Gene Delivery Seminar Series: Modeling Neurodegenerative Disease Risk Using Induced Pluripotent Stem Cells

Understanding the mechanisms underlying neurodegenerative diseases like Alzheimer’s Disease (AD) is a pressing challenge, with 30 million individuals currently affected worldwide—a number expected to rise to 100 million by 2050. Most AD cases are late-onset and linked to genetic risk factors, yet the mechanisms by which these risk genes contribute to disease remain elusive.

During a seminar in VectorBuilder’s Gene Delivery Seminar Series, Dr. Priyanka Narayan, an NIH Stadtman Investigator, shared insights into how induced pluripotent stem cells (iPSCs) are changing our ability to study AD and other neurodegenerative conditions. Her lab’s innovative research focuses on understanding how cellular processes like endocytosis and genetic risk variants interact to drive AD pathology.

The power of induced pluripotent stem cells (iPSCs)

Studying brain cells like neurons and glia directly is challenging due to the limited accessibility of human brain tissue, and some common models, such as cancer cell cultures, fail to capture the complex physiology of brain-specific cell types. However, the ability to reprogram somatic cells into pluripotent stem cells and then specialized cells using transcription factors has revolutionized neuroscience research.

Dr. Narayan’s lab leverages iPSC technology to generate brain cell types such as neurons, astrocytes, and microglia from patient-derived iPSCs. This approach enables researchers to model diseases and study risk genes in controlled environments. The two commonly used methods for generating specialized cells from iPSCs include:

1. Small molecule differentiation – Use of typically synthetic molecules that mimic developmental pathways, including cell cycle regulation.
2. Transcription factor-mediated differentiation – Directed differentiation into a target cell type using lentiviral or piggyBac transposon systems for controlled long-term transcription factor expression.

These advances have facilitated a variety of studies into cell biology and disease pathogenesis, including allowing the Narayan lab to study genetic risk factors by creating isogenic models, introducing or correcting mutations within the same individual’s cells using CRISPR technology.

Endocytosis and Alzheimer’s Disease

One major focus of Dr. Narayan’s work is on endocytosis, a process essential for internalizing extracellular cargo into cells. Disruptions in clathrin-mediated endocytosis, a key pathway involved in endosomal trafficking, have been implicated in AD. The lab’s studies on the APOE gene have provided important insights. APOE is involved in the transport of fats like cholesterol into the brain, and possession of variant 4 (APOE4) is linked to a higher probability of developing AD. A possible mechanism for this is due to disruption of endocytic pathways.

Importantly, Dr. Narayan’s lab used CRISPR edited isogenic cell lines from both late onset AD patients (possessing APOE4) and healthy individuals (possessing APOE3) to study APOE biology. This allowed for direct comparisons of the consequence of variant genotype in both genetic backgrounds without confounding variables. They found that in contrast to APOE4-positive neurons that exhibit increased expression of early endosomal antigen 1 (EEA1, which facilitates endocytic vesicle docking and fusion), astrocytes expressing APOE4 have decreased expression of EEA1 with reduced endosome size and impaired function. 

To alleviate these disruptions, Dr. Narayan explored whether overexpressing PICALM, an endocytic adaptor protein that is also linked to AD, could rescue the defects caused by APOE4. Using lentiviral vectors, she demonstrated that:

1. Overexpression of PICALM restored endocytic processes in astrocytes expressing the APOE4 variant.
2. Interestingly, the same overexpression disrupted normal endocytosis in astrocytes expressing the APOE3 variant, further highlighting the complex interplay between genetic variants.

This work raises other questions about how different endocytic adaptors and pathways might modulate clathrin-mediated endocytosis and interact with other known risk factors.

Partnering with VectorBuilder

The Narayan lab is now following up on these results to understand the mechanisms underlying APOE4-mediated endocytic disruptions and how PICALM may rescue these defects. To enable these investigations, the Narayan lab is partnering with VectorBuilder, leveraging their expertise in viral vector design to streamline experiments and ensure reliable and reproducible results. By offering tailored solutions, VectorBuilder enabled precise control of gene expression using optimized components. The ability to precisely manipulate specialized cell types supported Dr. Narayan’s research objectives in the discovery of novel mechanisms critical to advancing the understanding of neurodegenerative diseases.

Conclusion

Dr. Narayan’s seminar highlighted the application of CRISPR-edited iPSC technology and other advanced gene delivery tools for better understanding of the mechanisms of AD, providing avenues for more successful therapies. By combining patient-derived cellular models with advanced genetic engineering, her team is paving the way for better understanding and therapeutic interventions for neurodegenerative diseases.

You can learn more by watching Dr. Narayan’s seminar here, and as always the VectorBuilder team are on hand to help with all of your gene delivery needs.

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