bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydra Peptide Project 1993–2007
Authors: Fujisawa Toshitaka
Published: August 2010

A systematic screening of peptide signaling molecules (<5000 da) in Hydra magnipapillata (the Hydra Peptide Project) was launched in 1993 and at least the first phase of the project ended in 2007. From the project a number of interesting suggestions and results have been obtained. First, a simple metazoan‐like Hydra appears to contain a few hundred peptide signaling molecules: half of them neuropeptides and the rest epitheliopeptides that are produced by epithelial cells. Second, epitheliopeptides were identified for the first time in Hydra. Some exhibit morphogen‐like activities, which accord with the notion that epithelial cells are primarily responsible for patterning in Hydra. A family of epitheliopeptides was involved in regulating neuron differentiation possibly through neuron–epithelial cell interaction. Third, many novel neuropeptides were identified. Most of them act directly on muscle cells inducing contraction or relaxation. Some were involved in cell differentiation and morphogenesis. During the course of this study, a number of important technical innovations (e.g. genetic manipulations in transgenic Hydra, high‐throughput purification techniques, etc.) and expressed sequence tag (EST) and genome databases were introduced in Hydra research. They have already helped to identify and characterize novel peptides and will contribute even more to the Hydra Peptide Project in the near future.
Differing strategies for forming the arthropod body plan: Lessons from Dpp, Sog and Delta in the fly Drosophila and spider Achaearanea
Authors: Oda Hiroki , Akiyama‐Oda Yasuko
Published: August 2010

In the insect Drosophila embryo, establishment of maternal transcription factor gradients, rather than cell–cell interactions, is fundamental to patterning the embryonic axes. In contrast, in the chelicerate spider embryo, cell–cell interactions are thought to play a crucial role in the development of the embryonic axes. A grafting experiment by Holm using spider eggs resulted in duplication of the embryonic axes, similar to the Spemann's organizer experiment using amphibian eggs. Recent work using the house spider Achaearanea tepidariorum has demonstrated that the homologs of decapentaplegic (dpp), short gastrulation (sog) and Delta, which encode a bone morphogenetic protein (BMP)‐type ligand, its antagonist and a Notch ligand, respectively, are required in distinct aspects of axis formation. Achaearanea Dpp appears to function as a symmetry‐breaking signal, which could account for Holm's results to some extent. Experimental findings concerning Achaearanea sog and Delta have highlighted differences in the mechanisms underlying ventral and posterior development between Drosophila and Achaearanea. Achaearanea ventral patterning essentially depends on sog function, in contrast to the Drosophila patterning mechanism, which is based on the nuclear gradient of Dorsal. Achaearanea posterior (or opisthosomal) patterning relies on the function of the caudal lobe, which develops from cells surrounding the blastopore through progressive activation of Delta‐Notch signaling. In this review, we describe the differing strategies for forming the arthropod body plan in the fly and spider, and provide a perspective towards understanding the relationship between the arthropod and vertebrate body plans.
Neuronal stem/progenitor cells in the vertebrate eye
Authors: Ohta Kunimasa , Ito Ayako , Tanaka Hideaki
Published: August 2010

We acquire information from the outside world through our eyes which contain the retina, the photosensitive component of the central nervous system. Once the adult mammalian retina is damaged, the retinal neuronal death causes a severe loss of visual function. It has been believed that the adult mammalian retina had no regenerative capacity. However, the identification of neuronal progenitor cells in the retina sheds some light on cellular therapies for damaged retinal regeneration. In this review, we highlight three potential stem/progenitor cells in the eye, the ciliary body epithelium cells, the iris pigmented epithelium cells, and Müller glia. In order to make them prime candidates for the possible treatment of retinal diseases, it is important to understand their basic characters. In addition, we discuss the key signaling molecules that function extracellularly and determine whether neuronal progenitors remain quiescent, proliferate, or differentiate. Finally, we introduce a secreted protein, Tsukushi, which is a possible candidate as a niche molecule for retinal stem/progenitor cells.
Breakthroughs and future challenges in left–right patterning
Authors: Hamada Hiroshi
Published: August 2010

How left–right (LR) asymmetry emerges during development has been a classic problem in the field of developmental biology, but it is only since the 1990s that molecular and genetic approaches have become possible. Since current progress in LR patterning has been summarized in several other reviews, I would like to briefly describe how this topic developed in the early days and what remains to be solved. In particular, two breakthroughs in the mid to late 1990s made major contributions to recent progress. Despite the rapid progress, there remain many challenging issues that need to be addressed in future.
Cross talk between germ cells and gonadal somatic cells is critical for sex differentiation of the gonads in the teleost fish, medaka (Oryzias latipes)
Authors: Tanaka Minoru , Saito Daisuke , Morinaga Chikako , Kurokawa Hiromi
Published: August 2010

To evaluate the possible role of germ cells on sex differentiation of the gonads in vertebrates, the teleost fish, medaka (Oryzias latipes), was used to generate a gonad without germ cells. The germ cell‐deficient medaka reveals multiple effects of germ cells on the process of sex differentiation. The previously isolated mutant medaka, hotei, with the excessive number of germ cells may support the contention that the proliferation of germ cells is related to feminization of the gonad. Futhermore, we show that two modes of proliferation for either maintenance of germ cells or commitment to gametogenesis are important components of the sex differentiation of medaka developing gonads. An intimate cross talk between germ cells and gonadal somatic cells during the sex differentiation will be discussed.
The autopod: Its formation during limb development
Authors: Tamura Koji , Yonei‐Tamura Sayuri , Yano Tohru , Yokoyama Hitoshi , Ide Hiroyuki
Published: August 2010

