Tumor suppressor let-7 acts as a key regulator for pluripotency gene expression in Muse cells.

In embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), the expression of an RNA-binding pluripotency-relevant protein, LIN28, and the absence of its antagonist, the tumor-suppressor microRNA (miRNA) let-7, play a key role in maintaining pluripotency. Muse cells are non-tumorigenic pluripotent-like stem cells residing in the bone marrow, peripheral blood, and organ connective tissues as pluripotent surface marker SSEA-3(+). They express pluripotency genes, differentiate into triploblastic-lineage cells, and self-renew at the single cell level. Muse cells do not express LIN28 but do express let-7 at higher levels than in iPSCs. In Muse cells, we demonstrated that let-7 inhibited the PI3K-AKT pathway, leading to sustainable expression of the key pluripotency regulator KLF4 as well as its downstream genes, POU5F1, SOX2, and NANOG. Let-7 also suppressed proliferation and glycolysis by inhibiting the PI3K-AKT pathway, suggesting its involvement in non-tumorigenicity. Furthermore, the MEK/ERK pathway is not controlled by let-7 and may have a pivotal role in maintaining self-renewal and suppression of senescence. The system found in Muse cells, in which the tumor suppressor let-7, but not LIN28, tunes the expression of pluripotency genes, might be a rational cell system conferring both pluripotency-like properties and a low risk for tumorigenicity.

OLIG2 is an in vivo bookmarking transcription factor in the developing neural tube in mouse.

Cells possess intrinsic features that are inheritable via epigenetic regulation, such as DNA methylation and histone modification. These inheritable features maintain a unique gene expression pattern, underlying cellular memory. Because of the degradation or displacement of mitotic chromosomes, most transcription factors do not contribute to cellular memory. However, accumulating in vitro evidence indicates that some transcription factors can be retained in mitotic chromosomes called as bookmarking. Such transcription factors may contribute to a novel third mechanism of cellular memory. Since most findings of transcription factor bookmarking have been reported in vitro, little is currently known in vivo. In the neural tube of mouse embryos, we discovered that OLIG2, a basic helix loop helix (bHLH) transcription factor that regulates proliferation of neural progenitors and the cell fate of motoneurons and oligodendrocytes, binds to chromatin through every cell cycle including M-phase. OLIG2 chromosomal localization coincides with mitotic cell features such as the phosphorylation of histone H3, KI67, and nuclear membrane breakdown. Chromosomal localization of OLIG2 is regulated by an N-terminus triple serine motif. Photobleaching analysis revealed slow OLIG2 mobility, suggesting a high affinity of OLIG2 to DNA. In Olig2 N-terminal deletion mutant mice, motoneurons and oligodendrocyte progenitor numbers are reduced in the neural tube, suggesting that the bookmarking regulatory domain is important for OLIG2 function. We conclude that OLIG2 is a de novo in vivo bookmarking transcription factor. Our results demonstrate the presence of in vivo bookmarking in a living organism and illustrate a novel function of transcription factors.

Sulfatide with ceramide composed of phytosphingosine (t18:0) and 2-hydroxy FAs in renal intercalated cells.

Diverse molecular species of sulfatide with differences in FA lengths, unsaturation degrees, and hydroxylation statuses are expressed in the kidneys. However, the physiological functions of specific sulfatide species in the kidneys are unclear. Here, we evaluated the distribution of specific sulfatide species in the kidneys and their physiological functions. Electron microscopic analysis of kidneys of Cst-deficient mice lacking sulfatide showed vacuolar accumulation in the cytoplasm of intercalated cells in the collecting duct, whereas the proximal and distal tubules were unchanged. Immunohistochemical analysis revealed that vacuolar H+-ATPase-positive vesicles were accumulated in intercalated cells in sulfatide-deficient kidneys. Seventeen sulfatide species were detected in the murine kidney by iMScope MALDI-MS analysis. The distribution of the specific sulfatide species was classified into four patterns. Although most sulfatide species were highly expressed in the outer medullary layer, two unique sulfatide species of m/z 896.6 (predicted ceramide structure: t18:0-C22:0h) and m/z 924.6 (predicted ceramide structure: t18:0-C24:0h) were dispersed along the collecting duct, implying expression in intercalated cells. In addition, the intercalated cell-enriched fraction was purified by fluorescence-activated cell sorting using the anti-vacuolar H+-ATPase subunit 6V0A4, which predominantly contained sulfatide species (m/z 896.6 and 924.6). The Degs2 and Fa2h genes, which are responsible for ceramide hydroxylation, were expressed in the purified intercalated cells. These results suggested that sulfatide molecular species with ceramide composed of phytosphingosine (t18:0) and 2-hydroxy FAs, which were characteristically expressed in intercalated cells, were involved in the excretion of NH3 and protons into the urine.

