Kisspeptin neurones in the posterodorsal medial amygdala modulate sexual partner preference and anxiety in male mice

The posterodorsal medial amygdala (MePD) is a neural site in the limbic brain involved in regulating emotional and sexual behaviours. There is, however, limited information available on the specific neuronal cell type in the MePD functionally mediating these behaviours in rodents. The recent discovery of a significant kisspeptin neurone population in the MePD has raised interest in the possible role of kisspeptin and its cognate receptor in sexual behaviour. The present study therefore tested the hypothesis that the MePD kisspeptin neurone population is involved in regulating attraction towards opposite sex conspecifics, sexual behaviour, social interaction and the anxiety response by selectively stimulating these neurones using the novel pharmacosynthetic DREADDs (designer receptors exclusively activated by designer drugs) technique. Adult male Kiss-Cre mice received bilateral stereotaxic injections of a stimulatory DREADD viral construct (AAV-hSyn-DIO-hM3 D(Gq)-mCherry) targeted to the MePD, with subsequent activation by i.p. injection of clozapine-N-oxide (CNO). Socio-sexual behaviours were assessed in a counter-balanced fashion after i.p. injection of either saline or CNO (5 mg kg-1 ). Selective activation of MePD kisspeptin neurones by CNO significantly increased the time spent by male mice in investigating an oestrous female, as well as the duration of social interaction. Additionally, after CNO injection, the mice appeared less anxious, as indicated by a longer exploratory time in the open arms of the elevated plus maze. However, levels of copulatory behaviour were comparable between CNO and saline-treated controls. These data indicate that DREADD-induced activation of MePD kisspeptin neurones enhances both sexual partner preference in males and social interaction and also decreases anxiety, suggesting a key role played by MePD kisspeptin in sexual motivation and social behaviour.

Visualisation of Kiss1 Neurone Distribution Using a Kiss1-CRE Transgenic Mouse

Kisspeptin neuropeptides are encoded by the Kiss1 gene and play a critical role in the regulation of the mammalian reproductive axis. Kiss1 neurones are found in two locations in the rodent hypothalamus: one in the arcuate nucleus (ARC) and another in the RP3V region, which includes the anteroventral periventricular nucleus (AVPV). Detailed mapping of the fibre distribution of Kiss1 neurones will help with our understanding of the action of these neurones in other regions of the brain. We have generated a transgenic mouse in which the Kiss1 coding region is disrupted by a CRE-GFP transgene so that expression of the CRE recombinase protein is driven from the Kiss1 promoter. As expected, mutant mice of both sexes are sterile with hypogonadotrophic hypogonadism and do not show the normal rise in luteinising hormone after gonadectomy. Mutant female mice do not develop mature Graafian follicles or form corpora lutea consistent with ovulatory failure. Mutant male mice have low blood testosterone levels and impaired spermatogenesis beyond the meiosis stage. Breeding Kiss-CRE heterozygous mice with CRE-activated tdTomato reporter mice allows fluorescence visualisation of Kiss1 neurones in brain slices. Approximately 80-90% of tdTomato positive neurones in the ARC were co-labelled with kisspeptin and expression of tdTomato in the AVPV region was sexually dimorphic, with higher expression in females than males. A small number of tdTomato-labelled neurones was also found in other locations, including the lateral septum, the anterodorsal preoptic nucleus, the amygdala, the dorsomedial and ventromedial hypothalamic nuclei, the periaquaductal grey, and the mammillary nucleus. Three dimensional visualisation of Kiss1 neurones and fibres by CLARITY processing of whole brains showed an increase in ARC expression during puberty and higher numbers of Kiss1 neurones in the caudal region of the ARC compared to the rostral region. ARC Kiss1 neurones sent fibre projections to several hypothalamic regions, including rostrally to the periventricular and pre-optic areas and to the lateral hypothalamus.

Kiss1 mutant placentas show normal structure and function in the mouse

Introduction

Kisspeptins, encoded by the Kiss1 gene, are a set of related neuropeptides that are required for activation of the mammalian reproductive axis at puberty and to maintain fertility. In addition, kisspeptin signaling via the G-protein coupled receptor GPR54 (KISS1R) has been suggested to regulate human placental formation and correlations have been found between altered kisspeptin levels in the maternal blood and the development of pre-eclampsia.

Methods

We have used Kiss1 and Gpr54 mutant mice to investigate the role of kisspeptin signaling in the structure and function of the mouse placenta.

Results

Expression of Kiss1 and Gpr54 was confirmed in the mouse placenta but no differences in birth weight were found in mice that had been supported by a mutant placenta during fetal development. Stereological measurements found no differences between Kiss1 mutant and wild-type placentas. Measurement of amino-acid and glucose transport across the Kiss1 mutant placentas at E15.5 days did not reveal any functional defects.

Discussion

These data indicate that mouse placentas can develop a normal structure and function without kisspeptin signaling and can support normal fetal development and growth.

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The structure and function of Kiss1 and Gpr54 mutant placentas was examined in transgenic mice.

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Kiss1 and Gpr54 mutant placentas are not associated with fetal loss during gestation or reduced pup weight at birth.

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Kiss1 mutant placentas show normal structural components.

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Kiss1 mutant placentas show normal transport of glucose and amino-acids.

