The Caenorhabditis elegans distal-less ortholog ceh-43 is required for development of the anterior hypodermis.

Homeobox genes of the Distal-less (Dll) class are expressed in developing appendages as well as in the central nervous system in invertebrates and vertebrates. Mutant analyses in mice and Drosophila have implicated these genes in outgrowth of structures, cell adhesion, cell migration, and cell fate decisions. We have investigated the expression and function of ceh-43, the Dll ortholog from the nematode Caenorhabditis elegans, by using gfp reporter constructs and double-stranded RNA-mediated interference (RNAi). Our results show that, as in the fly, the C. elegans Dll ortholog seems to play a role in cell adhesion. An antibody against the butterfly Distal-less homeodomain stains the nervous system of C. elegans embryos (Panganiban et al. [1997] Proc Natl Acad Sci USA. 94:5162-5166). GFP expression under the control of the ceh-43 promoter looks similar, although strong expression is primarily confined to the head hypodermis and to neuronal support cells. ceh-43(RNAi) results in 100% lethality at embryonic or early larval stages. At the beginning of morphogenesis, ceh-43(RNAi) embryos start to lose cells through a hole in the head hypodermis. They either rupture anteriorly as elongation proceeds, or they elongate normally to threefold egg length with the pharynx not connected to the mouth. Elongated ceh-43(RNAi) animals die before or soon after hatching with a fluid-filled pseudocoel and large vacuoles. These phenotypes suggest a role for ceh-43 in development of adhesive properties in the head hypodermis that connects the epithelia of the skin and the digestive tract. Furthermore, possible defects in the excretory system may result at least in part from a requirement for ceh-43 in the CAN neurons where ceh-43:gfp is also expressed.     

The epicardium and epicardially derived cells (EPDCs) as cardiac stem cells

After its initial formation the epicardium forms the outermost cell layer of the heart. As a result of an epithelial-to-mesenchymal transformation (EMT) individual cells delaminate from this primitive epicardial epithelium and migrate into the subepicardial space (Pérez-Pomares et al., Dev Dyn 1997; 210:96-105; Histochem J 1998a;30:627-634). Several studies have demonstrated that these epicardially derived cells (EPDCs) subsequently invade myocardial and valvuloseptal tissues (Mikawa and Fischman, Proc Natl Acad Sci USA 1992;89:9504-9508; Mikawa and Gourdie, Dev Biol 1996;174:221-232; Dettman et al., Dev Biol 1998;193:169-181; Gittenberger de Groot et al., Circ Res 1998;82:1043-1052; Manner, Anat Rec 1999;255:212-226; Pérez-Pomares et al., Dev. Biol. 2002b;247:307-326). A subset of EPDCs continue to differentiate in a variety of different cell types (including coronary endothelium, coronary smooth muscle cells (CoSMCs), interstitial fibroblasts, and atrioventricular cushion mesenchymal cells), whereas other EPDCs remain in a more or less undifferentiated state. Based on its specific characteristics, we consider the EPDC as the ultimate 'cardiac stem cell'. In this review we briefly summarize what is known about events that relate to EPDC development and differentiation while at the same time identifying some of the directions where EPDC-related research might lead us in the near future.     

ROCK inhibitor (Y27632) increases apoptosis and disrupts the actin cortical mat in embryonic avian corneal epithelium.

