How to make spinal motor neurons

Abstract

All muscle movements, including breathing, walking, and fine motor skills rely on the function of the spinal motor neuron to transmit signals from the brain to individual muscle groups. Loss of spinal motor neuron function underlies several neurological disorders for which treatment has been hampered by the inability to obtain sufficient quantities of primary motor neurons to perform mechanistic studies or drug screens. Progress towards overcoming this challenge has been achieved through the synthesis of developmental biology paradigms and advances in stem cell and reprogramming technology, which allow the production of motor neurons in vitro. In this Primer, we discuss how the logic of spinal motor neuron development has been applied to allow generation of motor neurons either from pluripotent stem cells by directed differentiation and transcriptional programming, or from somatic cells by direct lineage conversion. Finally, we discuss methods to evaluate the molecular and functional properties of motor neurons generated through each of these techniques.

Signals from the surface modulate differentiation of human pluripotent stem cells through glycosaminoglycans and integrins

“…1G). This efficiency is consistent with previous protocols for motor neuron differentiation that use complex substrata (31). These results demonstrate that our modular approach can yield chemically defined substrates that are as effective for motor neuron differentiation as Matrigel.…”

“…Cells were subjected to dual SMAD inhibition for 6 d to produce neural progenitors, and then for 6 d using small molecule inhibitors of the Notch (DAPT) and FGF (SU 5402) pathways. Retinoic acid and a small molecule smoothened agonist (SAG) were included throughout for posterior and ventral patterning of the neurons (31). As expected, cells cultured on the GAG-binding peptide surface clustered and many detached, but surfaces displaying both GBP and cRGD were as effective for differentiation as Matrigel (Fig.…”

Glia-specific enhancers and chromatin structure regulate NFIA expression and glioma tumorigenesis

“…While expression and function of NFIA in glial progenitors has been well-studied, its role in motor neurons has remained undefined. Our studies reveal that key regulators of motor neuron development, Isl1/Lhx3 directly regulate NFIA expression, suggesting that NFIA may participate in the well-described transcriptional networks regulating motor neuron development and physiology 44 . While motor neurons do not demonstrate any overt developmental defects in the absence of NFIA (not shown), additional genetic, biochemical, physiological analysis in these populations will be required to explore this in more detail.…”

The roles and regulation of Polycomb complexes in neural development

“…The ventral region of the spinal neural tube is colonized by a progenitor population that will give rise to diverse subtypes of neurons, including motor neurons (MN). Spinal motor neuron progenitors are grouped into columns on the basis of their rosto-caudal location along the neuraxis, which is established by the expression of region-specific Hox transcription factors (Philippidou and Dasen 2013, Davis-Dusenbery, Williams et al 2014). MN columns are comprised of sets of MNs arranged longitudinally along the rostro-caudal axis of the spinal cord, and neurons of each column project to distinct regions in the periphery.…”

“…First, extracellular signals secreted from the adjacent rostral somitic mesoderm and caudal presomitic mesoderm create opposing morphogen gradients that establish broad territories of Hox gene expression in proliferating spinal progenitors (Philippidou and Dasen 2013, Davis-Dusenbery, Williams et al 2014). After spinal progenitors undergo their final mitosis, the boundaries of posterior Hox domains are further refined by cross-repressive interactions between the transcriptional programs originally induced by the various extracellular signals, a process that is required to sharpen and maintain expression borders.…”