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Mammalian Counterpart (mammalian + counterpart)
Selected AbstractsShh/BMP-4 signaling pathway is essential for intestinal epithelial development during Xenopus larval-to-adult remodelingDEVELOPMENTAL DYNAMICS, Issue 12 2006Atsuko Ishizuya-Oka Abstract During amphibian larval-to-adult intestinal remodeling, progenitor cells of the adult epithelium actively proliferate and differentiate under the control of thyroid hormone (TH) to form the intestinal absorptive epithelium, which is analogous to the mammalian counterpart. We previously found that TH,up-regulated expression of bone morphogenetic protein-4 (BMP-4) spatiotemporally correlates with adult epithelial development in the Xenopus laevis intestine. Here, we aimed to clarify the role of BMP-4 in intestinal remodeling. Our reverse transcriptase-polymerase chain reaction and in situ hybridization analyses indicated that mRNA of BMPR-IA, a type I receptor of BMP-4, is expressed in both the developing connective tissue and progenitor cells of the adult epithelium. More importantly, using organ culture and immunohistochemical procedures, we have shown that BMP-4 not only represses cell proliferation of the connective tissue but promotes differentiation of the intestinal absorptive epithelium. In addition, we found that the connective tissue-specific expression of BMP-4 mRNA is up-regulated by sonic hedgehog (Shh), whose epithelium-specific expression is directly induced by TH. These results strongly suggest that the Shh/BMP-4 signaling pathway plays key roles in the amphibian intestinal remodeling through epithelial,connective tissue interactions. Developmental Dynamics 235:3240,3249, 2006. © 2006 Wiley-Liss, Inc. [source] The chicken B-cell receptor complex and its role in avian B-cell developmentIMMUNOLOGICAL REVIEWS, Issue 1 2000Camil E. Sayegh Summary: The bursa of Fabricius is critical to normal B-lymphocyte development in birds. During embryonic life, B-cell precursors migrate to the bursal rudiment and those which have undergone productive V(D)J recombination colonize lymphoid follicles and undergo immunoglobulin V gene diversification by gene conversion. The chicken surface IgM complex appears structurally and functionally equivalent to its mammalian counterpart, with homologs to CD79a and CD79b. Expression of a truncated Ig chain is sufficient to drive the early stages of B-cell development in the embryo bursa. Bursal cells expressing the truncated receptor complex proliferate in bursal follicles, and those which contain V gene rearrangements undergo V gene diversification by gene conversion. The bursa is a gut-associated organ and antigen is focused to bursal lymphoid follicles after hatch. While expression of the truncated chain is sufficient to support B-cell development in the embryo, B cells expressing this receptor are rapidly eliminated after hatch. We suggest the possibility that B-cell development in the bursa after hatch is driven by encounter with antigen leading to redistribution of B cells within the lymphoid follicle, B-cell proliferation and V gene repertoire development by gene conversion. [source] Regeneration as an evolutionary variableJOURNAL OF ANATOMY, Issue 1-2 2001JEREMY P. BROCKES abstract Regeneration poses a distinctive set of problems for evolutionary biologists, but there has been little substantive progress since these issues were clearly outlined in the monograph of T. H. Morgan (1901). The champions at regeneration among vertebrates are the urodele amphibians such as the newt, and we tend to regard urodele regeneration as an exceptional attribute. The ability to regenerate large sections of the body plan is widespread in metazoan phylogeny, although it is not universal. It is striking that in phylogenetic contexts where regeneration occurs, closely related species are observed which do not possess this ability. It is a challenge to reconcile such variation between species with a conventional selective interpretation of regeneration. The critical hypothesis from phylogenetic analysis is that regeneration is a basic, primordial attribute of metazoans rather than a mechanism which has evolved independently in a variety of contexts. In order to explain its absence in closely related species, it is postulated to be lost secondarily for reasons which are not understood. Our approach to this question is to compare a differentiated newt cell with its mammalian counterpart in respect of the plasticity of differentiation. [source] Yeast apurinic/apyrimidinic endonuclease Apn1 protects mammalian neuronal cell line from oxidative stressJOURNAL OF NEUROCHEMISTRY, Issue 1 2007Renee Ho Abstract Reactive oxygen species (ROS) have been implicated as one of the agents responsible for many neurodegenerative