Adipose tissue is a source of regenerative cells that augment the repair of skeletal muscle after injury

Fibro-adipogenic progenitors (FAPs) play a crucial role in skeletal muscle regeneration, as they generate a favorable niche that allows satellite cells to perform efficient muscle regeneration. After muscle injury, FAP content increases rapidly within the injured muscle, the origin of which has been attributed to their proliferation within the muscle itself. However, recent single-cell RNAseq approaches have revealed phenotype and functional heterogeneity in FAPs, raising the question of how this differentiation of regenerative subtypes occurs. Here we report that FAP-like cells residing in subcutaneous adipose tissue (ScAT), the adipose stromal cells (ASCs), are rapidly released from ScAT in response to muscle injury. Additionally, we find that released ASCs infiltrate the damaged muscle, via a platelet-dependent mechanism and thus contribute to the FAP heterogeneity. Moreover, we show that either blocking ASCs infiltration or removing ASCs tissue source impair muscle regeneration. Collectively, our data reveal that ScAT is an unsuspected physiological reservoir of regenerative cells that support skeletal muscle regeneration, underlining a beneficial relationship between muscle and fat.

Lactate fluxes mediated by the monocarboxylate transporter-1 are key determinants of the metabolic activity of beige adipocytes

Activation of energy-dissipating brown/beige adipocytes represents an attractive therapeutic strategy against metabolic disorders. While lactate is known to induce beiging through the regulation of Ucp1 gene expression, the role of lactate transporters on beige adipocytes' ongoing metabolic activity remains poorly understood. To explore the function of the lactate-transporting monocarboxylate transporters (MCTs), we used a combination of primary cell culture studies, 13C isotopic tracing, laser microdissection experiments, and in situ immunofluorescence of murine adipose fat pads. Dissecting white adipose tissue heterogeneity revealed that the MCT1 is expressed in inducible beige adipocytes as the emergence of uncoupling protein 1 after cold exposure was restricted to a subpopulation of MCT1-expressing adipocytes suggesting MCT1 as a marker of inducible beige adipocytes. We also observed that MCT1 mediates bidirectional and simultaneous inward and outward lactate fluxes, which were required for efficient utilization of glucose by beige adipocytes activated by the canonical β3-adrenergic signaling pathway. Finally, we demonstrated that significant lactate import through MCT1 occurs even when glucose is not limiting, which feeds the oxidative metabolism of beige adipocytes. These data highlight the key role of lactate fluxes in finely tuning the metabolic activity of beige adipocytes according to extracellular metabolic conditions and reinforce the emerging role of lactate metabolism in the control of energy homeostasis.

From whole-organ imaging to in-silico blood flow modeling: A new multi-scale network analysis for revisiting tissue functional anatomy

We present a multi-disciplinary image-based blood flow perfusion modeling of a whole organ vascular network for analyzing both its structural and functional properties. We show how the use of Light-Sheet Fluorescence Microscopy (LSFM) permits whole-organ micro-vascular imaging, analysis and modelling. By using adapted image post-treatment workflow, we could segment, vectorize and reconstruct the entire micro-vascular network composed of 1.7 million vessels, from the tissue-scale, inside a ∼ 25 × 5 × 1 = 125mm3 volume of the mouse fat pad, hundreds of times larger than previous studies, down to the cellular scale at micron resolution, with the entire blood perfusion modeled. Adapted network analysis revealed the structural and functional organization of meso-scale tissue as strongly connected communities of vessels. These communities share a distinct heterogeneous core region and a more homogeneous peripheral region, consistently with known biological functions of fat tissue. Graph clustering analysis also revealed two distinct robust meso-scale typical sizes (from 10 to several hundred times the cellular size), revealing, for the first time, strongly connected functional vascular communities. These community networks support heterogeneous micro-environments. This work provides the proof of concept that in-silico all-tissue perfusion modeling can reveal new structural and functional exchanges between micro-regions in tissues, found from community clusters in the vascular graph.

Regionalization of browning revealed by whole subcutaneous adipose tissue imaging

OBJECTIVE

White and brown adipose tissues play a major role in the regulation of metabolic functions. With the explosion of obesity and metabolic disorders, the interest in adipocyte biology is growing constantly. While several studies have demonstrated functional differences between adipose fat pads, especially in their involvement in metabolic diseases, there are no data available on possible heterogeneity within an adipose depot.

METHODS

This study investigated the three-dimensional (3-D) organization of the inguinal fat pad in adult mice by combining adipose tissue clearing and autofluorescence signal acquisition by confocal microscopy. In addition, the study analyzed the expression of genes involved in adipocyte biology and browning at the mARN and protein levels in distinct areas of the inguinal adipose tissue, in control conditions and after cold exposure.

RESULTS

Semiautomated 3-D image analysis revealed an organization of the fat depot showing two regions: the core was structured into segmented lobules, whereas the periphery appeared unsegmented. Perilipin immunostaining showed that most of the adipocytes located in the core region had smaller lipid droplets, suggesting a brown-like phenotype. qPCR analysis showed a higher expression of the browning markers Ucp1, Prdm16, Ppargc1a, and Cidea in the core region than at the periphery. Finally, cold exposure induced upregulation of thermogenic gene expression associated with an increase of UCP1 protein, specifically in the core region of the inguinal fat depot.

CONCLUSIONS

Altogether, these data demonstrate a structural and functional heterogeneity of the inguinal fat pad, with an anatomically restricted browning process in the core area.

Browning of white adipose cells by intermediate metabolites: an adaptive mechanism to alleviate redox pressure

The presence of brown adipose tissue (BAT) in human adults opens attractive perspectives to treat metabolic disorders. Indeed, BAT dissipates energy as heat via uncoupling protein (UCP)1. Brown adipocytes are located in specific deposits or can emerge among white fat through the so-called browning process. Although numerous inducers have been shown to drive this process, no study has investigated whether it could be controlled by specific metabolites. Here, we show that lactate, an important metabolic intermediate, induces browning of murine white adipose cells with expression of functional UCP1. Lactate-induced browning also occurs in human cells and in vivo. Lactate controls Ucp1 expression independently of hypoxia-inducible factor-1α and PPARα pathways but requires active PPARγ signaling. We demonstrate that the lactate effect on Ucp1 is mediated by intracellular redox modifications as a result of lactate transport through monocarboxylate transporters. Further, the ketone body β-hydroxybutyrate, another metabolite that impacts redox state, is also a strong browning inducer. Because this redox-dependent increase in Ucp1 expression promotes an oxidative phenotype with mitochondria, browning appears as an adaptive mechanism to alleviate redox pressure. Our findings open new perspectives for the control of adipose tissue browning and its physiological relevance.