The autopod, including the mesopodium and the acropodium, is the most distal part of the tetrapod limb, and developmental mechanisms of autopod formation serve as a model system of pattern formation during development. Cartilage rudiments of the autopod develop after proximal elements have differentiated. The autopod region is marked by a change in the expression of two homeobox genes: future autopod cells are first Hoxa11/Hoxa13‐double‐positive and then Hoxa13‐single‐positive. The change in expression of these Hox genes is controlled by upstream mechanisms, including the retinoic acid pathway, and the expression of Hoxa13 is connected to downstream mechanisms, including the autopod‐specific cell surface property mediated by molecules, including cadherins and ephrins/Ephs, for cell‐to‐cell communication and recognition. Comparative analyses of the expression of Hox genes in fish fins and tetrapod limb buds support the notion on the origin of the autopod in vertebrates. This review will focus on the cellular and molecular regulation of the formation of the autopod during development and evolutionary developmental aspects of the origin of the autopod.
Bone development in the jaw of Nile tilapiaOreochromis niloticus(Pisces: Cichlidae)
Authors: Fujimura Koji , Okada Norihiro
Published: August 2010

East African cichlids have evolved feeding apparatus morphologies adapted to their diverse feeding behaviors. The evolution of the oral jaw morphologies is accomplished by the diversity of bone formation during development. To further understand this evolutionary process, we examined the skeletal elements of the jaw and their temporal and sequential emergence, categorized by developmental stages, using the Nile tilapiaOreochromis niloticusas a model cichlid. We found that chondrogenesis started in Stage 17. The deposition of osteoid for the dermal bones commenced in Stage 18. The uptake of calcium dramatically shifted from the surface of larvae to the gills in Stage 20. The bone mineralization of the skeleton began in Stage 25. These data provide important information regarding the sequential events of craniofacial development in East African cichlids and lay the groundwork for studying the molecular mechanisms underlying adaptation of jaw structure to feeding behavior.
Expression and localization of mesothelin in developing rat pancreas
Authors: Hou Liang‐Qin , Wang Yin‐He , Liu Li‐Jie , Guo Jing , Teng Li‐Ping , Cao Li‐Hua , Shi Hui , Yuan Li , De Wei
Published: August 2010

To define a genetic network that regulates development of the pancreas, we used high‐density microarray (Affymetrix) to generate transcriptional profiles of rat pancreas from five biologically significant stages of development: embryonic day 12.5 (E12.5), E15.5, E18.5, postnatal day 0 (P0) and adult. Many genes were notably highly expressed in the later gestation when islet architecture and function are gradually forming. The expression and localization of mesothelin, one of these genes, was further examined. Reverse transcription–polymerase chain reaction and Western blot analysis revealed that mRNA and protein levels of mesothelin were high from later gestation to 2–3 weeks after birth, and with relatively low but detectable expression levels in adult rat pancreas. Immunolocalization indicated that mesothelin localized not only in islet beta‐cells but also in the mesenchyme of developing rat pancreas. Transient mesothelin expression was concomitant with the development of islets architecture formation, remodeling and maturation. These findings indicate that mesothelin is dynamically expressed in the developing rat pancreas and that mesothelin might be involved in some developmental events during development of rat pancreas.
Expression of CD52 mRNA in the rat embryo
Authors: Ermini Leonardo , Aldi Silvia , Rosati Floriana
Published: August 2010

CD52 is a leukocyte differentiation antigen first discovered in humans as expressed on the surface of lymphocytes, monocytes and eosinophils. The human CD52 is found on chromosome 1, and two alleles are both known to be reasonably common. A closely homologous gene has been identified in the cynomologous monkey and related genes have been found in mouse, rat and dog. The role of CD52 in lymphocyte is still unclear but the anti‐CD52 antibodies named CAMPATH‐1 antibodies are largely used for therapy where depletion of lymphocytes is required. In the past expression of the antigen on progenitors of leukocytes in bone marrow had been excluded, but recent work indicates CD52 is highly expressed on cells with colony‐forming and NOD/SCID (non‐obese diabetic‐severe combined immunodeficiency)‐engrafting capacities, both at the mRNA and membrane protein level. We have investigated CD52 expression during development in rat embryos byin situhybridization. We report here that the antigen is highly expressed in the liver that is the major organ where multipotent hematopietic stem cells differentiate but also in the splancnopleuric mesoderm, at early stages of embryo differentiation, where hematopietic stem cells are suggested to arise. CD52+cells were found in areas active in vasculogenesis at early embryo stages and in the walls of the vessels in the liver at mid gestation. CD52+cells were also found to emerge among c‐Kit positive cells.
Specification process of animal plate in the sea urchin embryo
Authors: Sasaki Hiroki , Kominami Tetsuya
Published: August 2010