The role of kisspeptin signalling in the regulation of the GnRH-gonadotrophin ovarian axis in mice

Kisspeptins are a series of overlapping peptides encoded by the Kiss1 gene that are required for central activation of the hypothalamic-pituitary-ovarian axis at puberty. Mutations that interfere with kisspeptin signalling prevent normal pubertal development in humans and mice. Mutations in the kisspeptin receptor GPR54, cause infertility and hypogonadotrophic hypogonadism in humans. The failure of the Gpr54 and Kiss1 mutant mice to ovulate has led to the suggestion that kisspeptin signalling may be required for the preovulatory luteinizing hormone (LH) surge. Although kisspeptin signalling has been shown to have an important central role in regulating the physiology of the ovary, the expression profile of Kiss1 and Gpr54 suggests that they may also have direct functions in the ovary and the placenta.

Distribution of kisspeptin neurones in the adult female mouse brain

Kisspeptin-GPR54 signalling is essential for normal reproductive functioning. However, the distribution of kisspeptin neuronal cell bodies and their projections is not well established. The present study aimed to provide a detailed account of kisspeptin neuroanatomy in the mouse brain. Using a polyclonal rabbit antibody AC566, directed towards the final ten C-terminal amino acids of murine kisspeptin, three populations of kisspeptin-expressing cell bodies were identified in the adult female mouse brain. One exists as a dense periventricular continuum of cells within the rostral part of the third ventricle, another is found within the arcuate nucleus, and another is identified as a low-density group of scattered cells within the dorsomedial nucleus and posterior hypothalamus. Kisspeptin-immunoreactive fibres were abundant within the ventral aspect of the lateral septum and within the hypothalamus running in periventricular and ventral retrochiasmatic pathways. Notable exclusions from the kisspeptin fibre innervation were the suprachiasmatic and ventromedial nuclei. Outside of the hypothalamus, a small number of kisspeptin fibres were identified in the bed nucleus of the stria terminalis, subfornical organ, medial amygdala, paraventricular thalamus, periaqueductal grey and locus coerulus. All kisspeptin cell body and fibre immunoreactivity was absent in brain tissue from Kiss1 knockout mice. These observations provide a map of kisspeptin neurones in the mouse brain and indicate that a limited number of mostly medial hypothalamic and lateral septal brain regions are innervated by the three hypothalamic kisspeptin cell populations; the functions of these projections remain to be established.

Transgenic mouse models to study Gpr54/kisspeptin physiology

Four transgenic mouse lines have been generated with mutations in the Gpr54 gene and two lines with mutations in the Kiss1 gene. In general, the phenotypes of all these mutant mice are very similar and provide evidence that these molecules constitute an authentic receptor/ligand pair with no obvious redundancy or overlap with other signaling pathways. The mutant mice all fail to undergo pubertal maturation and show poor development of the gonads and infertility with low sex steroid and gonadotrophic hormone levels (hypogonadotrophic hypogonadism). Spermatogenesis and ovulation are severely impaired and mutant females do not show estrous cycling. The gonads and the anterior pituitary retain functional responses to hormonal stimulation however, consistent with the primary defect being a failure to secrete gonadotrophin releasing hormone (GnRH) from the hypothalamus. Slight differences between the phenotype of some of the mutant lines may reflect the type of mutation carried by each line. These mutant mice are being used to interrogate the function of Gpr54 and Kiss1 in key aspects of mammalian reproduction in vivo including the role of these proteins in the generation of the pre-ovulatory luteinizing hormone (LH) surge and aspects of sexual behavior. They provide a useful resource to further understand the hypothalamic regulation of mammalian reproduction, its integration with the pituitary-gonadal axis and to study the potential function of Gpr54 and Kiss1 in peripheral tissues.

Physiological consequences of the P2328S mutation in the ryanodine receptor (RyR2) gene in genetically modified murine hearts

Aim

To explore the physiological consequences of the ryanodine receptor (RyR2)-P2328S mutation associated with catecholaminergic polymorphic ventricular tachycardia (CPVT).

Methods

We generated heterozygotic (RyR2^p/s) and homozygotic (RyR2^s/s) transgenic mice and studied Ca²⁺ signals from regularly stimulated, Fluo-3-loaded, cardiac myocytes. Results were compared with monophasic action potentials (MAPs) in Langendorff-perfused hearts under both regular and programmed electrical stimulation (PES).

Results

Evoked Ca²⁺ transients from wild-type (WT), heterozygote (RyR2^p/s) and homozygote (RyR2^s/s) myocytes had indistinguishable peak amplitudes with RyR2^s/s showing subsidiary events. Adding 100 nm isoproterenol produced both ectopic peaks and subsidiary events in WT but not RyR2^p/s and ectopic peaks and reduced amplitudes of evoked peaks in RyR2^s/s. Regularly stimulated WT, RyR2^p/s and RyR2^s/s hearts showed indistinguishable MAP durations and refractory periods. RyR2^p/s hearts showed non-sustained ventricular tachycardias (nsVTs) only with PES. Both nsVTs and sustained VTs (sVTs) occurred with regular stimuli and PES with isoproterenol treatment. RyR2^s/s hearts showed higher incidences of nsVTs before but mainly sVTs after introduction of isoproterenol with both regular stimuli and PES, particularly at higher pacing frequencies. Additionally, intrinsically beating RyR2^s/s showed extrasystolic events often followed by spontaneous sVT.

