RESUMO
Progressive degeneration of motor neurons (MNs) is the hallmark of amyotrophic lateral sclerosis (ALS). Limb-innervating lateral motor column MNs (LMC-MNs) seem to be particularly vulnerable and are among the first MNs affected in ALS. Here, we report association of this differential susceptibility with reduced expression of the mir-17â¼92 cluster in LMC-MNs prior to disease onset. Reduced mir-17â¼92 is accompanied by elevated nuclear PTEN in spinal MNs of presymptomatic SOD1G93A mice. Selective dysregulation of the mir-17â¼92/nuclear PTEN axis in degenerating SOD1G93A LMC-MNs was confirmed in a double-transgenic embryonic stem cell system and recapitulated in human SOD1+/L144F-induced pluripotent stem cell (iPSC)-derived MNs. We further show that overexpression of mir-17â¼92 significantly rescues human SOD1+/L144F MNs, and intrathecal delivery of adeno-associated virus (AAV)9-mir-17â¼92 improves motor deficits and survival in SOD1G93A mice. Thus, mir-17â¼92 may have value as a prognostic marker of MN degeneration and is a candidate therapeutic target in SOD1-linked ALS. VIDEO ABSTRACT.
Assuntos
Esclerose Lateral Amiotrófica/genética , Proteínas de Membrana/metabolismo , MicroRNAs/genética , Neurônios Motores/fisiologia , PTEN Fosfo-Hidrolase/metabolismo , Adenoviridae , Animais , Linhagem Celular Tumoral , Extremidades/inervação , Humanos , Células-Tronco Pluripotentes Induzidas , Injeções Espinhais , Proteínas de Membrana/genética , Camundongos , Mutação/genética , Neuroproteção , PTEN Fosfo-Hidrolase/genética , RNA Longo não Codificante , Superóxido Dismutase-1/genéticaRESUMO
The mammalian imprinted Dlk1-Dio3 locus produces multiple long non-coding RNAs (lncRNAs) from the maternally inherited allele, including Meg3 (i.e., Gtl2) in the mammalian genome. Although this locus has well-characterized functions in stem cell and tumor contexts, its role during neural development is unknown. By profiling cell types at each stage of embryonic stem cell-derived motor neurons (ESC~MNs) that recapitulate spinal cord development, we uncovered that lncRNAs expressed from the Dlk1-Dio3 locus are predominantly and gradually enriched in rostral motor neurons (MNs). Mechanistically, Meg3 and other Dlk1-Dio3 locus-derived lncRNAs facilitate Ezh2/Jarid2 interactions. Loss of these lncRNAs compromises the H3K27me3 landscape, leading to aberrant expression of progenitor and caudal Hox genes in postmitotic MNs. Our data thus illustrate that these lncRNAs in the Dlk1-Dio3 locus, particularly Meg3, play a critical role in maintaining postmitotic MN cell fate by repressing progenitor genes and they shape MN subtype identity by regulating Hox genes.
When a gene is active, its DNA sequence is 'transcribed' to form a molecule of RNA. Many of these RNAs act as templates for making proteins. But for some genes, the protein molecules are not their final destinations. Their RNA molecules instead help to control gene activity, which can alter the behaviour or the identity of a cell. For example, experiments performed in individual cells suggest that so-called long non-coding RNAs (or lncRNAs for short) guide how stem cells develop into different types of mature cells. However, it is not clear whether lncRNAs play the same critical role in embryos.Yen et al. used embryonic stem cells to model how motor neurons develop in the spinal cord of mouse embryos. This revealed that motor neurons produce large amounts of a specific group of lncRNAs, particularly one called Meg3. Further experiments showed that motor neurons in mouse embryos that lack Meg3 do not correctly silence a set of genes called the Hox genes, which are crucial for laying out the body plans of many different animal embryos. These neurons also incorrectly continue to express genes that are normally active in an early phase of the stem-like cells that make motor neurons.There is wide interest in how lncRNAs help to regulate embryonic development. With this new knowledge of how Meg3 regulates the activity of Hox genes in motor neurons, research could now be directed toward investigating whether lncRNAs help other tissues to develop in a similar way.
Assuntos
Linhagem da Célula , Loci Gênicos , Peptídeos e Proteínas de Sinalização Intercelular/genética , Iodeto Peroxidase/genética , Mitose , Neurônios Motores/citologia , Neurônios Motores/metabolismo , RNA Longo não Codificante/metabolismo , Animais , Sequência de Bases , Proteínas de Ligação ao Cálcio , Diferenciação Celular/genética , Linhagem da Célula/genética , Núcleo Celular/metabolismo , Vértebras Cervicais/inervação , Embrião de Mamíferos/metabolismo , Epigênese Genética , Regulação da Expressão Gênica no Desenvolvimento , Impressão Genômica , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Camundongos , Mitose/genética , Mutação/genética , Fenótipo , RNA Longo não Codificante/genéticaRESUMO
Motor neurons (MNs) are unique because they project their axons outside of the CNS to innervate the peripheral muscles. Limb-innervating lateral motor column MNs (LMC-MNs) travel substantially to innervate distal limb mesenchyme. How LMC-MNs fine-tune the balance between survival and apoptosis while wiring the sensorimotor circuit en route remains unclear. Here, we show that the mir-17â¼92 cluster is enriched in embryonic stem cell (ESC)-derived LMC-MNs and that conditional mir-17â¼92 deletion in MNs results in the death of LMC-MNs in vitro and in vivo. mir-17â¼92 overexpression rescues MNs from apoptosis, which occurs spontaneously during embryonic development. PTEN is a primary target of mir-17â¼92 responsible for LMC-MN degeneration. Additionally, mir-17â¼92 directly targets components of E3 ubiquitin ligases, affecting PTEN subcellular localization through monoubiquitination. This miRNA-mediated regulation modulates both target expression and target subcellular localization, providing LMC-MNs with an intricate defensive mechanism that controls their survival.