The most animal part of the ciliated band of sea urchin larvae, the animal plate, is a specialized region in which elongated cells form long and non‐beating cilia. To learn how this region is specified, animal halves were isolated from the early cleavage to pregastrulation stages. As is well known, the animal half that is isolated at the eight‐cell stage develops into a ‘dauerblastula’, which forms long and non‐beating cilia all around the surface. The region with long cilia, however, became restricted toward the animal pole when separation was delayed. If separated before primary mesenchyme ingression, even a small animal‐pole‐side fragment formed a normal‐sized animal plate. Thus, the prospective animal plate region is gradually restricted by some signal from the vegetal hemisphere, and the specification process terminates before the mesenchyme blastula stage. It was also known that a normal‐sized animal plate was formed in micromere‐less embryos, indicating that the signal does not depend on micromeres or their descendants. Further, the animal‐pole‐side fragments were isolated from embryos in which the third cleavage plane was shifted toward the vegetal pole. They formed a normal‐sized animal plate, containing more than 75% of the egg volume from the animal pole. This indicates that the egg cytoplasm delivered to veg1‐lineage blastomeres plays an important role in the animal plate specification. Interestingly, the an1‐less embryo formed long and non‐beating cilia at its top region, but thickening did not occur. The cytoplasm near the animal pole might contain some factors necessary for the animal plate to become thick.
Retinoic acid affects craniofacial patterning by changing Fgf8 expression in the pharyngeal ectoderm
Authors: Abe Makoto , Maeda Takashi , Wakisaka Satoshi
Published: August 2010

Retinoic acid signaling plays important roles in establishing normal patterning and cellular differentiation during embryonic development. In this study, we show that single administration of retinoic acid at embryonic day 8.5 causes homeotic transformation of the lower jaw into upper jaw‐like structures. This homeosis was preceded by downregulation of Fgf8 and Sprouty expression in the proximal domain of the first pharyngeal arch. Downregulation of mesenchymal genes such as Dlx5, Hand2, Tbx1 and Pitx2 was also observed. The oropharynx in retinoic acid‐treated embryos was severely constricted. Consistent with this observation, Patched expression in the arch endoderm and mesenchyme was downregulated. Thus, retinoic acid affects the expression of subsets of epithelial and mesenchymal genes, possibly disrupting the regional identity of the pharyngeal arch.
Epithelial to mesenchymal transition during gastrulation: An embryological view
Authors: Nakaya Yukiko , Sheng Guojun
Published: August 2010

Gastrulation is a developmental process to generate the mesoderm and endoderm from the ectoderm, of which the epithelial to mesenchymal transition (EMT) is generally considered to be a critical component. Due to increasing evidence for the involvement of EMT in cancer biology, a renewed interest is seen in using in vivo models, such as gastrulation, for studying molecular mechanisms underlying EMT. The intersection of EMT and gastrulation research promises novel mechanistic insight, but also creates some confusion. Here we discuss, from an embryological perspective, the involvement of EMT in mesoderm formation during gastrulation in triploblastic animals. Both gastrulation and EMT exhibit remarkable variations in different organisms, and no conserved role for EMT during gastrulation is evident. We propose that a ‘broken‐down’ model, in which these two processes are considered to be a collective sum of separately regulated steps, may provide a better framework for studying molecular mechanisms of the EMT process in gastrulation, and in other developmental and pathological settings.
Adult‐type pigment cells, which color the ocular sides of flounders at metamorphosis, localize as precursor cells at the proximal parts of the dorsal and anal fins in early larvae
Authors: Watanabe Kohei , Washio Youhei , Fujinami Yuichiro , Aritaki Masato , Uji Susumu , Suzuki Tohru
Published: August 2010

Flounders form left‐right asymmetry in body coloration during metamorphosis through differentiation of adult‐type melanophores and xanthophores on the ocular side. As the first step in investigating the formation of flounder body coloration asymmetry, in this study, we aimed to determine where the precursors of adult‐type chromatophores distribute in larvae before metamorphosis. In Paralichthys olivaceus and Verasper variegatus, GTP cyclohydrolase 2 (gch2), a common marker of melanoblasts and xanthoblasts, was found to be transiently expressed in cells located along the bilateral skeletal muscles at the basal parts of the dorsal and anal fins of premetamorphic larvae. When V. variegatus larvae were fed with a strain of Artemia collected in Brazil, this gch2 expression was abolished and the differentiation of adult‐type melanophores was completely inhibited, while the density of larval melanophores was not affected. In a cell trace test in which the cells at the basal part of the dorsal fin were labeled with DiI at the premetamorphic stage, adult‐type melanophores labeled with DiI were found in the skin on the ocular side after metamorphosis. These data suggest that, in flounder larvae, adult‐type melanophores are distributed at the basal parts of the dorsal and anal fins as unpigmented precursor cells.
Absence of tissue inhibitor of metalloproteinases 3 disrupts alveologenesis in the mouse
Authors: Gill Sean E. , Pape M. Cynthia , Leco Kevin J.
Published: August 2010

Tissue inhibitors of metalloproteinases (TIMPs) regulate extracellular matrix (ECM) degradation by matrix metalloproteinases (MMPs) throughout lung development. We examined lungs from TIMP3 null mice and found significant air space enlargement compared with wild type (WT) animals during a time course spanning early alveologenesis (post‐partum days 1, 5, 9 and 14). Trichrome staining revealed a similar pattern of collagen distribution in the walls of nascent alveoli; however, the alveolar walls of TIMP3 mutant mice appeared to be thinner than controls. Assessment of MMP2 and MMP9 activities by gelatin zymography demonstrated a significant elevation in the active form of MMP2 at post‐partum days 1 and 5. Treatment of null pregnant dams with a broad spectrum synthetic metalloproteinase inhibitor, GM6001, on embryonic day 16.5 enhanced the formation of primitive alveoli during the saccular stage of lung development as evidenced by a partial, but significant, rescue of alveolar size in post‐partum day 1 animals. We propose that increased MMP activity in the absence of TIMP3 enhances ECM proteolysis, upsetting proper formation of primitive alveolar septa during the saccular stage of alveologenesis. Therefore, TIMP3 indirectly regulates alveolar formation in the mouse. To our knowledge, ours is the first study to demonstrate that in utero manipulation of the TIMP/MMP proteolytic axis, to specifically inhibit proteolysis, significantly affects lung development.
Vocal control area‐related expression of neuropilin‐1, plexin‐A4, and the ligand semaphorin‐3A has implications for the evolution of the avian vocal system
Authors: Matsunaga Eiji , Okanoya Kazuo
Published: August 2010

