Identification of the reporter gene combination that shows high contrast for cellular level MRI.

Currently, we can label the certain cells by transducing specific genes, called reporter genes, and distinguish them from other cells. For example, fluorescent protein such as green fluorescence protein (GFP) is commonly used for cell labeling. However, fluorescent protein is difficult to observe in living animals. We can observe the reporter signals of the luciferin-luciferase system from the outside of living animals using in vivo imaging systems, although the resolution of this system is low. Therefore, in this study, we examined the reporter genes, which allowed the MRI-mediated observation of labeled cells in living animals. As a preliminary stage of animal study, we transduced some groups of plasmids that coded the protein that could take and store metal ions to the cell culture, added metal ions solutions, and measured their T1 or T2 relaxation values. Finally, we specified the best reporter gene combination for MRI, which was the combination of transferrin receptor, DMT1, and Ferritin-M6A for T1WI, and Ferritin-M6A for T2WI.

Elavl3 is essential for the maintenance of Purkinje neuron axons.

Neuronal Elav-like (nElavl or neuronal Hu) proteins are RNA-binding proteins that regulate RNA stability and alternative splicing, which are associated with axonal and synaptic structures. nElavl proteins promote the differentiation and maturation of neurons via their regulation of RNA. The functions of nElavl in mature neurons are not fully understood, although Elavl3 is highly expressed in the adult brain. Furthermore, possible associations between nElavl genes and several neurodegenerative diseases have been reported. We investigated the relationship between nElavl functions and neuronal degeneration using Elavl3-/- mice. Elavl3-/- mice exhibited slowly progressive motor deficits leading to severe cerebellar ataxia, and axons of Elavl3-/- Purkinje cells were swollen (spheroid formation), followed by the disruption of synaptic formation of axonal terminals. Deficit in axonal transport and abnormalities in neuronal polarity was observed in Elavl3-/- Purkinje cells. These results suggest that nElavl proteins are crucial for the maintenance of axonal homeostasis in mature neurons. Moreover, Elavl3-/- mice are unique animal models that constantly develop slowly progressive axonal degeneration. Therefore, studies of Elavl3-/- mice will provide new insight regarding axonal degenerative processes.

The use of induced pluripotent stem cells to reveal pathogenic gene mutations and explore treatments for retinitis pigmentosa.

BACKGROUND: Retinitis pigmentosa (RP) is an inherited human retinal disorder that causes progressive photoreceptor cell loss, leading to severe vision impairment or blindness. However, no effective therapy has been established to date. Although genetic mutations have been identified, the available clinical data are not always sufficient to elucidate the roles of these mutations in disease pathogenesis, a situation that is partially due to differences in genetic backgrounds. RESULTS: We generated induced pluripotent stem cells (iPSCs) from an RP patient carrying a rhodopsin mutation (E181K). Using helper-dependent adenoviral vector (HDAdV) gene transfer, the mutation was corrected in the patient's iPSCs and also introduced into control iPSCs. The cells were then subjected to retinal differentiation; the resulting rod photoreceptor cells were labeled with an Nrl promoter-driven enhanced green fluorescent protein (EGFP)-carrying adenovirus and purified using flow cytometry after 5 weeks of culture. Using this approach, we found a reduced survival rate in the photoreceptor cells with the E181K mutation, which was correlated with the increased expression of endoplasmic reticulum (ER) stress and apoptotic markers. The screening of therapeutic reagents showed that rapamycin, PP242, AICAR, NQDI-1, and salubrinal promoted the survival of the patient's iPSC-derived photoreceptor cells, with a concomitant reduction in markers of ER stress and apoptosis. Additionally, autophagy markers were found to be correlated with ER stress, suggesting that autophagy was reduced by suppressing ER stress-induced apoptotic changes. CONCLUSION: The use of RP patient-derived iPSCs combined with genome editing provided a versatile cellular system with which to define the roles of genetic mutations in isogenic iPSCs with or without mutation and also provided a system that can be used to explore candidate therapeutic approaches.

Generation of stratified squamous epithelial progenitor cells from mouse induced pluripotent stem cells.

