Subcellular localization of dystrophin isoforms in cardiomyocytes and phenotypic analysis of dystrophin-deficient mice reveal cardiac myopathy is predominantly caused by a deficiency in full-length dystrophin.

Duchenne muscular dystrophy (DMD) is an X-linked recessive progressive muscle degenerative disorder that causes dilated cardiomyopathy in the second decade of life in affected males. Dystrophin, the gene responsible for DMD, encodes full-length dystrophin and various short dystrophin isoforms. In the mouse heart, full-length dystrophin Dp427 and a short dystrophin isoform, Dp71, are expressed. In this study, we intended to clarify the functions of these dystrophin isoforms in DMD-related cardiomyopathy. We used two strains of mice: mdx mice, in which Dp427 was absent but Dp71 was present, and DMD-null mice, in which both were absent. By immunohistochemical staining and density-gradient centrifugation, we found that Dp427 was located in the cardiac sarcolemma and also at the T-tubules, whereas Dp71 was specifically located at the T-tubules. In order to determine whether T tubule-associated Dp71 was involved in DMD-related cardiac disruption, we compared the cardiac phenotypes between DMD-null mice and mdx mice. Both DMD-null mice and mdx mice exhibited severe necrosis, which was followed by fibrosis in cardiac muscle. However, we could not detect a significant difference in myocardial fibrosis between mdx mice and DMD-null mice. Based on the present results, we have shown that cardiac myopathy is caused predominantly by a deficiency of full-length dystrophin Dp427.

Loss of short dystrophin isoform Dp71 in olfactory ensheathing cells causes vomeronasal nerve defasciculation in mouse olfactory system.

The Duchenne muscular dystrophy (DMD) gene encodes dystrophin, which is a protein defective in DMD patients, as well as a number of shorter isoforms, which have been shown to be expressed in various non-muscle, primarily neural, tissues. As of yet, the physiological function of the various dystrophin isoforms is not fully understood. In the present study, we investigated the neurological phenotype that arises in the DMD-null mice, where expression of all dystrophin isoforms had been disrupted. We demonstrate that vomeronasal axons in the DMD-null mice are defasciculated, and some of the defasciculated vomeronasal axons aberrantly entered into the main olfactory bulb, which indicates that the product(s) of the DMD gene plays an important role in vomeronasal nerve organization. Through western blot and immunofluorescence analyses, we determined that the dystrophin isoform Dp71 was exclusively expressed in the mouse olfactory system: mainly in the olfactory ensheathing cells (OECs), an olfactory system-specific glia cell that ensheaths fascicles of the olfactory nerve. In the OECs, Dp71 was co-localized with beta-dystroglycan, utrophin, laminin, and perlecan. Since beta-dystroglycan and perlecan expression was decreased in the OECs of DMD-null mice, we hypothesize that Dp71 expressed in the OECs participates in fasciculation of the vomeronasal nerve, most likely through interactions with extracellular matrix.

Functional analysis of homeodomain-containing transcription factor Lbx1 in satellite cells of mouse skeletal muscle.

Satellite cells are usually mitotically quiescent muscle stem cells, located between the sarcolemma and the basement membrane of muscle fibers. When muscles are damaged, satellite cells become activated, proliferate and differentiate to form multinucleate myofibers. The molecular mechanisms underlying these processes are poorly understood. In the present study, we found that, following treatment with cardiotoxin, homeodomain-containing transcription factor Lbx1 was strongly expressed in the satellite cells of regenerating adult skeletal muscle. Our immunohistochemical and northern blot analyses indicate that Lbx1 is expressed in activated but not quiescent satellite cells. In vitro, this Lbx1 expression was gradually downregulated when satellite cells differentiate into mature myofibers. Transfection and forced expression of Lbx1 in satellite-cell-derived C2C12 myoblast cells resulted in severe depression of myogenic differentiation and incomplete myotube formation, concomitantly with the activation of the paired-box transcription factor Pax7 and depression of the myogenic regulatory factor MyoD. Moreover, knockdown of Lbx1 in in-vitro-cultured satellite cells resulted in downregulation of Pax7. These results suggest that Lbx1 plays important roles in differentiation and maintenance of satellite cells of mature myofibers, probably through the regulation of Pax7.