Mouse adipose tissue stromal cells give rise to skeletal and cardiomyogenic cell sub-populations

We previously reported that adipose tissue could generate cardiomyocyte-like cells from crude stromal vascular fraction (SVF) in vitro that improved cardiac function in a myocardial infarction context. However, it is not clear whether these adipose-derived cardiomyogenic cells (AD-CMG) constitute a homogenous population and if AD-CMG progenitors could be isolated as a pure population from the SVF of adipose tissue. This study aims to characterize the different cell types that constitute myogenic clusters and identify the earliest AD-CMG progenitors in vitro for establishing a complete phenotype and use it to sort AD-CMG progenitors from crude SVF. Here, we report cell heterogeneity among adipose-derived clusters during their course of maturation and highlighted sub-populations that exhibit original mixed cardiac/skeletal muscle phenotypes with a progressive loss of cardiac phenotype with time in liquid culture conditions. Moreover, we completed the phenotype of AD-CMG progenitors but we failed to sort them from the SVF. We demonstrated that micro-environment is required for the maturation of myogenic phenotype by co-culture experiments. These findings bring complementary data on AD-CMG and suggest that their emergence results from in vitro events.

Native adipose stromal cells egress from adipose tissue in vivo: evidence during lymph node activation

Adipose tissue (AT) has become accepted as a source of multipotent progenitor cells, the adipose stromal cells (ASCs). In this regard, considerable work has been performed to harvest and characterize this cell population as well as to investigate the mechanisms by which transplanted ASCs mediate tissue regeneration. In contrast the endogenous release of native ASCs by AT has been poorly investigated. In this work, we show that native ASCs egress from murine AT. Indeed, we demonstrated that the release of native ASCs from AT can be evidenced both using an ex vivo perfusion model that we set up and in vivo. Such a mobilization process is controlled by CXCR4 chemokine receptor. In addition, once mobilized from AT, circulating ASCs were found to navigate through lymph fluid and to home into lymph nodes (LN). Therefore, we demonstrated that, during the LN activation, the fat depot encapsulating the activated LN releases native ASCs, which in turn invade the activated LN. Moreover, the ASCs invading the LN were visualized in close physical interaction with podoplanin and ER-TR7 positive structures corresponding to the stromal network composing the LN. This dynamic was impaired with CXCR4 neutralizing antibody. Taken together, these data provide robust evidences that native ASCs can traffic in vivo and that AT might provide stromal cells to activated LNs.

Age-related changes in the features of porcine adult stem cells isolated from adipose tissue and skeletal muscle

A better understanding of the control of body fat distribution and muscle development is of the upmost importance for both human and animal physiology. This requires a better knowledge of the features and physiology of adult stem cells in adipose tissue and skeletal muscle. Thus the objective of the current study was to determine the type and proportion of these cells in growing and adult pigs. The different cell subsets of stromal vascular cells isolated from these tissues were characterized by flow cytometry using cell surface markers (CD11b, CD14, CD31, CD34, CD45, CD56, and CD90). Adipose and muscle cells were predominantly positive for the CD34, CD56, and CD90 markers. The proportion of positive cells changed with age especially in intermuscular adipose tissue and skeletal muscle where the percentage of CD90(+) cells markedly increased in adult animals. Further analysis using coimmunostaining indicates that eight populations with proportions ranging from 12 to 30% were identified in at least one tissue at 7 days of age, i.e., CD90(+)/CD34(+), CD90(+)/CD34(-), CD90(+)/CD56(+), CD90(+)/CD56(-), CD90(-)/CD56(+), CD56(+)/CD34(+), CD56(+)/CD34(-), and CD56(-)/CD34(+). Adipose tissues appeared to be a less heterogeneous tissue than skeletal muscle with two main populations (CD90(+)/CD34(-) and CD90(+)/CD56(-)) compared with five or more in muscle during the studied period. In culture, cells from adipose tissue and muscle differentiated into mature adipocytes in adipogenic medium. In myogenic conditions, only cells from muscle could form mature myofibers. Further studies are now needed to better understand the plasticity of those cell populations throughout life.

Metabolic endotoxemia directly increases the proliferation of adipocyte precursors at the onset of metabolic diseases through a CD14-dependent mechanism

Metabolic endotoxemia triggers inflammation, targets cells from the stroma-vascular fraction of adipose depots, and metabolic disease. To identify these cells we here infused mice with lipopolysaccharides and showed by FACS analyses and BrdU staining that the number of small subcutaneous adipocytes, preadipocytes and macrophages increased in wild type but not in CD14-knockout (KO) mice. This mechanism was direct since in CD14KO mice grafted subcutaneously and simultaneously with fat pads from CD14KO and wild-type mice the concentration of cytokine mRNA was increased in the wild-type fat pad only. Conversely, the mRNA concentration of genes involved in glucose and lipid metabolism and the number of large adipocytes was reduced. Eventually, a pretreatment with LPS enhanced HFD-induced metabolic diseases. Altogether, these results show that metabolic endotoxemia increases the proliferation of preadipocytes through a CD14-dependent mechanism directly, without recruiting CD14-positive cells from non-adipose depot origin. This mechanism could precede the onset of metabolic diseases.

Aging-related decrease of human ASC angiogenic potential is reversed by hypoxia preconditioning through ROS production

Adipose stroma/stem cells (ASC) represent an ideal source of autologous cells for cell-based therapy. Their transplantation enhances neovascularization after experimental ischemic injury. Aging is associated with a progressive decrease in the regenerative potential of mesenchymal stem cells (MSCs) from bone marrow. This work aims to determine the aging effect on human ASC capacities. First, we show that aging impairs angiogenic capacities of human ASC (hASC) in a mouse ischemic hindlimb model. Although no change in hASC number, phenotype, and proliferation was observed with aging, several mechanisms involved in the adverse effects of aging have been identified in vitro combining a concomitant decrease in (i) ASC ability to differentiate towards endothelial cells, (ii) secretion of proangiogenic and pro-survival factors, and (iii) oxidative stress. These effects were counteracted by a hypoxic preconditioning that improved in vivo angiogenic capacities of hASC from older donors, while hASC from young donors that have a strong ability to manage hypoxic stress were not. Finally, we identified reactive oxygen species (ROS) generation as a key signal of hypoxia on hASC angiogenic capacities. This study demonstrates for the first time that age of donor impaired angiogenic capacities of hASC in ischemic muscle and change in ROS generation by hypoxic preconditioning reverse the adverse effect of aging.

