SUMMARYHuman pluripotent stem cells (hPSCs) have opened new opportunities for understanding human development, modeling disease processes and developing new therapeutics. However, these applications are hindered by low-efficiency and heterogeneity of target cell types differentiated from hPSCs, such as motor neurons (MNs), as well as our inability to maintain the potency of lineage committed progenitors. Here, by using a combination of small molecules that regulate multiple signaling pathways, we develop a method to guide human embryonic stem cells to a near-pure population (>95%) of motor neuron progenitors (MNPs) in 12 days, and an enriched population (>90%) of functionally mature MNs in an additional 16 days. More importantly, the MNPs can be expanded for at least 5 passages so that a single MNP can be amplified to 1×104. This method is reproducible in human induced pluripotent stem cells and is applied to model MNdegenerative diseases and in proof-of-principle drug screening assays.

SUMMARY Amyotrophic lateral sclerosis (ALS) presents motoneuron (MN)-selective protein inclusions and axonal degeneration but the underlying mechanisms of such are unknown. Using induced pluripotent cells (iPSCs) from patients with mutation in the Cu/Zn superoxide dismutase (SOD1)gene, we show that spinal MNs, but rarely non-MNs, exhibited neurofilament (NF) aggregation followed by neurite degeneration when glia were not present. These changes were associated with decreased stability of NF-L mRNA and binding of its 3′ UTR by mutant SOD1 and thus altered protein proportion of NF subunits. Such MN-selective changes were mimicked by expression of a single copy of the mutant SOD1 in human embryonic stem cells and were prevented by genetic correction of the SOD1 mutation in patient’s iPSCs. Importantly, conditional expression of NF-L in the SOD1 iPSC-derived MNs corrected the NF subunit proportion, mitigating NF aggregation and neurite degeneration. Thus, NF misregulation underlies mutant SOD1-mediated NF aggregation and axonal degeneration in ALS MNs.

Summary EPAC proteins are the guanine nucleotide exchange factors that act as the intracellular receptors for cyclic AMP. Two variants of EPAC genes including EPAC1 and EPAC2 are cloned and are widely expressed throughout the brain. But, their functions in the brain remain unknown. Here, we genetically delete EPAC1 (EPAC1-/-), or EPAC2 (EPAC2-/-) or both EPAC1 and EPAC2 genes (EPAC-/-) in the forebrain of mice. We show that EPAC null mutation impairs long-term potentiation (LTP) and that this impairment is paralleled with the severe deficits in spatial learning and social interactions and is mediated in a direct manner by miR-124 transcription and Zif268 translation. Knockdown of miR-124 restores Zif268 and hence reverses all aspects of the EPAC-/- phenotypes, whereas expression of miR-124 or knockdown of Zif268 reproduces the effects of EPAC null mutation. Thus, EPAC proteins control miR-124 transcription in the brain for processing spatial learning and social interactions.

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Despite the critical role of microRNA in inflammatory response, little is known about its function in inflammation-induced Acute Lung Injury (ALI)/Acute Respiratory Distress Syndrome (ARDS). To investigate the potential role of microRNA146a (miR-146a) in ALI, we used lipopolysaccharide (LPS)-induced ALI rat model. Our data revealed that LPS-induced lung injury in rats resulted in significant upregulation of proinflammatory cytokine tumor necrosis factor-alpha (TNF-α), IL-6, IL-1β, and miR-146a expression. LPS treatment also leads to higher expression of miR-146a as well as increase in secretion of TNF-α, IL-6, and IL-1β in alveolar macrophage (AM) NR8383 cells in a time-dependent manner. Manipulation with miR146a mimic significantly suppressed LPS-mediated TNF-α, IL-6, and IL-1β induction in NR8383 cells by repressing expression of IRAK-1 and TRAF-6. These data clearly indicate that the upregulation of miR146a suppresses inflammatory mediators in LPS induced-ALI model. Therefore, miR-146a may be therapeutically targeted as a mean to repress inflammatory response following ALI.

SummaryAstrocytes from familial amyotrophic lateral sclerosis (ALS) patients or transgenic mice are toxic specifically to motor neurons (MNs). It is not known if astrocytes from sporadic ALS (sALS) patients cause MN degeneration in vivo and whether the effect is specific to MNs. By transplanting spinal neural progenitors, derived from sALS and healthy induced pluripotent stem cells (iPSCs), into the cervical spinal cord of adult SCID mice for 9 months, we found that differentiated human astrocytes were present in large areas of the spinal cord, replaced endogenous astrocytes, and contacted neurons to a similar extent. Mice with sALS but not non-ALS cells showed reduced non-MNs numbers followed by MNs in the host spinal cord. The surviving MNs showed reduced inputs from inhibitory neurons and exhibited disorganized neurofilaments and aggregated ubiquitin. Correspondingly, mice with sALS but not non-ALS cells showed declined movement deficits. Thus, sALS iPSC-derived astrocytes cause ALS-like degeneration in both MNs and non-MNs.

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