The embryonic chicken corneal epithelium is a unique tissue that has been used as an in vitro epithelial sheet organ culture model for over 30 years (Hay and Revel [1969] Fine structure of the developing Avian cornea. Basel, Switzerland: S. Karger A.G.). This tissue was used to establish that epithelial cells could produce extracellular matrix (ECM) proteins such as collagen and proteoglycans (Dodson and Hay [1971] Exp Cell Res 65:215-220; Meier and Hay [1973] Dev Biol 35:318-331; Linsenmayer et al. [1977] Proc Natl Acad Sci U S A 74:39-43; Hendrix et al. [1982] Invest Ophthalmol Vis Sci 22:359-375). This historic model was also used to establish that ECM proteins could stimulate actin reorganization and increase collagen synthesis (Sugrue and Hay [1981] J Cell Biol 91:45-54; Sugrue and Hay [1982] Dev Biol 92:97-106; Sugrue and Hay [1986] J Cell Biol 102:1907-1916). Our laboratory has used the model to establish the signal transduction pathways involved in ECM-stimulated actin reorganization (Svoboda et al. [1999] Anat Rec 254:348-359; Chu et al. [2000] Invest Ophthalmol Vis Sci 41:3374-3382; Reenstra et al. [2002] Invest Ophthalmol Vis Sci 43:3181-3189). The goal of the current study was to investigate the role of ECM in epithelial cell survival and the role of Rho-associated kinase (p160 ROCK, ROCK-1, ROCK-2, referred to as ROCK), in ECM and lysophosphatidic acid (LPA) -mediated actin reorganization. Whole sheets of avian embryonic corneal epithelium were cultured in the presence of the ROCK inhibitor, Y27632 at 0, 0.03, 0.3, 3, or 10 microM before stimulating the cells with either collagen (COL) or LPA. Apoptosis was assessed by Caspase-3 activity assays and visualized with annexin V binding. The ROCK inhibitor blocked actin cortical mat reformation and disrupted the basal cell lateral membranes in a dose-dependent manner and increased the apoptosis marker annexin V. In addition, an in vitro caspase-3 activity assay was used to determine that caspase-3 activity was higher in epithelia treated with 10 microM Y-27632 than in those isolated without the basal lamina or epithelia stimulated with fibronectin, COL, or LPA. In conclusion, ECM molecules decreased apoptosis markers and inhibiting the ROCK pathway blocked ECM stimulated actin cortical mat reformation and increased apoptosis in embryonic corneal epithelial cells.     

Chordin affects pronephros development in Xenopus embryos by anteriorizing presomitic mesoderm.

Spemann's organizer emits signals that pattern the mesodermal germ layer during Xenopus embryogenesis. In a previous study, we demonstrated that FGFR1 activity within the organizer is required for the production of both the somitic muscle- and pronephros-patterning signals by the organizer and the expression of chordin, an organizer-specific secreted protein (Mitchell and Sheets [2001] Dev. Biol. 237:295-305). Studies from others in both chicken and Xenopus embryos provide compelling evidence that pronephros forms by means of secondary induction signals emitted from anterior somites (Seufert et al. [1999] Dev. Biol. 215:233-242; Mauch et al. [2000] Dev. Biol. 220:62-75). Here we provide several lines of evidence in support of the hypothesis that chordin influences pronephros development by directing the formation of anterior somites. Chordin mRNA was absent in ultraviolet (UV) -irradiated embryos lacking pronepheros (average DAI<2) but was always found in UV-irradiated embryos that retain pronepheros (average DAI>2). Furthermore, ectopic expression of chordin in embryos and in tissue explants leads to the formation of anterior somites and pronephros. In these experiments, pronephros was only observed in association with muscle. Chordin diverted somatic muscle cells to more anterior positions within the somite file in chordin-induced secondary trunks and induced the expression of the anterior myogenic gene myf5. Finally, depletion of chordin mRNA with DEED antisense oligonucleotides substantially reduced somitic muscle and pronephric tubule and duct formation in whole embryos. These data and previous studies on ectoderm and endoderm (Sasai et al. [1995] Nature 377:757) support the idea that chordin functions as an anteriorizing signal in patterning the germ layers during vertebrate embryogenesis. Our data support the hypothesis that chordin directs the formation of anterior somites that in turn are necessary for pronephros development.     