Conclusion

The RyR2-P2328S mutation results in marked alterations in cellular Ca²⁺ homeostasis and arrhythmogenic properties resembling CPVT with greater effects in the homozygote than the heterozygote demonstrating an important gene dosage effect.

Arrhythmogenic mechanisms in the isolated perfused hypokalaemic murine heart

Aim

Hypokalaemia is associated with a lethal form of ventricular tachycardia (VT), torsade de pointes, through pathophysiological mechanisms requiring clarification.

Methods

Left ventricular endocardial and epicardial monophasic action potentials were compared in isolated mouse hearts paced from the right ventricular epicardium perfused with hypokalaemic (3 and 4 mm [K⁺]_o) solutions. Corresponding K⁺ currents were compared in whole-cell patch-clamped epicardial and endocardial myocytes.

Results

Hypokalaemia prolonged epicardial action potential durations (APD) from mean APD₉₀s of 37.2 ± 1.7 ms (n = 7) to 58.4 ± 4.1 ms (n =7) and 66.7 ± 2.1 ms (n = 11) at 5.2, 4 and 3 mm [K⁺]_o respectively. Endocardial APD₉₀s correspondingly increased from 51.6 ± 1.9 ms (n = 7) to 62.8 ± 2.8 ms (n = 7) and 62.9 ± 5.9 ms (n = 11) giving reductions in endocardial–epicardial differences, ΔAPD₉₀, from 14.4 ± 2.6 to 4.4 ± 5.0 and −3.4 ± 6.0 ms respectively. Early afterdepolarizations (EADs) occurred in epicardia in three of seven spontaneously beating hearts at 4 mm [K⁺]_o with triggered beats followed by episodes of non-sustained VT in nine of 11 preparations at 3 mm. Programmed electrical stimulation never induced arrhythmic events in preparations perfused with normokalemic solutions yet induced VT in two of seven and nine of 11 preparations at 4 and 3 mm [K⁺]_o respectively. Early outward K⁺ current correspondingly fell from 73.46 ± 8.45 to 61.16±6.14 pA/pF in isolated epicardial but not endocardial myocytes (n = 9) (3 mm [K⁺]_o).

Conclusions

Hypokalaemic mouse hearts recapitulate the clinical arrhythmogenic phenotype, demonstrating EADs and triggered beats that might initiate VT on the one hand and reduced transmural dispersion of repolarization reflected in ΔAPD₉₀ suggesting arrhythmogenic substrate on the other.

A LacZ-based transgenic mouse for detection of somatic gene repair events in vivo

Somatic gene repair of disease-causing chromosomal mutations is a novel approach for gene therapy. This method would ensure that the corrected gene is regulated by its endogenous promoter and expressed at physiological levels in the appropriate cell types. A reporter mouse, Gtrosa26(tm1Col), was generated by targeting a mutated LacZ gene to the Rosa26 locus in mouse embryonic stem (ES) cells. The LacZ gene contains a G to A point mutation, resulting in a Glu to Lys amino-acid substitution at position 461, which abrogates enzymatic activity. The gene is expressed in ES cells, primary embryonic fibroblasts, and in all tissues examined in the adult mouse, including the lung, liver, kidney, spleen, heart, brain and smooth muscle. This transgenic mouse will allow testing of gene repair strategies in vivo and identification of which cell types can be successfully targeted by chromosomal gene repair. Although low levels of gene repair were achieved in the ES cells used to generate the Gtrosa26(tm1Col) mouse, preliminary attempts at gene repair in vivo were unsuccessful, thus highlighting the difficulties that will have to be overcome to get this approach to work.

Null mutation of the Lmo4 gene or a combined null mutation of the Lmo1/Lmo3 genes causes perinatal lethality, and Lmo4 controls neural tube development in mice

The LIM-only family of proteins comprises four members; two of these (LMO1 and LMO2) are involved in human T-cell leukemia via chromosomal translocations, and LMO2 is a master regulator of hematopoiesis. We have carried out gene targeting of the other members of the LIM-only family, viz., genes Lmo1, Lmo3 and Lmo4, to investigate their role in mouse development. None of these genes has an obligatory role in lymphopoiesis. In addition, while null mutations of Lmo1 or Lmo3 have no discernible phenotype, null mutation of Lmo4 alone causes perinatal lethality due to a severe neural tube defect which occurs in the form of anencephaly or exencephaly. Since the Lmo1 and Lmo3 gene sequences are highly related and have partly overlapping expression domains, we assessed the effect of compound Lmo1/Lmo3 null mutations. Although no anatomical defects were apparent in compound null pups, these animals also die within 24 h of birth, suggesting that a compensation between the related Lmo1 and 3 proteins can occur during embryogenesis to negate the individual loss of these genes. Our results complete the gene targeting of the LIM-only family in mice and suggest that all four members of this family are important in regulators of distinct developmental pathways.

