addiction in mice. The progression of addiction has previously been closely linked with epigenetic mechanisms in the brain, and an understanding of these may accelerate the development of targeted therapies.

In the study presented, the team repurposed the CRSIPR-Cas9 gene-editing process, developing a novel tool that allowed them to assess the influence of the CREB protein in driving addiction-associated epigenetic changes. Using mouse models, the researchers introduced CREB into neurons in regions of the brain associated with pleasure and reward, discovering that this protein acted as a ‘switch’ for genes that had previously been linked to drug addiction, moreover, CREB introduction caused mice to seek cocaine more frequently.

CRISPR-Cas9 technology was also used to investigate why individuals with 15q13.3 microdeletion syndrome have a higher risk of developing brain disorders such as autism, epilepsy and schizophrenia.

The team used CRISPR-Cas9 to insert OTUD7A, a gene that is absent in 15q13.3 microdeletion but has also been implicated in autism spectrum disorders, into the brain cells of mice missing the 15q13.3 genes. The researchers discovered that the genetically engineered mice were typically underdeveloped compared with controls, however, when OTUD7A was reintroduced the mice appeared to mature at a normal rate, suggesting this gene may be a contributor in 15q13.3 microdeletion-associated brain defects. It is hoped these findings could be used to develop targeted treatments for the syndrome and the technique could help to isolate genes in other genetic neurological conditions.

Another technique highlighted at Neuroscience 2017 was the use of induced pluripotent stem cells (iPSCs). For example, researchers reported the use of these cells to produce neurons containing a genetic mutation that increased schizophrenia risk by ten-times when compared with healthy cells. These findings could present not only a novel model for uncovering the biological causes of schizophrenia but also perhaps a screening tool for new drugs.

Lead author, Changhui Pak (Stanford University, CA, USA) commented: “Using human iPSCs, we were able to generate and analyze neurons from patients with schizophrenia who carry neurexin-1 deletions and compare to those who do not have the disease or the deletion. Examining how these neurons grow, mature, and communicate with one another will shed light on the pathogenesis of this illness.”

In addition, mouse and human iPSCs have also been utilized to build ‘mini-brain’ models, allowing scientists to uncover a protein produced by Zika virus that may cause microcephaly.  The researchers introduced 10 individual proteins generated by Zika into the neural stem cells of a developing mouse brain, discovering that presence of Zika non-structural protein 2A (NS2A) led to reduced proliferation and premature differentiation of the neural cells. The protein was also observed to destabilize adherens junctions between neural cells, affecting cell division.

When the team introduced NS2A to iPSC-based human ‘mini-brains’ grown in 3D culture, they discovered the protein had similar microcephaly-associated effects. Author, Ki-Jun Yoon, who conducted the research during his postdoctoral fellowship at Johns Hopkins University (MD, USA) explained the implications: “These results not only reveal a critical component of Zika virus responsible for microcephaly-related effects, but also illuminate a previously unidentified mechanism for how Zika impacts neural stem cell properties.”

These relatively recent technologies, combined with the novel applications seen in these studies, are facilitating research at a gene-specific level, allowing better understanding of neurological diseases and creating the potential for new therapies.

Source: Society for Neuroscience