Lamina Formation Research Articles

Requirement of cAMP signaling for Schwann cell differentiation restricts the onset of myelination.

Isolated Schwann cells (SCs) respond to cAMP elevation by adopting a differentiated post-mitotic state that exhibits high levels of Krox-20, a transcriptional enhancer of myelination, and mature SC markers such as the myelin lipid galactocerebroside (O1). To address how cAMP controls myelination, we performed a series of cell culture experiments which compared the differentiating responses of isolated and axon-related SCs to cAMP analogs and ascorbate, a known inducer of axon ensheathment, basal lamina formation and myelination. In axon-related SCs, cAMP induced the expression of Krox-20 and O1 without a concomitant increase in the expression of myelin basic protein (MBP) and without promoting axon ensheathment, collagen synthesis or basal lamina assembly. When cAMP was provided together with ascorbate, a dramatic enhancement of MBP expression occurred, indicating that cAMP primes SCs to form myelin only under conditions supportive of basal lamina formation. Experiments using a combination of cell permeable cAMP analogs and type-selective adenylyl cyclase (AC) agonists and antagonists revealed that selective transmembrane AC (tmAC) activation with forskolin was not sufficient for full SC differentiation and that the attainment of an O1 positive state also relied on the activity of the soluble AC (sAC), a bicarbonate sensor that is insensitive to forskolin and GPCR activation. Pharmacological and immunological evidence indicated that SCs expressed sAC and that sAC activity was required for morphological differentiation and the expression of myelin markers such as O1 and protein zero. To conclude, our data indicates that cAMP did not directly drive myelination but rather the transition into an O1 positive state, which is perhaps the most critical cAMP-dependent rate limiting step for the onset of myelination. The temporally restricted role of cAMP in inducing differentiation independently of basal lamina formation provides a clear example of the uncoupling of signals controlling differentiation and myelination in SCs.

Hematogenous macrophage depletion reduces the fibrotic scar and increases axonal growth after spinal cord injury

Spinal cord injury (SCI) leads to formation of a fibrotic scar that is inhibitory to axon regeneration. Recent evidence indicates that the fibrotic scar is formed by perivascular fibroblasts, but the mechanism by which they are recruited to the injury site is unknown. Using bone marrow transplantation in mouse model of spinal cord injury, we show that fibroblasts in the fibrotic scar are associated with hematogenous macrophages rather than microglia, which are limited to the surrounding astroglial scar. Depletion of hematogenous macrophages results in reduced fibroblast density and basal lamina formation that is associated with increased axonal growth in the fibrotic scar. Cytokine gene expression analysis after macrophage depletion indicates that decreased Tnfsf8, Tnfsf13 (tumor necrosis factor superfamily members) and increased BMP1-7 (bone morphogenetic proteins) expression may serve as anti-fibrotic mechanisms. Our study demonstrates that hematogenous macrophages are necessary for fibrotic scar formation and macrophage depletion results in changes in multiple cytokines that make the injury site less fibrotic and more conducive to axonal growth.

Olfactory sensory system develops from coordinated movements within the neural plate.

The peripheral olfactory sensory system arises from morphologically identifiable structures called placodes. Placodes are relatively late developing structures, evident only well after the initiation of somitogenesis. Placodes are generally described as being induced from the ectoderm suggesting that their development is separate from the coordinated cell movements generating the central nervous system. With the advent of modern techniques it is possible to follow the development of the neurectoderm giving rise to the anterior neural tube, including the olfactory placodes. The cell movements giving rise to the optic cup are coordinated with those generating the olfactory placodes and adjacent telencephalon. The formation of the basal lamina separating the placode from the neural tube is coincident with the anterior migration of cranial neural crest. Olfactory placodes are transient morphological structures arising from a continuous sheet of neurectoderm that gives rise to the peripheral and central nervous system. This field of cells is specified at the end of gastrulation and not secondarily induced from ectoderm. The separation of olfactory placodes and telencephalon occurs through complex cell movements within the developing neural plate similar to that observed for the developing optic cup.

