Hanako Ohashi Ikeda

Expanded polyglutamine in the Machado–Joseph disease protein induces cell death in vitro and in vivo

Recently, we identified a novel gene, MJD1, which contains an expanded GAG triplet repeat in Machado–Joseph disease. Here we report the induction of apoptosis in cultured cells expressing a portion of the MJD1 gene that includes the expanded GAG repeats. Cell death occurs only when the GAG repeat is translated into polyglutamine residues, which apparently precipitate in large covalently modified forms. We also created ataxic transgenic mice by expressing the expanded polyglutamine stretch in Purkinje cells. Our results demonstrate the potential involvement of the expanded polyglutamine as the common aetiological agent for inherited neurodegenerative diseases with GAG expansions.

Toward the generation of rod and cone photoreceptors from mouse, monkey and human embryonic stem cells.

We previously reported the differentiation of mouse embryonic stem (ES) cells into retinal progenitors. However, these progenitors rarely differentiate into photoreceptors unless they are cultured with embryonic retinal tissues. Here we show the in vitro generation of putative rod and cone photoreceptors from mouse, monkey and human ES cells by stepwise treatments under defined culture conditions, in the absence of retinal tissues. With mouse ES cells, Crx+ photoreceptor precursors were induced from Rx+ retinal progenitors by treatment with a Notch signal inhibitor. Further application of fibroblast growth factors, Shh, taurine and retinoic acid yielded a greater number of rhodopsin+ rod photoreceptors, in addition to default cone production. With monkey and human ES cells, feeder- and serum-free suspension culture combined with Wnt and Nodal inhibitors induced differentiation of Rx+ or Mitf+ retinal progenitors, which produced retinal pigment epithelial cells. Subsequent treatment with retinoic acid and taurine induced photoreceptor differentiation. These findings may facilitate the development of human ES cell–based transplantation therapies for retinal diseases.

GENERATION OF RETINAL CELLS FROM MOUSE AND HUMAN INDUCED PLURIPOTENT STEM CELLS

We previously reported a technique for generating retinal pigment epithelia (RPE) and putative photoreceptors from embryonic stem (ES) cells. Here we tested whether our procedure can promote retinal differentiation of mouse and human induced pluripotent stem cells (iPSCs). Treating iPSCs with Wnt and Nodal antagonists in suspension culture induced expression of markers of retinal progenitor cells and generated RPE cells. Subsequently, treatment with retinoic acid and taurine generated cells positive for photoreceptor markers in all but one human cell lines. We propose that iPSCs can be induced to differentiate into retinal cells which have a possibility to be used as patient-specific donor cells for transplantation therapies.

In vitro differentiation of retinal cells from human pluripotent stem cells by small-molecule induction

The use of stem-cell therapy to treat retinal degeneration holds great promise. However, definitive methods of retinal differentiation that do not depend on recombinant proteins produced in animal or Escherichia coli cells have not been devised. Here, we report a defined culture method using low-molecular-mass compounds that induce differentiation of human embryonic stem (ES) cells and induced pluripotent stem (iPS) cells into retinal progenitors, retinal pigment epithelium cells and photoreceptors. The casein kinase I inhibitor CKI-7, the ALK4 inhibitor SB-431542 and the Rho-associated kinase inhibitor Y-27632 in serum-free and feeder-free floating aggregate culture induce retinal progenitors positive for RX, MITF, PAX6 and CHX10. The treatment induces hexagonal pigmented cells that express RPE65 and CRALBP, form ZO1-positive tight junctions and exhibit phagocytic functions. Subsequent treatment with retinoic acid and taurine induces photoreceptors that express recoverin, rhodopsin and genes involved in phototransduction. Both three-factor (OCT3/4, SOX2 and KLF4) and four-factor (OCT3/4, SOX2, KLF4 and MYC) human iPS cells could be successfully differentiated into retinal cells by small-molecule induction. This method provides a solution to the problem of cross-species antigenic contamination in cell-replacement therapy, and is also useful for in vitro modeling of development, disease and drug screening.