Cellular responses of the ciliate, Tetrahymena thermophila, to far infrared irradiation.

Infrared rays from sunlight permeate the earth's atmosphere, yet little is known about their interactions with living organisms. To learn whether they affect cell structure and function, we tested the ciliated protozoan, Tetrahymena thermophila. These unicellular eukaryotes aggregate in swarms near the surface of freshwater habitats, where direct and diffuse solar radiation impinge upon the water-air interface. We report that populations irradiated in laboratory cultures grew and mated normally, but major changes occurred in cell physiology during the stationary phase. Early on, there were significant reductions in chromatin body size and the antibody reactivity of methyl groups on lysine residues 4 and 9 in histone H3. Later, when cells began to starve, messenger RNAs for key proteins related to chromatin structure, intermediary metabolism and cellular motility increased from two- to nearly nine-fold. Metabolic activity, swimming speed and linearity of motion also increased, and spindle shaped cells with a caudal cilium appeared. Our findings suggest that infrared radiation enhances differentiation towards a dispersal cell-like phenotype in saturated populations of Tetrahymena thermophila.

Coordination between CCR7- and CCR9-mediated chemokine signals in prevascular fetal thymus colonization.

Thymus seeding by T-lymphoid progenitor cells is a prerequisite for T-cell development. However, molecules guiding thymus colonization and their roles before and after thymus vascularization are unclear. Here we show that mice doubly deficient for chemokine receptors CCR7 and CCR9 were defective specifically in fetal thymus colonization before, but not after, thymus vascularization. The defective prevascular fetal thymus colonization was followed by selective loss of the first wave of T-cell development generating epidermal Vgamma3(+) gammadelta T cells. Unexpectedly, CCL21, a CCR7 ligand, was expressed not by Foxn1-dependent thymic primordium but by Gcm2-dependent parathyroid primordium, whereas CCL25, a CCR9 ligand, was predominantly expressed by Foxn1-dependent thymic primordium, revealing the role of the adjacent parathyroid in guiding fetal thymus colonization. These results indicate coordination between Gcm2-dependent parathyroid and Foxn1-dependent thymic primordia in establishing CCL21/CCR7- and CCL25/CCR9-mediated chemokine guidance essential for prevascular fetal thymus colonization.

Prefabricated engineered skin flap using an arteriovenous vascular bundle as a vascular carrier in rabbits.

BACKGROUND: The authors previously described induction of spontaneous tissue generation by implanting a collagen matrix and a ligated pedicle (arteriovenous bundle) into a hollow porous chamber in vivo in the rabbit. They hypothesized that increased tissue volume could be obtained by the application of basic fibroblast growth factor (bFGF) and/or by increasing the chamber size and porosity. METHODS: In rabbits, a saphenous arteriovenous pedicle and a collagen sponge were inserted into a porous chamber in the groin. Small-volume pore chambers (experiment 1, n = 7) and larger-volume, wider pore chambers (experiment 2, n = 13) were compared, and each was compared with and without bFGF. An additional three flaps of experiment 2 with bFGF were skin grafted, microsurgically transplanted to the ear, and evaluated at 6 months for stability. RESULTS: All patent chambers grew tissue; chambers with bFGF were almost filled, and those without were only half-filled. Histomorphometric analysis confirmed a significant difference. The larger-volume, larger-pore chambers produced more than twice the volume of tissue as the smaller chambers did, and this was significant. Tissue volume in both the control and bFGF groups of experiment 2 was significantly greater than that in the respective groups of experiment 1. Histology, angiography, and scanning electron microscopy confirmed greater vascularity in the bFGF groups and demonstrated vascular connections penetrating the chamber pores linking with angiogenic sprouts, probably from the vasa vasorum of the pedicle, to contribute to new growth. Transplanted flaps survived and appeared normal 6 months later. CONCLUSIONS: Patent pedicles, bFGF, large pore size, and larger-volume chambers all seemed to contribute to increased tissue growth in this model. The tissue is stable long term.

Roles of jumonji and jumonji family genes in chromatin regulation and development.