Cyclic AMP-dependent regulation of P-type calcium channels expressed in Xenopus oocytes

Xenopus oocytes injected with rat cerebellum mRNA, express voltage-dependent calcium channels (VDCC). These were identified as P-type Ca²⁺ channels by their insensitivity to dihydropyridines and -conotoxin and by their blockade by Agelenopsis aperta venom (containing the funnel-web spider toxins: FTX and -Aga-IV-A). Coinjection of cerebellar mRNA and antisense oligonucleotide complementary to the dihydropyridine-resistant brain Ca²⁺ channel, named BI [Mori Y. et al. (1991) Nature 350:398–402] or rbA [Starr T. V. B. et al. (1991) Proc Natl Acad Sci USA 88:5621–5625], strongly reduced the expressed Ba²⁺ current suggesting that these clones encode a P-type VDCC. The macroscopic Ca²⁺ channel activity was increased by direct intraoocyte injection of cAMP. This increase in current amplitude was concomitant with a slowing of current inactivation, and was attributed to activation of protein kinase A, since it could be antagonized by a peptidic inhibitor of this enzyme. Positive regulation of P-type VDCC could be of importance in Purkinje neurons and motor nerve terminals where this channel is predominant.     

Effects of paired-pulse and repetitive stimulation on neurons in the rat medial geniculate body

Many behaviorally relevant sounds, including language, are composed of brief, rapid, repetitive acoustic features. Recent studies suggest that abnormalities in producing and understanding spoken language are correlated with abnormal neural responsiveness to such auditory stimuli at higher auditory levels [Tallal et al., Science 271 (1996) 81-84; Wright et al., Nature 387 (1997) 176-178; Nagarajan et al., Proc. Natl. Acad. Sci. USA 96 (1999) 6483-6488] and with abnormal anatomical features in the auditory thalamus [Galaburda et al., Proc. Natl. Acad. Sci. USA 91 (1994) 8010-8013]. To begin to understand potential mechanisms for normal and abnormal transfer of sensory information to the cortex, we recorded the intracellular responses of medial geniculate body thalamocortical neurons in a rat brain slice preparation. Inferior colliculus or corticothalamic axons were excited by pairs or trains of electrical stimuli. Neurons receiving only excitatory collicular input had tufted dendritic morphology and displayed strong paired-pulse depression of their large, short-latency excitatory postsynaptic potentials. In contrast, geniculate neurons receiving excitatory and inhibitory collicular inputs could have stellate or tufted morphology and displayed much weaker depression or even paired-pulse facilitation of their smaller, longer-latency excitatory postsynaptic potentials. Depression was not blocked by ionotropic glutamate, GABA(A) or GABA(B) receptor antagonists. Facilitation was unaffected by GABA(A) receptor antagonists but was diminished by N-methyl-D-aspartate (NMDA) receptor blockade. Similar stimulation of the corticothalamic input always elicited paired-pulse facilitation. The NMDA-independent facilitation of the second cortical excitatory postsynaptic potential lasted longer and was more pronounced than that seen for the excitatory collicular inputs. Paired-pulse stimulation of isolated collicular inhibitory postsynaptic potentials generated little change in the second GABA(A) potential amplitude measured from the resting potential, but the GABA(B) amplitude was sensitive to the interstimulus interval. Train stimuli applied to collicular or cortical inputs generated intra-train responses that were often predicted by their paired-pulse behavior. Long-lasting responses following train stimulation of the collicular inputs were uncommon. In contrast, corticothalamic inputs often generated long-lasting depolarizing responses that were dependent on activation of a metabotropic glutamate receptor. Our results demonstrate that during repetitive afferent firing there are input-specific mechanisms controlling synaptic strength and membrane potential over short and long time scales. Furthermore, they suggest that there may be two classes of excitatory collicular input to medial geniculate neurons and a single class of small-terminal corticothalamic inputs, each of which has distinct features.     

A low molecular weight allergen of white birch (Betula verrucosa) is highly homologous to human profilin

Cloning of allergens has contributed substantially to the understanding of mechanisms in allergic diseases by providing information about the sequence and hence biological functions of allergens. The major birch pollen allergen, Bet v I [Breiteneder H, et al: EMBO J 1989;8:1935-1938] and the white-faced hornet venom allergen (antigen 5) [Si Yun Fang K, et al: Proc. Natl. Acad. Sc. USA 1988;85:895-899] were shown to be highly homologous to pathogenesis-related proteins of plants. In the case of the major allergen of house dust mite, Der p I, homology to proteases was demonstrated. Therefore, the proposed biological function of these IgE-binding proteins might be related to their allergenic potential. In this paper we tentatively identify a ubiquitous family of low molecular weight allergens as profilins. The identification is based on a sequence homology, (b) binding to poly(L-proline), and (c) immunological cross-reactivity. Recombinant birch profilin was purified to homogeneity and showed the same properties as natural profilins.     