Processes Forming Daily Lamination in a Microbe-Rich Travertine Under Low Flow Condition at the Nagano-yu Hot Spring, Southwestern Japan

A daily rhythm of microbial processes, in terms of sub-mm order lamination, was identified for a microbe-rich aragonite travertine formed at a low-flow site of the Nagano-yu Hot Spring in Southwestern Japan. Continuous observation and sampling clearly showed that the lamination consisted of diurnal microbe-rich layers (M-layers) and nocturnal crystalline layers (C-layers). The M-layers originated from biofilm formed by growth and upward migration of filamentous cyanobacteria related to Microcoleus sp., which can rapidly glide and secrete extracellular polymeric substances (EPS). During the daytime, cyanobacterial biofilm development inhibited aragonite precipitation on the travertine surface due to the calcium-binding ability of EPS. After sunset, aragonite precipitation started on the surface where aerobic heterotrophic bacteria decomposed EPS, which induced precipitation of micritic crystals. This early stage of C-layer formation was followed by abiotic precipitation of fan-shaped aragonite aggregates. Despite their major role in lamina formation, the cyanobacteria were readily degraded within 6–10 days after embedding, and the remaining open spaces in the M-layers were sparsely filled with crystal clots. These lamina-forming processes were different from those observed in a high-flow site where the travertine has a dense texture of aragonite crystals. The microbial travertine at Nagano-yu is similar to some Precambrian stromatolites in terms of in situ mineral precipitation, regular sub-mm order lamination, and arrangement of filamentous microbes; therefore, the lamination of these stromatolites possibly occur with a daily rhythm. The microbial processes demonstrated in this study may revise the interpretation of ancient stromatolite formation.

AGO61-dependent GlcNAc modification primes the formation of functional glycans on α-dystroglycan

Dystroglycanopathy is a major class of congenital muscular dystrophy that is caused by a deficiency of functional glycans on α-dystroglycan (α-DG) with laminin-binding activity. A product of a recently identified causative gene for dystroglycanopathy, AGO61, acted in vitro as a protein O-mannose β-1, 4-N-acetylglucosaminyltransferase, although it was not functionally characterized. Here we show the phenotypes of AGO61-knockout mice and demonstrate that AGO61 is indispensable for the formation of laminin-binding glycans of α-DG. AGO61-knockout mouse brain exhibited abnormal basal lamina formation and a neuronal migration defect due to a lack of laminin-binding glycans. Furthermore, our results indicate that functional α-DG glycosylation was primed by AGO61-dependent GlcNAc modifications of specific threonine-linked mannosyl moieties of α-DG. These findings provide a key missing link for understanding how the physiologically critical glycan motif is displayed on α-DG and provides new insights on the pathological mechanisms of dystroglycanopathy.

ANALYSIS OF THE REGENERATIVE PROCESS OF THE OPTIC TECTUM IN AN ANURAN (XENOPUS LAEVIS DAUDIN) FOLLOWING REMOVAL OF BOTH OPTIC LOBES

SUMMARY Seventy Xenopus laevis Daudin larvae (55 at stage 50 and 15 at stage 52–53, according to NIEUWKOOP & FABER, 1956) were submitted to bilateral ablation of the optic lobes and a study was made on the gradual evolution of the regenerative process from the 10th-90th day after the operation. The results obtained demonstrated that: 1. Regeneration of the optic tectum takes place by means of neural elements originating in the ependymal layer of the mesencephalic body. These cells, after covering the resection surface, multiply actively and, attaching themselves to the internal surface of the primitive pia mater, they migrate dorsally. The formation of a primary tectal lamina can be observed on about the 10th post-operative day. 2. In the early stages of the regenerative process of the optic tectum two factors have been shown to be of fundamental importance, regeneration of the pia mater and the pressure exerted by the rachidian-encephalic fluid. 3. Up to the 10th post-operative day the primary tectal lam...

Preservation potential of seasonal laminated deposits as a useful tool for environmental analysis in mesotrophic Lake Kizaki, central Japan

In this paper discusses the aquatic environment at Lake Kizaki, central Japan, during the last ca. 60years and describes the importance of laminated sediments in environmental analyses. The flux of total algal carbon increased between 1965 and 1996 while the BSi flux, which can be used in diatom production, showed a larger increase between 1960 and 1998 than typically occurs on average. The flux of dinosterol, an indicator of dinoflagellate production, also increased from 1966 to 1998, and the sedimentary dinoflagellate record correlated with observations of freshwater red tides caused by dinoflagellate blooms. Parallel laminated sediment was determined to have appeared between 1960 and 1995, corresponding to a period of high total algal carbon levels and BSi fluxes. For lamina formation and its preservation process, the thickness of the oxygen-poor layer depended on excessive total algal production during stagnant periods and appeared to be important because nutrients were diffused and accumulated in the oxygen-poor layer from bottom sediments. This could result in diatom blooms at the next overturn period. The development of the thick oxygen-poor layer appeared to be triggered primarily by the presence of excessive nutrients generated by human activities. In general, the occurrence of laminated sediments can provide a useful tool for understanding the eutrophic state in Lake Kizaki.