Markedly reduced effects of (-)-isoprenaline but not of (-)-CGP12177 and unchanged affinity of beta-blockers at Gly389-beta1-adrenoceptors compared to Arg389-beta1-adrenoceptors

1. Substitution of arginine by glycine at position 389, a frequent beta(1)-adrenoceptor polymorphism, reduces adenylyl cyclase stimulation by (-)-isoprenaline. beta(1)-Adrenoceptors mediate the effects of catecholamines and nonconventional partial agonists ((-)-CGP12177) through different sites. We investigated the influence of the 389 polymorphism on beta blocker affinity, as well as on the responses to (-)-isoprenaline and the nonconventional partial agonist (-)-CGP12177 on cyclic AMP levels in CHO cells expressing recombinant Arg389-beta(1)-adrenoceptors (101 fmol mg(-1) protein) or Gly389-beta(1)-adrenoceptors (94 fmol mg(-1)). 2. The affinity of beta-blockers and partial agonists, estimated from competition binding with (-)-[(125)I]-cyanopindolol, was not different for Arg389-beta(1)-adrenoceptors and Gly389-beta(1)-adrenoceptors. 3. The maximum cAMP increases by (-)-isoprenaline and (-)-CGP12177 at Gly389-beta(1)-adrenoceptors were reduced by 97 and 46%, but the potencies enhanced 2 and 0.5 log units, respectively, compared to Arg389-beta(1)-adrenoceptors. The intrinsic activity of (-)-CGP12177 with respect to the (-)-isoprenaline was 0.057 at Arg389-beta(1)-adrenoceptors and 1.05 at Gly389-beta(1)-adrenoceptors. 4. We confirm in intact CHO cells that responses to (-)-isoprenaline are markedly reduced at Gly389-beta(1)-adrenoceptors compared to Arg389-beta(1)-adrenoceptors. However, the 389 polymorphism reduces considerably less the agonist responses to (-)-CGP12177, indicating that coupling to G(s) protein is different for beta(1)-adrenoceptors activated by catecholamines than for receptors activated by nonconventional partial agonists. The affinity of beta-blockers is conserved across the Arg389Gly polymorphism.

Mice lacking pro-opiomelanocortin are sensitive to high-fat feeding but respond normally to the acute anorectic effects of peptide-YY(3-36)

Inactivating mutations of the pro-opiomelanocortin (POMC) gene in both mice and humans leads to hyperphagia and obesity. To further examine the mechanisms whereby POMC-deficiency leads to disordered energy homeostasis, we have generated mice lacking all POMC-derived peptides. Consistent with a previously reported model, Pomc(-/-) mice were obese and hyperphagic. They also showed reduced resting oxygen consumption associated with lowered serum levels of thyroxine. Hypothalami from Pomc(-/-) mice showed markedly increased expression of melanin-concentrating hormone mRNA in the lateral hypothalamus, but expression of neuropeptide Y mRNA in the arcuate nucleus was not altered. Provision of a 45% fat diet increased energy intake and body weight in both Pomc(-/-) and Pomc(+/-) mice. The effects of leptin on food intake and body weight were blunted in obese Pomc(-/-) mice whereas nonobese Pomc(-/-) mice were sensitive to leptin. Surprisingly, we found that Pomc(-/-) mice maintained their acute anorectic response to peptide-YY(3-36) (PYY(3-36)). However, 7 days of PYY(3-36) administration had no effect on cumulative food intake or body weight in wild-type or Pomc(-/-) mice. Thus, POMC peptides seem to be necessary for the normal response of energy balance to high-fat feeding, but not for the acute anorectic effect of PYY(3-36) or full effects of leptin on feeding. The finding that the loss of only one copy of the Pomc gene is sufficient to render mice susceptible to the effects of high fat feeding emphasizes the potential importance of this locus as a site for gene-environment interactions predisposing to obesity.

A comparison of gene repair strategies in cell culture using a lacZ reporter system

Synthetic oligonucleotides and DNA fragments of less than 1 kilobase (kb) have been shown to cause site-specific genetic alterations in mammalian cells in culture and in vivo. We have used a lacZ reporter gene system to compare the efficiency of episomal and chromosomal gene repair in human embryonic kidney epithelial cells (HEK293), Chinese Hamster Ovary fibroblasts (CHOK1), human bronchial epithelial cells (16HBE), and mouse embryonic stem (ES) cells. The lacZ gene contains a G to A nucleotide change, (Glu to Lys mutation) that abrogates beta-galactosidase activity. We compared the efficiency of different gene repair methods to correct this mutation and restore beta-galactosidase activity. We evaluated PCR-generated double-stranded DNA fragments of 0.52-1.9 kb, single-stranded DNA oligonucleotides of 20, 35, or 80 bases containing internal phosphorothioate links, and a 68 base RNA:DNA oligonucleotide. All of the oligonucleotides and DNA fragments showed some gene repair ability with an episomal plasmid. Short DNA fragments of 0.52 kb or greater gave the highest frequencies of episomal gene repair while single-stranded DNA oligonucleotides gave the highest frequency of chromosomal repair. In the context of a chromosomal target, antisense DNA oligonucleotides gave 5-fold higher frequencies of gene repair than their sense counterparts. The RNA:DNA chimeric oligonucleotide gave little or no gene repair on either a chromosomal or episomal target.