diseases. A critical target for ROS is DNA. Most oxidative stress-induced DNA damage in the nucleus and mitochondria is removed by the base excision repair pathway. Apn1 is a yeast enzyme in this pathway which possesses a wider substrate specificity and greater enzyme activity than its mammalian counterpart for removing DNA damage, making it a good therapeutic candidate. For this study we targeted Apn1 to mitochondria in a neuronal cell line derived from the substantia nigra by using a mitochondrial targeting signal (MTS) in an effort to hasten the removal of DNA damage and thereby protect these cells. We found that following oxidative stress, mitochondrial DNA (mtDNA) was repaired more efficiently in cells containing Apn1 with the MTS than controls. There was no difference in nuclear repair. However, cells that expressed Apn1 without the MTS showed enhanced repair of both nuclear and mtDNA. Both Apn1-expressing cells were more resistant to cell death following oxidative stress compared with controls. Therefore, these results reveal that the expression of Apn1 in neurons may be of potential therapeutic benefit for treating patients with specific neurodegenerative diseases. [source] Comparative Biochemistry of Eumelanogenesis and the Protective Roles of Phenoloxidase and Melanin in InsectsPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2002Manickam Sugumaran The phenolic biopolymer eumelanin is an important skin pigment found throughout the animal kingdom. The enzyme, tyrosinase, initiates melanogenesis in mammals. The biogenesis is assisted by a number of mammalian protein factors including dopachrome tautomerase and 5,6-dihydroxyindole-2-carboxylate oxidase. Invertebrates, such as insects, employ phenoloxidase and dopachrome (decarboxylating) isomerase for melanin biosynthesis. Recently generated molecular biological and biochemical data indicate that tyrosinase and phenoloxidase are distinctly different enzymes in spite of possessing both monophenol monooxygenase activity as well as o -diphenoloxidase activity. Similarly, insect dopachrome isomerase also differs significantly from its mammalian counterpart in several of its properties including the nature of the enzymatic reaction. In addition, there are considerable differences in the eumelanogenic pathways of these two animal groups that include the utility of substrates, use of dihydroxyindoles and the nature of eumelanin pigment. Thus, the biochemistry and molecular biology of melanogenesis in mammals and insects are significantly different. The advantages of generating different eumelanin pigments and intermediates by the insects are discussed. [source] Drosophila NAB (dNAB) is an orphan transcriptional co-repressor required for correct CNS and eye developmentDEVELOPMENTAL DYNAMICS, Issue 1 2003Mark Clements Abstract The mammalian NAB proteins have been identified previously as potent co-repressors of the EGR family of zinc finger transcription factors. Drosophila NAB (dNAB), like its mammalian counterparts, binds EGR1 and represses EGR1-mediated transcriptional activation from a synthetic promoter. In contrast, dNAB does not bind the Drosophila EGR-related protein klumpfuss. dnab RNA is expressed exclusively in a subset of neuroblasts in the embryonic and larval central nervous system (CNS), as well as in several larval imaginal disc tissues. Here, we describe the creation of targeted deletion mutations in the dnab gene and the identification of additional, EMS-induced dnab mutations by genetic complementation analysis. Null alleles in dnab cause larval locomotion defects and early larval lethality (L1,L2). A putative hypomorphic allele in dnab instead causes early adult lethality due to severe locomotion defects. In the dnab -/- CNS, axon outgrowth/guidance and glial development appear normal; however, a subset of eve+ neurons forms in reduced numbers. In addition, mosaic analysis in the eye reveals that dnab -/- clones are either very small or absent. Similarly, dNAB overexpression in the eye causes eyes to be very small with few ommatidia. These dramatic eye-specific phenotypes will prove useful for enhancer/suppressor screens to identify dnab-interacting genes. © 2002 Wiley-Liss, Inc. [source] Proliferative responses to growth factors decline rapidly during postnatal maturation of mammalian hair cell epitheliaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Rende Gu Abstract Millions of lives are affected by hearing and balance deficits that arise as a consequence of sensory hair cell loss. Those deficits affect mammals permanently, but hearing and balance recover in nonmammals after epithelial supporting cells divide and produce replacement hair cells. Hair cells are not effectively replaced in mammals, but balance epithelia cultured from the ears