Heart development in Drosophila requires the segment polarity gene wingless

Mesoderm induction has been studied in many systems and some of the factors involved have been identified. Although the heart is mesodermal in origin, the molecular basis of heart development is essentially unknown. The Drosophila heart is a simple tubular structure similar to the early heart tube in vertebrates. The homeobox gene, tinman, has been shown to be crucial for heart formation in Drosophila. Several genes with considerable sequence similarities to tinman are expressed in cardiac primordial tissue of vertebrates and are likely to be required for heart development of higher organisms as well. In addition to transcriptional control factors, heart development might also depend on inductive signals. Here, we demonstrate that the gene wingless (wg), which is known to specify segmental polarity and neuroblast identity in Drosophila, has a novel role in mesoderm development: wg function is specifically required for heart development. A temperature-sensitive mutation of wg was used to inactivate wg function during precise developmental time periods. Elimination of wg function for a short time period after gastrulation results in the selective loss of heart precursors, without significantly affecting the formation of the body wall or visceral muscles, although some pattern defects are observed. This developmental requirement of wg for cardiac organogenesis is distinct from its function in segmentation and neurogenesis. We conclude that wg signaling is a crucial component of heart formation.

The wingless signaling pathway is directly involved in Drosophila heart development

Heart development in both vertebrates and Drosophila is initiated by bilaterally symmetrical primordia that may be of equivalent embryological origin: the anterior lateral plate mesoderm in vertebrates and the dorsal-most mesoderm in arthropods. These mesodermal progenitors then merge into a heart tube at the ventral midline (vertebrates) or the dorsal midline (Drosophila). These observations suggest that there may be similarities between vertebrate and invertebrate heart development. The homeobox gene, tinman, is required for heart as well as visceral mesoderm formation in Drosophila, and at least one of several vertebrate genes with similarities in protein sequence and cardiac expression to tinman is crucial for heart development in vertebrates. Inductive signals are also required for Drosophila heart development: The secreted gene product of wingless (wg) is critical for heart development during a time period distinct from its function in segmentation and neurogenesis. Here, we show that wg is epistatic to hedgehog (hh), another secreted segmentation gene product, in its requirement for heart formation. We also provide evidence show that downstream of wg in the signal transduction cascade, dishevelled (dsh, a pioneer protein) and armadillo (arm, beta-catenin homolog) are mediating the cardiogenic Wg signal. In particular, overexpression of dsh can restore heart formation in the absence of wg function. We discuss the possibility that Wg signaling is part of a combinatorial mechanism to specify the cardiac mesoderm.

Primary structure, neural-specific expression, and chromosomal localization of Cux-2, a second murine homeobox gene related to Drosophila cut

The cut locus of Drosophila encodes a diverged homeodomain-containing protein that is required for the development of external sensory (es) organs and other tissues. A homologous gene (Cux-1) that encodes a transcriptional repressor has been identified in the mouse and other mammals. We have identified a second murine homeobox-containing gene (designated Cux-2) that is structurally related to Drosophila cut. The murine Cux-2 homeobox was similar to Drosophila cut and encoded a homeodomain that contained a characteristic histidine residue at position 50. The predicted Cux-2 protein contained 1426 amino acids and included three internal 60-amino acid repeats (Cut repeats) that were previously found in Drosophila Cut and murine Cux-1. Unlike Cux-1, expression of Cux-2 was restricted to neural tissue. In the adult brain, Cux-2 was prominently expressed in neurons in the thalamus and limbic system. In embryos, Cux-2 was expressed in the developing central and peripheral nervous systems, including the telencephalon and peripheral ganglia of the trigeminal and glossopharyngeal nerves. A glutathione S-transferase fusion protein containing the carboxyl-terminal Cut repeat and homeodomain of Cux-2 exhibited sequence-specific binding to oligonucleotides derived from the promoter of the Ncam gene. Using an interspecific backcross panel, Cux-1 and Cux-2 were mapped to distinct loci that were genetically linked on distal chromosome 5. These results demonstrate that a family of homeobox genes related to Drosophila cut is located on chromosome 5 in the mouse. Cux-2 is expressed exclusively in the central and peripheral nervous systems, and the Cux-2 gene product binds to DNA in a sequence-specific manner. Cux-2 may encode a transcription factor that is involved in neural specification in mammals.