Importance of mitochondrial dynamin-related protein 1 in hypothalamic glucose sensitivity in rats

AIMS

Hypothalamic mitochondrial reactive oxygen species (mROS)-mediated signaling has been recently shown to be involved in the regulation of energy homeostasis. However, the upstream signals that control this mechanism have not yet been determined. Here, we hypothesize that glucose-induced mitochondrial fission plays a significant role in mROS-dependent hypothalamic glucose sensing.

RESULTS

Glucose-triggered translocation of the fission protein dynamin-related protein 1 (DRP1) to mitochondria was first investigated in vivo in hypothalamus. Thus, we show that intracarotid glucose injection induces the recruitment of DRP1 to VMH mitochondria in vivo. Then, expression was transiently knocked down by intra-ventromedial hypothalamus (VMH) DRP1 siRNA (siDRP1) injection. 72 h post siRNA injection, brain intracarotid glucose induced insulin secretion, and VMH glucose infusion-induced refeeding decrease were measured, as well as mROS production. The SiDRP1 rats decreased mROS and impaired intracarotid glucose injection-induced insulin secretion. In addition, the VMH glucose infusion-induced refeeding decrease was lost in siDRP1 rats. Finally, mitochondrial function was evaluated by oxygen consumption measurements after DRP1 knock down. Although hypothalamic mitochondrial respiration was not modified in the resting state, substrate-driven respiration was impaired in siDRP1 rats and associated with an alteration of the coupling mechanism.

INNOVATION AND CONCLUSION

Collectively, our results suggest that glucose-induced DRP1-dependent mitochondrial fission is an upstream regulator for mROS signaling, and consequently, a key mechanism in hypothalamic glucose sensing. Thus, for the first time, we demonstrate the involvement of DRP1 in physiological regulation of brain glucose-induced insulin secretion and food intake inhibition. Such involvement implies DRP1-dependent mROS production.

Endothelial and cardiac regeneration from adipose tissues

For a long time, adipose tissue was only considered for its crucial role in energy balance and associated diseases. The discovery of the presence of immature cells highlights a putative role for these tissues as reservoirs of therapeutic cells. Indeed, since fat pads can be sampled by liposuction under local anesthesia in adult patients, adipose tissue represents a promising source of regenerative cells, particularly in cardiovascular regeneration. Indeed among other potentials, we and others have demonstrated the great angiogenic properties of adipose-derived stromal cells (ASCs) and the existence of peculiar cells, at least in mice, that are able to spontaneously give rise to functional cardiomyocytes. This review deciphers the different steps necessary to isolate, characterize, and manipulate such striking cells.

Xenobiotic-metabolizing cytochromes p450 in human white adipose tissue: expression and induction

Lipophilic pollutants can accumulate in human white adipose tissue (WAT), and the consequences of this accumulation are still poorly understood. Cytochromes P450 (P450s) have recently been found in rat WAT and shown to be inducible through mechanisms similar to those in the liver. The aim of our study was to describe the cytochrome P450 pattern and their induction mechanisms in human WAT. Explants of subcutaneous and visceral WAT and primary culture of subcutaneous adipocytes were used as WAT models, and liver biopsies and primary culture of hepatocytes were used as liver models to characterize P450 expression in both tissues. The WAT and liver models were then treated with typical P450 inducers (rifampicin, phenobarbital, and 2,3,7,8-tetrachlorodibenzo-p-dioxin) and lipophilic pollutants (lindane, prochloraz, and chlorpyrifos), and the effects on P450 expression were studied. P450 expression was considerably lower in WAT than in the liver, except for CYP1B1 and CYP2U1, which were the most highly expressed adipose P450s in all individuals. 2,3,7,8-Tetrachlorodibenzo-p-dioxin and prochloraz induced CYP1A1 and CYP1B1 expression in both tissues. The aryl hydrocarbon receptor was also present in WAT. In contrast, neither phenobarbital nor rifampicin treatment induced CYP2 or CYP3 mRNA in WAT, and constitutive androstane receptor and pregnane X receptor were almost undetectable. These results suggest that the mechanisms by which P450s of family 1 are regulated in the liver are also functional in human WAT, but those regulating CYP2 and CYP3 expression are not.

Preconditioning by mitochondrial reactive oxygen species improves the proangiogenic potential of adipose-derived cells-based therapy

OBJECTIVE

Transplantation of adipose-derived stroma cells (ADSCs) stimulates neovascularization after experimental ischemic injury. ADSC proangiogenic potential is likely mediated by their ability to differentiate into endothelial cells and produce a wide array of angiogenic and antiapoptotic factors. Mitochondrial reactive oxygen species (ROS) have been shown to control ADSC differentiation. We therefore hypothesized that mitochondrial ROS production may change the ADSC proangiogenic properties.

METHODS AND RESULTS

The use of pharmacological strategies (mitochondrial inhibitors, antimycin, and rotenone, with or without antioxidants) allowed us to specifically and precisely modulate mitochondrial ROS generation in ADSCs. We showed that transient stimulation of mitochondrial ROS generation in ADSCs before their injection in ischemic hindlimb strongly improved revascularization and the number of ADSC-derived CD31-positive cells in ischemic area. Mitochondrial ROS generation increased the secretion of the proangiogenic and antiapoptotic factors, VEGF and HGF, but did not affect ADSC ability to differentiate into endothelial cells, in vitro. Moreover, mitochondrial ROS-induced ADSC preconditioning greatly protect ADSCs against oxidative stress-induced cell death.

CONCLUSIONS

Our study demonstrates that in vitro preconditioning by moderate mitochondrial ROS generation strongly increases in vivo ADSC proangiogenic properties and emphasizes the crucial role of mitochondrial ROS in ADSC fate.

Post-transcriptional regulation in Xenopus embryos: role and targets of EDEN-BP

EDEN (embryo deadenylation element)-dependent deadenylation is a regulatory process that was initially identified in Xenopus laevis early embryos and was subsequently shown to exist in Drosophila oocytes. Recent data showed that this regulatory process is required for somitic segmentation in Xenopus. Inactivation of EDEN-BP (EDEN-binding protein) causes severe segmentation defects, and the expression of segmentation markers in the Notch signalling pathway is disrupted. We showed that the mRNA encoding XSu(H) (Xenopus suppressor of hairless), a protein central to the Notch pathway, is regulated by EDEN-BP. Our data also indicate that other segmentation RNAs are targets for EDEN-BP. To identify new EDEN-BP targets, a microarray analysis has been undertaken.