The jumonji (jmj) gene was identified by a mouse gene trap approach and has essential roles in the development of multiple tissues. The Jmj protein has a DNA binding domain, ARID, and two conserved jmj domains (jmjN and jmjC). In many diverse species including bacteria, fungi, plants, and animals, there are many jumonji family proteins that have only the jmjC domain or both jmj domains. Recently, Jmj protein was found to be a transcriptional repressor. Several proteins in the jumonji family are involved in transcriptional repression and/or chromatin regulation. Most recently, one of the human members has been shown to be a histone demethylase, and the jmjC domain is essential for the demethylase activity. Meanwhile, more and more evidence indicating that the jumonji family proteins play important roles during development is accumulating. Many proteins in the jumonji family may regulate chromatin and gene expression, and control development through various signaling pathways. Here, we highlight the roles of jmj and jumonji family proteins in chromatin regulation and development.

Mechanism of neurotrophic action of nobiletin in PC12D cells.

Nobiletin is a nonpeptide compound with a low molecular weight from a citrus fruit and has the activity to rescue bulbectomy-induced memory impairment. Here we describe that nobiletin itself induces neurite outgrowth in PC12D cells, a rat pheochromocytoma cell line, like NGF, and the molecular mechanism of its neurotrophic action. As cultured in the presence of nobiletin or NGF for 48 h and then assayed using a scanning electron microscope, PC12D cells treated with nobiletin showed morphology with flatter and larger cell bodies than the cells cultured with NGF. Nobiletin-induced neurite outgrowth was inhibited by PD98059 and U0126 but not K252a. Consistently, nobiletin caused a concentration-dependent enhancement of Erk/MAP kinase phosphorylation and a sustained increment of phosphorylation of MEK and Erk/MAP kinase, resulting in a stimulation of CREB phosphorylation and CRE-mediated transcription. This compound also increased intracellular cAMP and CRE-mediated transcription in the presence of forskolin and enhanced PKA activity to stimulate phosphorylation of multiple PKA substrates in PC12D cells. Furthermore, nobiletin preferentially inhibited Ca2+/CaM-dependent phosphodiesterase in vitro. This compound failed to stimulate phosphorylation of Erk5, which is known to be induced by NGF/TrkA signaling. These results suggest that nobiletin induces neurite outgrowth by activating a cAMP/PKA/MEK/Erk/MAP kinase-dependent but not TrkA-dependent signaling pathway coupling with CRE-mediated gene transcription and may thus become a novel type of biochemical probe for elucidation of the molecular mechanism of neuronal differentiation.

The ken and barbie gene encoding a putative transcription factor with a BTB domain and three zinc finger motifs functions in terminalia development of Drosophila.

Mutations in the ken and barbie locus are accompanied by the malformation of terminalia in adult Drosophila. Male and female genitalia often remain inside the body, and the same portions of genitalia and analia are missing in a fraction of homozygous flies. Rotated and/or duplicated terminalia are also observed. Terminalia phenotypes are enhanced by mutations in the gap gene tailless, the homeobox gene caudal, and the decapentaplegic gene that encodes a TGFbeta-like morphogen. The ken and barbie gene encodes a protein with three CCHH-type zinc finger motifs that are conserved in several transcription factors such as Krüppel and BCL-6. All defects in ken and barbie mutants are fully rescued by the expression of a wild-type genomic construct, which establishes the causality between phenotypes and the gene.

Nardosinone enhances nerve growth factor-induced neurite outgrowth in a mitogen-activated protein kinase- and protein kinase C-dependent manner in PC12D cells.

The mechanism to enhance nerve growth factor (NGF, 2 ng/ml)-induced neurite outgrowth from PC12D cells by nardosinone isolated from Nardostachys chinensis was examined. It was shown that the potentiation of the NGF-induced neurite outgrowth by nardosinone was mitogen-activated protein (MAP) kinase-dependent, but was not accompanied by stimulation of NGF-induced increase in MAP kinase phosphorylation. Furthermore, this augmentation of NGF-induced neurite outgrowth was abolished by GF109203X, a protein kinase C (PKC) inhibitor. These results suggest that the enhancement of NGF-induced neurite outgrowth from PC12D cells by nardosinone involves activation of a down-stream step of the MAP kinase-dependent cascade of NGF coupled with PKC.

