Detailed Expression Analysis of Regulatory Genes in the Early Developing Human Neural Tube

Abstract

Studies in model organisms constitute the basis of our understanding of the principal molecular mechanisms of cell fate determination in the developing central nervous system. Considering the emergent applications in stem cell-based regenerative medicine, it is important to demonstrate conservation of subtype specific gene expression programs in human as compared to model vertebrates. We have examined the expression patterns of key regulatory genes in neural progenitor cells and their neuronal and glial descendants in the developing human spinal cord, hindbrain, and midbrain, and compared these with developing mouse and chicken embryos. As anticipated, gene expression patterns are highly conserved between these vertebrate species, but there are also features that appear unique to human development. In particular, we find that neither tyrosine hydroxylase nor Nurr1 are specific markers for mesencephalic dopamine neurons, as these genes also are expressed in other neuronal subtypes in the human ventral midbrain and in human embryonic stem cell cultures directed to differentiate towards a ventral mesencephalic identity. Moreover, somatic motor neurons in the ventral spinal cord appear to be produced by two molecularly distinct ventral progenitor populations in the human, raising the possibility that the acquisition of unique ventral progenitor identities may have contributed to the emergence of neural subtypes in higher vertebrates.

Single cell transcriptional and functional analysis of human dopamine neurons in 3D fetal ventral midbrain organoid like cultures

“…The cells separated into 10 distinct clusters. As expected, the majority of the cells at these early developmental timepoints were RG and FPP, in agreement to what was observed in the study by La Manno et al However, three distinct neuronal subtypes were also detected: DA neurons, OTN neurons, which are formed in VM, and a small population of serotoninergic neurons, known to be located in close proximity to DA neurons during development [22]. Moreover, already at these early developmental stages, DA neurons/progenitors of molecularly distinct identities were present, suggesting an early emergence of molecular sub-identities.…”

V2a interneuron differentiation from mouse and human pluripotent stem cells

“…Comparative studies of mouse and human development have demonstrated that the same transcription factors drive similar phenotypic pattern generation during neural tube formation between the two species 11 . The key signaling molecules that are necessary to induce V2a interneuron differentiation are retinoic acid (RA), a Sonic Hedgehog (Shh) agonist, and a γ-secretase inhibitor to impede Notch signaling.…”

Midbrain Dopaminergic Neuron Development at the Single Cell Level: In vivo and in Stem Cells

“…Additionally, mouse NbM was found to express Nr4a2 (Nurr1) ( Figure 1D), a nuclear receptor required for mDA neuron development (Zetterström et al, 1997). While expression levels of NR4A2 were lower in human NbM, histological analysis of the developing human VM has shown that NR4A2 is present in tyrosine hydroxylase-negative (TH − ) neuroblasts in the floor plate and TH + mDA neurons in the VM (Marklund et al, 2014). The same expression pattern of Nr4a2 can also be seen in histological analysis of the mouse developing midbrain (Villaescusa et al, 2016), indicating that in both the human and mouse VM, NbM differentiate into mDA neurons.…”

“…Furthermore, human mDA neuron development also appears to follow a similar sequence of events to that of murine mDA neuron development. For instance, the human midbrain floor plate is defined by the expression of LMX1A and FOXA2, with the FOXA2 domain extending further laterally into the basal plate (Nelander et al, 2009;Marklund et al, 2014). Moreover, in the VZ of the human floor plate, the pro-neural factor NEUROG2 overlaps with the expression of LMX1A, and in the IZ and MZ, cells expressing key determinants of post-mitotic mDA neurons, NR4A2, PITX3, and TH, can be observed (Nelander et al, 2009).…”