Establishment of neural stem cell culture from the central nervous system of the Iberian ribbed newt Pleurodeles waltl.

Urodele amphibians have exceptional regeneration ability in various organs. Among these, the Iberian ribbed newt (Pleurodeles waltl) has emerged as a useful model organism for investigating the mechanisms underlying regeneration. Neural stem cells (NSCs) are an important source of regeneration in the central nervous system (CNS) and their culture method in vitro has been well established. NSCs form spherical cell aggregates called neurospheres and their formation has been demonstrated in various vertebrates, including some urodele species, but not in P. waltl. In this study, we reported neurosphere formation in brain- and spinal cord-derived cells of post-metamorphic P. waltl. These neurospheres showed proliferative activity and similar expression of marker proteins. However, the surface morphology was found to vary according to their origin, implying that the characteristics of the neurospheres generated from the brain and spinal cord could be similar but not identical. Subsequent in vitro differentiation analysis demonstrated that spinal cord-derived neurospheres gave rise to neurons and glial cells. We also found that cells in neurospheres from P. waltl differentiated to oligodendrocytes, whereas those from axolotls were reported not to differentiate to this cell type under standard culture conditions. Based on our findings, implantation of genetically modified neurospheres together with associated technical advantages in P. waltl could reveal pivotal gene(s) and/or signaling pathway(s) essential for the complete spinal cord regeneration ability in the future.

The transcription factor HAND2 up-regulates transcription of the IL15 gene in human endometrial stromal cells.

Cyclic changes of the human endometrium, such as proliferation, secretion, and decidualization, occur during regular menstrual cycles. Heart- and neural crest derivatives-expressed transcript 2 (HAND2) is a key transcription factor in progestin-induced decidualization of human endometrial stromal cells (ESCs). It has been suggested that HAND2 regulates interleukin 15 (IL15), a key immune factor required for the activation and survival of uterine natural killer (uNK) cells. Activated uNK cells can promote spiral artery remodeling and secrete cytokines to induce immunotolerance. To date, no studies have evaluated the transcription factors that regulate IL15 expression in human ESCs. In the present study, we examined whether HAND2 controls IL15 transcriptional regulation in human ESCs. Quantitative RT-PCR and histological analyses revealed that HAND2 and IL15 levels increase considerably in the secretory phase of human endometrium tissues. Results from ChIP-quantitative PCR suggested that HAND2 binds to a putative HAND2 motif, which we identified in the upstream region of the human IL15 gene through in silico analysis. Using a luciferase reporter assay, we found that the upstream region of the human IL15 gene up-regulates reporter gene activities in response to estradiol and a progestin representative (medroxyprogesterone) in ESCs. The upstream region of the human IL15 gene also exhibited increasing responsiveness to transfection with a HAND2 expression vector. Of note, deletion and substitution variants of the putative HAND2 motif in the upstream region of IL15 did not respond to HAND2 transfection. These findings confirm that HAND2 directly up-regulates human IL15 transcription in ESCs.

Matrix Metalloproteinases in Human Decidualized Endometrial Stromal Cells.