Evidence of microbiocoenosis in the formation of laminae in modern stromatolites

The first appearance of laminated stromatolites in sedimentary rocks around 3.5 billion years ago is generally accepted as evidence for the earliest advanced ecosystem. However, the bio-mechanisms leading to the construction of stromatolites continue to be poorly understood. Using a combination of microscopic and advanced spectroscopic techniques (STXM/NEXAFS/EELS) to analyze lithified laminae, living biomass, reference microorganisms and their byproducts, it is demonstrated that lithified laminae contain the bio-molecular signatures of sulphide oxidizers and sulphate reducers, as well as cyanobacterial extracellular polymeric substances. From this, it is concluded that a combination of microbial processes, such as the degradation of cyanobacterial biomass, phototrophic sulphide oxidation, and sulphate reduction, results in the formation of laminae, a process here called amalgamation. In summary, the described microbialite formation process is biochemically controlled with minimal external particle input and serves as an alternative biotic explanation for the trapping and binding model of lamina formation.

Acetylcholinesterase and agrin: Different functions, similar expression patterns, multiple roles

Acetylcholinesterase (AChE) and agrin play unique functional roles in the neuromuscular junction (NMJ). AChE is a cholinergic and agrin a synaptogenetic component. In spite of their different functions, they share several common features: their targeting is determined by alternative splicing; unlike most other NMJ components they are expressed in both, muscle and motor neuron and both reside on the synaptic basal lamina of the NMJ. Also, both were reported to play various nonjunctional roles. However, while the origin of basal lamina bound agrin is undoubtedly neural, the neural origin of AChE, which is anchored to the basal lamina with collagenic tail ColQ, is elusive. Hypothesizing that motor neuron proteins targeted to the NMJ basal lamina share common temporal pattern of expression, which is coordinated with the formation of basal lamina, we compared expression of agrin isoforms with the expression of AChE-T and ColQ in the developing rat spinal cord at the stages before and after the formation of NMJ basal lamina. Cellular origin of AChE-T and agrin was determined by in situ hybridization and their quantitative levels by RT PCR. We found parallel increase in expression of the synaptogenetic (agrin 8) isoform of agrin and ColQ after the formation of basal lamina supporting the view that ColQ bound AChE and agrin 8 isoform are destined to the basal lamina. Catalytic AChE-T subunit and agrin isoforms 19 and 0 followed different expression patterns. In accordance with the reports of other authors, our investigations also revealed various alternative functions for AChE and agrin. We have already demonstrated participation of AChE in myoblast apoptosis; here we present the evidence that agrin promotes the maturation of heavy myosin chains and the excitation–contraction coupling. These results show that common features of AChE and agrin extend to their capacity to play multiple roles in muscle development.

Tooth development in a model reptile: functional and null generation teeth in the gecko Paroedura picta.

This paper describes tooth development in a basal squamate, Paroedura picta. Due to its reproductive strategy, mode of development and position within the reptiles, this gecko represents an excellent model organism for the study of reptile development. Here we document the dental pattern and development of non-functional (null generation) and functional generations of teeth during embryonic development. Tooth development is followed from initiation to cytodifferentiation and ankylosis, as the tooth germs develop from bud, through cap to bell stages. The fate of the single generation of non-functional (null generation) teeth is shown to be variable, with some teeth being expelled from the oral cavity, while others are incorporated into the functional bone and teeth, or are absorbed. Fate appears to depend on the initiation site within the oral cavity, with the first null generation teeth forming before formation of the dental lamina. We show evidence for a stratum intermedium layer in the enamel epithelium of functional teeth and show that the bicuspid shape of the teeth is created by asymmetrical deposition of enamel, and not by folding of the inner dental epithelium as observed in mammals.

