Asymmetric leaves1 mediates leaf patterning and stem cell function in Arabidopsis

Meristem function in plants requires both the maintenance of stem cells and the specification of founder cells from which lateral organs arise. Lateral organs are patterned along proximodistal, dorsoventral and mediolateral axes. Here we show that the Arabidopsis mutant asymmetric leaves1 (as1) disrupts this process. AS1 encodes a myb domain protein, closely related to PHANTASTICA in Antirrhinum and ROUGH SHEATH2 in maize, both of which negatively regulate knotted-class homeobox genes. AS1 negatively regulates the homeobox genes KNAT1 and KNAT2 and is, in turn, negatively regulated by the meristematic homeobox gene SHOOT MERISTEMLESS. This genetic pathway defines a mechanism for differentiating between stem cells and organ founder cells within the shoot apical meristem and demonstrates that genes expressed in organ primordia interact with meristematic genes to regulate shoot morphogenesis.

P element homing to the Drosophila bithorax complex

P elements containing a 7 kb DNA fragment from the middle of the Drosophila bithorax complex insert preferentially into the bithorax complex or into the adjacent chromosome regions. This ‘homing’ property is similar to that reported for the engrailed promoter (Hama, C., Ali, Z. and Kornberg, T. B. (1990) Genes Dev. 4, 1079–1093). The 7 kb fragment does not contain any known promoter, but it acts as a boundary element separating adjacent segmental domains. An enhancer-trap P element was constructed with the homing fragment and the selectable marker flanked by FRT sites. P insertions can be trimmed down by Flp-mediated recombination to just the lacZ reporter, so that the (beta)-galactosidase pattern is not influenced by sequences inside the P element. Twenty insertions into the bithorax complex express (beta)-galactosidase in segmentally limited patterns, reflecting the segmental domains of the bithorax complex where the elements reside. The mapping of segmental domains has now been revised, with enlargement of the abx/bx, bxd/pbx, and the iab-3 domains. The FRT sites in the P elements permit recombination between pairs of elements on opposite chromosomes, to generate duplications or deletions of the DNA between the two insertion sites. Using this technique, the length of the Ultrabithorax transcription unit was varied from 37 to 138 kb, but there was surprisingly little effect on Ultrabithorax function.

Restricted patterning of vestigial expression in Drosophila wing imaginal discs requires synergistic activation by both Mad and the drifter POU domain transcription factor

The Drosophila Vestigial protein has been shown to play an essential role in the regulation of cell proliferation and differentiation within the developing wing imaginal disc. Cell-specific expression of vg is controlled by two separate transcriptional enhancers. The boundary enhancer controls expression in cells near the dorsoventral (DV) boundary and is regulated by the Notch signal transduction pathway, while the quadrant enhancer responds to the Decapentaplegic and Wingless morphogen gradients emanating from cells near the anteroposterior (AP) and DV boundaries, respectively. MAD-dependent activation of the vestigial quadrant enhancer results in broad expression throughout the wing pouch but is excluded from cells near the DV boundary. This has previously been thought to be due to direct repression by a signal from the DV boundary; however, we show that this exclusion of quadrant enhancer-dependent expression from the DV boundary is due to the absence of an additional essential activator in those cells. The Drosophila POU domain transcriptional regulator, Drifter, is expressed in all cells within the wing pouch expressing a vgQ-lacZ transgene and is also excluded from the DV boundary. Viable drifter hypomorphic mutations cause defects in cell proliferation and wing vein patterning correlated with decreased quadrant enhancer-dependent expression. Drifter misexpression at the DV boundary using the GAL4/UAS system causes ectopic outgrowths at the distal wing tip due to induction of aberrant Vestigial expression, while a dominant-negative Drifter isoform represses expression of vgQ-lacZ and causes severe notching of the adult wing. In addition, we have identified an essential evolutionarily conserved sequence element bound by the Drifter protein with high affinity and located adjacent to the MAD binding site within the quadrant enhancer. Our results demonstrate that Drifter functions along with MAD as a direct activator of Vestigial expression in the wing pouch.

