Human pluripotent stem cells (hPSCs) are a powerful tool for modeling brain development and disease. The human cortex is composed of two major neuronal populations, projection neurons and local interneurons. Cortical interneurons comprise a diverse class of cell types expressing the neurotransmitter GABA. Dysfunction of cortical interneurons has been implicated in neuropsychiatric diseases, including schizophrenia, autism and epilepsy. Here we demonstrate the highly efficient derivation of human cortical interneurons in a NKX2.1::GFP hESC reporter line. Manipulating the timing of SHH activation yields three distinct GFP+ populations with specific transcriptional profiles, neurotransmitter phenotypes and migratory behaviors. Further differentiation in a murine cortical environment yields parvalbumin and somatostatin expressing neurons that exhibit synaptic inputs and electrophysiological properties of cortical interneurons. Our study defines the signals sufficient to model human ventral forebrain development in vitro and lays the foundation for studying cortical interneuron involvement in human disease pathology.

NKX2-5 is expressed in the heart throughout life. We targeted eGFP sequences to the NKX2-5 locus of human embryonic stem cells (hESCs); NKX2-5(eGFP/w) hESCs facilitate quantification of cardiac differentiation, purification of hESC-derived committed cardiac progenitor cells (hESC-CPCs) and cardiomyocytes (hESC-CMs) and the standardization of differentiation protocols. We used NKX2-5 eGFP(+) cells to identify VCAM1 and SIRPA as cell-surface markers expressed in cardiac lineages.

We have used homologous recombination in human embryonic stem cells (hESCs) to insert sequences encoding green fluorescent protein (GFP) into the NKX2

The first step in the generation of genetically tagged human embryonic stem cell (HESC) reporter lines is the isolation of cells that contain a stably integrated copy of the reporter vector. These cells are identified by their continued growth in the presence of a specific selective agent, usually conferred by a cassette encoding antibiotic resistance. In order to mitigate potential interference between the regulatory elements driving expression of the antibiotic resistance gene and those controlling the reporter gene, it is advisable to remove the positive selection cassette once the desired clones have been identified. This report describes a protocol for the removal of loxP-flanked selection cassettes from genetically modified HESCs by transient transfection with a vector expressing Cre recombinase. An integrated procedure for the clonal isolation of these genetically modified lines using single-cell deposition flow cytometry is also detailed. When performed sequentially, these protocols take approximately 1 month.

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