Cell-specific expression of human HGF by alveolar type II cells induces remodeling of septal wall tissue in the lung: a morphometric study

Hepatocyte growth factor (HGF) is involved in development and regeneration of the lungs. Human HGF, which was expressed specifically by alveolar epithelial type II cells after gene transfer, attenuated the bleomycin-induced pulmonary fibrosis in an animal model. As there are also regions that appear morphologically unaffected in fibrosis, the effects of this gene transfer to normal lungs is of interest. In vitro studies showed that HGF inhibits the formation of the basal lamina by cultured alveolar epithelial cells. Thus we hypothesized that, in the healthy lung, cell-specific expression of HGF induces a remodeling within septal walls. Electroporation of a plasmid of human HGF gene controlled by the surfactant protein C promoter was applied for targeted gene transfer. Using design-based stereology at light and electron microscopic level, structural alterations were analyzed and compared with a control group. HGF gene transfer increased the volume of distal air spaces, as well as the surface area of the alveolar epithelium. The volume of septal walls, as well as the number of alveoli, was unchanged. Volumes per lung of collagen and elastic fibers were unaltered, but a marked reduction of the volume of residual extracellular matrix (all components other than collagen and elastic fibers) and interstitial cells was found. A correlation between the volumes of residual extracellular matrix and distal air spaces, as well as total surface area of alveolar epithelium, could be established. Cell-specific expression of HGF leads to a remodeling of the connective tissue within the septal walls in the healthy lung, which is associated with more pronounced stretching of distal air spaces at a given hydrostatic pressure during instillation fixation.

Leaf adaxial-abaxial polarity specification and lamina outgrowth: evolution and development

A key innovation in leaf evolution is the acquisition of a flat lamina with adaxial-abaxial polarity, which optimizes the primary function of photosynthesis. The developmental mechanism behind leaf adaxial-abaxial polarity specification and flat lamina formation has long been of interest to biologists. Surgical and genetic studies proposed a conceptual model wherein a signal derived from the shoot apical meristem is necessary for adaxial-abaxial polarity specification, and subsequent lamina outgrowth is promoted at the juxtaposition of adaxial and abaxial identities. Several distinct regulators involved in leaf adaxial-abaxial polarity specification and lamina outgrowth have been identified. Analyses of these genes demonstrated that the mutual antagonistic interactions between adaxial and abaxial determinants establish polarity and define the boundary between two domains, along which lamina outgrowth regulators function. Evolutionary developmental studies on diverse leaf forms of angiosperms proposed that alteration to the adaxial-abaxial patterning system can be a major driving force in the generation of diverse leaf forms, as represented by 'unifacial leaves', in which leaf blades have only the abaxial identity. Interestingly, unifacial leaf blades become flattened, in spite of the lack of adaxial-abaxial juxtaposition. Modification of the adaxial-abaxial patterning system is also utilized to generate complex organ morphologies, such as stamens. In this review, we summarize recent advances in the genetic mechanisms underlying leaf adaxial-abaxial polarity specification and lamina outgrowth, with emphasis on the genetic basis of the evolution and diversification of leaves.

Characterization of NE81, the first lamin-like nucleoskeleton protein in a unicellular organism

Lamins build the nuclear lamina and are required for chromatin organization, gene expression, cell cycle progression, and mechanical stabilization. Despite these universal functions, lamins have so far been found only in metazoans. We have identified protein NE81 in Dictyostelium, which has properties that justify its denomination as a lamin-like protein in a lower eukaryote. This is based on its primary structure, subcellular localization, and regulation during mitosis, and its requirement of the C-terminal CaaX box as a posttranslational processing signal for proper localization. Our knockout and overexpression mutants revealed an important role for NE81 in nuclear integrity, chromatin organization, and mechanical stability of cells. All our results are in agreement with a role for NE81 in formation of a nuclear lamina. This function is corroborated by localization of Dictyostelium NE81 at the nuclear envelope in human cells. The discovery of a lamin-like protein in a unicellular organism is not only intriguing in light of evolution, it may also provide a simple experimental platform for studies of the molecular basis of laminopathies.

