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Biomedical subjects

J Drago

Publications and source records attributed to J Drago.

At least 55 records · Page 3Linked to original sources
PubMed1997

Lhx2, a LIM homeobox gene, is required for eye, forebrain, and definitive erythrocyte development.

We investigated the function of Lhx2, a LIM homeobox gene expressed in developing B-cells, forebrain and neural retina, by analyzing embryos deficient in functional Lhx2 protein. Lhx2 mutant embryos are anophthalmic, have malformations of the cerebral cortex, and die in utero due to severe anemia. In Lhx2-/- embryos specification of the optic vesicle occurs; however, development of the eye arrests prior to formation of an optic cup. Deficient cellular proliferation in the forebrain results in hypoplasia of the neocortex and aplasia of the hippocampal anlagen. In addition to the central nervous system malformations, a cell non-autonomous defect of definitive erythropoiesis causes severe anemia in Lhx2-/- embryos. Thus Lhx2 is necessary for normal development of the eye, cerebral cortex, and efficient definitive erythropoiesis.

Anemia↗
PubMed1996

Modulatory actions of dopamine on NMDA receptor-mediated responses are reduced in D1A-deficient mutant mice.

The role of D1 dopamine (DA) receptors in mediating the ability of DA to modulate responses attributable to activation of NMDA receptors was examined in mice lacking D1A dopamine receptors. Specifically, experiments were designed to test the hypothesis that the ability of DA to potentiate responses mediated by activation of NMDA receptors was attributable to activation of D1 receptors. Based on this hypothesis, we would predict that in the D1A mutant mouse, either DA would not induce enhancement of NMDA-mediated responses, or the enhancement would be severely attenuated. The results provided evidence to support the hypothesis. In mutant mice, DA and D1 receptor agonists did not potentiate responses mediated by activation of NMDA receptors. In contrast, in control mice, both DA and D1 receptor agonists markedly potentiated responses mediated by activation of NMDA receptors. The effects of DA in attenuating responses mediated by activation of non-NMDA receptors also were altered in the mutant, suggesting that this action of DA may require coupling or interactions between D1 and D2 receptors. The present studies also provided an opportunity to assess some of the basic electrophysiological and morphological properties of neostriatal neurons in mice lacking D1A DA receptors. Resting membrane potential, action potential parameters, input resistance, excitability, somatic size, dendritic extent, and estimates of spine density in mutants and controls were similar, suggesting that these basic neurophysiological and structural properties have not been changed by the loss of the D1A DA receptor.

Animals↗
PubMed1996

Defects in enteric innervation and kidney development in mice lacking GDNF.

Glial-lial-cell-line-derived neurotrophic factor (GDNF) has been isolated as neurotrophic factor for midbrain dopaminergic neurons. Because of its neurotrophic activity on a wide range of neuronal populations in vitro and in vivo, GDNF is being considered as a potential therapeutic agent for neuronal disorders. During mammalian development, it is expressed not only in the nervous system, but also very prominently in the metanephric kidney and the gastrointestinal tract, suggesting possible functions during organogenesis. We have investigated the role of GDNF during development by generating a null mutation in the murine GDNF locus, and found that mutant mice show kidney agenesis or dysgenesis and defective enteric innervation. We demonstrate that GDNF induces ureter bud formation and branching during metanephros development, and is essential for proper innervation of the gastrointestinal tract.

Animals↗
PubMed1996

Role of the D1A dopamine receptor in the pathogenesis of genetic hypertension.