Stepwise differentiation of pluripotent stem cells into retinal cells

Embryonic stem (ES) cells are pluripotent cells derived from the inner cell mass of blastocyst-stage embryos. They can maintain an undifferentiated state indefinitely and can differentiate into derivatives of all three germ layers, namely ectoderm, endoderm and mesoderm. Although much progress has been made in the propagation and differentiation of ES cells, induction of photoreceptors has generally required coculture with or transplantation into developing retinal tissue. Here, we describe a protocol for generating retinal cells from ES cells by stepwise treatment with defined factors. This method preferentially induces photoreceptor and retinal pigment epithelium (RPE) cells from mouse and human ES cells. In our protocol, differentiation of RPE and photoreceptors from mouse ES cells requires 28 d and the differentiation of human ES cells into mature RPE and photoreceptors requires 120 and 150 d, respectively. This differentiation system and the resulting pluripotent stem cell-derived retinal cells will facilitate the development of transplantation therapies for retinal diseases, drug testing and in vitro disease modeling. It will also improve our understanding of the development of the central nervous system, especially the eye.

Minimization of exogenous signals in ES cell culture induces rostral hypothalamic differentiation

Embryonic stem (ES) cells differentiate into neuroectodermal progenitors when cultured as floating aggregates in serum-free conditions. Here, we show that strict removal of exogenous patterning factors during early differentiation steps induces efficient generation of rostral hypothalamic-like progenitors (Rax+/Six3+/Vax1+) in mouse ES cell-derived neuroectodermal cells. The use of growth factor-free chemically defined medium is critical and even the presence of exogenous insulin, which is commonly used in cell culture, strongly inhibits the differentiation via the Akt-dependent pathway. The ES cell-derived Rax+ progenitors generate Otp+/Brn2+ neuronal precursors (characteristic of rostral–dorsal hypothalamic neurons) and subsequently magnocellular vasopressinergic neurons that efficiently release the hormone upon stimulation. Differentiation markers of rostral–ventral hypothalamic precursors and neurons are induced from ES cell-derived Rax+ progenitors by treatment with Shh. Thus, in the absence of exogenous growth factors in medium, the ES cell-derived neuroectodermal cells spontaneously differentiate into rostral (particularly rostral–dorsal) hypothalamic-like progenitors, which generate characteristic hypothalamic neuroendocrine neurons in a stepwise fashion, as observed in vivo. These findings indicate that, instead of the addition of inductive signals, minimization of exogenous patterning signaling plays a key role in rostral hypothalamic specification of neural progenitors derived from pluripotent cells.

A novel method to detect local ganglion cell loss in early glaucoma using spectral-domain optical coherence tomography.

PURPOSE To test the glaucoma-discriminating ability of a new method for detecting local ganglion cell loss using spectral-domain optical coherence tomography (OCT). METHODS This study included 58 glaucomatous and 48 healthy eyes from Japanese subjects. Combined thickness of the ganglion cell layer and inner plexus layer (GCIPL) was measured on a macular cube scan in Cirrus HD-OCT. Average GCIPL thickness within a macular elliptical annulus and minimum GCIPL thickness on 360 spokes extending from the inner to the outer radius of the elliptical annulus were calculated. Area under the receiver operating characteristic curve (AROC) to discriminate between healthy eyes and early (mean deviation [MD], ≥-6 dB)/advanced (MD, <-6 dB) glaucomatous were compared between parameters. RESULTS Forty-three were normal-tension glaucoma, and 15 were high-tension glaucoma. The mean minimum GCIPL thickness was 77.0 μm in healthy eyes and 60.6 μm in glaucomatous eyes (P < 0.001). For the intersession repeatability, the coefficients of variation for average GCIPL and minimum GCIPL were 0.98 and 1.85 in glaucomatous eyes, and 0.89 and 1.85 in healthy eyes, respectively. Minimum GCIPL thickness AROC (0.896) was significantly higher (P = 0.0062) than average GCIPL thickness (0.821) for early glaucoma, whereas minimum GCIPL AROC (0.991) was comparable (P = 0.103) to average GCIPL (0.964) for advanced glaucoma. The minimum GCIPL thickness AROC was comparable (P = 0.861) to average circumpapillary retinal nerve fiber layer (cpRNFL) thickness (0.890) for early glaucoma. CONCLUSIONS In Japanese patients with 74.1% of normal-tension glaucoma, the minimum GCIPL on spokes may be useful for detecting early glaucoma.