STENOFOLIARegulates Blade Outgrowth and Leaf Vascular Patterning inMedicago truncatulaandNicotiana sylvestris

Dicot leaf primordia initiate at the flanks of the shoot apical meristem and extend laterally by cell division and cell expansion to form the flat lamina, but the molecular mechanism of lamina outgrowth remains unclear. Here, we report the identification of STENOFOLIA (STF), a WUSCHEL-like homeobox transcriptional regulator, in Medicago truncatula, which is required for blade outgrowth and leaf vascular patterning. STF belongs to the MAEWEST clade and its inactivation by the transposable element of Nicotiana tabacum cell type1 (Tnt1) retrotransposon insertion leads to abortion of blade expansion in the mediolateral axis and disruption of vein patterning. We also show that the classical lam1 mutant of Nicotiana sylvestris, which is blocked in lamina formation and stem elongation, is caused by deletion of the STF ortholog. STF is expressed at the adaxial-abaxial boundary layer of leaf primordia and governs organization and outgrowth of lamina, conferring morphogenetic competence. STF does not affect formation of lateral leaflets but is critical to their ability to generate a leaf blade. Our data suggest that STF functions by modulating phytohormone homeostasis and crosstalk directly linked to sugar metabolism, highlighting the importance of coordinating metabolic and developmental signals for leaf elaboration.

Quantitative assessment of lactate and progerin production in normal human cutaneous cells during normal ageing: effect of an Alaria esculenta extract.

Anti-ageing products are of a great importance in cosmetic fields. However, even if numerous strategies have been proposed to fight against skin ageing or to minimize its aesthetic impact since the beginning of the 'scientific cosmetology' era, the products basing their efficacy on the observation of pathological situations are rare. The most obvious pathology linked to the ageing of skin (notably) consists in the Hutchinson-Gilford Progeria Syndrome (HGPS), a rare disorder characterized by accelerated ageing and early death. In this disease the lamin A, a protein participating (with others lamins) in the formation of the nuclear lamina and implicated in nuclear stability, chromatin structure and gene expression, is present in a truncated version called progerin. In this study, we have examined the lactate and the progerin production of human normal cutaneous cells issued from subjects of different ages. Using a sensitive and specific progerin ELISA assay developed in house, we so provide the first quantitative demonstration of an increased progerin expression and lactate production in skin during ageing. Moreover, we have also demonstrated that in the selected experimental conditions, it was possible to down-regulate the progerin production of aged cells by using an algae extract. As this extract, an Alaria esculenta extract, could be used in cosmetic formulations, we suggest that a better understanding of the skin pathologies could be a useful tool in developing efficient active compounds, attractive for but not limited to cosmetic purposes.

The serine/threonine kinase Par1b regulates epithelial lumen polarity via IRSp53-mediated cell–ECM signaling

The serine/threonine kinase Par1b promotes cell-cell adhesion and determines the polarity of the luminal domain in epithelial cells. In this study, we demonstrate that Par1b also regulates cell-extracellular matrix (ECM) signaling in kidney-derived Madin-Darby canine kidney (MDCK) cells and identified the rho-guanosine triphosphatase adaptor and scaffolding protein IRSp53 as a Par1b substrate involved in this pathway. Par1b overexpression inhibits basal lamina formation, cell spreading, focal adhesion, stress fiber formation, and compaction, whereas Par1b depletion has the opposite effect. IRSp53 depletion mimics Par1b overexpression on cell-ECM signaling and lumen polarity but had no effect on adherens junction formation. Par1b directly phosphorylates IRSp53 on S366 in cell lysates and stimulates phosphorylation on S453/3/5 via an indirect mechanism. A Par1b phosphorylation-deficient IRSp53 mutant but not the wild-type protein efficiently rescues both the cell spreading and the lumen polarity defects in Par1b MDCK cells. Our data suggest a model in which Par1b phosphorylation prevents recruitment of IRSp53 effector proteins to its Src homology domain 3 by promoting 14-3-3 binding in the vicinity of that domain.