BACKGROUND: Application of induced pluripotent stem (iPS) cells in regenerative medicine will bypass ethical issues associated with use of embryonic stem cells. In addition, patient-specific IPS cells can be useful to elucidate the pathophysiology of genetic disorders, drug screening, and tailor-made medicine. However, in order to apply iPS cells to mitotic tissue, induction of tissue stem cells that give rise to progeny of the target organ is required. METHODOLOGY/PRINCIPAL FINDINGS: We induced stratified epithelial cells from mouse iPS cells by co-culture with PA6 feeder cells (SDIA-method) with use of BMP4. Clusters of cells positive for the differentiation markers KRT1 or KRT12 were observed in KRT14-positive colonies. We successfully cloned KRT14 and p63 double-positive stratified epithelial progenitor cells from iPS-derived epithelial cells, which formed stratified epithelial sheets consisting of five- to six-polarized epithelial cells in vitro. When these clonal cells were cultured on denuded mouse corneas, a robust stratified epithelial layer was observed with physiological cell polarity including high levels of E-cadherin, p63 and K15 expression in the basal layer and ZO-1 in the superficial layer, recapitulating the apico-basal polarity of the epithelium in vivo. CONCLUSIONS/SIGNIFICANCE: These results suggest that KRT14 and p63 double-positive epithelial progenitor cells can be cloned from iPS cells in order to produce polarized multilayer epithelial cell sheets.

Epiplakin1 is expressed in the cholangiocyte lineage cells in normal liver and adult progenitor cells in injured liver.

We have previously identified Epiplakin1 (Eppk1) as a gene expressed in pancreatic progenitor cells. Here we studied the expression of Eppk1 in developing and regenerating livers in mice. Eppk1 is initially expressed in the early bipotential hepatoblasts and is later confined to the cholangiocytes. After birth, Eppk1 is expressed in the bile duct. In the livers of mice fed with a choline-deficient ethionine-supplemented (CDE) diet, Eppk1-positive cells dramatically increase in number. The Eppk1-positive cells express A6, thereby indicating that they are hepatic progenitor cells. Other cholangiocyte markers, such as Cytokeratins, E-cadherin, osteopontin and Sox9, are also co-expressed in the hepatic progenitor cells. Some of the Eppk1-positive cells express PCNA, a proliferation marker, thereby suggesting their identities as transient amplifying cells. In conclusion, we have shown that Eppk1 serves as a useful marker for detecting the hepatic progenitor population in the developing and adult liver. The use of Eppk1 as a marker will facilitate studies of mouse hepatic progenitor cells.

Expression patterns of epiplakin1 in pancreas, pancreatic cancer and regenerating pancreas.

Epiplakin1 (Eppk1) is a plakin family gene with its function remains largely unknown, although the plakin genes are known to function in interconnecting cytoskeletal filaments and anchoring them at plasma membrane-associated adhesive junction. Here we analyzed the expression patterns of Eppk1 in the developing and adult pancreas in the mice. In the embryonic pancreas, Eppk1+/Pdx1+ and Eppk1+/Sox9+ pancreatic progenitor cells were observed in early pancreatic epithelium. Since Pdx1 expression overlapped with that of Sox9 at this stage, these multipotent progenitor cells are Eppk1+/Pdx1+/Sox9+ cells. Then Eppk1 expression becomes confined to Ngn3+ or Sox9+ endocrine progenitor cells, and p48+ exocrine progenitor cells, and then restricted to the duct cells and a cells at birth. In the adult pancreas, Eppk1 is expressed in centroacinar cells (CACs) and in duct cells. Eppk1 is observed in pancreatic intraepithelial neoplasia (PanIN), previously identified as pancreatic ductal adenocarcinoma (PDAC) precursor lesions. In addition, the expansion of Eppk1-positive cells occurs in a caerulein-induced acute pancreatitis, an acinar cell regeneration model. Furthermore, in the partial pancreatectomy (Px) regeneration model using mice, Eppk1 is expressed in "ducts in foci", a tubular structure transiently induced. These results suggest that Eppk1 serves as a useful marker for detecting pancreatic progenitor cells in developing and regenerating pancreas.

Guided differentiation of embryonic stem cells into Pdx1-expressing regional-specific definitive endoderm.

The generation of specific lineages of the definitive endoderm from embryonic stem (ES) cells is an important issue in developmental biology, as well as in regenerative medicine. This study demonstrates that ES cells are induced sequentially into regional-specific gut endoderm lineages, such as pancreatic, hepatic, and other cell lineages, when they are cultured directly on a monolayer of mesoderm-derived supporting cells. A detailed chronological analysis revealed that Activin, fibroblast growth factor, or bone morphogenetic protein signals are critical at various steps and that additional short-range signals are required for differentiation into Pdx1-expressing cells. Under selective culture conditions, definitive endoderm (47%) or Pdx1-positive pancreatic progenitors (30%) are yielded at a high efficiency. When transplanted under the kidney capsule, the Pdx1-positive cells further differentiated into all three pancreatic lineages, namely endocrine, exocrine, and duct cells.