Human subcutaneous adipose cells support complete differentiation but not self-renewal of hematopoietic progenitors

Adipose tissue is now considered as an endocrine organ implicated in energy regulation, inflammation and immune response, and as a source of multipotent cells with a broad range of differentiation capacities. Some of these cells are of a mesenchymal type which can -- like their bone marrow (BM) counterpart -- support hematopoiesis, since in a previous study we were able to reconstitute lethally irradiated mice by cells isolated from adipose tissue. In the present study, we established that cells derived from the stroma-vascular fraction of human subcutaneous fat pads support the complete differentiation of hematopoietic progenitors into myeloid and B lymphoid cells. However, these cells are unable to maintain the survival and self-renewal of hematopoietic stem cells. These features, similar to those of BM adipocytes, are the opposite of those of other cell types derived from mesenchymal progenitors such as BM myofibroblasts or osteoblasts. Because it is abundant and accessible, adipose tissue could be a convenient source of cells for the short-term reconstitution of hematopoiesis in man.

Immunomodulatory effect of human adipose tissue-derived adult stem cells: comparison with bone marrow mesenchymal stem cells

Like mesenchymal stem cells from bone marrow (BM-MSCs), adipose tissue-derived adult stem cells (ADAS cells) can differentiate into several lineages and present therapeutical potential for repairing damaged tissues. The use of allogenic stem cells can enlarge their therapeutical interest, provided that the grafted cells could be tolerated. We investigate here, for the first time, the immunosuppressive properties of ADAS cells compared with the well-characterized immunosuppressive properties of BM-MSCs. ADAS cells did not provoke in vitro alloreactivity of incompatible lymphocytes and, moreover, suppressed mixed lymphocyte reaction (MLR) and lymphocyte proliferative response to mitogens. The impairment of inhibition when ADAS cells and BM-MSCs were separated from lymphocytes by a permeable membrane suggests that cell contact is required for a full inhibitory effect. Hepatocyte growth factor is secreted by both stem cells but, similar to interleukin-10 and transforming growth factor-beta (TGF-beta), the levels of which were undetectable in supernatants of MLR inhibited by ADAS cells or BM-MSCs, it did not seem implicated in the stem cell suppressive effect. These findings support that ADAS cells share immunosuppressive properties with BM-MSCs. Therefore, ADAS cell-based reconstructive therapy could employ allogenic cells and because of their immunosuppressive properties, ADAS cells could be an alternative source to BM-MSCs to treat allogenic conflicts.

Altered antibody repertoires of plasma IgM and IgG toward nonself antigens in patients with warm autoimmune hemolytic anemia

Warm autoimmune hemolytic anemia (WAIHA) is characterized by an accelerated extravascular clearance of red blood cells (RBC) mediated by RBC-bound IgG autoantibodies. We have recently demonstrated significantly altered self-reactive antibody (Ab) repertoires of plasma IgM in WAIHA patients. The natural IgM Ab repertoire in plasma is critical in modulating both autoimmune and alloimmune responses. In the present study, we investigated IgM and IgG Ab repertoires of WAIHA patients toward nonself antigens (Ag) using a quantitative immunoblotting technique, followed by multiparametric statistical analysis of the data. We demonstrate significantly altered Ab repertoires of IgM and IgG toward nonself Ag in WAIHA patients. The reactivity of plasma IgM of WAIHA patients was reduced compared to that of healthy individuals, independent of administering an immunosuppressive therapy. We observed that an increase in reactivity of plasma IgM during clinical remission of the disease was associated with the development of allo-Ab toward RBC-antigens during RBC transfusions. Taken together, the data indicate altered Ab repertoires of plasma IgM and IgG toward nonself Ag in WAIHA patients. A broadly reduced reactivity of plasma IgM toward nonself Ag might influence the adaptive immune response in WAIHA patients.

Defects in components of the proteasome enhance transcriptional silencing at fission yeast centromeres and impair chromosome segregation

Fission yeast centromeres are transcriptionally silent and form a heterochromatin-like structure essential for normal centromere function; this appears analogous to heterochromatin and position effect variegation in other eukaryotes. Conditional mutations in three genes designated cep (centromere enhancer of position effect) were found to enhance transcriptional silencing within centromeres. Cloning of the cep1(+) and cep2(+) genes by functional complementation revealed that they are identical to the previously described genes pad1(+) and mts2(+), respectively, which both encode subunits of the proteasome 19S cap. Like Mts2 and Mts4, epitope-tagged Cep1/Pad1 localizes to or near the nuclear envelope throughout the cell cycle. The cep mutants display a range of phenotypes depending on the temperature. Silencing within the central domain of centromeres is increased at 36 degrees C. This suggests that the proteasome is involved in regulating silencing and thus centromeric chromatin architecture, possibly by lowering the level of some chromatin-associated protein by ubiquitin-dependent degradation. This is the first report of defective proteasome function affecting heterochromatin-mediated transcriptional silencing. At 36 and 32 degrees C, the cep mutants lose chromosomes at an elevated rate, and at 18 degrees C, the mutants are cryosensitive for growth. Cytological analysis at 18 degrees C revealed a defect in sister chromatid separation while other mitotic events occurred normally, indicating that cep mutations might interfere specifically with the degradation of inhibitor(s) of sister chromatid separation. These observations suggest that 19S subunits confer a level of substrate specificity on the proteasome and raise the possibility of a link between components involved in centromere architecture and sister chromatid cohesion.