Origin and hierarchy of basal lamina-forming and -non-forming myogenic cells in mouse skeletal muscle in relation to adhesive capacity and Pax7 expression in vitro

As a novel approach to distinguish skeletal myogenic cell populations, basal lamina (BL) formation of myogenic cells was examined in the mouse compensatory enlarged plantaris muscles in vivo and in fiber-bundle cultures in vitro. MyoD(+) myogenic cells located inside the regenerative muscle fiber BL were laminin(-) but interstitial MyoD(+) cells were laminin(+). This was also confirmed by electron microscopy as structural BL formation. Similar trends were observed in the fiber-bundle cultures including satellite cells and interstitial myogenic cells and laminin(+) myogenic cells predominantly showed non-adhesive (non-Ad) behavior with Pax7(-), whereas laminin(-) cells were adhesive (Ad) with Pax7(+). Moreover, non-Ad/laminin(+) and Ad/laminin(-) myotubes were also observed and the former type showed spontaneous contractions, while the latter type did not. The origin and hierarchy of Ad/Pax7(+)/laminin(-) and non-Ad/Pax7(-)/laminin(+) myogenic cells were also examined using skeletal muscle interstitium-derived CD34(+)/45(-) (Sk-34) and CD34(-)/45(-) (Sk-DN) multipotent stem cells, which were composed of non-committed myogenic cells with a few (<1%) Pax7(+) cells in the Sk-DN cells at fresh isolation. Both cell types were separated by Ad/non-Ad capacity in repetitive culture. As expected, both Ad/Pax7(+)/laminin(-) and non-Ad/Pax7(-)/laminin(+) myogenic cells consistently appeared in the Ad and non-Ad cell culture. However, Ad/Pax7(+)/laminin(-) cells were repeatedly detected in the non-Ad cell culture, while the opposite phenomenon did not occur. This indicates that the source of non-Ad/ Pax7(-)/laminin(+) myogenic cells was present in the Sk-34 and Sk-DN stem cells and they were able to produce Ad/ Pax7(+)/ laminin(-) myogenic cells during myogenesis as primary myoblasts and situated hierarchically upstream of the latter cells.

Disruption of Laminin-γ1 Expression Induces Rapid Decrease In Spleen Size.

AbstractAbstract 2596Laminins are heterotrimeric proteins composed of an alpha, beta, and gamma subunit, and are expressed in a majority of organ systems, including hematopoietic and lymphoid tissues. Specific laminin subunits have been identified in prognostic stromal gene expression profiles from diffuse large B-cell lymphomas (Lenz et al. 2008). Laminin g1 is the gamma-subunit present in a majority of physiologically expressed laminin heterotrimers. Global laminin-g1 deficiency in mice is embryologically lethal at E5.5 and results in part from failure of the primordial basal lamina to form (Smyth et al. 1998). Conditional knockout mouse lines have therefore been developed to examine the role of laminin-g1 in specific tissues. Disruption of Schwann cell-specific expression of laminin-g1 prevents basal lamina formation within peripheral nerves, decreases glial cell proliferation, and increases glial cell apoptosis leading to a severe dysmyelinated phenotype (Chen and Strickland 2003; Yu et al. 2005).Here we present data that global disruption of laminin- g1 expression in adult animals induces involution of the spleen and suggests a fundamental role for laminins in maintenance of spleen integrity. Mice homozygous for the LoxP flanked laminin-g1 allele (floxed allele) were crossed with mice expressing a global Cre-ERT2 transgene. Mice homozygous or heterozygous for the floxed laminin-g1 allele that carry the inducible Cre transgene are hereafter referred to as homozygous and heterozygous mutant mice, respectively. Adult heterozygous and homozygous mutant animals were treated with either tamoxifen (TM) or corn oil (control), and three weeks afterwards, tissues were harvested for analysis. Treatment of homozygous mutant mice with TM, but not corn oil, induced laminin-g1 gene recombination. There was a significant decrease in spleen size in TM-treated but not control-treated homozygous mutant animals. Neither TM nor control treatment induced changes in the spleen size of heterozygous mutant animals. Similarly, TM treatment did not alter spleen size of animals that expressed Cre-transgene but were wild type with respect to the floxed laminin-g1 gene, or which were homozygous for the floxed laminin-g1 gene but lacked the Cre-transgene (Figure 1). [Display omitted] This is the first animal model to show that continued expression of laminins are critical for maintenance of the normal spleen and suggests a potential new target for disorders of lymphoid or splenic hyperproliferation.Chen ZL, Strickland S. 2003. Laminin gamma1 is critical for Schwann cell differentiation, axon myelination, and regeneration in the peripheral nerve. J Cell Biol 163(4):889-99.Lenz G, Wright G, Dave SS, Xiao W, Powell J, Zhao H, Xu W, Tan B, Goldschmidt N, Iqbal J and others. 2008. Stromal gene signatures in large-B-cell lymphomas. N Engl J Med 359(22):2313–23.Smyth N, Vatansever HS, Meyer M, Frie C, Paulsson M, Edgar D. 1998. The targeted deletion of the LAMC1 gene. Ann N Y Acad Sci 857:283–6.Yu WM, Feltri ML, Wrabetz L, Strickland S, Chen ZL. 2005. Schwann cell-specific ablation of laminin gamma1 causes apoptosis and prevents proliferation. J Neurosci 25(18):4463–72. Disclosures:No relevant conflicts of interest to declare

