Directly Reprogrammed Human Neurons Retain Aging-Associated Transcriptomic Signatures and Reveal Age-Related Nucleocytoplasmic Defects

Abstract

SUMMARY Aging is a major risk factor for many human diseases, and in vitro generation of human neurons is an attractive approach for modeling aging-related brain disorders. However, modeling aging in differentiated human neurons has proved challenging. We generated neurons from human donors across a broad range of ages, either by iPSC-based reprogramming and differentiation or by direct conversion into induced neurons (iNs). While iPSCs and derived neurons did not retain aging-associated gene signatures, iNs displayed age-specific transcriptional profiles and revealed age-associated decreases in the nuclear transport receptor RanBP17. We detected an age-dependent loss of nucleocytoplasmic compartmentalization (NCC) in donor fibroblasts and corresponding iNs and found that reduced RanBP17 impaired NCC in young cells, while iPSC rejuvenation restored NCC in aged cells. These results show that iNs retain important aging-related signatures, thus allowing modeling of the aging process in vitro, and they identify impaired NCC as an important factor in human aging.

When stem cells grow old: phenotypes and mechanisms of stem cell aging

“…For example reprogramming aged HSCs to a pluripotent state and then differentiating them back to HSCs results in functional rejuvenation (Wahlestedt et al, 2013). Similarly, generating induced pluripotent stem cells (iPSCs) from aged human fibroblasts, and then differentiating them to NSCs generates NSCs with a young phenotype, whereas the direct lineage conversion of aged fibroblasts to NSCs retains the aged phenotype (Mertens et al, 2015). Of course, such reprogramming factors are hardly a fountain of youth because transitioning one's own cells through a pluripotent state is a recipe for cancer, not rejuvenation.…”

Direct neuronal reprogramming: learning from and for development

“…Indeed, this approach has been used for inducing many other neuronal subtypes lost in traumatic injury or neurodegenerative diseases, and generation of which in vitro could be potentially useful for cellbased therapies as well as for disease modelling (Blanchard et al, 2015;Caiazzo et al, 2011;Gascón et al, 2016;Rouaux and Arlotta, 2013;Son et al, 2011;Victor et al, 2014;Wainger et al, 2015). Especially for the latter, direct reprogramming has the advantage of maintaining the age of the starter cell (Mertens et al, 2015), in contrast to the re-setting that occurs when generating induced pluripotent stem cells (Lapasset et al, 2011). In the next section, we will review successful attempts to generate very distinct neuronal subtypes (Fig.…”

New In Vitro Models to Study Amyotrophic Lateral Sclerosis

“…Observations from other neurological disorders, such as Alzheimer's (62) and Parkinson's disease (63), show a similar trend as what we have observed in ALS. A very elegant recent study (64) has provided important information that might explain why iPSC-derived neurons and glia might display mild signs of pathology (39,50,54,47). RNA-Sequencing analysis of fibroblasts, iPSCs, iPSC-derived neurons, neurons reprogrammed directly from fibroblasts (iNeurons) and post-mortem brain tissues revealed that iPSC-derived neurons lose their aging signatures.…”

“…RNA-Sequencing analysis of fibroblasts, iPSCs, iPSC-derived neurons, neurons reprogrammed directly from fibroblasts (iNeurons) and post-mortem brain tissues revealed that iPSC-derived neurons lose their aging signatures. This does not happen in iNeurons and directly converted cells (64). Since ageing is the main risk factors for most neurodegenerative diseases, and in particular ALS, this characteristic might be of high relevance when modeling adult-onset neurodegenerative diseases.…”