Cyclic changes, such as growth, decidualization, shedding, and regeneration, in the human endometrium are regulated by the reciprocal action of female hormones, such as estradiol (E2), and progesterone (P4). Matrix metalloproteases (MMPs) and tissue inhibitors of MMPs (TIMPs) control the invasion of extravillous trophoblast cells after implantation. Several MMPs and TIMPs function in the decidua and endometrial stromal cells (ESCs). Here, we aimed to systematically investigate the changes in MMPs and TIMPs associated with ESC decidualization. We evaluated the expression of 23 MMPs, four TIMPs, and four anti-sense non-coding RNAs from MMP loci. Primary ESC cultures treated with E2 + medroxyprogesterone acetate (MPA), a potent P4 receptor agonist, showed significant down-regulation of MMP3, MMP10, MMP11, MMP12, MMP20, and MMP27 in decidualized ESCs, as assessed by quantitative reverse transcription PCR. Further, MMP15 and MMP19 were significantly upregulated in decidualized ESCs. siRNA-mediated silencing of Heart and Neural Crest Derivatives Expressed 2 (HAND2), a master transcriptional regulator in ESC decidualization, significantly increased MMP15 expression in untreated human ESCs. These results collectively indicate the importance of MMP15 and MMP19 in ESC decidualization and highlight the role of HAND2 in repressing MMP15 transcription, thereby regulating decidualization.

AUF1, an mRNA decay factor, has a discordant role in Cpeb1 expression.

Cytoplasmic polyadenylation element binding protein 1 (CPEB1) regulates polyadenylation and subsequent translation of CPE-containing mRNAs involved in various physiological and pathological phenomena. Although the significance of CPEB1-mediated translational regulation has recently been reported, the detailed regulatory mechanism of Cpeb1 expression remains unclear. To elucidate the post-transcriptional regulatory mechanisms of Cpeb1 expression, we constructed reporter plasmids containing various deletions or mutations in the Cpeb1 mRNA 3' untranslated region (3'UTR). We investigated their expression levels in Neuro2a neuroblastoma cells. We found that Cpeb1 expression is regulated through an AU-rich element in its 3'UTR. Furthermore, the mRNA decay factor AU-rich binding factor 1 (AUF1) regulates Cpeb1 expression, and knockdown of AUF1 upregulates Cpeb1 mRNA expression but results in a decrease in CPEB1 protein levels. These findings indicate that AUF1 has a discordant role in the expression of Cpeb1.

Transcriptional regulation of LGALS9 by HAND2 and FOXO1 in human endometrial stromal cells in women with regular cycles.

Uterine natural killer cells are regulated via surface inhibitory receptors for IL15 and galectin-9 (LGALS9) secreted by endometrial stromal cells (ESCs). However, the mechanism that regulates LGALS9 mRNA levels in ESCs is unclear. The aim of this study is to clarify the transcriptional regulation of LGALS9 in ESCs. Here, LGALS9 mRNA expression levels significantly decreased in the endometrial tissue in the early- to mid-secretory phase, and recovered in the mid- to late-secretory phase, compared to that in the proliferative phase. In ESCs, LGALS9 mRNA expression significantly decreased following estradiol + medroxyprogesterone acetate treatment for 1 day and increased after 12 days compared to that in the control. The transcriptional activity of the LGALS9 upstream region was upregulated by heart and neural crest derivatives expressed 2 (HAND2) and downregulated by forkhead box O1 (FOXO1). In ESCs, HAND2 expression significantly increased throughout the 12 days treatment with steroid hormones, whereas FOXO1 expression significantly increased on Day 1, reached a plateau, and significantly increased again after 6 days of treatment. Levels of FOXO1 phosphorylation (pFOXO1) remained unchanged after a 3-day treatment of ESCs with steroid hormones, but significantly increased following a 12-day treatment. pFOXO1 could not bind to the DNA and was thus unable to directly suppress LGALS9 transcription. Therefore, expression level of HAND2 and phosphorylation status of FOXO1 may determine LGALS9 mRNA expression. This study provides a novel molecular mechanism underlying the transcriptional regulation of LGALS9 mRNA in ESCs, which could be valuable in the treatment of diseases associated with decidualization failure.