The dominant Basilicum Leaf mutation of sunflower controls leaf development multifariously and modifies the photosynthetic traits

Despite the remarkable morphological diversity in the leaf shape, usually higher plants maintain a flat lamina to ensure the desirable surface-to-volume ratio. The control of expansion of a flattened lateral organ is only partially known and the characterization of leaf mutants can be a useful strategy to add new information, as demonstrated in dicots with recessive mutants of model species. In sunflower, the dominant mutant Basilicum Leaf ( BL) is characterized by prominent downward leaf curling. The central end of the present work is the detailed study of the BL phenotype to characterize the effects of this mutation, at organ and cellular levels, on both morphological and physiological traits. The geometry of mature leaves is obviously altered in BL plants because the lamina surfaces are downward curled and display a different length/width ratio with respect to wild type. The area of BL leaves is higher than that of wild type while the BL leaf perimeter is reduced. In BL leaves, the perimeter to the square root of area ratio is also abnormally low compared to the value of a flat sunflower lamina. These results suggest that the dominant mutation induces a deep change of the ratio between lamina and marginal growth. In addition, the epidermis and mesophyll of BL leaves comprised higher size pavement and palisade cells compared to those of wild type, indicating that the BL gene also control cell shape changes in the formation of the leaf lamina. Other leaf traits such as photosynthetic pigment content, pattern of minor vein architecture, margin type and stomatal density are affected by the mutation. In BL plants, the longitudinal axis of both cotyledons and ray flower corollas shows an unusual curvature while the diameter of shoot and inflorescence meristems is reduced. In mutant leaves, the gas exchange performance is influenced by low stomata conductance while the CO 2 assimilation rate is also depressed by a depleted Rubisco activity. Together, these data demonstrate the pleiotropic nature of the BL mutation, which affects a number of morphological aspects of flattened lateral organs as well as physiological parameters in sunflower.

Plasticity and Physiological Role of Stem Cells Derived from Skeletal Muscle Interstitium: Contribution to Muscle Fiber Hyperplasia and Therapeutic Use

Stem cells other than satellite cells that can give rise to primary myoblasts, which are able to form additional new fibers postnatally, are present in the interstitial spaces of skeletal muscle. These cells are sorted into CD34(+)/45(-) (Sk-34) and CD34(-)/45(-) (Sk-DN) cell fractions, and they are wholly (>99%) negative for Pax7 at initial isolation. Colony-forming units of these cells typically include non-adherent type myogenic cells, while satellite cells are known to be adherent in cell culture. In addition, both Pax7(-) and Pax7(+) cells are produced, depending on asymmetric cell division. A large number of myotubes are also formed in each colony, thus suggesting that putative Pax7(+) satellite cells also present in each colony. Interestingly, interstitial myogenic cells show basal lamina formation at early stages of myogenesis in response to various types of stimulation in compensatory enlarged muscle, a property that satellite cells do not possess in the parent fiber basal lamina cylinder. Basal lamina formation and production of satellite cells are essential before muscle fiber establishment in vivo. It is therefore likely that myogenic cells in skeletal muscle can be divided into two populations: 1) basal lamina-producing myogenic cells; and 2) basal lamina-non-producing myogenic cells. The latter population may be Pax7(+) satellite cells showing adherent capacity in cell culture, while the lamina-producing myogenic population derived from interstitial multipotent stem cells, which is predominant among Sk-34 and Sk-DN cells, plays a role in primary myoblast generation and shows non-adherent behavior in culture. Therefore, the physiological role of interstitial myogenic cells is as a source for new postnatal muscle fiber formation, and multinucleated muscle fibers (cells) are potentially formed clonally.