gutfeeling, a Drosophila gene encoding an antizyme-like protein, is required for late differentiation of neurons and muscles

The gutfeeling (guf) gene was uncovered in a genetic screen for genes that are required for proper development of the embryonic peripheral nervous system. Mutations in guf cause defects in growth cone guidance and fasciculation and loss of expression of several neuronal markers in the embryonic peripheral and central nervous systems. guf is required for terminal differentiation of neuronal cells. Mutations in guf also affect the development of muscles in the embryo. In the absence or guf activity, myoblasts are formed properly, but myoblast fusion and further differentiation of muscle fibers is severely impaired. The guf gene was cloned and found to encode a 21-kD protein with a significant sequence similarity to the mammalian ornithine decarboxylase antizyme (OAZ). In mammals, OAZ plays a key regulatory role in the polyamine biosynthetic pathway through its binding to, and inhibition of, ornithine decarboxylase (ODC), the first enzyme in the pathway. The elaborate regulation of ODC activity in mammals still lacks a defined developmental role and little is known about the involvement of polyamines in cellular differentiation. GUF is the first antizyme-like protein identified in invertebrates. We discuss its possible developmental roles in light of this homology.

De Madres a Madres: a community partnership for health

To increase the number of Hispanic women who begin early prenatal care, a community partnership for health was initiated among the general public, businesses, 14 volunteer mothers, and one community health nurse. Volunteer mothers living in the targeted community were taught how to identify Hispanic women at risk for not starting early prenatal care, and how to provide social support and community resource information within a culturally acceptable milieu. At the end of the first year of the partnership, over 2000 women at risk for not starting early prenatal care had been contacted by the volunteer mothers.

The pioneer gene, apontic, is required for morphogenesis and function of the Drosophila heart

In an effort to isolate genes required for heart development and to further our understanding of cardiac specification at the molecular level, we screened PlacZ enhancer trap lines for expression in the Drosophila heart. One of the lines generated in this screen, designated B2-2-15, was particularly interesting because of its early pattern of expression in cardiac precursor cells, which is dependent on the homeobox gene tinman, a key determinant of heart development in Drosophila. We isolated and characterized a gene in the vicinity of B2-2-15 that exhibits an identical expression pattern than the reporter gene of the enhancer trap. The product of his gene, apontic (apt; see also "Gellon et al., 1997"), does not appear to have any homology with known genes. apt mutant embryos show distinct abnormalities in heart morphology as early as mid-embryonic stages when the heart tube assembles, in that segments of heart cells (those of myocardial and pericardial identity) are often missing. Most strikingly, however, apt mutant embryos or larvae only develop a much reduced heart rate, perhaps because of defects in the assembly of an intact heart tube and/or because of defects in the function or physiological control of the myocardial cells, which normally mediate heart contractions. These cardiac defects may be the cause of death of these mutants during late embryonic or early larval stages.

Studies on the mechanism by which prolactin stimulates alpha-aminoisobutyric acid uptake into cultured mouse mammary tissues

Studies were carried out to determine the possible roles of the polyamines, cyclic nucleotides, icosanoid products, and protein kinase C in the prolactin regulation of amino acid transport in cultured mammary gland explants derived from 12-14 day pregnant mice. Elevated cyclic AMP concentrations impaired the PRL stimulation of AIB transport. DBcAMP as well as the phosphodiesterase inhibitors theophylline and methyl isobutylxanthine, when added to the cultures, attenuated or abolished the PRL responses. 8-Bromo cyclic GMP elicited a modest stimulation of AIB transport. Ongoing polyamine synthesis appears to be necessary for PRL to effect a stimulation of AIB transport since methylglyoxal bis(guanyl hydrazone), an inhibitor of S-adenosyl methionine decarboxylase, abolishes the PRL response; specificity of this effect was established by its reversal with the addition of spermidine to the culture medium. Ongoing icosanoid product synthesis also appears to be required for the PRL stimulation of AIB transport since indomethacin abolishes the PRL response. Finally, the inhibition of the PRL response by the protein kinase C inhibitor H-7 suggests that the activation of kinase C activity may also be involved in the PRL stimulation of AIB transport.