Distribution, fine structure, and three-dimensional innervation of lamellar corpuscles in rat plantar skin.

Lamellar corpuscles function as mechanoreceptors in the skin, composed of axon terminals and lamellae constructed by terminal Schwann cells. They are classified into Pacinian, Meissner, and simple corpuscles based on histological criteria. Lamellar corpuscles in rat dermal papilla cells have been reported; however, the morphological aspects have yet to be thoroughly investigated. In the present study, we analyzed the enzyme activity, distribution, fine structure, and three-dimensional innervation of lamellar corpuscles in rat plantar skin. The lamellar corpuscles exhibiting non-specific cholinesterase were densely distributed in rat footpads, evident as notable skin elevations, especially at the apex, the highest portion of the ridges in each footpad. In contrast, only a few lamellar corpuscles were found in other plantar skin areas. Lamellar corpuscle was considered composed of a flat axon terminal Schwann cell lamellae, which were roughly concentrically arranged in the dermal papilla. These histological characteristics correspond to those of the simple corpuscle. Moreover, the axon tracing method revealed that one trunk axon innervated several simple corpuscles. The territory of the trunk axons overlapped with each other. Finally, the animals' footprints were analyzed. During the pausing and walking phases, footpads are often in contact with the floor. These results demonstrate that the type of lamellar corpuscles in the dermal papillae of rat plantar skin is a simple corpuscle and implies that their distribution pattern in the plantar skin is convenient for efficient sensing and transmission of mechanical stimuli from the ground.

Direct conversion of adult human skin fibroblasts into functional Schwann cells that achieve robust recovery of the severed peripheral nerve in rats.

Direct conversion is considered a promising approach to obtain tissue-specific cells for cell therapies; however, this strategy depends on exogenous gene expression that may cause undesired adverse effects such as tumorigenesis. By optimizing the Schwann cell induction system, which was originally developed for trans-differentiation of bone marrow mesenchymal stem cells into Schwann cells, we established a system to directly convert adult human skin fibroblasts into cells comparable to authentic human Schwann cells without gene introduction. Serial treatments with beta-mercaptoethanol, retinoic acid, and finally a cocktail of basic fibroblast growth factor, forskolin, platelet-derived growth factor-AA, and heregulin-ß1 (EGF domain) converted fibroblasts into cells expressing authentic Schwann cell markers at an efficiency of approximately 75%. Genome-wide gene expression analysis suggested the conversion of fibroblasts into the Schwann cell-lineage. Transplantation of induced Schwann cells into severed peripheral nerve of rats facilitated axonal regeneration and robust functional recovery in sciatic function index comparable to those of authentic human Schwann cells. The contributions of induced Schwann cells to myelination of regenerated axons and re-formation of neuromuscular junctions were also demonstrated. Our data clearly demonstrated that cells comparable to functional Schwann cells feasible for the treatment of neural disease can be induced from adult human skin fibroblasts without gene introduction. This direct conversion system will be beneficial for clinical applications to peripheral and central nervous system injuries and demyelinating diseases.

Intracellular signaling similarity reveals neural stem cell-like properties of ependymal cells in the adult rat spinal cord.

Proliferation of ependymal cells of the adult spinal cord (SCEp cells) in the intact condition has been considered as a quite rare event. To visualize proliferating/proliferated SCEp cells, we used the intensive 5-bromo-2'-deoxyuridine (BrdU) administration method to find that about two cells in the ependymal layer incorporated BrdU in a 10-µm-thick section. Because these two cells were not considered to undergo further proliferation, we analyzed the positioning and motility of two neighboring BrdU-incorporated proliferated cells and elucidated the tendency of the movement of SCEp cells to the outer side inside the ependymal layer. Even if it was rare, one of the proliferated cells in the ependymal layer differentiated into astrocytes. Gene introduction of Notch intracellular domain (NICD), a constitutively active form of Notch1, into SCEp cells demonstrated both increase in proliferation and induction of differentiation into astrocytes. Overexpression of Sox2 promoted proliferation in SCEp cells. The reaction of gene introduction of NICD and Sox2 indicates the similarity of intracellular signaling between SCEp cells and neural stem cells. Also, considering the fact that SCEp cells express these two factors in the intact condition, Notch and Sox2 are important for the cell fate control of SCEp cells in the intact condition.