Linkage disequilibrium, haplotype and association studies of a chromosome 4 GABA receptor gene cluster: candidate gene variants for addictions.

Strong genetic contributions to individual differences in vulnerability to addictions are well supported by classical genetic studies. Linkage and association genome scans for addiction vulnerability have provided converging evidence for several chromosomal regions which are likely to harbor allelic variants that contribute to such vulnerability. We and others have delineated a candidate addiction-associated chromosome 4p12 "rSA3" region based on convergent data from association genome scanning studies in polysubstance abusers [Uhl et al. (2001); Am J Hum Genet 69(6):1290-1300], linkage-based studies in alcoholism [Long et al. (1998); Am J Med Genet 81(3):216-221; Reich et al. (1998); Am J Med Genet 81(3):207-215] and association-based studies for alcoholism and association-based studies for individual differences in electroencephalographic (EEG) spectral power phenotypes [Porjesz et al. (2002); Proc Natl Acad Sci USA 99(6):3729-3733; Edenberg et al. (2004); Am J Hum Genet 74(4):705-714]. The rSA3 region contains interesting candidate genes that encode the alpha 2, alpha 4, beta 1, and gamma 1 receptor subunits for the principal brain inhibitory neurotransmitter, gamma-aminobutyric acid (GABA) [Covault et al. (2004); Am J Med Genet Part B 129B:104-109; Edenberg et al. (2004); Am J Hum Genet 74(4):705-714; Lappalainen et al. (2005); Alcohol Clin Exp Res 29(4):493-498]. We now report assessment of single nucleotide polymorphism (SNP) genotypes in this region in three samples of substance abusers and controls. These results delineate the haplotypes and patterns of linkage disequilibrium in this region, focus attention of the GABRA2 gene and identify modest associations between GABRA2 genotypes and addiction phenotypes. These results are consistent with modest roles for GABRA2 variants in addiction vulnerabilities.     

Reverse genetics of influenza virus

Reverse genetics of negative-sense RNA viruses, which enables one to generate virus entirely from cloned cDNA, has progressed rapidly over the past decade. However, despite the relative ease with which nonsegmented negative-sense RNA viruses can now be produced from plasmids, the ability to generate viruses with segmented genomes has lagged considerably, largely because of the inherent technical difficulties in providing all viral RNAs and proteins from cloned cDNA. A breakthrough in reverse genetics technology in the influenza virus field came in 1999, when we (Neumann et al., 1999, Proc. Natl. Acad. Sci. USA 96, 9345-9350) and others (Fodor et al., 1999, J. Virol. 73, 9679-9682) exploited a new approach to viral RNA production. In this review, we discuss the background for this advance, the systems that are now available for the generation of influenza viruses, and the implications of these developments for the future of virus research.     

Cortical connectivity in high frequency beta-rhythm in schizophrenics with positive and negative symptoms.

During the last decade the role of high frequency EEG activity in the 'binding phenomenon' was discovered. It was supposed that this phenomenon provided the integration between different brain structures underlying higher nervous functions and possibly even consciousness [Proc. Natl. Acad. Sci. 90 (1993) 2078; Annu. Rev. Neurosci. 18 (1995) 555; J. Neurosci. V 16 (1996) 4240; Am. Physiol. Soc. (1998) 1567; Induced Rhythms in the Brain (1992) 425; NeuroReport 8 (1997) 531; Proc. Natl. Acad. Sci. USA 94 (1997) 12198]. Schizophrenia is considered as a disorder of the integration between different brain regions [Review of Psychiatry 18 (1999a) 29; Conceptual Advances in Russian Neuroscience: Complex Brain Functions (1999) 151; Brain Res. Rev. 31 (2000) 301], and in the present work we have studied cortical connectivity, focusing on those connections which are maintained by high frequency EEG-rhythm (20-40 Hz). The results showed a high degree of biopotential synchronisation between definite cortical areas during cognitive processes in normal subjects and have evidenced significant functional connectivity disturbances in schizophrenia in this EEG frequency domain.     