Identification of surface molecules on salivary glands of the mosquito, Aedes aegypti, by a panel of monoclonal antibodies

Malaria transmission by the mosquito vector requires sporozoite invasion into mosquito salivary glands. Parasites probably enter the glands by specific receptor-ligand interactions with molecules on the surface of the glands. We have undertaken the characterization of salivary gland surface molecules of Aedes aegypti to identify candidate receptors for Plasmodium gallinaceum sporozoite invasion. Monoclonal antibodies (mAbs) were generated against antigen enriched for salivary gland membranes and basal lamina. A panel of 44 mAbs were generated that bound to surface molecules of mosquito tissues. Twenty-four mAbs bound exclusively to salivary glands, six bound to salivary glands and ovaries, one bound to salivary gland and midgut, and 13 bound to all tissues tested. We present data on the immunolocalization and biochemical characteristics of the antigens. Many of the salivary gland-specific mAbs bound preferentially to the median and distal lateral lobes of the salivary glands, indicating that there are anatomical region-specific biochemical differences on the gland surface. These lobes of the salivary glands are the preferential sites of malaria sporozoite invasion. Therefore, antigens specific for these regions are promising candidate receptors for sporozoite invasion. The present identification of surface molecules of mosquito salivary glands by means of monoclonal antibodies represents the first description of individual molecules on the mosquito salivary gland surface. This work lays the basis for further studies on the molecular mechanisms involved in malaria sporozoite invasion of mosquito salivary glands.

Lactobacillus species identification, H2O2 production, and antibiotic resistance and correlation with human clinical status

Lactobacilli recovered from the blood, cerebrospinal fluid, respiratory tract, and gut of 20 hospitalized immunocompromised septic patients were analyzed. Biochemical carbohydrate fermentation and total soluble cell protein profiles were used to identify the species. Hydrogen peroxide production was measured. Susceptibility to 19 antibiotics was tested by a diffusion method, and the MICs of benzylpenicillin, amoxicillin, imipenem, erythromycin, vancomycin, gentamicin, and levofloxacin were determined. A small number of species produced H2O2, and antibiotic susceptibilities were species related. Eighteen (90%) of the isolates were L. rhamnosus, one was L. paracasei subsp. paracasei, and one was L. crispatus. L. rhamnosus, L. paracasei subsp. paracasei isolates, and the type strains were neither H2O2 producers nor vancomycin susceptible (MICs, >/=256 microgram/ml). L. crispatus, as well as most of the type strains of lactobacilli which belong to the L. acidophilus group, was an H2O2 producer and vancomycin susceptible (MICs, <4 microgram/ml).

Regulation of gene expression during the vegetative incompatibility reaction in Podospora anserina. Characterization of three induced genes

Vegetative incompatibility in fungi limits the formation of viable heterokaryons. It results from the coexpression of incompatible genes in the heterokaryotic cells and leads to a cell death reaction. In Podospora anserina, a modification of gene expression takes place during this reaction, including a strong decrease of total RNA synthesis and the appearance of a new set of proteins. Using in vitro translation of mRNA and separation of protein products by two-dimensional gel electrophoresis, we have shown that the mRNA content of cells is qualitatively modified during the progress of the incompatibility reaction. Thus, gene expression during vegetative incompatibility is regulated, at least in part, by variation of the mRNA content of specific genes. A subtractive cDNA library enriched in sequences preferentially expressed during incompatibility was constructed. This library was used to identify genomic loci corresponding to genes whose mRNA is induced during incompatibility. Three such genes were characterized and named idi genes for genes induced during incompatibility. Their expression profiles suggest that they may be involved in different steps of the incompatibility reaction. The putative IDI proteins encoded by these genes are small proteins with signal peptides. IDI-2 protein is a cysteine-rich protein. IDI-2 and IDI-3 proteins display some similarity in a tryptophan-rich region.

Use of a linear plasmid containing telomeres as an efficient vector for direct cloning in the filamentous fungus Podospora anserina

In Podospora anserina a linear plasmid with telomeric ends behaves as an artificial acentric minichromosome. Transformation is at least 100 times more efficient than with integrative vectors. Genomic DNA was inserted in this plasmid in vitro and the mixture used to transform a leu1-1 strain. Many fungal clones containing the leu1 gene as a genomic insert in the linear plasmid were identified. The leu1 gene was rescued as a circular plasmid in Escherichia coli demonstrating that a direct cloning procedure can be applied for the fungus P. anserina. The conservation of telomeric sequences among filamentous fungi suggests that a telomere-based linear plasmid could provide a general cloning vector for filamentous fungi.

The mod-A suppressor of nonallelic heterokaryon incompatibility in Podospora anserina encodes a proline-rich polypeptide involved in female organ formation

Vegetative incompatibility in fungi results from the control of heterokaryon formation by the genes present at het loci. Coexpression of antagonistic het genes in the same hyphae leads to a lethal process. In Podospora anserina, self-incompatible strains containing nonallelic incompatible genes in the same nucleus are inviable as the result of a growth arrest and a lytic process. Mutations in suppressor genes (mod genes) can restore the viability. These mod mutations also interfere with developmental processes, which suggests common steps between the incompatibility reaction and cellular differentiation. The mod-A locus, responsible for growth arrest in the self-incompatible strains, is also involved in the control of the development of female organs. The mod-A gene was isolated. An open reading frame 687 amino acids long was identified. The MOD-A-encoded polypeptide is rich in proline residues, which are clustered in a domain containing a motif that displays similarity to SH3-binding motifs, which are known to be involved in protein-protein interactions. Construction of a strain deleted for mod-A confirmed that the product of this gene involved in differentiation is a key regulator of growth arrest associated with vegetative incompatibility.

Identification of Rhodococcus, Gordona and Dietzia species using carbon source utilization tests ("Biotype-100" strips)

The "Biotype-100" identification system (BioMérieux, La Balme-Ies-Grottes, France) based on carbon source utilization was evaluated for its ability to discriminate among 10 species of Rhodococcus, 7 species of Gordona and one species of Dietzia. The type strains of three species of Tsukamurella and 8 species of Nocardia were also included in the study. Results were compared with chemotaxonomic and conventional data. Carbon source utilization was shown to be reliable, rapid and easy to use when compared with standard identification methods. The 29 species tested were unambiguously separated by carbon source utilization tests. Rhodococcus equi was found to be heterogenous.

Analysis of antibody reactivities toward self antigens of IgM of patients with Waldenström's macroglobulinemia

By using a quantitative immunoblotting technique, we have analyzed the repertoires of antibody reactivities of IgM directed toward self antigens in the serum of patients with Waldenström's macroglobulinemia (WM) and in the serum of healthy adults. Monoclonal IgM of patients with WM expressed various degrees of polyreactivity and a high degree of heterogeneity with regard to the number and the nature of the protein bands that were recognized in homologous tissue extracts. Heterogeneous patterns of reactivity of WM IgM contrasted with the conserved profiles of reactivity of IgM in the serum of healthy blood donors. Protein bands that were recognized by WM IgM belonged to the restricted set of self antigens recognized in homologous tissues by normal polyclonal IgM, indicating the absence of a disease-specific reactivity profile of monoclonal WM IgM. Thus, monoclonal IgM that is present in large amounts in WM distorts the homogeneous pattern of reactivity of natural antibodies with self antigens which characterizes the natural antibody repertoire of healthy individuals.