Beneficial Effects of Systemically Administered Human Muse Cells in Adriamycin Nephropathy.

Multilineage-differentiating stress-enduring (Muse) cells are nontumorigenic endogenous pluripotent-like stem cells that can be collected from various organs. Intravenously administered Muse cells have been shown to spontaneously migrate to damaged tissue and replenish lost cells, but the effect in FSGS is unknown. We systemically administered human bone marrow-derived Muse cells without concurrent administration of immunosuppressants to severe combined immune-deficient (SCID) and BALB/c mouse models with adriamycin-induced FSGS (FSGS-SCID and FSGS-BALB/c, respectively). In FSGS-SCID mice, human Muse cells preferentially integrated into the damaged glomeruli and spontaneously differentiated into cells expressing markers of podocytes (podocin; 31%), mesangial cells (megsin; 13%), and endothelial cells (CD31; 41%) without fusing to the host cells; attenuated glomerular sclerosis and interstitial fibrosis; and induced the recovery of creatinine clearance at 7 weeks. Human Muse cells induced similar effects in FSGS-BALB/c mice at 5 weeks, despite xenotransplant without concurrent immunosuppressant administration, and led to improvement in urine protein, creatinine clearance, and plasma creatinine levels more impressive than that in the FSGS-SCID mice at 5 weeks. However, functional recovery in FSGS-BALB/c mice was impaired at 7 weeks due to immunorejection, suggesting the importance of Muse cell survival as glomerular cells in the FSGS kidney for tissue repair and functional recovery. In conclusion, Muse cells are unique reparative stem cells that preferentially home to damaged glomeruli and spontaneously differentiate into glomerular cells after systemic administration. Introduction of genes to induce differentiation is not required before Muse cell administration; thus, Muse cells may be a feasible therapeutic strategy in FSGS.

Regulation of DM-20 mRNA expression and intracellular translocation of glutathione-S-transferase pi isoform during oligodendrocyte differentiation in the adult rat spinal cord.

We previously demonstrated that NG2-positive oligodendrocyte precursor cells (OPCs) do not express DM-20 mRNA and identified a distinct DM-20 mRNA-positive cell population expressing glutathione-S-transferase pi isoform (GST-pi) in the nucleus (GST-pi(Nuc)) of the adult rat spinal cord. As GST-pi intranuclear localization correlates with progenitor cell properties, we examined the differentiation status of this cell population under the intensive 5-bromo-2'-deoxyuridine (BrdU) administration method, consisting of intraperitoneal BrdU injections every 2 h for 48 h. We observed that a certain population of proliferating/proliferated cells expressed DM-20 mRNA, and sometimes two proliferating/proliferated cells were observed still attached to each other. We performed triple staining for BrdU, DM-20 mRNA, and NG2 and found pairs of neighboring BrdU-positive cells, which were considered to originate from the same progenitor cells and where both cells expressed DM-20 mRNA. Triple staining for BrdU, DM-20 mRNA, and GST-pi detected proliferating/proliferated cells exhibiting the GST-pi(Nuc)/DM-20 mRNA-positive expression pattern. These findings suggested the presence of a GST-pi(Nuc)/DM-20 mRNA-positive oligodendrocyte-lineage progenitor cell population in the adult rat spinal cord. However, we did not find any pair of neighboring BrdU-positive cells with this expression pattern. These observations collectively support the idea that GST-pi(Nuc)/DM-20 mRNA-expressing cells are the progeny of NG2-positive OPCs rather than a novel type of oligodendrocyte-lineage progenitor cells and that DM-20 mRNA expression is dynamically regulated during differentiation of OPCs into oligodendrocytes.