Association Between Abnormal Autofluorescence and Photoreceptor Disorganization in Retinitis Pigmentosa

PURPOSE To evaluate the association between the third high-reflectance band on high-resolution optical coherence tomography (OCT), fundus autofluorescence (AF), and kinetic perimetry results in patients with typical retinitis pigmentosa (RP). DESIGN Retrospective, observational case series. METHODS Thirty-four patients with typical RP who were referred to our institute were examined, with a diagnosis made by full-field electroretinography. We evaluated the fundus AF and the third high-reflectance band by high-resolution OCT, both qualitatively and quantitatively. We investigated whether the vertical length of the AF diameter or the third high-reflectance band correlated with Goldmann kinetic perimetry results. RESULTS We classified three types of abnormal fundus AF: ring AF, central AF, and the absence of both patterns. In eyes with ring AF, the length of the third high-reflectance band was almost equal to the diameter of the abnormal ring AF with significant correlation (P < .001), whereas the band length did not correlate with the diameter of the visual field (P = .237). Eyes with central AF did not have a continuous third high-reflectance band. In eyes with neither ring nor central AF, the length of the third high-reflectance band correlated with the AF length and the diameter of the visual field (P = .024 and P < .001, respectively). CONCLUSIONS A novel classification based on the fundus AF and the third high-reflectance band determined by OCT suggests different patterns of pathogenesis in the retinal pigment epithelium and photoreceptor degeneration in the progression of RP.

Three-dimensional imaging of lamina cribrosa defects in glaucoma using swept-source optical coherence tomography.

PURPOSE To visualize lamina cribrosa defects using three-dimensional (3D) swept-source optical coherence tomography (SS-OCT), and to determine the factors associated with this feature. METHODS All subjects were examined using an SS-OCT prototype system, which uses a tunable laser as a light source, operated at 100,000 Hz A-scan repetition rate in the 1050-nm wavelength. A 3D raster scan protocol consisting of 256×256 A-scans was acquired over a square area of 3 mm×3 mm centered on the optic disc. En face sectioned volume and serial en face images and orthogonal (horizontal and vertical) serial B-scans were evaluated. RESULTS A total of 182 eyes of 111 patients with glaucoma and 29 healthy eyes of 26 subjects were included. Twenty full-thickness focal lamina cribrosa defects were found in 12 (6.6%) of 182 eyes with glaucoma, whereas no lamina defects were found in healthy eyes. Nine eyes (75.0%) showed 15 full-thickness lamina cribrosa defects near the margin of the lamina cribrosa, and 3 eyes showed 4 lamina defects at the margin, as if detached from the sclera. Focal lamina cribrosa defects corresponded with neuroretinal rim thinning, concurrent or previous disc hemorrhages, abnormal circumpapillary retinal nerve fiber layer thickness, and visual field defects. The presence of lamina cribrosa defects was significantly associated with longer axial length and disc hemorrhages (P=0.033 and 0.024, respectively). CONCLUSIONS 3D SS-OCT imaging allows visualization of the lamina cribrosa defects, which may be more prevalent in eyes with longer axial length and related to disc hemorrhages.

Identifying Pathogenic Genetic Background of Simplex or Multiplex Retinitis Pigmentosa Patients: A Large-Scale Mutation Screening Study

Background and purpose: More than half of the retinitis pigmentosa (RP) cases are genetically simplex or multiplex. To date, 37 causative genes of RP have been identified; however, the elucidation of gene defects in simplex or multiplex RP patients/families remains problematic. The aim of our study was to identify the genetic causes of RP in patients with unknown or non-Mendelian inheritance. Methods and results: Since 2003, 52 simplex RP patients, 151 patients from 141 multiplex RP families, and six sporadic patients with retinal degeneration were studied. A total of 108 exons of 30 RP-causing genes that harboured the reported mutations were screened by an efficient denaturing high performance liquid chromatography (dHPLC) based assay. Aberrant fragments were subsequently analysed by automatic sequencing. Twenty-six mutations, including two frameshift mutations, one single amino acid deletion, and 23 missense mutations, were identified in 28 probands (14.07%). Eighteen mutations have not been reported to date. Three pairs of combined mutations in different genes were identified in two sporadic cases and one multiplex family, indicating the possibility of novel digenic patterns. Of the 23 missense mutations, 21 were predicted as deleterious mutations by computational methods using PolyPhen, SIFT, PANTHER, and PMut programs. Conclusion: We elucidated the mutation spectrum in Japanese RP patients and demonstrated the validity of the mutation detection system using dHPLC sequencing for genetic diagnosis in RP patients independent of familial incidence, which may provide a model strategy for identifying genetic causes in other diseases linked to a wide range of genes.