DEVELOPMENT OF SYMMETRY IN PLANTS

Plant development involves specification and elaboration of axes of asymmetry. The apical-basal and inside-outside axes arise in embryogenesis, and are probably oriented maternally. They are maintained during growth post-germination and interact to establish novel axes of asymmetry in flowers and lateral organs (such as leaves). Whereas the genetic control of axis elaboration is now partially understood in embryos, floral meristems, and organs, the underlying mechanisms of axis specification remain largely obscure. Less functionally significant aspects of plant asymmetry (e.g. the handedness of spiral phyllotaxy) may originate in random events and therefore have no genetic control.

Plant development: YABBYs claw to the fore

The YABBY gene family was identified recently by homology to CRABS CLAW, a gene involved in carpel and nectary development in Arabidopsis. Several of the transcription factors encoded by the YABBY genes appear to have conserved roles in specifying abaxial cell fate in leaves, floral organs and ovules.

ROUGH SHEATH2: a Myb protein that represses knox homeobox genes in maize lateral organ primordia

The regulation of members of the knotted1-like homeobox (knox) gene family is required for the normal initiation and development of lateral organs. The maize rough sheath2 (rs2) gene, which encodes a Myb-domain protein, is expressed in lateral organ primordia and their initials. Mutations in the rs2 gene permit ectopic expression of knox genes in leaf and floral primordia, causing a variety of developmental defects. Ectopic KNOX protein accumulation in rs2 mutants occurs in a subset of the normal rs2-expressing cells. This variegated accumulation of KNOX proteins in rs2 mutants suggests that rs2 represses knox expression through epigenetic means.

Adult survivors of childhood sexual abuse as patients: two case studies

Adult survivors of childhood sexual abuse comprise a high percentage of the patients seen in gastrointestinal and genitourinary clinics and are commonly found among the patient population treated by WOC nurses. The physical and emotional consequences of sexual abuse may permeate the survivor's life, but rise to the forefront only with the additional stress of an ostomy or urinary diversion. Two case studies are described involving women the authors encountered in their practices.

Axioms and axes in leaf formation?

Formation of leaves and floral organs involves down-regulation of meristem-specific homeobox genes, and de novo expression of genes for organ identity, growth and patterning. Genes required for all these aspects of organ formation have been identified. The challenge now is to establish how they interact to direct organogenesis.

The Vestigial and Scalloped proteins act together to directly regulate wing-specific gene expression in Drosophila

A small number of major regulatory (selector) genes have been identified in animals that control the development of particular organs or complex structures. In Drosophila, the vestigial gene is required for wing formation and is able to induce wing-like outgrowths on other structures. However, the molecular function of the nuclear Vestigial protein, which bears no informative similarities to other proteins, was unknown. Here, we show that Vestigial requires the function of the Scalloped protein, a member of the TEA family of transcriptional regulators, to directly activate the expression of genes involved in wing morphogenesis. Genetic and molecular analyses reveal that Vestigial regulates wing identity by forming a complex with the Scalloped protein that binds sequence specifically to essential sites in wing-specific enhancers. These enhancers also require the direct inputs of signaling pathways, and the response of an enhancer can be switched to another pathway through changes in signal-transducer binding sites. Combinatorial regulation by selector proteins and signal transducers is likely to be a general feature of the tissue-specific control of gene expression during organogenesis.

The PHANTASTICA gene encodes a MYB transcription factor involved in growth and dorsoventrality of lateral organs in Antirrhinum

The organs of a higher plant show two fundamental axes of asymmetry: proximodistal and dorsoventral. Dorsoventrality in leaves, bracts, and petal lobes of Antirrhinum majus requires activity of the PHANTASTICA (PHAN) gene. Conditional mutants revealed that PHAN is also required for earlier elaboration of the proximodistal axis. PHAN was isolated and shown to encode a MYB transcription factor homolog. PHAN mRNA is first detected in organ initials before primordium initiation. The structure and expression pattern of PHAN, together with its requirement in two key features of organ development, are consistent with a role in specifying lateral organ identity as distinct from that of the stem or meristem. PHAN also appears to maintain meristem activity in a non-cell-autonomous manner.