Venereal and vertical transmission of the Aedes albopictus parvovirus in Aedes aegypti mosquitoes

Following per oral infection of Aedes aegypti larvae with Aedes albopictus parvovirus (AaPV), infected males and females adults were tested for their ability to transmit the virus venereally and vertically, respectively. Both types of transmission were observed. A low percentage (2.2%) of AaPV-free females were found contaminated by the virus after mating with AaPV-infected males. Although no significant difference was observed in the fecundity of orally infected and virus-free females, 17.1% of infected ones died before egg laying, whereas no mortality occurred during the same period in virus-free females. There was a clear relationship between the virus titer in the orally infected females and both mortality and infection in their offspring. The virus titer averaged 10(6.2) 50% tissue culture infective doses (TCID50s) in F1 females and 10(3.3) TCID50 in F1 females. Nevertheless, AaPV did not persist in an experimentally infected population of mosquitoes beyond the second generation.

The repertoire of serum IgM in normal mice is largely independent of external antigenic contact

Antigen-free (AGF) and germ-free (GF) mice, although essentially free of serum IgG, maintain normal levels of circulating IgM. Using a quantitative immunoblot assay, we have now analyzed the repertoire of serum IgM from AGF, GF, and specific pathogen-free (SPF) BALB/c mice, on large panels of natural antigens from homologous tissues and bacteria. The reactivity profiles were very similar in the three groups of mice. Multiparametric statistic evaluation of the data showed that BALB/c animals, SPF, GF, and AGF mice constitute an homogeneous group with similar immunoreactivity profiles when compared to C57BL/6. Differences between immunoreactivity profiles of GF and AGF mice were observed, but were not statistically significant. These results suggest that the serum IgM repertoire of normal mice is strictly regulated and selected by endogenous ligands.

Pathogenicity of the Aedes albopictus parvovirus (AaPV), a denso-like virus, for Aedes aegypti mosquitoes

AaPV, a denso-like virus isolated from a C6/36 clone of the Aedes albopictus cell line, proved to be very pathogenic for Aedes aegypti first and third instar larvae following per os infection. The mortality reached 90% in 10 days for larvae infected at the first instar. Several factors, such as temperature, larval density and stage, and duration of contact with infectious particles, influenced infection. The virus titer in females surviving infection at the third larval instar reached 10(8) TCID50. Adult mosquitoes were sensitive to virus inoculation and to cytotransfection by viral DNA. Histological and ultrastructural studies revealed the presence of dense nuclei in almost all of the larval tissues with the exception of the midgut.

Identification of Turicella otitidis isolated from a patient with otorrhea associated with surgery: differentiation from Corynebacterium afermentans and Corynebacterium auris

Turicella otitidis is a newly described coryneform bacterium isolated from middle ear fluids. We report here on the diagnosis of a strain isolated from otorrhea. The API Coryne system (bioMérieux, Marcy I'Etoile, France) used alone failed to differentiate T. otitidis, Corynebacterium afermentans, and Corynebacterium auris (ANF group). Biochemical tests such as DNase, enzymatic reactions (API ZYM; bioMérieux), and carbon substrate assimilation tests (Biotype 100; bioMérieux) allow presumptive identification. However, only chemotaxonomy and molecular biology can achieve unequivocal differentiation among these three species.

The self-reactive antibody repertoire of normal human serum IgM is acquired in early childhood and remains conserved throughout life

The authors have used a quantitative immunoblotting technique to analyse the antibody repertoire of IgM in cord blood and in the serum of young children, young adult males and aged males directed towards antigens in homologous tissues utilized as sources of self antigens. The reactivities of IgM with self antigens exhibited striking homogeneity and invariance among newborns. Self-reactive IgM repertoires of children, young adults and aged males were markedly conserved among individuals and comprised most of the anti-self reactivities that prevailed in neonates. Reactivities of IgM with bacterial antigens showed a high degree of homogeneity among newborns but were more diverse in children, young adults and elderly individuals. Diversity of IgM reactivities with self and non-self antigens did not vary significantly with aging. Principal component analysis (PCA) and linear discriminant analysis (LDA) of the data discriminated between self-reactive IgM repertoires of newborns and children, but failed to discriminate between repertoires of children, young adults and aged males. The data indicate that the self-reactive antibody repertoire of IgM differentiates during the first years of life and remains relatively constant thereafter.

PCR methods for identification and specific detection of probiotic lactic acid bacteria

Probiotics are defined as "microbes improving animal feed." Three lactic acid bacteria, previously selected as probiotic for pig feeding, were identified by sequencing the variable V1 region of the 16S rDNA after PCR amplification primed in the flanking constant region. A VR region showing strong nucleotide differences between the three probiotic and the reference strains was delimited. Oligonucleotides specific for each strain were designed. A specific assay for probiotic detection was developed, based on a PCR reaction with three primers.

Plasmodium: a quantitative molecular assay for detection of sporogonic-stage malaria parasites

We present a molecular assay to detect malaria parasites during sporogonic development in the mosquito host. Specific primers for Plasmodium-specific small-subunit ribosomal RNA sequences not present in mosquito RNA were used in a reverse transcriptase-polymerase chain reaction (RT-PCR) assay. A synthetic RNA quantitative competitor was made which included targets for two primers and a target sequence for a hybridization probe which is also present in the natural parasite ribosome. The heterobifunctional Tth polymerase was used to carry out both reverse transcription and DNA-dependent polymerase chain reaction in a single reaction tube. Ookinetes and sporozoites, the stages from the beginning and end of sporogonic development, respectively, were both recognized in the assay. The assay was calibrated for quantitation of sporozoites by making a standard curve with counted sporozoites. The linear range of the calibrated assay allowed accurate quantitation of parasite number over at least two orders of magnitude, from 10 to 1000 sporozoites, in each RT-PCR reaction.