Effect of prolactin on alpha-aminoisobutyric acid uptake in mouse mammary gland explants

Studies were carried out to characterize the effect of prolactin (PRL) on amino acid uptake into mammary gland explants derived from 12- to 14-day pregnant mice. PRL approximately doubles the rate of uptake of alpha-aminoisobutyrate (AIB), arginine, and hydroxyproline but has no effect on the intracellular accumulation of unincorporated leucine. PRL increases the apparent maximum velocity of AIB uptake from 0.16 to 0.43 nmol.l intracellular water-1.min-1. No effect of PRL, however, on the apparent Michaelis constant (0.75 mM) of AIB uptake was observed. The onset of the PRL stimulation of AIB uptake occurs 4-5 h after PRL addition to the cultured mammary tissues. The lowest stimulatory concentration of PRL on AIB uptake is 5-10 ng/ml, and a maximum response is achieved with 75 ng/ml. The action of PRL on AIB uptake requires both ongoing RNA and protein synthesis, since puromycin (50 micrograms/ml), cycloheximide (5 micrograms/ml), and actinomycin D (1 microgram/ml) abolished the PRL response.

Independent learning: a self-instructional videotape approach in psychiatry

In response to the increased need to train well-rounded general practitioners within a limited time schedule, the teaching staff developed a self-instructional videotape programme devoted to suicide assessment. This tape, if successful, was to serve as a pilot for a full series of 18 tapes devoted to the assessment and treatment of normally stable patients suffering acute situational stress. In order to avoid the passivity induced by most educational tapes and films, a self-instructional format was adapted to the videotape medium and extensively tested. Students in the experimental group scored significantly higher on three of four measures of effectiveness than did the control group. Students and teachers both strongly supported the production of tapes using a similar format.

Cardiac enhancer activity of the homeobox gene tinman depends on CREB consensus binding sites in Drosophila

The Drosophila homeobox gene tinman plays a critical role in subdividing the early mesoderm. In particular, tinman is absolutely required for formation of the heart and visceral mesoderm. tinman expression is initiated throughout the mesoderm of the trunk region under the control of the bHLH transcription factor encoded by the twist gene, a determinant of all mesoderm. Later, tinman expression is restricted to the dorsal portion of the mesoderm, a process that is directed by decapentaplegic (dpp) whose product (a TGF-beta-related protein) is secreted by the overlaying ectoderm. Further restriction of tinman expression to the cardiac progenitors, in which it will persist throughout development, involves the secreted segmentation gene product encoded by wingless (wg, a Drosophila Wnt gene). Here, we show that strong early expression depends on the synergistic action of an enhancer element at the 5' end of the gene in conjunction with an element in the first intron. Moreover, two distinct enhancer regions are responsible for tinman expression in the heart: one region confers expression in the heart-tube-associated pericardial cells, the other element drives expression in the contractile, myocardial cells. The latter element contains two CREB consensus binding sites that are essential for cardiac-specific expression. genesis 26:55-66, 2000.

Ab initio prediction of specific phospholipid complexes and membrane association of HIV-1 MPER antibodies by multi-scale simulations

A potent class of HIV-1 broadly neutralizing antibodies (bnAbs) targets the envelope glycoprotein's membrane proximal exposed region (MPER) through a proposed mechanism where hypervariable loops embed into lipid bilayers and engage headgroup moieties alongside the epitope. We address the feasibility and determinant molecular features of this mechanism using multi-scale modeling. All-atom simulations of 4E10, PGZL1, 10E8, and LN01 docked onto HIV-like membranes consistently form phospholipid complexes at key complementarity-determining region loop sites, solidifying that stable and specific lipid interactions anchor bnAbs to membrane surfaces. Ancillary protein-lipid contacts reveal surprising contributions from antibody framework regions. Coarse-grained simulations effectively capture antibodies embedding into membranes. Simulations estimating protein-membrane interaction strength for PGZL1 variants along an inferred maturation pathway show bilayer affinity is evolved and correlates with neutralization potency. The modeling demonstrated here uncovers insights into lipid participation in antibodies' recognition of membrane proteins and highlights antibody features to prioritize in vaccine design.