A comparison of linear and branched polyethylenimine (PEI) with DCChol/DOPE liposomes for gene delivery to epithelial cells in vitro and in vivo

Polyethylenimine (PEI), a polycation with high ionic charge density, has recently been used as a gene therapy delivery agent. We have defined the optimal conditions for PEI-based transfection of airway epithelial cells in vitro and in vivo and used these conditions to restore Cl(-) channel activity in a CF mouse model. Three forms of PEI, a linear 22 kDa (ExGen 500) form and branched 25 or 50 kDa forms were evaluated. All forms of PEI significantly increased luciferase reporter gene expression compared to the liposome DCChol/DOPE in a human bronchial epithelial cell line (16HBE) irrespective of the extent of cell confluency. With subconfluent cells, gene expression was around 1000-, 200- and 25-fold higher than liposomes using linear 22, 25 and 50 kDa PEI, respectively. The transfection efficiency was reduced in confluent and polarized epithelial cells but linear 22 kDa PEI showed the smallest decrease and gave 8000-fold better transfection in polarized cells compared to liposomes. A comparison of linear 22 or 25 kDa PEI with DCChol/DOPE for airway delivery in vivo via intranasal instillation was also performed. Linear 22 kDa PEI gave significantly better luciferase reporter gene expression of 350-fold in the lung, 180-fold in the nose and 85-fold in the trachea compared to liposome. In contrast, the 25 kDa form of PEI was no better than DCChol/DOPE. Repeat dosing with linear 22 kDa PEI failed to give reporter gene delivery comparable to the initial dose. To establish that PEI can be used to deliver a physiologically relevent gene in vivo, we used it to restore Cl(-) secretion by CFTR gene delivery in the airways of a CF mouse model.

Expression and regulation of the Na+-K+-2Cl- cotransporter NKCC1 in the normal and CFTR-deficient murine colon

Defective regulation and/or reduced expression of the Na+-K+-2Cl- cotransporter NKCC1 may contribute to the severe secretory defect that is observed in cystic fibrosis, but data concerning the expression and function of NKCC1 in cystic fibrosis transmembrane conductance regulator (CFTR)-deficient cells are equivocal. We therefore investigated NKCC1 mRNA expression, Na+-K+-2Cl- cotransport activity and regulation by cAMP in crypts isolated from the proximal colon of CFTR-containing (CFTR (+/+)) and CFTR-deficient (CFTR (-/-)) mice. mRNA expression levels were determined by semiquantitative PCR, transport rates were measured fluorometrically in 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein acetomethylester (BCECF)-loaded crypts, cytoplasmic volume changes were assessed by confocal microscopy, and [Cl-]i changes were examined by N-(ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE) quenching. NKCC1 mRNA expression levels were not significantly reduced in CFTR (-/-) crypts compared to controls. Azosemide-sensitive NH4+ influx (used as a measure of Na+-K+-2Cl- cotransport) was 2.23 +/- 0.72 vs. 1.56 +/- 0.16 mM min-1, and increased by 63.6 % in (+/+) and 87.3 % in (-/-) crypts upon stimulation for 5 min with forskolin. After 20 min of stimulation with forskolin, the Na+-K+-2Cl- cotransport rates in (-/-) and (+/+) crypts were identical. Crypt cross-sectional area and [Cl-]i decreased only in (+/+) crypts upon stimulation. In conclusion, normal NKCC1 expression levels, somewhat reduced Na+-K+-2Cl- cotransport rates, but preserved activation by cAMP were found in colonic crypts from CFTR (-/-) mice, ruling out a severe dysfunction of the Na+-K+-2Cl- cotransporter in the CF intestine. Furthermore, these studies establish the existence of a direct, cell-volume- and [Cl-]i-independent activation of colonic NKCC1 by an increase in intracellular cAMP.

cAMP-mediated regulation of murine intestinal/pancreatic Na+/HCO3- cotransporter subtype pNBC1

Basolateral Na(+)-HCO(3)(-) cotransport is essential for intestinal anion secretion, and indirect evidence suggests that it may be stimulated by a rise of intracellular cAMP. We therefore investigated the expression, activity, and regulation by cAMP of the Na(+)-HCO(3)(-) cotransporter isoforms NBC1 and NBCn1 in isolated murine colonic crypts. Na(+)-HCO(3)(-) transport rates were measured fluorometrically in BCECF-loaded crypts, and mRNA expression levels and localization were determined by semiquantitative PCR and in situ hybridization. Acid-activated Na(+)-HCO(3)(-) cotransport rates were 5.07 +/- 0.7 mM/min and increased by 62% after forskolin stimulation. NBC1 mRNA was more abundant in colonic crypts than in surface cells, and crypts expressed far more NBC1 than NBCn1. To investigate whether the cAMP-induced Na(+)-HCO(3)(-) cotransport activation was secondary to secretion-associated changes in HCO(3)(-) or cell volume, we measured potential forskolin-induced changes in intracellular pH and assessed Na(+)-HCO(3)(-) transport activity in CFTR -/- crypts (in which no forskolin-induced cell shrinkage occurs). We found 30% reduced Na(+)-HCO(3)(-) transport rates in CFTR -/- compared with CFTR +/+ crypts but similar Na(+)-HCO(3)(-) cotransport activation by forskolin. These studies establish the existence of an intracellular HCO(3)(-) concentration- and cell volume-independent activation of colonic NBC by an increase in intracellular cAMP.