Interleukin 4 (IgG1 induction factor): a multifunctional lymphokine acting also on T cells

A cDNA encoding the murine interleukin 4 (IL4) (IgG1 induction factor/B cell-stimulating factor no. 1) was recently cloned (Noma et al., Nature 1986.319: 640; Lee et al., Proc. Natl. Acad. Sci. USA 1986. 83: 2061). In this report we tested recombinant IL 4 in various T cell assays. It was found that IL 4 activated the murine T cell line CTLL to increased DNA synthesis but not to growth. It also activated normal concanavalin A (Con A)-stimulated T cells both to increased DNA synthesis and to growth. These T cell growth factor-like activities were not inhibitable by anti-IL 2 receptor antibodies. Evidence is given that both Lyt-2+ and L3T4+ T cells responded to IL 4. Finally, IL 4 acted synergistically with phytohemagglutinin or Con A on normal T lymphocytes as well as on thymocytes. These data, as well as those of others, imply that lymphokines have a broader range of activity than previously anticipated.     

Just how does the cII selection system work in Muta™Mouse?

The lambda CII protein is an essential component in the lytic vs. lysogeny decision a bacteriophage makes upon infection of a host at low temperatures. The protein interacts with numerous phage promoters modulating the expression of the CI repressor, thus providing the mechanism for lysogenization soon after infection. The Big Blue and Muta Mouse are two widely used in vivo mutational model systems. The assays rely on retrievable lambda-based transgenes housing mutational targets (lacI or lacZ, respectively). The transgenes provide an elegant vehicle for the quantification of mutations sustained in virtually any tissue of the rodent. The use of the bacteriophage cII locus as an alternative, or additional mutational target for use with the Big Blue rodent system was first reported by Jakubczak et al. ([1996]: Proc Natl Acad Sci USA 93:9073-9078). More recently, this selection assay has been applied successfully to the Muta Mouse (Swiger et al. [1999]: Environ Mol Mutagen 33:201-207). The use of an Hfl bacterial strain and low temperature allows the determination of mutations sustained at the cII locus in either system, with high fidelity. The cII selection assay in the Big Blue relies on the presence of the lambda repressor protein CI. In contrast, the recombinant construct used to make the Muta Mouse transgene lacks functional CI protein. Nevertheless, we report an excellent system for quantifying mutations at the cII locus in Muta Mouse. Just how does cII selection work in the Muta Mouse? Written in the context of lambda recombinant genetics, this paper explores the question further.     

Novel mutation in the Delta-sterol reductase gene in three Lebanese sibs with Smith-Lemli-Opitz (RSH) syndrome

The Smith-Lemli-Opitz syndrome (SLOS), or RSH syndrome, is a well-characterized multiple congenital anomalies/mental retardation syndrome. The phenotype has been redefined to include mildly affected individuals with minor anomalies and developmental delay, and severe malformations with pre- and perinatal mortality. The condition is due to the deficient activity of the enzyme 7-dehydrocholesterol (7-DHC) reductase [Shefer et al., 1995: J Clin Invest 96:1779-1785], and the gene has been mapped to chromosome 11q13 [Moebius et al., 1998: Proc Natl Acad Sci USA 95:1899-1902]. We describe here a consanguineous family of Syrian-Lebanese ancestry with three sibs affected with SLOS: two with a mild variant, while the other had severe disease and died in the first year of life. Mutation analysis demonstrated a novel mutation in the DHCR7 gene, present in homozygous form in the two affected individuals available for testing, and heterozygous in the parents. The wide intrafamilial variation of clinical severity in these three sibs is an important finding in SLOS.