Assessing similarity to primary tissue and cortical layer identity in induced pluripotent stem cell-derived cortical neurons through single-cell transcriptomics

Adam E Handel,Rory Bowden,Alice Giustacchini,Karene Argoud,Paul Sopp,Jane Vowles,Sally Cowley,Emma Whiteley,Mahito Nakanishi,Tatjana Lalic,Colin Akerman,Satyan Chintawar,Sarah Newey,Chris P Ponting,M Zameel Cader

doi:10.1093/hmg/ddv637

Abstract

Induced pluripotent stem cell (iPSC)-derived cortical neurons potentially present a powerful new model to understand corticogenesis and neurological disease. Previous work has established that differentiation protocols can produce cortical neurons, but little has been done to characterize these at cellular resolution. In particular, it is unclear to what extent in vitro two-dimensional, relatively disordered culture conditions recapitulate the development of in vivo cortical layer identity. Single-cell multiplex reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) was used to interrogate the expression of genes previously implicated in cortical layer or phenotypic identity in individual cells. Totally, 93.6% of single cells derived from iPSCs expressed genes indicative of neuronal identity. High proportions of single neurons derived from iPSCs expressed glutamatergic receptors and synaptic genes. And, 68.4% of iPSC-derived neurons expressing at least one layer marker could be assigned to a laminar identity using canonical cortical layer marker genes. We compared single-cell RNA-seq of our iPSC-derived neurons to available single-cell RNA-seq data from human fetal and adult brain and found that iPSC-derived cortical neurons closely resembled primary fetal brain cells. Unexpectedly, a subpopulation of iPSC-derived neurons co-expressed canonical fetal deep and upper cortical layer markers. However, this appeared to be concordant with data from primary cells. Our results therefore provide reassurance that iPSC-derived cortical neurons are highly similar to primary cortical neurons at the level of single cells but suggest that current layer markers, although effective, may not be able to disambiguate cortical layer identity in all cells.

Highlights

Investigating the cellular basis of neurological diseases, especially those affecting the central nervous system (CNS), is rendered challenging by the inaccessibility of the tissues involved
The development of single-cell gene expression platforms, such as microfluidic chips, as well as evolving chip-free single-cell RNA-seq technologies, make such studies a viable method to investigate Induced pluripotent stem cell (iPSC)-derived cortical neuron cultures at single-cell resolution [9,10]. This has the advantage that the relative abundance of different cell types may be discerned, and so comparisons between iPSC-derived and primary tissues can be made at the level of individual cells
Cells were dissociated into a single-cell suspension, and single cells (178 cells from AH017-3, 153 from AH017-7 and 75 from NHDF1) were sorted into polymerase chain reaction (PCR) plates using fluorescenceactivated cell sorting (FACS) (Supplementary Material, Fig. S2)

Summary

Introduction

Investigating the cellular basis of neurological diseases, especially those affecting the central nervous system (CNS), is rendered challenging by the inaccessibility of the tissues involved. The development of single-cell gene expression platforms, such as microfluidic chips, as well as evolving chip-free single-cell RNA-seq technologies, make such studies a viable method to investigate iPSC-derived cortical neuron cultures at single-cell resolution [9,10]. This has the advantage that the relative abundance of different cell types may be discerned, and so comparisons between iPSC-derived and primary tissues can be made at the level of individual cells

Methods

Results

Conclusion