Plasmodium gallinaceum: sporozoite invasion of Aedes aegypti salivary glands is inhibited by anti-gland antibodies and by lectins

There is evidence which suggests that malaria sporozoites recognize mosquito salivary glands by specific receptor-ligand interactions. We are interested in identifying the putative salivary gland receptor(s) for sporozoite invasion. We used an in vivo bioassay for sporozoite invasion of salivary glands. In this assay, purified sporozoites from mature oocytes of Plasmodium gallinaceum were injected into Aedes aegypti mosquitoes and salivary glands were dissected at different time points after injection. One half of the maximum invasion of salivary glands by sporozoites occurred by 6 hr, and salivary gland sporozoite load did not increase further after 24 hr postinjection. This assay was used to determine the effect of experimental treatments with antibodies and lectins at 24 hr postinjection. We raised a rabbit polyclonal antiserum against female Ae. aegypti salivary glands which recognized tissue-specific determinants in the basal lamina of salivary glands. Purified IgG antibody fraction of the immune serum blocked sporozoite invasion in vivo. We tested a panel of 19 lectins and found 7 which bound to salivary glands. Of these 7, succinylated wheat germ agglutinin and wheat germ agglutinin completely blocked sporozoite invasion; Pisum sativum agglutinin and soybean agglutinin partially blocked; and concanavalin A, Dolichos biflorus agglutinin, and Phaseolus vulgaris erythroagglutinin did not block. Our results suggest that sporozoites interact with glycosylated salivary gland surface molecules which serve as receptors for invasion, and which may be in the salivary gland basal lamina. Because the putative sporozoite receptors contain immunogenic determinants, it is feasible to identify them by an immunological strategy.

Analysis of the normal human IgG antibody repertoire. Evidence that IgG autoantibodies of healthy adults recognize a limited and conserved set of protein antigens in homologous tissues

We have used a quantitative immunoblot technique to analyze the Ab repertoire of IgG in the serum of healthy adults with a large panel of homologous and foreign Ags in tissue extracts. Densitometric patterns of reactivity of purified IgG with self-Ags exhibited striking homogeneity among individuals with regard to the protein bands that were recognized. Purified IgG showed higher levels of reactivity with self-Ags than IgG in whole serum. Reactivity with self-Ags of IgG in whole serum was restricted to a small number of protein bands (fewer than 10). There were significant inter-individual differences in the intensity and nature of immunoreactivities. Purified IgG of different individuals exhibited heterogeneous patterns of immunoreactivity with Ags in bacterial extracts. Comparative analysis of repertoires of IgG and IgM indicated that all protein Ags recognized by IgM were also reactive with purified IgG. Some proteins in homologous and in foreign tissue extracts reacted solely with IgG. Our observations provide direct evidence for the restricted and conserved character of the antiself-repertoire of IgG of healthy adults and suggest that natural IgG Ab repertoires in serum are specifically selected for reactivity with a limited set of self-Ags. In addition, IgG autoreactivity in whole serum is controlled by non-IgG factors that determine the unique reactivity pattern of each individual.

Analysis of the normal human IgG antibody repertoire. Evidence that IgG autoantibodies of healthy adults recognize a limited and conserved set of protein antigens in homologous tissues

We have used a quantitative immunoblot technique to analyze the Ab repertoire of IgG in the serum of healthy adults with a large panel of homologous and foreign Ags in tissue extracts. Densitometric patterns of reactivity of purified IgG with self-Ags exhibited striking homogeneity among individuals with regard to the protein bands that were recognized. Purified IgG showed higher levels of reactivity with self-Ags than IgG in whole serum. Reactivity with self-Ags of IgG in whole serum was restricted to a small number of protein bands (fewer than 10). There were significant inter-individual differences in the intensity and nature of immunoreactivities. Purified IgG of different individuals exhibited heterogeneous patterns of immunoreactivity with Ags in bacterial extracts. Comparative analysis of repertoires of IgG and IgM indicated that all protein Ags recognized by IgM were also reactive with purified IgG. Some proteins in homologous and in foreign tissue extracts reacted solely with IgG. Our observations provide direct evidence for the restricted and conserved character of the antiself-repertoire of IgG of healthy adults and suggest that natural IgG Ab repertoires in serum are specifically selected for reactivity with a limited set of self-Ags. In addition, IgG autoreactivity in whole serum is controlled by non-IgG factors that determine the unique reactivity pattern of each individual.

Invariance and restriction toward a limited set of self-antigens characterize neonatal IgM antibody repertoires and prevail in autoreactive repertoires of healthy adults

Analysis of the reactivity of IgM with self-antigens in tissues by a quantitative immunoblotting technique showed striking invariance among newborns in the human and in the mouse. The self-reactive repertoire of IgM of adults was also markedly conserved; it comprised most anti-self reactivities that prevailed among neonates. Multivariate analysis confirmed the homogeneity of IgM repertoires of neonates toward self- and non-self-antigens. Multivariate analysis discriminated between newborn and adult repertoires for reactivity with two of five sources of self-proteins and with non-self-antigens. Our observations support the concept that naturally activated B lymphocytes are selected early in development and throughout life for reactivity with a restricted set of self-antigens.

Primary identification of Microbacterium spp. encountered in clinical specimens as CDC coryneform group A-4 and A-5 bacteria

Over nearly two decades, 13 yellow- or orange-pigmented, fermentative gram-positive rods belonging to the genus Microbacterium were encountered in clinical specimens. All 13 strains, 10 of which came from blood cultures, were initially identified as CDC coryneform group A-4 and A-5 bacteria according to the scheme of Hollis and Weaver for the identification of gram-positive rods. The clinical isolates were compared with the type strains of the six species constituting the genus Microbacterium as well as with three Microbacterium strains isolated from hospital environments. By biochemical methods only 5 of 13 clinical isolates could be identified to species level. Peptidoglycan analysis proved to be a valuable tool for differentiation between Microbacterium spp. and related genera, whereas cellular fatty acid analysis did not allow species identification within the genus Microbacterium. The 22 Microbacterium strains studied were, in general, susceptible to antimicrobial agents used in the treatment of infections caused by gram-positive rods. This report is the first one concerning the isolation of Microbacterium strains from clinical specimens. The sources as well as the mode of transmission remain to be established.

An efficient and easy method of infection of mosquito larvae from virus-contaminated cell cultures

A new method for efficient infection of Aedes aegypti larvae by the Aedes albopictus densovirus, AaPV is described. It consists of placing first or third instar larvae in culture flasks containing a chronically infected mosquito cell line. After 24 or 48 h of exposure to the contaminated culture, the larvae acquired the virus by feeding on infected cells. Using this technique, up to 95% of first instar Ae. aegypti larvae were found infected by the AaPV.