Since dopamine produced by the kidney is an intrarenal regulator of sodium transport, an abnormality of the dopaminergic system may be important in the pathogenesis of hypertension. In the spontaneously hypertensive rat (SHR), in spite of normal renal production of dopamine and receptor density, there is defective transduction of the D1 receptor signal in renal proximal tubules, resulting in decreased inhibition of sodium transport (Na+/H+ exchanger [NHE] and Na+/K+ATPase activity) by dopamine. To determine if impaired D1 receptor regulation of NHE in proximal tubules is related to hypertension, studies were performed in a F2 generation from female Wistar Kyoto (WKY) and male SHR crosses. A D1 agonist, SKF 81297, inhibited (37.6 +/- 4.7%) NHE activity in brush border membranes of normotensive F2s (systolic blood pressure < 140 mm Hg, n = 7) but not in hypertensive F2s (n = 21). Furthermore, a D1 agonist, SKF 38393, when infused into the renal artery, dose dependently increased sodium excretion in normotensive F2s (n = 3) without altering renal blood flow but was inactive in hypertensive F2s (n = 21). Since the major D1 receptor gene expressed in renal proximal tubules is the D1A subtype, we determined the importance of this gene in the control of blood pressure in mice lacking functional D1A receptors. Systolic blood pressure was greater in homozygous (n = 6) and heterozygous (n = 5) mice compared to normal sex matched litter mate controls (n = 12); moreover, the mice lacking one or both D1A alleles developed diastolic hypertension. The cosegregation with hypertension of an impaired D1 receptor regulation of renal sodium transport and the development of elevated systolic and diastolic pressure in mice lacking one or both D1A alleles suggest a causal relationship of the D1A receptor gene with hypertension.

Animals↗
PubMed1996

A targeted mutation of the D3 dopamine receptor gene is associated with hyperactivity in mice.

While most effects of dopamine in the brain are mediated by the D1 and D2 receptor subtypes, other members of this G protein-coupled receptor family have potentially important functions. D3 receptors belong to the D2-like subclass of dopamine receptors, activation of which inhibits adenylyl cyclase. Using targeted mutagenesis in mouse embryonic stem cells, we have generated mice lacking functional D3 receptors. A premature chain-termination mutation was introduced in the D3 receptor gene after residue Arg-148 in the second intracellular loop of the predicted protein sequence. Binding of the dopamine antagonist [125I]iodosulpride to D3 receptors was absent in mice homozygous for the mutation and greatly reduced in heterozygous mice. Behavioral analysis of mutant mice showed that this mutation is associated with hyperactivity in an exploratory test. Homozygous mice lacking D3 receptors display increased locomotor activity and rearing behavior. Mice heterozygous for the D3 receptor mutation show similar, albeit less pronounced, behavioral alterations. Our findings indicate that D3 receptors play an inhibitory role in the control of certain behaviors.

Amino Acid Sequence↗
PubMed1996

D1 dopamine receptor-deficient mouse: cocaine-induced regulation of immediate-early gene and substance P expression in the striatum.

Psychomotor stimulants such as cocaine alter gene expression in neurons of the striatum. Whereas many of these effects are mediated by D1 dopamine receptors, the involvement of other dopamine receptor subtypes or neurotransmitters is likely. To distinguish between these possibilities, regulation by cocaine of immediate-early genes and genes encoding neuropeptides was analysed in mice that lack functional D1 receptors. Gene expression was examined with in situ hybridization histochemistry. In these animals, cocaine failed to induce the immediate-early genes c-fos and zif 268. In contrast, substance P expression was abnormally increased by this drug. These results demonstrate that some of the effects of cocaine on gene regulation are mediated via D1 receptor-dependent mechanisms, as evidenced by the absence of immediate-early gene induction in D1-deficient mice, whereas others also involve additional, non-D1 receptor mechanisms, as shown for substance P expression.

Animals↗
PubMed1996

Dopamine receptor signaling defects in spontaneous hypertension.

Dopamine produced by renal proximal tubules acts as an intrarenal natriuretic factor by direct tubular action; this paracrine effect is influenced by the state of sodium balance. Up to 60% of sodium excretion with volume (2%-10%) expansion may be mediated by D1-like receptors. The renal paracrine effect of dopamine is impaired in genetic hypertension; this is due to defects in renal dopamine production or transduction of the dopamine signal. The Dahl salt sensitive rat and the spontaneously hypertensive rat (SHR), which have normal renal dopamine production and expression of dopamine receptors, have a defect in the coupling of a D1-like receptor to G-protein/effector enzyme complex. A consequence of the defective D1-like receptor/effector enzyme coupling in SHR is a decreased ability of D1 agonists to inhibit Na+/H+ exchange and Na+/K+-ATPase activity. The defect is 1) genetic, since it precedes the onset of and cosegregates with the hypertension; 2) receptor specific, since it is not shared by other humoral agents; and 3) confined to the renal proximal tubule. Two of the cloned dopamine receptors in mammals are D1-like (D1A and D1B). The D1A receptor gene is expressed to a greater extent in renal proximal tubules than the D1B receptor gene. The D1-like receptor is important in the pathogenesis of hypertension. Chronic blockade of dopamine receptors accelerates the development of hypertension in normotensive and hypertensive rats. Moreover, disruption of the D1A receptor gene in mice increases systolic blood pressure and results in diastolic hypertension. The abnormal D1-like receptor in SHR may be the D1A receptor; its uncoupling from the G-protein/effector enzyme complex in renal proximal tubules of SHR may be due to mistargeting. The mechanism for this "mistargeting" of the D1A receptor is not due to a mutation in the primary sequence and remains to be determined.