Optimisation of real-time quantitative RT-PCR for the evaluation of non-viral mediated gene transfer to the airways

Naked plasmid DNA and DNA/liposome complexes are currently being considered as gene therapy treatments for cystic fibrosis (CF) pulmonary disease. Current methods of gene delivery to the airways result only in transient correction of the CF ion transport defect, and disease treatment is likely to require repeated administrations of vector. However, it is unclear if repeat administration will be tolerated by CF individuals. Technologies including TaqMan (Applied Biosystems) real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) can be used to determine the efficacy of gene transfer formulations. TaqMan RT-PCR assays were designed and optimised to detect plasmid vector-derived and endogenous gene expression. Subsequently, these assays were used to quantify vector-derived mRNA after delivery of naked DNA and DNA/liposome formulations expressing human and murine cystic fibrosis transmembrane conductance regulator (CFTR) to the mouse airways. Vector-derived mRNA was detected in samples following the delivery of naked DNA or DNA/liposomes to the mouse airways, and no reduction in vector-derived mRNA was observed upon repeat administration, a finding that is consistent with the murine and human CFTR being tolerated by the mouse. Although it remains to be seen if CF patients can tolerate long-term expression of wild-type CFTR, these data demonstrate that TaqMan RT-PCR is an effective tool to accurately quantify transgene expression in the airways.

Effect of acute saline volume expansion in the anaesthetised DeltaF508 cystic fibrosis mouse

It has been suggested that CFTR Cl(-) channels in the renal inner medullary collecting duct may be involved in mediating increased renal salt excretion during extracellular fluid volume expansion. To investigate this hypothesis, in-vivo clearance experiments were performed comparing wild-type (WT) and DeltaF508-CFTR transgenic mice (cftr (tm2Cam)). Control animals were given a 0.1-ml bolus of 0.9% saline, followed by I.V. infusion at 0.3 ml x h(-1). Volume expansion was applied by infusing a 1-ml bolus of 0.9% saline followed by infusion at 0.6 ml x h(-1). No significant differences in renal NaCl handling between WT mice ( C(Na)=1.2 +/- 0.3 microl x min(-1), C(Cl)=4.0 +/- 0.5 microl x min(-1)) and DeltaF508-CFTR mice ( C(Na)=1.7 +/- 0.5 microl x min(-1), C(Cl)=4.1 +/- 0.8 microl x min(-1)) were observed under control conditions. Volume expansion resulted in large significant increases in NaCl clearance in both WT mice ( C(Na)=7.0 +/- 0.9 microl x min(-1), C(Cl)=12.0 +/- 0.6 microl x min(-1)) and DeltaF508-CFTR mice ( C(Na)=7.2 +/- 1.6 microl x min(-1), C(Cl)=11.0 +/- 2.2 microl x min(-1)). However, there was no significant difference between WT and DeltaF508-CFTR mice. In conclusion, renal NaCl excretion is not significantly different under basal conditions and during saline volume expansion in DeltaF508-CFTR mice. The data suggest that CFTR is not a physiologically important mediator of volume natriuresis.

Ultrastructural changes in exocrine tissues of a DeltaF-508 CFTR mouse model

Cystic fibrosis (CF) is characterized by abnormal secretion from epithelial cells. We wanted to detect changes in the ultrastructural characteristics of cells within a number of exocrine tissues, including the colon, submandibular and parotid salivary glands of DeltaF-508 CFTR animals. Therefore, in the present study a DeltaF-508 CFTR mouse model was compared to control, by applying conventional and complex carbohydrates staining techniques to tissue sections at the electron microscope level. The colon of DeltaF-508 CFTR mice contained thick mucous secretions that harbored many bacteria, along with cytoplasmic fragments and leukocytes. Leukocytes were also seen to infiltrate the cytoplasm of goblet cells. Tissues were taken before, 10 min after isoprenaline, and 30 min after a further injection of methacholine. In the submandibular gland, there is limited secretory activity after isoprenaline treatment, and this increases further with methacholine treatment. Depletion of the secretory granules of acinar cells is observed, following the combined isoprenaline and methacholine treatment, but no significant changes in granule numbers occurred in granular tubule cells. Glycogen, abundant before treatment, is reduced within 10 min of isoprenaline treatment and is completely exhausted by 30 min, especially in the convoluted granular tubule cells. A few secretory granules in acinar and in granular tubule cells of the DeltaF-508 CFTR submandibular glands displayed two electron densities. The secretory responses of the parotid gland cells were similar to those in submandibular gland cells, except that in these DeltaF-508 CFTR cells, secretory granules appeared more polymorphic in structure than those found in control animals.

Steroid hormone enhancement of gene delivery to a human airway epithelial cell line in vitro and mouse airways in vivo

Current liposome-based delivery protocols for gene therapy are relatively inefficient. In a pharmacological approach to enhance liposome-mediated gene delivery we have evaluated beta-estradiol and methyl-prednisolone as enhancing agents. We have shown that beta-estradiol in combination with lipoplex can significantly increase luciferase gene expression in sub-confluent, confluent and polarized human bronchial epithelial (16HBE) cells 23-fold, 100-fold and 900-fold, respectively, when compared with lipoplex alone. Similarly, incorporation of methyl-prednisolone into lipoplexes increases luciferase gene expression in confluent and polarized 16HBE cells 70.8-fold and 48-fold, respectively. Greater levels of gene expression were obtained when beta-estradiol (9.5-fold enhancement) or methyl-prednisolone (14-fold enhancement) were mixed with the liposome before addition of the plasmid compared with addition of the steroid after lipoplex formation. Beta-estradiol-containing lipoplexes were also evaluated in vivo where in the murine lung and nasal epithelium an eight-fold and 7.5-fold enhancement in gene expression were found compared with lipoplex alone. Incorporating beta-estradiol into lipoplexes increased both the total number of cells transfected and the amount of intracellular plasmid within the cell, including the nuclear compartment, compared with lipoplex alone. These results demonstrate the ability of steroids to enhance gene delivery in vitro and in vivo and thus may have the potential to improve gene therapy strategies.