The avian vocal system is a good model for exploring the molecular basis of neural circuit evolution related to behavioral diversity. Previously, we conducted a comparative gene expression analysis among two different families of vocal learner, the Bengalese finch (Lonchura striata var. domestica), a songbird, and the budgerigar (Melopsittacus undulatus), a parrot; and a non‐learner, the quail (Coturnix coturnix), to identify various axon guidance molecules such as cadherin and neuropilin‐1 as vocal control area‐related genes. Here, we continue with this study and examine the expression of neuropilin and related genes in these species in more detail. We found that neuropilin‐1 and its coreceptor, plexin‐A4, were expressed in several vocal control areas in both Bengalese finch and budgerigar brains. In addition, semaphorin‐3A, the ligand of neuropilin‐1, expression was not detected in vocal control areas in both species. Furthermore, there was some similar gene expression in the quail brain. These results suggest the possibility that a change in the expression of a combination of semaphorin/neuropilin/plexin was involved in the acquisition of vocal learning ability during evolution.
Spatio‐temporal control of neural epithelial cell migration and epithelium‐to‐mesenchyme transition during avian neural tube development
Authors: Duband Jean‐Loup , Blavet Cédrine , Jarov Artem , Fournier‐Thibault Claire
Published: August 2010

As opposed to the neural crest, the neural epithelium is generally viewed as a static and cohesive structure. Here, using an ex vivo system free of the environmental influences and physical constraints encountered in the embryo, we show that neural epithelial cells are on the contrary intrinsically motile, although they do not undergo spontaneous epithelium‐to‐mesenchyme transition and display molecular and cellular characteristics distinct from those of neural crest cells. However, they can be instructed to undergo epithelium‐to‐mesenchyme conversion independently of the acquisition of neural crest traits. Migration potentialities of neural epithelial cells are transient and are progressively restricted during neural tube development. Restriction of cell migration is irreversible and can be in part accounted for by increase in N‐cadherin in cellular junctions and in cell polarity. In conclusion, our study reveals that the neural epithelium is a highly flexible tissue in which cells are maintained cohesive under the control of a combination of extrinsic factors and physical constraints.
Formation and patterning of the forebrain and olfactory system by zinc‐finger genes Fezf1 and Fezf2
Authors: Shimizu Takeshi , Hibi Masahiko
Published: August 2010

The zinc finger genes Fezf1 (Fez) and Fezf2 (Fez‐like, Fezl, Zfp312) were initially identified as anterior neuroectoderm‐specific genes in Xenopus and zebrafish. They encode transcriptional regulators containing an Engrailed homology 1 (Eh1) repressor motif, which is known to interact with Groucho/TLE (Transducin‐Like Enhancer of Split)‐type transcriptional co‐repressors. Both Fezf1 and Fezf2 are expressed in the prospective forebrain region during early embryogenesis, and they subsequently show both overlapping and distinct expression domains in the olfactory epithelium and forebrain. Loss‐of‐function studies in mouse and zebrafish revealed roles for Fezf1 and Fezf2 in the development of the olfactory system and forebrain. In mice, Fezf1, expressed in olfactory sensory neurons, is required for the axonal projection of olfactory sensory neurons, and controls the layer formation of the olfactory bulb in a non‐cell autonomous manner. Fezf2 is involved in the differentiation of subplate neurons and the formation of the fimbria and fornix. Fezf2 is also essential for specification of the subcerebral projection neurons in the neocortex. Fezf1 and Fezf2 control the rostro‐caudal patterning of the diencephalon by repressing the caudal diencephalon fate in the rostral diencephalon in mice and zebrafish. In zebrafish, fezf2 is also required for the development of monoaminergic (dopaminergic and serotonergic) neurons in the basal forebrain.
Fate map of the chick embryo neural tube
Authors: Garcia‐Lopez Raquel , Pombero Ana , Martinez Salvador
Published: August 2010

Fate‐map studies have provided important information in relation to the regional topology of brain areas in different vertebrate species. Moreover, these studies have demonstrated that the distribution of presumptive territories in neural plate and neural tube are highly conserved in vertebrates. The aim of this review is to re‐examine and correlate the distribution of presumptive neuroepithelial domains in the chick neural tube with molecular information and discuss recent data. First, we review descriptive fate map studies of neural plate in different vertebrate species that have been studied using diverse fate‐mapping methods. Then, we summarize the available data on the localization of neuroepithelial progenitors for the brain subregions in the chick neural tube at stage HH10–11, the most used stage for experimental embryology. This analysis is mainly focused on experimental fate mapping results using quail‐chick chimeras.
Evolution and regeneration of the planarian central nervous system
Authors: Umesono Yoshihiko , Agata Kiyokazu
Published: August 2010