Full reconstitution of hematopoietic system by murine umbilical cord blood.

BACKGROUND: Murine umbilical cord blood cells (UCBCs) were studied for their ability to reconstitute the hematopoietic system. METHODS: On average, 150 microL of cord blood per fetus containing 1.2 to 2 x 10(4) nucleated cells were collected from day 18.5 fetal umbilical cord, and 3 to 6 x 10(3) cells per fetus were obtained after separation by gradient centrifugation. RESULTS: Although lineage marker-, c-Kit+, and Sca-1+ cells were detectable among UCBCs, cells designated to be in the side population (SP) by Hoechst 33342 staining were hardly detectable within this population; the frequency of cells of this phenotype was less than 1 of 105. Instead, the lineage marker-, c-Kit+, and Sca-1- population contained a considerable number of SP cells. Nevertheless, UCBCs obtained from fetuses of green fluorescent protein-transgenic mice successfully reconstituted the blood cells of lethally irradiated recipients. Fluorescent cells could be readily detected in every blood cell lineage and among immature cell populations. Furthermore, fluorescent SP cells sorted from the recipient bone marrow cells could also reconstitute the blood cells in the secondary recipients, indicating that UCBCs also replenished bone marrow stem cells. CONCLUSION: Murine UCBC could fully reconstitute the hematopoietic system of lethally irradiated recipients including hematopoietic stem cells in bone marrow.

Enhanced phosphorylation and enzymatic activity of phosphoglucomutase by the Btk29A tyrosine kinase in Drosophila.

The Drosophila Btk29A tyrosine kinase is suggested to be involved in diverse processes, although its target proteins are unknown. In the present study, we investigated substrates of Btk29A tyrosine kinase by expressing a catalytically activated form of Btk29A-P1 (Btk-EG) in Drosophila compound eyes. Expression in eye disks led to the development of the rough-eye phenotype and increased tyrosine phosphorylation of a 65-kDa protein. Partial amino acid sequence analysis of this protein showed that it was phosphoglucomutase. Phosphoglucomutase activity in heads from Btk-EG-expressing flies was higher than that in controls, suggesting that the levels of tyrosine phosphorylation and activity of the enzyme are associated with Btk29A tyrosine kinase activity.

Repetitive activation of protein kinase A induces slow and persistent potentiation associated with synaptogenesis in cultured hippocampus.

Mammalian brain memory is hypothesized to be established through two phases; short-term plasticity, as exemplified by long-term potentiation (LTP) where pre-existing synapses change transmission efficiency, and long-lasting plasticity where new synapses are formed. This hypothesis, however, has not been verified experimentally. Using cultured hippocampal slices, we show that the repeated induction of late-phase LTP by brief applications of forskolin (FK) led to a slowly-developing long-lasting synaptogenesis, as judged from electrophysiological, cytological and ultrastructural indices. These indices include (1) field postsynaptic potential standardized by field action potential, which should represent the number of synapses per neuron; (2) the amounts of synaptic marker proteins; (3) the number of synaptophysin-immunopositive puncta; (4) the number of dendritic spines per length; (5) the density of synaptic ultrastructures; (6) ultrastructures similar to synapse perforation. Increment in these indices occurred approximately 10 days after FK-application and outlasted the following weeks. The increment depended on the times and intervals of FK-application. A biologically inert FK analogue failed to produce the similar effect. An inhibitor for cyclic AMP-dependent protein kinase (PKA) blocked the synaptogenesis. The cultured brain slice repeatedly exposed to FK should serve as a good model system for the analysis of persistent synaptogenesis possibly related to long-term memory in mammalian CNS.

lingerer, a Drosophila gene involved in initiation and termination of copulation, encodes a set of novel cytoplasmic proteins.