Increased persistence of lung gene expression using plasmids containing the ubiquitin C or elongation factor 1alpha promoter

For effective gene therapy of chronic disease, persistent transgene expression at therapeutic levels is required. Clinical studies of airway gene transfer in patients with cystic fibrosis (CF) have resulted in short-lived transgene expression. We used intra-nasal dosing of naked plasmid DNA to the murine lung as a model for investigating the duration of airway gene transfer from a series of reporter expression plasmids. Transgene expression was transient when mediated by the viral promoters CMV, RSV and SV40, falling to less than 10% of peak expression after 2 weeks, although the presence of the adenoviral E4ORF3 gene in cis, resulted in extended duration of reporter activity from the CMV promoter. Transient expression from these promoters was not due to loss of the vector as determined by quantitative TaqMan PCR analysis. However, use of the promoters from the human polybiquitin C (UbC) and the elongation factor 1alpha (EF1alpha) genes resulted in persistent gene expression in the mouse lung. The UbC promoter directed high-level reporter activity which was maintained for up to 8 weeks and was still detectable 6 months after a single administration. Such persistent airway transgene expression from a nonviral vector without the concomitant expression of a potential antigen has not been reported previously. Thus, despite the persistence of vector DNA in vivo, attenuation of promoter function may lead to silencing of transgene expression and careful selection of promoter sequences is recommended for in vivo gene transfer.

Mucus altering agents as adjuncts for nonviral gene transfer to airway epithelium

Nonviral vectors have been shown to be a safe and valid alternative to recombinant viruses for gene therapy of cystic fibrosis (CF). Nevertheless, gene transfer efficiency needs to be increased before clinical efficacy is likely in man. One barrier to increased efficacy is normal airway mucus. Using an ex vivo model of sheep tracheal epithelium, we show that this barrier can, in part, be overcome by treatment with the mucolytic agents, Nacystelyn or N-acetylcysteine using either a cationic lipid or a cationic polymer as the gene transfer agent. Further, in vivo application of either Nacystelyn or the anticholinergic glycopyrrolate, both clinically used agents, resulted in increased reporter gene expression in the mouse lung, but no significant correction of the bioelectric defect in CF null mice. These results, whilst unlikely to be sufficient in themselves to achieve clinically relevant gene therapy, may be a further useful step in the attainment of this goal.

Murine CFTR channel and its role in regulatory volume decrease of small intestine crypts

Cystic fibrosis (CF) is caused by mutations in the secretory Cl(-) channel CFTR (cystic fibrosis transmembrane conductance regulator). Variation in the severity of disease has been attributed to mutations in the CFTR gene that cause different degrees of dysfunction of the CFTR Cl(-) channel. However, studies of mouse models of CF indicate that the severity of intestinal pathology is not correlated with activity of the CFTR chloride channel. This observation suggests that other 'environmental' factors might be important in determining the severity of disease. In this respect, we have identified and characterised an additional cellular defect in intestinal epithelial cells of CF mice, the inability of these cells to regulate their volume after hypotonic challenge. Here, we review the function of murine CFTR as both a Cl(-) channel and as a regulator of volume-dependent homeostatic cell mechanisms.

Enhanced gene delivery to human airway epithelial cells using an integrin-targeting lipoplex

BACKGROUND

Current liposome-based delivery methods for cystic fibrosis (CF) gene therapy are limited by their poor efficiencies. One way to improve this is to use a receptor/ligand interaction to increase binding of the transfection complex with the target cell.

METHODS AND RESULTS

We have tested a synthetic peptide containing an alphav integrin-binding motif (arginine-glycine-aspartic acid, RGD) and a DNA-binding domain (polylysine) for enhancement of liposome-mediated gene delivery. We have shown that integrin proteins capable of binding the RGD motif are located on the apical surface of a polarized human bronchial epithelial cell line (16HBE). Luciferase gene transfer efficiency to subconfluent 16HBE cells was 10-200 times higher than gene transfer using either liposome or peptide alone. This peptide-mediated enhancement was observed at all cellular contact times including those as short as 1 min. Although the transfection efficiency is reduced when the 16HBE cells are grown as polarized monolayers, peptide-mediated enhancement of lipofection is maintained. Transfection with a lipopolyplex containing an RGE (arginine-glucine-glutamic acid) control peptide that cannot bind to the alphav integrin molecules, or competitive inhibition with antibodies against RGD-binding integrins, reduced gene transfer. Confocal microscopy indicated that the peptide increased plasmid delivery to the cell via receptor-mediated endocytosis.

CONCLUSION

These results indicate that integrin-binding peptides represent one way to enhance liposome-mediated gene delivery to pulmonary epithelia.