Animals↗
PubMed1996

Mice homozygous for an insertional mutation in the Zp3 gene lack a zona pellucida and are infertile.

Mammalian oocytes synthesize and secrete a zona pellucida that surrounds the growing oocytes, ovulated eggs and preimplantation embryos. The extracellular zona matrix is composed of three glycoproteins (ZP1, ZP2, ZP3) that are involved in folliculogenesis, species-specific fertilization, and passage of the early embryo down the oviduct. We have established a mouse line in which Zp3 has been inactivated by homologous recombination with an insertional mutation. Neither Zp3 transcripts nor ZP3 protein was detected in female mice homozygous for the mutation (Zp3-/-), whereas both ZP1 and ZP2 were present in mutant oocytes. Homozygous mutant Zp3-/- mice had follicles with germinal-vesicle-intact oocytes but that lacked a zona pellucida matrix and had a disorganized corona radiata. Although mutant oocytes underwent germinal vesicle breakdown (GVBD) prior to ovulation, the cumulus-oocyte complex was markedly disrupted and the oocytes were often separate from the cumulus cells. After hormone-induced ovulation, cumulus masses were present in the oviducts of homozygous mutant mice, but zona-free eggs were observed in only half of the females and, in these, less than 10% of the normal number [correction of mumber] of eggs were detected. No zona-free 2-cell embryos were recovered from homozygous mutant Zp3-/- female mice after mating with males proven to be fertile, and none became visibly pregnant or produced offspring. These results demonstrate that a genetic defect in a zona pellucida gene causes infertility and, given the conserved nature of the zona pellucida, a similar phenotype is expected in other mammals.

Animals↗
PubMed1995

Retained cocaine conditioned place preference in D1 receptor deficient mice.

The role of the D1 dopamine receptor subtype in mediating cocaine effects was examined in mice in which the D1 receptor gene had been ablated by homologous recombination. Cocaine reward was assessed by conditioned place preference experiments using mice which had either one allele (+/-) or both alleles (-/-) of the D1 dopamine receptor gene disrupted and in their wild type (+/+) littermates. Cocaine conditioning resulted in similar increases in preference for drug-paired environments in mice of each of the three genotypes. Cocaine did not alter locomotor activity levels in homozygous, D1 knockout mice -/-, whereas increased activity was noted in both +/+ and +/- animals. These results are consistent with the idea that the D1 receptor is involved in the locomotor stimulant effects of cocaine, but has little role in a major test of the rewarding and reinforcing effects of the drug.

Animals↗
PubMed1995

Defective lymphoid development in mice lacking expression of the common cytokine receptor gamma chain.

The common gamma chain (gamma c) of the IL-2, IL-4, IL-7, IL-9, and IL-15 receptors is defective in humans with XSCID. Mice lacking gamma c expression had hypoplastic thymuses; the thymocytes responded to gamma c-independent mitogens, but not gamma c-dependent stimuli. Splenic T cells were diminished at 3 weeks of age, but CD4+ T cells markedly increased by 4 weeks. B cells were greatly diminished in contrast with the situation in XSCID. NK cells, gamma delta intestinal intraepithelial lymphocytes, dendritic epidermal T cells, peripheral lymph nodes, and gut-associated lymphoid tissue were absent. These findings underscore the importance of gamma c in lymphoid development. Moreover, differences in humans and mice lacking gamma c expression indicate species-specific differences in the roles of gamma c-dependent cytokines or in the existence of redundant pathways. These mice provide an important model for studying the pathophysiology provide an important model for studying the pathophysiology of and gene therapy for human XSCID.