of rodents and adult humans can respond to hair cell loss with low levels of supporting cell proliferation. We have sought to stimulate vestibular proliferation; and we report here that treatment with glial growth factor 2 (rhGGF2) yields a 20-fold increase in cell proliferation within sheets of pure utricular hair cell epithelium explanted from adult rats into long-term culture. In epithelia from neonates, substantially greater proliferation responses are evoked by rhGGF2 alone, insulin alone and to a lesser degree by serum even during short-term cultures, but all these responses progressively decline during the first 2 weeks of postnatal maturation. Thus, sheets of utricular epithelium from newborn rats average >,40% labelling when cultured for 72 h with bromo-deoxyuridine (BrdU) and either rhGGF2 or insulin. Those from 5- and 6-day-olds average 8,15%, 12-day-olds average <,1% and after 72 h there is little or no labelling in epithelia from 27- and 35-day-olds. These cells are the mammalian counterparts of the progenitors that produce replacement hair cells in nonmammals, so the postnatal quiescence described here is likely to be responsible for at least part of the mammalian ear's unique vulnerability to permanent sensory deficits. [source] Molecular cloning of the Matrix Gla Protein gene from Xenopus laevisFEBS JOURNAL, Issue 7 2002Functional analysis of the promoter identifies a calcium sensitive region required for basal activity To analyze the regulation of Matrix Gla Protein (MGP) gene expression in Xenopus laevis, we cloned the xMGP gene and its 5, region, determined their molecular organization, and characterized the transcriptional properties of the core promoter. The Xenopus MGP (xMGP) gene is organized into five exons, one more as its mammalian counterparts. The first two exons in the Xenopus gene encode the DNA sequence that corresponds to the first exon in mammals whereas the last three exons show homologous organization in the Xenopus MGP gene and in the mammalian orthologs. We characterized the transcriptional regulation of the xMGP gene in transient transfections using Xenopus A6 cells. In our assay system the identified promoter was shown to be transcriptionally active, resulting in a 12-fold induction of reporter gene expression. Deletional analysis of the 5, end of the xMGP promoter revealed a minimal activating element in the sequence from ,70 to ,36 bp. Synthetic reporter constructs containing three copies of the defined regulatory element delivered 400-fold superactivation, demonstrating its potential for the recruitment of transcriptional activators. In gel mobility shift assays we demonstrate binding of X. laevis nuclear factors to an extended regulatory element from ,180 to ,36, the specificity of the interaction was proven in competition experiments using different fragments of the xMGP promoter. By this approach the major site of factor binding was demonstrated to be included in the minimal activating promoter fragment from ,70 to ,36 bp. In addition, in transient transfection experiments we could show that this element mediates calcium dependent transcription and increasing concentrations of extracellular calcium lead to a significant dose dependent activation of reporter gene expression. [source] Primitive complement system of invertebratesIMMUNOLOGICAL REVIEWS, Issue 1 2004Masaru Nonaka Summary:, Most components of the human complement system have unmistakable domain architectures, making evolutionary tracing feasible. In contrast to the major genes of the adaptive immune system, which are present only in jawed vertebrates, complement component genes with unique domain structures are present not only in jawed vertebrates but also in jawless fish and non-vertebrate deuterostomes. Recent progress in genome analysis in several eukaryotes, occupying the phylogenetically critical positions, showed that most individual domains found in the complement components are metazoa specific, being found both in deuterostomes and in protostomes but not in yeast or plant. However, unique domain architecture of complement components is not present in protostomes, suggesting that the complement system has been established in the deuterostome lineage not by invention of new domains but by innovation of unique combination of the pre-existing domains. The recently assembled Ciona intestinalis draft genome contained the most modular complement genes, except for factor I. However, some possible C. intestinalis complement components show critical structural divergence from the mammalian counterparts, casting doubt on their mutual interaction. Thus, another integrative step seems to have been required to establish the modern complement system of higher vertebrates. 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