Ultrabithorax regulates genes at several levels of the wing-patterning hierarchy to shape the development of the Drosophila haltere

Arthropods and vertebrates are constructed of many serially homologous structures whose individual patterns are regulated by Hox genes. The Hox-regulated target genes and developmental pathways that determine the morphological differences between any homologous structures are not known. The differentiation of the Drosophila haltere from the wing through the action of the Ultrabithorax (Ubx) gene is a classic example of Hox regulation of serial homology, although no Ubx-regulated genes in the haltere have been identified previously. Here, we show that Ubx represses the expression of the Wingless (Wg) signaling protein and a subset of Wg- and Decapentaplegic-activated genes such as spalt-related, vestigial, Serum Response Factor, and achaete-scute, whose products regulate morphological features that differ between the wing and haltere. In addition, we found that some genes in the same developmental pathway are independently regulated by Ubx. Our results suggest that Ubx, and Hox genes in general, independently and selectively regulate genes that act at many levels of regulatory hierarchies to shape the differential development of serially homologous structures.

Early events in leaf development

Morphological studies of early events in leaf development have been hindered by the lack of stereotypic patterns of cell division and markers for cell identity. However, molecular genetic analysis, particularly in maize, has begun to suggest the mechanisms which partition meristematic cells into a leaf primordium, define regional identities within the primordium and direct localised growth which leads to outgrowth and flattening of the leaf. Therefore, the leaf may provide a model for pattern formation applicable to other parts of the plant.

Synaptojanin 1: localization on coated endocytic intermediates in nerve terminals and interaction of its 170 kDa isoform with Eps15

Synaptojanin 1 is an inositol 5-phosphatase with a putative role in clathrin-mediated endocytosis. Goal of this study was to provide new evidence for this hypothesis. We show that synaptojanin 1 is concentrated at clathrin-coated endocytic intermediates in nerve terminals. Furthermore, we report that synaptojanin-170, an alternatively spliced isoform of synaptojanin 1, binds Eps15, a clathrin coat-associated protein. Binding is mediated by the COOH-terminal region of synaptojanin-170 which we show here to be poorly conserved from rat to humans, but to contain in both species three asparagine-proline-phenylalanine (NPF) repeats. This motif has been found to be the core of the binding site for the EH domains of Eps15. Together with previous data, our results suggest that synaptojanin 1 can be recruited to clathrin-coated pits via a multiplicity of interactions.

Plant meristems: cell signalling keeps the balance

Genetic and molecular analysis in Arabidopsis has identified components of a putative cell signalling pathway that appears to regulate the balance between stem cell proliferation and fate specification in meristems.

Meeting patients' needs: quality care in a changing environment

Recent surveys of patients in New York and Cleveland, among other cities, indicate that there is substantial room for improvement in meeting patients' needs and preferences, particularly in the areas of emotional support, coordination of care, discharge preparation, and the involvement of family and friends. Hospitals are using a variety of techniques to improve patient care and organizational efficiency in this challenging environment. One prominent approach, reengineering, offers a means by which hospitals can integrate highly specialized departmental structures and functions by focusing on interdisciplinary teamwork and organizing the delivery of care around patients. Key elements of successful hospital reengineering efforts have included: - the involvement and commitment of senior management and other key stakeholders, particularly physicians, nurses, and union representatives; - investment in staff training and retraining, and the redesign of staff evaluation and compensation systems; - timely, unit-specific measures of patient satisfaction and the clinical quality of care; - consistent and frequent internal communication between staff and leadership; and - treatment that emphasizes communication among caregivers, patients, and their family members. Several basic issues need to be addressed if hospitals are to offer technically sophisticated medical care that is also responsive to their patients' personal needs, including: - variations among patients regarding the amount of information they want and need, and the amount of involvement they want in their care; - the means by which patients will get information about their medical care, and who will provide any additional support that may be needed by non-English-speaking or socioeconomically disadvantaged patients; and - the specific changes in medical practice and hospital processes that will promote the involvement of patients in their care.