More than 100 years ago, early workers realized that planarians offer an excellent system for regeneration studies. Another unique aspect of planarians is that they occupy an interesting phylogenetic position with respect to the nervous system in that they possess an evolutionarily primitive brain structure and can regenerate a functional brain from almost any tiny body fragment. Recent molecular studies have revisited planarian regeneration and revealed key information about the cellular and molecular mechanisms underlying brain regeneration in planarians. One of our great advances was identification of a gene,nou‐darake, which directs the formation of a proper extrinsic environment for pluripotent stem cells to differentiate into brain cells in the planarianDugesia japonica. Our recent findings have provided mechanistic insights into stem cell biology and also evolutionary biology.
Cell type and function of neurons in the ascidian nervous system
Authors: Horie Takeo , Nakagawa Masashi , Sasakura Yasunori , Kusakabe Takehiro G.
Published: August 2010

Ascidians, or sea squirts, are primitive chordates, and their tadpole larvae share a basic body plan with vertebrates, including a notochord and a dorsal tubular central nervous system (CNS). The CNS of the ascidian larva is formed through a process similar to vertebrate neurulation, while the ascidian CNS is remarkably simple, consisting of about 100 neurons. Recent identification of genes that are specifically expressed in a particular subtype of neurons has enabled us to reveal neuronal networks at single‐cell resolution. Based on the information on neuron subtype‐specific genes, different populations of neurons have been visualized by whole‐mount in situ hybridization, immunohistochemical staining using specific antibodies, and fluorescence labeling of cell bodies and neurites by a fluorescence protein reporter driven by neuron‐specific promoters. Neuronal populations that have been successfully visualized include glutamatergic, cholinergic, γ‐aminobutyric acid/glycinergic, and dopaminergic neurons, which have allowed us to propose functional regionalization of the CNS and a neural circuit for locomotion. Thus, the simple nervous system of the ascidian larva can serve as an attractive model system for studying the development, function, and evolution of the chordate nervous system.
Drosophila multiplexin (Dmp) modulates motor axon pathfinding accuracy
Authors: Meyer Frauke , Moussian Bernard
Published: August 2010

Multiplexins are multidomain collagens typically composed of an N‐terminal thrombospondin‐related domain, an interrupted triple helix and a C‐terminal endostatin domain. They feature a clear regulatory function in the development of different tissues, which is chiefly conveyed by the endostatin domain. This domain can be found in proteolytically released monomeric and trimeric versions, and their diverse and opposed effects on the migratory behavior of epithelial and endothelial cell types have been demonstrated in cell culture experiments. The only Drosophila multiplexin displays specific features of both vertebrate multiplexins, collagens XV and XVIII. We characterized the Drosophila multiplexin (dmp) gene and found that three main isoforms are expressed from it, one of which is the monomeric endostatin version. Generation of dmp deletion alleles revealed that Dmp plays a role in motor axon pathfinding, as the mutants exhibit ventral bypass defects of the intersegmental nerve b (ISNb) similar to other motor axon guidance mutants. Transgenic overexpression of monomeric endostatin as well as of full‐length Dmp, but not trimeric endostatin, were able to rescue these defects. In contrast, trimeric endostatin increased axon pathfinding accuracy in wild type background. We conclude that Dmp plays a modulating role in motor axon pathfinding and may be part of a buffering system that functions to avoid innervation errors.
Two states of active spermatogenesis switch between reproductive and non‐reproductive seasons in the testes of the medaka, Oryzias latipes
Authors: Iwasaki Yuko , Ohkawa Keiko , Sadakata Hisato , Kashiwadate Akiko , Takayama‐Watanabe Eriko , Onitake Kazuo , Watanabe Akihiko
Published: August 2010

Seasonal change in spermatogenesis was examined in the restricted spermatogonium‐type testes of a teleost, Oryzias latipes. Histological observation revealed that the number of each stage of germ cells during most of the non‐reproductive season, from October to January (O–J period) was nearly half of that during the reproductive season, from May to July (M–J period), except for type B spermatogonia (B‐gonia), which was actually equal. As a result, the ratio of primary spermatocytes (P‐cytes) to B‐gonia was remarkably small in the O–J period. Despite the differences between both time periods, the proliferative activity of type A spermatogonia (A‐gonia), B‐gonia, or P‐cytes was at a similar level in both periods. Moreover, in cultured testes treated with bromodeoxyuridine as a cell‐lineage tracer, P‐cytes differentiated to spermatids in 11–15 days in both M–J and O–J periods. These indicate that spermatogenesis is active in each period at a different state. In the spermatogenic testis, A‐gonial proliferation was maintained by human follicle stimulating hormone/luteinizing hormone in culture. Whereas cell death of B‐gonia and/or P‐cytes gradually increased in the M–J period in spite of those cells being constant in population sizes. In transition to the O–J period, A‐gonia and P‐cytes first decreased, which was accompanied by a decrease in proliferative activity of A‐gonia and relative increase of dead cells from B‐gonia and/or P‐cytes against live P‐cytes. These suggest that A‐gonial proliferation and cell death of B‐gonia and/or P‐cytes that is induced coordinately with B‐gonial differentiation are critical for the spermatogenic control.
Repressive but not activating epigenetic modifications are aberrant on the inactive X chromosome in live cloned cattle
Authors: Geng‐Sheng Cao , Yu Gao , Kun Wang , Fang‐Rong Ding , Ning Li
Published: August 2010

