Erratum: Dendritic spine formation and synapse maturation in transcription factor-induced human iPSC-derived neurons.

[This corrects the article DOI: 10.1016/j.isci.2023.106285.].

Dendritic spine formation and synapse maturation in transcription factor-induced human iPSC-derived neurons.

Synaptic maturation is reportedly limited in human induced pluripotent stem cell (iPSC)-derived neurons. Notably, their ability to reach postnatal-like stages and form dendritic spines has been difficult to demonstrate unless using long-term cultured organoids. Recent transcription factor (TF)-based induction methods allow the accelerated generation of differentiated neurons, which offers an unprecedented opportunity to address further progression into late developmental stages. Herein, we report on a comprehensive time-course study of TF-induced iPSC neurons cultured in vitro through an intrinsic maturation program following neurogenesis. Moreover, we determined the transcriptional and morphological sequences of key developmental events associated with spinogenesis, including the conversion of drebrin to its brain-specific isoform A and the N-methyl-D-aspartate (NMDA) receptor subunit switch. TF-induced iPSC neurons successfully acquired structural and functional synaptic maturity, which will critically expand their utility in modeling higher brain functions and disorders.

Evaluation of the effects of cell-dispensing using an inkjet-based bioprinter on cell integrity by RNA-seq analysis.

Bioprinting technology is expected to be applied in the fields of regenerative medicine and drug discovery. There are several types of bioprinters, especially inkjet-based bioprinter, which can be used not only as a printer for arranging cells but also as a precision cell-dispensing device with controlled cell numbers similar to a fluorescence activated cell sorter (FACS). Precise cell dispensers are expected to be useful in the fields of drug discovery and single-cell analysis. However, there are enduring concerns about the impacts of cell dispensers on cell integrity, particularly on sensitive cells, such as stem cells. In response to the concerns stated above, we developed a stress-free and media-direct-dispensing inkjet bioprinter. In the present study, in addition to conventional viability assessments, we evaluated the gene expression using RNA-seq to investigate whether the developed bioprinter influenced cell integrity in mouse embryonic stem cells. We evaluated the developed bioprinter based on three dispensing methods: manual operation using a micropipette, FACS and the developed inkjet bioprinter. According to the results, the developed inkjet bioprinter exhibited cell-friendly dispensing performance, which was similar to the manual dispensing operation, based not only on cell viability but also on gene expression levels.

Novel Bioprinting Application for the Production of Reference Material Containing a Defined Copy Number of Target DNA.

Nucleic acid amplification methods, such as polymerase chain reaction (PCR), are extensively used in many applications to detect target DNA because of their high sensitivity, good reproducibility, and wide dynamic range of quantification. However, analytical quality control when detecting low copy number target DNA is often missing because of a lack of appropriate reference materials. Recent advances in analytical sciences require a method to accurately quantify DNA at the single molecule level. Herein, we have developed a novel method to produce reference material containing a defined copy number of target DNA (referred to as "cell number-based DNA reference material"). In this method, a suspension of cells carrying a single target DNA sequence was ejected by an inkjet head, and the number of cells in each droplet was counted using highly sensitive cameras. The resulting solutions contained a defined copy number of target DNA and could be used as reference materials. The use of the newly developed reference material was compared with that of diluted solutions of target DNA to evaluate the performance of qualitative real-time PCR in terms of the limit of detection (LOD). Our results demonstrated that cell number-based DNA reference material provides more accurate information regarding performance quality. The reference material produced by this method is a promising tool to evaluate assay performance.