Animals↗
PubMed1995

Targeted disruption of the alpha isoform of the peroxisome proliferator-activated receptor gene in mice results in abolishment of the pleiotropic effects of peroxisome proliferators.

To gain insight into the function of peroxisome proliferator-activated receptor (PPAR) isoforms in rodents, we disrupted the ligand-binding domain of the alpha isoform of mouse PPAR (mPPAR alpha) by homologous recombination. Mice homozygous for the mutation lack expression of mPPAR alpha protein and yet are viable and fertile and exhibit no detectable gross phenotypic defects. Remarkably, these animals do not display the peroxisome proliferator pleiotropic response when challenged with the classical peroxisome proliferators, clofibrate and Wy-14,643. Following exposure to these chemicals, hepatomegaly, peroxisome proliferation, and transcriptional-activation of target genes were not observed. These results clearly demonstrate that mPPAR alpha is the major isoform required for mediating the pleiotropic response resulting from the actions of peroxisome proliferators. mPPAR alpha-deficient animals should prove useful to further investigate the role of this receptor in hepatocarcinogenesis, fatty acid metabolism, and cell cycle regulation.

Animals↗
PubMed1994

Altered striatal function in a mutant mouse lacking D1A dopamine receptors.

Of the five known dopamine receptors, D1A and D2 represent the major subtypes expressed in the striatum of the adult brain. Within the striatum, these two subtypes are differentially distributed in the two main neuronal populations that provide direct and indirect pathways between the striatum and the output nuclei of the basal ganglia. Movement disorders, including Parkinson disease and various dystonias, are thought to result from imbalanced activity in these pathways. Dopamine regulates movement through its differential effects on D1A receptors expressed by direct output neurons and D2 receptors expressed by indirect output neurons. To further examine the interaction of D1A and D2 neuronal pathways in the striatum, we used homologous recombination to generate mutant mice lacking functional D1A receptors (D1A-/-). D1A-/- mutants are growth retarded and die shortly after weaning age unless their diet is supplemented with hydrated food. With such treatment the mice gain weight and survive to adulthood. Neurologically, D1A-/- mice exhibit normal coordination and locomotion, although they display a significant decrease in rearing behavior. Examination of the striatum revealed changes associated with the altered phenotype of these mutants. D1A receptor binding was absent in striatal sections from D1A-/- mice. Striatal neurons normally expressing functional D1A receptors are formed and persist in adult homozygous mutants. Moreover, substance P mRNA, which is colocalized specifically in striatal neurons with D1A receptors, is expressed at a reduced level. In contrast, levels of enkephalin mRNA, which is expressed in striatal neurons with D2 receptors, are unaffected. These findings show that D1A-/- mice exhibit selective functional alterations in the striatal neurons giving rise to the direct striatal output pathway.

Animals↗
PubMed1994

Neuronal progenitors identified by their inability to express class I histocompatibility antigens in response to interferon-gamma.

Interferon-gamma (IFN-gamma) can induce class I major histocompatibility complex (MHC) antigen (H-2) expression on virtually all neuroepithelial cells isolated from embryonic day 9 (E9) mice. However, a subpopulation of cells become refractory to H-2 induction (H-21-) by E10 and the percentage of H-2 noninducible cells increases during development. Cell sorting, by flow cytometry or magnetic bead immunoselection, has shown that H-21- cells give rise exclusively to neuronal cells, and by E12, the majority of the neuronal progenitors are found within this population. It has also been found that 98% of the H-21- also express the neuron-associated marker, A2B5. Cells of the glial cell lineage retain the ability to express class I antigens throughout development. From these studies, it is clear that the neuroepithelium contains cells committed to the neuronal cell lineage as early as E10 in the mouse.

Animals↗
PubMed1992

L-myc and N-myc influence lineage determination in the central nervous system.

The N-myc and the L-myc proto-oncogenes are expressed during embryonal development mainly in the developing brain. Studies of their expression in single neuroepithelial cells revealed that neural precursors not yet committed to the glial or the neuronal lineage expressed both genes, but after lineage commitment they expressed either N-myc or L-myc. Moreover, enforced expression of L-myc in the neural precursor cell line 2.3D caused neuronal differentiation, while the expression of N-myc promoted glial differentiation. These results indicate that L-myc and N-myc play critical roles in lineage determination for the central nervous system.

Animals↗