X inactivation is the process of a chromosome‐wide silencing of the majority of genes on the X chromosome during early mammalian development. This process may be aberrant in cloned animals. Here we show that repressive modifications, such as methylation of DNA, and the presence of methylated histones, H3K9me2 and H3K27me3, exhibit distinct aberrance on the inactive X chromosome in live clones. In contrast, H3K4me3, an active gene marker, is obviously missing from the inactive X chromosome in all cattle studied. This suggests that the disappearance of active histone modifications (H3K4me3) seems to be more important for X inactivation than deposition of marks associated with heterochromatin (DNA methylation, H3K27me3 and H3K9me2). It also implies that even apparently normal clones may have subtle abnormalities in repressive, but not activating epigenetic modifications on the inactive X when they survive to term. We also found that the histone H3 methylations were enriched and co‐localized at q21‐31 of the active X chromosome, which may be associated with an abundance of LINE1 repeat elements.
Xtr, a plural tudor domain‐containing protein, coexists with FRGY2 both in cytoplasmic mRNP particle and germ plasm in Xenopus embryo: Its possible role in translational regulation of maternal mRNAs
Authors: Golam Mostafa Md. , Sugimoto Tetsuharu , Hiyoshi Masateru , Kawasaki Hiroshi , Kubo Hideo , Matsumoto Ken , Abe Shin‐Ichi , Takamune Kazufumi
Published: August 2010

Xtr is present exclusively in early embryonic and germline cells. We have previously shown that loss‐of‐function of the Xtr in embryos causes arrest of karyokinesis progression. Since Xtr contains plural tudor domains, which are known to associate with target proteins directly, we examined Xtr‐interacting proteins by immunoprecipitation with an anti‐Xtr monoclonal antibody and detected a few RNA‐binding proteins such as FRGY2, a component of messenger ribonucleoprotein (mRNP) particle. The coexistence of Xtr with FRGY2 by constituting an mRNP particle was further confirmed by gel filtration assay. Search of mRNAs in the immunoprecipitate with Xtr suggested that the Xtr‐associated molecules included several mRNAs, of which translational products were known to play crucial roles in karyokinesis progression (RCC1, XRHAMM, and so on) and in germ cell development (XDead end). Immunohistochemical observation clearly showed the co‐localization of Xtr with FRGY2 also in germ plasm, in which XDead end mRNA has been shown to be localized specifically. Taken together, we proposed the possible role of Xtr in translational activation of the maternal mRNAs repressed in mRNP particle.
Early zygotic expression of transcription factors and signal molecules in fully dissociated embryonic cells of Ciona intestinalis: A microarray analysis
Authors: Noda Takeshi , Hamada Mayuko , Hamaguchi Makoto , Fujie Manabu , Satoh Nori
Published: August 2010

Specification of early embryonic cells of animals is established by maternally provided factors and interactions of neighboring cells. The present study addressed a question of autonomous versus non‐autonomous specification of embryonic cells by using the Ciona intestinalis embryo, in particular the genetic cascade of zygotic expression of transcription factor genes responsible for notochord specification. To examine this issue, we combined the classic experiment of continuous dissociation of embryonic cells with the modern technique of oligonucleotide‐based microarrays. We measured early zygotic expression of 389 core transcription factors genes and 118 major signal molecule genes in embryonic cells that were fully dissociated from the first cleavage. Our results indicated that even if cells are free from contact with neighbors, the major transcription factor genes that have primary roles in embryonic cell specification commence their zygotic expression at the same time as in normal embryos. Dissociation of embryonic cells did not affect extracellular signal‐regulated kinases (ERK) activity. Although normal embryos treated with U0126 failed to express Bra and Twist‐like‐1, dissociated embryonic cells treated with U0126 expressed the genes. These results are discussed in relation to the grade of autonomous versus non‐autonomous genetic cascades that are responsible for the specification of early Ciona embryonic cells.
Primordial germ cells contain subpopulations that have greater ability to develop into pluripotential stem cells
Authors: Matsui Yasuhisa , Tokitake Yuko
Published: August 2010

Primordial germ cells (PGCs) are undifferentiated germ cells in embryos. We previously found that some mouse PGCs develop into pluripotential cells (EG cells) when cultured on a feeder layer expressing the membrane bound form of Steel factor with culture medium containing leukemia inhibitory factor and basic fibroblast growth factor. To understand the mechanisms of the conversion of PGCs into EG cells, we attempted to identify PGC subpopulations that have the ability to develop into EG cells. Using flow cytometry, we fractionated PGCs by the expression of the cell surface antigen integrin α6, as well as by the detection of side‐population (SP) cells in which stem cells are enriched in various tissues. PGCs with negative or low integrin α6 expression and with SP cell phenotype showed higher potential to convert to EG cells. Negative or low integrin α6 expression in PGCs was also correlated with lower expression of Ddx4, which is specifically expressed in PGCs after embryonic day 10.5. The results indicate that the primitive PGC population showing the SP cell phenotype among undifferentiated PGCs has a higher ability of being converted into EG cells. Thus, conversion of PGCs into pluripotential stem cells may be regulated by being influenced by the natural status of individual PGCs as well as the reprogramming process after starting culture.
Interaction of ZFPIP with PBX1 is crucial for proper expression of neural genetic markers during Xenopus development
Authors: Laurent Audrey , Masse Julie , Deschamps Stéphane , Burel Agnes , Omilli Francis , Richard‐Parpaillon Laurent , Pellerin Isabelle
Published: August 2010