Assignment of linkage groups to the electrophoretically-separated chromosomes of the fungus Podospora anserina

An electrophoretic karyotype of the filamentous fungus Podospora anserina has been obtained using contour-clamped homogeneous electric field gel electrophoresis. Six chromosomal bands were separated with one migrating as a doublet. The size of the chromosomes was estimated to be between 3.8 and 6.0 megabase pairs (mb) using the chromosomes of Schizosaccharomyces pombe as size standards, giving a total genome size of about 34 mb for the P. anserina genome. Homologous probes were used to assign five of the seven linkage groups (LGs) to chromosomal bands on the gel. Analysis of reciprocal translocation strains allowed us to complete the karyotype. In decreasing size order, the P. anserina chromosomes are LG I (6.0 mb); LG II (5.5 mb); LG V (5.1 mb); LG III (4.9 mb); LGs VI and VII (4.3 mb) and LG IV (3.8 mb).

A parvo-like virus persistently infecting a C6/36 clone of Aedes albopictus mosquito cell line and pathogenic for Aedes aegypti larvae

We have isolated and partially characterized from an apparently healthy C6/36 subclone of Aedes albopictus cell line a small icosahedral non-enveloped DNA virus, designated AaPV. This virus proved to be highly pathogenic for Aedes aegypti neonate larvae. Viral infection persisted for over 4 years in the cell culture without any cytopathic effect. Attempts to infect suckling mice, Drosophila melanogaster adults and Spodoptera littoralis larvae with AaPV were unsuccessful. Similarly, the AaPV failed to replicate in vertebrate and Drosophila cell lines. Virions, about 22 nm in diameter, had a buoyant density of 1.43 g/cm3 and contained three capsid polypeptides with molecular weights of 53, 41 and 40 kDa. A preliminary study of the viral genome indicated the presence of single-stranded DNA. By its biophysical and biochemical properties, this virus appears to be related to the genus Densovirus within the family Parvoviridae, but lacks serological relationships with the other members of this genus.

Comparative chemotaxonomic studies of mycolic acid-free coryneform bacteria of human origin

Forty-two clinical isolates were classified as Corynebacterium minutissimum, Corynebacterium striatum, and Corynebacterium CDC group I by the API Coryne system. The chemotaxonomic characteristics of the isolates were determined by thin-layer chromatographic analysis. Twenty-six isolates were found to have a type IV cell wall (meso-di-aminopimelic acid arabinose, galactose) but did not contain mycolic acids. These 26 isolates shared chemotaxonomic characteristics with those of mycolic acid-free reference strains (including the Corynebacterium amycolatum NCFB 2768 type strain, "Corynebacterium asperum," and coryneform CDC groups I2 and F2). The total protein profiles of the isolates determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis were similar to each other and to that of the C. amycolatum type strain. The profiles of the reference strains "Corynebacterium asperum" (CIP 100836, CIP 80.54, CIP 79.37, CIP 52.13), coryneform bacteria CDC groups I2 and F2 (CDC F5771, F5890, G723, G1970), and C. amycolatum were closely related. Thus, the mycolic acid-negative strains with a chemotype IV wall may belong to a single taxon. DNA hybridization studies could confirm this hypothesis. The present study shows the importance of chemotaxonomic analysis for verifying strain identifications and completing results from biochemical tests, particularly for coryneform bacteria.

Purification and characterisation of an Aspergillus niger invertase and its DNA sequence

A secreted invertase was purified 23-fold by ultrafiltration, ion-exchange, and gel filtration chromatography from the culture supernatant of 18 h sucrose-grown cultures of Aspergillus niger. The purified enzyme hydrolysed sucrose and raffinose but there was no detectable hydrolysis of inulin, melezitose or PNPG. Invertase activity was optimal at pH 5.5 and 50 degrees C. The molecular mass of reduced invertase was 115 kDa, as determined by SDS gel electrophoresis. The native molecular weight of between 225 kDa and 250 kDa, estimated by electrophoresis under non-denaturing conditions, suggests that the protein is a dimer of identical subunits. The suc1 gene encoding this protein was completely-sequenced. The translated sequence yields a protein of 566 amino acids with a calculated molecular mass of 61 kDa, suggesting that carbohydrates represent about 50% of the mass of the protein.

Cloning of an Aspergillus niger invertase gene by expression in Trichoderma reesei

The filamentous fungus Aspergillus niger produces two glycosylated forms of the sucrose-hydrolysing enzyme, invertase. In contrast, some Trichoderma species lack invertase and are unable to utilise sucrose as a sole carbon source. Using an A. niger genomic library constructed in a cosmid vector containing the ura5 gene of Podospora anserina as a selectable marker, and the T. reesei ura5- strain as a sucrose-minus recipient strain, an A. niger invertase gene (suc1) has been cloned by a sib selection procedure. PAGE and enzyme analysis confirmed that transformants had acquired invertase activity. The cloned gene contained DNA sequences which were complementary to the amino-acid sequences of tryptic peptides found in invertase purified from A. niger. The suc1 invertase gene can be used as a dominant selectable marker for the transformation of Trichoderma strains.

Isolation of telomeric DNA from the filamentous fungus Podospora anserina and construction of a self-replicating linear plasmid showing high transformation frequency

It has been previously shown that linear plasmids bearing Tetrahymena telomeric sequences are able to replicate autonomously in the filamentous fungus Podospora anserina (1). However, autonomous replication occurs in only 50-70% of the transformants, suggesting a defect in the recognition of the Tetrahymena telomeric template by the putative P. anserina telomerase so that only a fraction of entering DNA is stabilized into linear extrachromosomal molecules. We have cloned DNA sequences added to the Tetrahymena (T2G4)n ends of the linear plasmid. Nucleotide sequencing showed that these sequences are exclusively composed of T2AG3 repeat units. Hybridization experiments of Bal31 treated DNA showed that T2AG3 repeats are confined within 200 bp in chromosomal P. anserina telomeres. A new plasmid has been constructed so that after linearization, the terminal sequences contain T2AG3 repeats. This linear molecule transforms P. anserina with a high frequency (up to 1.75 x 10(4) transformants/micrograms), autonomous replication occurs in 100% of the transformants and the plasmid copy number is about 2-3 per nucleus. These results underscore the importance of the telomeric repeat nucleotide sequence for efficient recognition as functional telomeric DNA in vivo and provide the first step toward the development of an artificial chromosome cloning system for filamentous fungi.