The expression of PLP/DM-20 mRNA is restricted to the oligodendrocyte-lineage cells in the adult rat spinal cord.

Proteolipid protein (PLP) is the major component of myelin; its gene encodes two major splicing variants: PLP and DM-20. Compared with PLP, DM-20 lacks the amino acids encoded by exon IIIb. The expression of PLP/DM-20 in cells outside the oligodendrocyte-lineage is unclear. To address this issue, we analyzed the detailed expression pattern of PLP/DM-20 mRNA in the adult rat spinal cord by in situ hybridization (ISH) with a cRNA probe complementary to DM-20 mRNA, which has been used to detect both PLP and DM-20 both mRNA. ISH did not label the cells expressing NeuN nor glial fibrillary acidic protein but detected those expressing Olig2, indicating that PLP/DM-20 mRNA are expressed only in oligodendrocyte-lineage cells. This cell population was expected to contain NG2-expressing oligodendrocyte precursor cells (OPCs), because some exhibited the expression of glutathione S-transferase pi isoform in the nucleus. A recent publication showed that OPCs express PLP but not DM-20 mRNA. However, no OPCs were detected. We performed ISH with a cRNA probe that specifically recognizes PLP mRNA to successfully detect some OPCs. Additionally, OPCs were detected by ISH with a cRNA probe complementary to DM-20 mRNA that was digested via alkaline hydrolysis prior to ISH. These findings collectively demonstrate that PLP and DM-20 mRNA expression is restricted to oligodendrocyte-lineage cells, and imply that the undigested cRNA probe complementary to the full-length DM-20 mRNA sequence only recognizes DM-20 mRNA and not the PLP counterpart when applied to ISH without denaturation/digestion methods.

Multilineage-differentiating stress-enduring (Muse) cells are a primary source of induced pluripotent stem cells in human fibroblasts.

The stochastic and elite models have been proposed for the mechanism of induced pluripotent stem (iPS) cell generation. In this study we report a system that supports the elite model. We previously identified multilineage-differentiating stress-enduring (Muse) cells in human dermal fibroblasts that are characterized by stress tolerance, expression of pluripotency markers, self-renewal, and the ability to differentiate into endodermal-, mesodermal-, and ectodermal-lineage cells from a single cell. They can be isolated as stage-specific embryonic antigen-3/CD105 double-positive cells. When human fibroblasts were separated into Muse and non-Muse cells and transduced with Oct3/4, Sox2, Klf4, and c-Myc, iPS cells were generated exclusively from Muse cells but not from non-Muse cells. Although some colonies were formed from non-Muse cells, they were unlike iPS cells. Furthermore, epigenetic alterations were not seen, and some of the major pluripotency markers were not expressed for the entire period during iPS cell generation. These findings were confirmed further using cells transduced with a single polycistronic virus vector encoding all four factors. The results demonstrate that in adult human fibroblasts a subset of preexisting adult stem cells whose properties are similar in some respects to those of iPS cells selectively become iPS cells, but the remaining cells make no contribution to the generation of iPS cells. Therefore this system seems to fit the elite model rather than the stochastic model.

The elite and stochastic model for iPS cell generation: multilineage-differentiating stress enduring (Muse) cells are readily reprogrammable into iPS cells.

Induced pluripotent stem (iPS) cells have attracted a great deal of attention, although the mechanism by which they are generated is still not fully understood. Currently, two theories, the stochastic and elite models, have been proposed. Some reports provide theoretical support for the stochastic model. Other reports, however, support the elite model. For example, some human fibroblasts, such as Multilineage-differentiating stress enduring (Muse) cells, are reported to be pluripotent and a primary source of iPS cells. Thus, the mechanism of iPS cell generation continues to be debated. In this review, we discuss the properties of the original cell source, such as the components of the original populations and the potential of each population to become iPS cells, and further discuss the implications of the two theories for iPS cell research.

Muse cells and induced pluripotent stem cell: implication of the elite model.