Alteration of Chlamydia trachomatis biologic behavior in synovial membranes. Suppression of surface antigen production in reactive arthritis and Reiter's syndrome

OBJECTIVE

To investigate the biologic state of Chlamydia and its surface antigen expression in the synovial membranes of patients with Chlamydia-associated reactive arthritis/Reiter's syndrome (ReA/RS).

METHODS

Expression of chlamydial lipopolysaccharide (LPS), major outer membrane protein (MOMP), and elementary body (EB) antigens was studied by gold labeling immunoelectron microscopy on 6 synovial membrane and 2 synovial fluid (SF) pellet samples from 6 patients with Chlamydia-associated arthritis. The study findings were compared with 24-hour cultures of HeLa cells infected with Chlamydia trachomatis EB.

RESULTS

Persistent C trachomatis infection was found in all 6 synovial membrane samples from patients who had either early or chronic arthritis. The infection persisted despite antibiotic treatment, including a 1-month course of doxycycline therapy. Most persistent organisms were atypical reticulate bodies (RBs) found in both fibroblasts and macrophages. Specific, but weak, immunogold staining for all 3 antibodies was found on both intracellular RBs and extracellular EBs. In the SF samples, Chlamydia surface antigens were detected only in phagosomes containing degraded electron-dense materials.

CONCLUSION

The synovial membrane biopsies conducted in this study of Chlamydia-associated ReA/RS revealed atypical RBs with diminished MOMP and LPS expression. Such altered organisms may escape immune surveillance and contribute to disease chronicity; moreover, these organisms may be difficult to detect and treat in some ReA/RS patients.

phantastica: a gene required for dorsoventrality of leaves in Antirrhinum majus

To understand better the mechanisms that lead to dorsoventrality in the lateral organs of plants, mutants at the phantastica (phan) locus of Antirrhinum majus have been identified and characterised. The leaves, bracts and petal lobes of phan mutants show varying degrees of reduction in dorsal tissues, indicating that phan is required for establishing dorsal cell identity. Each phan mutant produces a variety of different leaf morphologies, but has a characteristic and relatively constant floral phenotype. In several different forms of phan mutant leaves and petal lobes, novel boundaries between dorsal and ventral cell types form ectopic axes of growth, suggesting that phan-dependent dorsal cell identity is required for lateral growth of the wild-type leaf and petal lobe. Comparisons between the development of wild-type and mutant petals or leaves reveal that phan acts early in development of these lateral organs. The possible role of the phan gene in evolution of different leaf forms is discussed.

Sex differences in the distribution of EEG frequencies during sleep: unipolar depressed outpatients

Sex differences in period-amplitude-analysed (PAA) sleep EEG activity were evaluated in 20 symptomatic, unmedicated, unipolar, depressed outpatients. 19/20 PAA measures showed significant gender main effects or interactions. Overall, depressed females showed a higher incidence and amplitude of fast frequency, beta activity than males, particularly in the right hemisphere. Moreover, gender effects were also evident in sleep-stage-independent analysis of PAA measures. These findings are in striking contrast to normal controls for whom only slow-frequency activity differentiates males from females. These findings suggest that sex differences are stronger in depressed patients than those observed in normals and that these effects are more pronounced than age-related changes in sleep EEG activity.

Genetic and cellular characteristics of bladder outlet obstruction

Urinary bladder outlet obstruction is a common medical problem. In order to understand the effects of outlet obstruction on bladder morphology, physiology, and pharmacology, several animal models of obstruction have been developed using a variety of species. Although there are marked differences in bladder size, capacity, compliance, physiology, and pharmacology among these species, responses to outlet obstruction have many common characteristics. This article will be separated into six areas: introduction, genetic factors mediating the response during the initial period of partial outlet obstruction and overdistension, cytostructural alterations that accompany compensated bladder function, alterations in innervation accompanying bladder hypertrophy secondary to partial outlet obstruction, alterations in calcium translocation during bladder hypertrophy, and metabolic factors involved in the response to partial outlet obstruction.