In an effort to uncover genetic components underlying the courtship behavior of Drosophila melanogaster, we have characterized a novel gene, lingerer (lig), mutations of which result in abnormal copulation. Males carrying a hypomorphic mutation in lig fail to withdraw their genitalia upon termination of copulation, but display no overt abnormalities in their genitalia. A severe reduction in the dosage of the lig gene causes repeated attempted copulations but no successful copulations. Complete loss of lig function results in lethality during early pupal stages. lig is localized to polytene segment 44A on the second chromosome and encodes three alternatively spliced transcripts that generate two types of 150-kD proteins, Lig-A and Lig-B, differing only at the C terminus. Lig proteins show no similarity to known proteins. However, a set of homologous proteins in mammals suggest that Drosophila Lig belongs to a family of proteins that share five highly conserved domains. Lig is a cytoplasmic protein expressed in the central nervous system (CNS), imaginal discs, and gonads. Lig-A expression is selectively reduced in lig mutants and the ubiquitous supply of this protein at the beginning of metamorphosis restores the copulatory defects of the lig mutant. We propose that lig may act in the nervous system to mediate the control of copulatory organs during courtship.

Genetic interactions of pokkuri with seven in absentia, tramtrack and downstream components of the sevenless pathway in R7 photoreceptor induction in Drosophila melanogaster.

The sevenless (sev) cascade plays an inductive role in formation of the R7 photoreceptor, whilst the pokkuri (pok) and tramtrack (ttk) gene products are known to repress R7 induction in developing ommatidia of Drosophila melanogaster. To elucidate how these positive and negative signalling mechanisms co-operate in the normal fate determination of R7, genetic interactions of mutations in the pok locus with ttk and downstream elements of sev including Gap1, raf1, rolled (r1) and seven in absentia (sina) were examined. The eye phenotype of a weak hypomorph, pok 15, was enhanced dominantly by Gap1-mip, a recessive mutation in a gene encoding a down-regulator of Ras1, producing multiple R7 in ommatidia. Ras1 has been reported to activate r1-encoded mitrogen-activated protein (MAP) kinase via Raf1 that is associated physically with Rasl. Ommatidia of raf1 c110 and rl 2/rlEMS64 typically lacked R7 and a few outer photoreceptors. The pok 1 mutation suppressed dominantly the rafl c110 rl2/rlEMS64 eye phenotypes, allowing single R7 cells to develop in ommatidia. The rafl c110 mutation improved adult viability of pok 1 homozygotes. An in vitro experiment demonstrated that MAP kinase phosphorylates Pok protein. Ttk is a transcriptional repressor which binds to the regulatory sequence upstream of the fushi-tarazu (ftz), even skipped (eve) and engrailed (en) coding region. A reduced activity in ttk resulted in enhancement of the pok phenotype. ttk mutations produced extra R7 cells even in sina homozygotes whilst the pok mutation did not. This result indicates that Ttk represses R7 induction downstream of the sites where Pok and Sina function.

Trypsin-like Hatching Enzyme of Mouse Blastocysts: Evidence for Its Participation in Hatching Process before Zona Shedding of Embryos6 : (embryo/hatching enzyme/protease/trypsin/strypsin).

Effects of twelve protease inhibitors on hatching of mouse embryos were investigated. Mouse hatching was strongly or moderately inhibited by trypsin inhibitors including p-toluenesulfonyl-Lys-CH2 Cl (TLCK) and chicken ovomucoid, while inhibitors for chymotrypsin and elastase showed weak or no inhibition. These results indicate the participation of a trypsin-like protease in the hatching of mouse embryos as a hatching enzyme., Since TLCK is the strongest and an irreversible inhibitor for the enzyme, timing of the participation of the hatching enzyme in the hatching process was examined by pulse treatment of embryos with TLCK before and during the zona shedding. The results indicated that a trypsin-like hatching enzyme functions before, but not during, the zona shedding of embryos, especially during a 15 h period immediately before the beginning of the shedding.

Internalization of Embryonal Carcinoma Cells when Aggregated with Normal Mouse Embryos: (blastocyst/aggregation/teratocarcinoma/segregation/ICM).

In the present study, we examined in detail the process of forming chimeric blastocysts between B242g embryonal carcinoma (EC) cells and normal mouse embryos. Electron microscopic observations of the developing aggregates revealed that the embryonic cells spread over the surface of the EC cells, resulting in the internalization of EC cells in the aggregates. When a single blastomere of an 8-cell embryo was aggregated with EC cells, the blastomere spread over and engulfed the EC cells. These results strongly suggest that EC cells are segregated and become situated in the inside position as the development of an aggregate proceeds, and then they are incorporated into the ICM of a blastocyst.