ZFPIP/Zfp462 has been recently identified as a new vertebrate zinc finger encoding gene whose product interacts with Pbx1. Previous work indicates that ZFPIP is maternally expressed in Xenopus laevis oocytes and plays a key role during the cleavage phase of embryogenesis. This early expression is followed by a zygotic expression which overlaps with the neural Pbx1 expression pattern, suggesting an interaction between these two partners during Xenopus neurogenesis. In order to test the physiological interaction between ZFPIP and Pbx1, we carried out a dominant negative assay in which the Pbx1 interacting domain of ZFPIP (ZFPIPp) was overexpressed in Xenopus laevis embryos. We observed that ZFPIPp ectopic expression led to abnormal en2 and N‐cam expression patterns, whereas krox‐20 expression was not affected. Furthermore, we showed that while ZFPIPp alone was localized in the nucleus of Cos‐7 cells, additional expression of Pbx1 induced a location of ZFPIPp at the perinuclear region of the cells. These overall data suggest that ZFPIP and Pbx1 could be partners and cooperate in the regulation of essential neural genes during Xenopus development.
Differentiation inducing factors in Dictyostelium discoideum: A novel low molecular factor functions at an early stage(s) of differentiation
Authors: Oohata Akiko A. , Fukuzawa Masashi , Hotta Rie , Nakagawa Manabu , Niwa Masatake , Takaya Yoshiaki
Published: August 2010

There are reports that secreted factor(s) are involved in prespore cell differentiation in Dictyostelium discoideum, but the structures and functions of the various factors have not been elucidated. Previously, we described two prespore cell‐inducing factors in conditioned medium; one was a glycoprotein named prespore cell‐inducing factor (ψ factor, or PSI‐1), and the other, a heat stable dialyzable factor(s). In the present paper, we purified and characterized the most potent prespore cell‐inducing activity in dialysates. The factor began to be secreted after the onset of starvation and stopped being secreted once the cells had aggregated, which was earlier than the onset of the ψ factor gene expression. In addition, unlike ψ factor, its secretion did not appear to depend on activation of protein kinase A. Interestingly, the purified factor not only induced prespore cell specific genes such as pspA and cotC but also a prestalk‐cell specific gene, ecmB in vitro. The purified factor is tentatively designated polyketide‐like factor (PLF), because it seems to be a novel polyketide with 208 Da. Half maximal induction of prespore cell was obtained with 26 nmol/L of PLF. We propose that PLF plays a key role in the acquisition of differentiation commitment, before the ψ factor induces specifically prespore cell differentiation.
Mammary epithelial‐specific knockout of the ephrin‐B2 gene leads to precocious epithelial cell death at lactation
Authors: Weiler Stéphanie , Rohrbach Valeria , Pulvirenti Thekla , Adams Ralf , Ziemiecki Andrew , Andres Anne‐Catherine
Published: August 2010

The family of Eph receptor tyrosine kinases and their membrane bound ligands, the ephrins, are involved in a wide variety of morphogenic processes during embryonic development and adult tissue homeostasis. Receptor‐ligand interaction requires direct cell–cell contact and results in forward and reverse signaling originating from the receptor and ligand, respectively. We have previously shown that EphB4 and ephrinB2 are differentially expressed during the development of the adult mammary parenchyma. Overexpression of EphB4 in the mammary epithelium of transgenic mice leads to perturbations in mammary epithelial morphology, motility and growth. To investigate the role of ephrinB2 signaling in mammary gland biology, we have established transgenic mice exhibiting conditional ephrinB2 knockout in the mammary epithelium. In homozygote double transgenic CreLox mice, specific knockout of ephrinB2 occurred in the mammary epithelium during the first pregnancy‐lactating period. Abolishing ephrinB2 function led to severe interference with the architecture and functioning of the mammary gland at lactation. The morphology of the transgenic lactating glands resembled that of involuting controls, with decreased epithelial cell number and collapsed lobulo‐alveolar structures. Accordingly, massive epithelial cell death and expression of involution‐specific genes were observed. Interestingly, in parallel to cell death, significant cell proliferation was apparent, suggestive of tissue regeneration.
Hemoblasts in colonial tunicates: Are they stem cells or tissue‐restricted progenitor cells?
Authors: Kawamura Kaz , Sunanaga Takeshi
Published: August 2010

Colonial tunicates have hemoblasts, which are undifferentiated coelomic cells that play a key role in tissue renewal during reproduction and regeneration. Some hemoblasts differentiate into somatic lineage cells such as endodermal multipotent epithelial, cardiac and body‐wall muscle, and blood cells. There is no well established evidence that somatic hemoblasts are stem cells. Rather, like tissue‐restricted progenitor cells, some peripheral hemoblasts give rise to terminally differentiated cells, while other hemoblasts differentiate into germ cells and accessory cells. Unlike somatic lineage cells, germ cells and their precursors express vasa homologues in common. In some colonial tunicates, vasa is indispensable for germ cell development. All vasa‐positive hemoblasts appear to differentiate into germ cells, suggesting that most of them are tissue‐restricted progenitor cells. When a colony is naturally or experimentally depleted of vasa‐expressing cells, vasa and vasa‐expressing germ cells can reappear in the colony. We speculate that, in addition to tissue‐restricted progenitor cells, highly potent stem cells which regulate the activities of blastogenesis and gametogenesis and eventually cause soma‐germ conflict in colonial tunicates may exist in colonial tunicates.
Multiple sequences and factors are involved in stability/degradation of Awnt‐1, Awnt‐5A and Awnt‐5B mRNAs during axolotl development
Authors: Caulet Stéphane , Pelczar Hélène , Andéol Yannick
Published: August 2010