Induced pluripotent stem (iPS) cells have attracted a great deal attention as a new pluripotent stem cell type that can be generated from somatic cells, such as fibroblasts, by introducing the transcription factors Oct3/4, Sox2, Klf4, and c-Myc. The mechanism of generation, however, is not fully understood. Two mechanistic theories have been proposed; the stochastic model purports that every cell type has the potential to be reprogrammed to become an iPS cell and the elite model proposes that iPS cell generation occurs only from a subset of cells. Some reports have provided theoretical support for the stochastic model, but a recent publication demonstrated findings that support the elite model, and thus the mechanism of iPS cell generation remains under debate. To enhance our understanding of iPS cells, it is necessary to clarify the properties of the original cell source, i.e., the components of the original populations and the potential of each population to become iPS cells. In this review, we discuss the two theories and their implications in iPS cell research.

Unique multipotent cells in adult human mesenchymal cell populations.

We found adult human stem cells that can generate, from a single cell, cells with the characteristics of the three germ layers. The cells are stress-tolerant and can be isolated from cultured skin fibroblasts or bone marrow stromal cells, or directly from bone marrow aspirates. These cells can self-renew; form characteristic cell clusters in suspension culture that express a set of genes associated with pluripotency; and can differentiate into endodermal, ectodermal, and mesodermal cells both in vitro and in vivo. When transplanted into immunodeficient mice by local or i.v. injection, the cells integrated into damaged skin, muscle, or liver and differentiated into cytokeratin 14-, dystrophin-, or albumin-positive cells in the respective tissues. Furthermore, they can be efficiently isolated as SSEA-3(+) cells. Unlike authentic ES cells, their proliferation activity is not very high and they do not form teratomas in immunodeficient mouse testes. Thus, nontumorigenic stem cells with the ability to generate the multiple cell types of the three germ layers can be obtained through easily accessible adult human mesenchymal cells without introducing exogenous genes. These unique cells will be beneficial for cell-based therapy and biomedical research.

Cpeb1 expression is post-transcriptionally regulated by AUF1, CPEB1, and microRNAs.

Cytoplasmic polyadenylation element binding protein 1 (CPEB1) regulates the translation of numerous mRNAs. We previously showed that AU-rich binding factor 1 (AUF1) regulates Cpeb1 expression through the 3' untranslated region (3'UTR). To investigate the molecular basis of the regulatory potential of the Cpeb1 3'UTR, here we performed reporter analyses that examined expression levels of Gfp reporter mRNA containing the Cpeb1 3'UTR. Our findings indicate that CPEB1 represses the translation of Cpeb1 mRNA and that miR-145a-5p and let-7b-5p are involved in the reduction in Cpeb1 expression in the absence of AUF1. These results suggest that Cpeb1 expression is post-transcriptionally regulated by AUF1, CPEB1, and microRNAs.

Cytoplasmic Polyadenylation Element-Binding Protein 1 Post-transcriptionally Regulates Fragile X Mental Retardation 1 Expression Through 3' Untranslated Region in Central Nervous System Neurons.

Fragile X syndrome (FXS) is an inherited intellectual disability caused by a deficiency in Fragile X mental retardation 1 (Fmr1) gene expression. Recent studies have proposed the importance of cytoplasmic polyadenylation element-binding protein 1 (CPEB1) in FXS pathology; however, the molecular interaction between Fmr1 mRNA and CPEB1 has not been fully investigated. Here, we revealed that CPEB1 co-localized and interacted with Fmr1 mRNA in hippocampal and cerebellar neurons and culture cells. Furthermore, CPEB1 knockdown upregulated Fmr1 mRNA and protein levels and caused aberrant localization of Fragile X mental retardation protein in neurons. In an FXS cell model, CPEB1 knockdown upregulated the mRNA levels of several mitochondria-related genes and rescued the intracellular heat shock protein family A member 9 distribution. These findings suggest that CPEB1 post-transcriptionally regulated Fmr1 expression through the 3' untranslated region, and that CPEB1 knockdown might affect mitochondrial function.