Following fertilization in amphibian, early cleavage stages are maternally controlled at a post‐transcriptional level before initiation of zygotic transcriptions at the mid blastula transition (MBT). We document the expression levels of the axolotl Awnt‐1, Awnt‐5A and Awnt‐5B genes as well as the adenylation states of their corresponding mRNAs from the end of oogenesis until the tailbud stages. Awnt‐1/‐5A RNAs are stable until MBT then degraded before gastrulation. Awnt‐5B RNAs are degraded at fertilization and zygotically expressed after MBT with high level expression from gastrulation. Estimation of the poly(A) tail lengths reveals no direct link between deadenylation and degradation periods for each Awnt transcript. To investigate the molecular mechanisms involved in Awnt‐1/‐5A/‐5B RNAs stability, synthetic full‐length or 3′ untranslated region (UTR) Awnt RNAs progressively deleted from their 3′ end were microinjected in axolotl oocytes, unfertilized and fertilized eggs. We identified degrading and stabilizing sequences in the 3′UTR whose activities depend on the cellular context and are also modulated by the 5′UTR and coding sequence within each RNA. Using axolotl nuclear extracts from stage VI oocytes, we further produced evidence of destabilizing factors targeting the Awnt‐5B RNAs. Altogether, these results show that oocyte maturation and late cleavages following MBT are two important periods when axolotl Wnt RNAs are highly regulated.
The stem cell system in demosponges: Insights into the origin of somatic stem cells
Authors: Funayama Noriko
Published: August 2010

The stem cell system is one of the unique systems that have evolved only in multicellular organisms. Major questions about this system include what type(s) of stem cells are involved (pluri‐, multi‐ or uni‐potent stem cells), and how the self‐renewal and differentiation of stem cells are regulated. To understand the origin of the stem cell system in metazoans and to get insights into the ancestral stem cell itself, it is important to discover the molecular and cellular mechanisms of the stem cell system in sponges (Porifera), the evolutionarily oldest extant metazoans. Histological studies here provided a body of evidence that archeocytes are the stem cells in sponges, and recent molecular studies of sponges, especially the finding of the expression of Piwi homologues in archeocytes and choanocytes in a freshwater sponge, Ephydatia fluviatilis, have provided critical insights into the stem cell system in demosponges. Here I introduce archeocytes and discuss (i) modes of archeocyte differentiation, (ii) our current model of the stem cell system in sponges composed of both archeocytes and choanocytes based on our molecular analysis and previous microscopic studies suggesting the maintenance of pluripotency in choanocytes, (iii) the inference that the Piwi and piRNA function in maintaining stem cells (which also give rise to gametes) may have already been achieved in the ancestral metazoan, and (iv) possible hypotheses about how the migrating stem cells arose in the urmetazoan (protometazoan) and about the evolutionary origin of germline cells in the urbilaterian (protobilaterian).
Alternative splicing of SMADs in differentiation and tissue homeostasis
Authors: Tao Shijie , Sampath Karuna
Published: August 2010

Tissue‐specific alternate splicing is an important means of regulating gene expression during development. The effector proteins for the transforming growth factor‐β signaling pathway, the SMADs, encode distinct isoforms generated via alternate splicing, which appear to have distinct tissue‐specific expression profiles and functions. Here, we discuss the roles of various SMAD isoforms, and the consequences of mis‐regulation of SMAD splicing in development and tissue homeostasis.
Comparative study of the speed of acid‐suppressing effects of oral administration of cimetidine and famotidine
Authors: ADACHI KYOICHI , KOMAZAWA YOSHINORI , MIHARA TAKAFUMI , AZUMI TAKANE , FUJISAWA TOMOO , KATSUBE TOMOKO , FURUTA KENJI , KINOSHITA YOSHIKAZU
Published: August 2010

Background and Aim:  H2 histamine receptor antagonists (H2RAs) are widely used in patients with acid‐related diseases, and the onset of antisecretory activity of H2RAs is reported to be faster than that of proton pump inhibitors (PPIs). The aim of this study was to compare the rapidity of onset of antisecretory activity of cimetidine and famotidine when orally administered.

Methods:  Fifteen healthy male Japanese volunteers (five H. pylori‐positive and 10 H. pylori‐negative) participated in a randomized cross‐over study. All subjects were examined three times by ambulatory 6‐h pH monitoring (from 17:30 to 23:30) with no medication or oral administration of 400 mg of cimetidine or 20 mg of famotidine. Drugs were administered at 19:30 after eating a standard meal, and plasma concentrations were also examined for 4 h periods.

Results:  The plasma concentration of cimetidine increased rapidly after oral administration, while that of famotidine increased gradually. Intragastric pH was increased and percentage time with pH < 4.0 decreased significantly 2 h after administration of either cimetidine or famotidine. There was no statistically significant difference in acid‐suppressing effect between cimetidine and famotidine during the short‐term post‐administration period.

Conclusion:  Rapidity of antisecretory activity did not differ between oral cimetidine and famotidine administered orally.