Acetylcholine induces cytosolic Ca2+ mobilization in isolated distal colonic crypts from normal and cystic fibrosis mice

In intestinal biopsies from cystic fibrosis (CF) patients acetylcholine fails to elicit a chloride secretion response, and this observation can be explained by a defect in the Ca2+ signalling pathway in CF secretory cells. We tested the hypothesis that in CF intestine, the generation of an intracellular Ca2+ signal upon cholinergic stimulation is absent. A transgenic CF mouse model was used. Electrical measurements on intact jejunum and unstripped colon were performed in Ussing chambers. Intact distal colonic crypts were isolated, and the intracellular Ca2+ concentration was monitored using the Ca2+-sensitive dye fura-2. Acetylcholine increased the short-circuit current generated by wild-type jejunum and colon, but failed to induce a response in CF tissues. Acetylcholine caused a transient elevation in the intracellular Ca2+ concentration in colonic crypts from both wild-type and CF mice; the amplitude and timing of the response in CF crypts was indistinguishable from that in wild-type crypts. The response to acetylcholine was also observed in the absence of extracellular calcium, indicating intracellular stores as the source from which the cytosolic Ca2+ concentration increased. We conclude that the absence of a cholinergically-induced secretory response in CF intestine is not due to a defect in the generation of a Ca2+ signal in intestinal cells upon cholinergic stimulation.

Inflammation in cystic fibrosis airways: relationship to increased bacterial adherence

It is unclear whether inflammation in the cystic fibrosis (CF) lung relates predominantly to bacterial infection, or occurs as a direct consequence of mutant cystic fibrosis transmembrane conductance regulator (CFTR) protein. Interleukin (IL)-8 secretion from CF and non-CF cell lines, and from CF and non-CF human primary nasal epithelial cells incubated with or without Pseudomonas aeruginosa, was measured. Activation of nuclear factor-kappaB (NF-kappaB) in unstimulated CF and non-CF nasal epithelial cells, cell lines and murine tissues was measured by gel-shift assays. No significant difference in basal IL-8 production or NF-kappaB activation was observed between CF and non-CF primary nasal cells. However, CF cells exhibited a significantly (p<0.01) increased IL-8 secretion following P. aeruginosa stimulation. Equalization of the increased P. aeruginosa adherence observed in CF cells, to non-CF levels, resulted in comparable IL-8 secretion. Further, IL-8 production did not differ with mutations which result in either correctly localized CFTR, or in partial/total mislocalization of this protein. Similar levels of NF-kappaB activation were observed in a number of organs of wildtype and CF mice. Finally, IL-8 secretion and NF-kappaB activity were not consistently increased in CF cell lines. Cos-7 cell transfection with plasmids expressing deltaF508 or G551D mutant CFTR protein resulted in increased activation of a p50-containing NF-kappaB complex, but IL-8 secretion was similar to wild-type cells. The authors conclude that the stimulus produced by Pseudomonas aeruginosa is the predominant inflammatory trigger in their models.

Genistein activates CFTR-mediated Cl(-) secretion in the murine trachea and colon

The action of the isoflavone genistein on the cystic fibrosis transmembrane conductance regulator (CFTR) has been studied in many cell systems but not in intact murine tissues. We have investigated the action of genistein on murine tissues from normal and cystic fibrosis (CF) mice. Genistein increased the short-circuit current (I(sc)) in tracheal (16.4 +/- 2.8 microA/cm(2)) and colonic (40.0 +/- 4.4 microA/cm(2)) epithelia of wild-type mice. This increase was inhibited by furosemide, diphenylamine-2-carboxylate, and glibenclamide, but not by DIDS. In contrast, genistein produced no significant change in the I(sc) of the tracheal epithelium (0.9 +/- 1.1 microA/cm(2)) and decreased the I(sc) of colons from CF null (-13.1 +/- 2.3 microA/cm(2)) and DeltaF508 mice (-10.3 +/- 1.3 microA/cm(2)). Delivery of a human CFTR cDNA-liposome complex to the airways of CF null mice restored the genistein response in the tracheas to wild-type levels. Tracheas from DeltaF508 mice were also studied: 46% of trachea showed no response to genistein, whereas 54% gave an increase in I(sc) similar to that in wild type. We conclude that genistein activates CFTR-mediated Cl(-) secretion in the murine trachea and distal colon.

Repeat administration of DNA/liposomes to the nasal epithelium of patients with cystic fibrosis

The major cause of mortality in patients with cystic fibrosis (CF) is lung disease. Expression of the cystic fibrosis transmembrane conductance regulator (CFTR) gene product in the airways is a potential treatment. Clinical studies in which the CFTR cDNA was delivered to the respiratory epithelia of CF patients have resulted in modest, transient gene expression. It seems likely that repeated administration of the gene transfer vector will be required for long-term gene expression. We have undertaken a double-blinded study in which multiple doses of a DNA/liposome formulation were delivered to the nasal epithelium of CF patients. Ten subjects received plasmid DNA expressing the CFTR cDNA complexed with DC-Chol/DOPE cationic liposomes, whilst two subjects received placebo. Each subject received three doses, administered 4 weeks apart. There was no evidence of inflammation, toxicity or an immune response towards the DNA/liposomes or the expressed CFTR. Nasal epithelial cells were collected 4 days after each dose for a series of efficacy assays including quantitation of vector-specific DNA and mRNA, immunohistochemistry of CFTR protein, bacterial adherence, and detection of halide efflux ex vivo. Airway ion transport was also assessed in vivo by repeated nasal potential difference (PD) measurements. On average, six of the treated subjects were positive for CFTR gene transfer after each dose. All subjects positive for CFTR function were also positive for plasmid DNA, plasmid-derived mRNA and CFTR protein. The efficacy measures suggest that unlike high doses of recombinant adenoviral vectors, DNA/liposomes can be successfully re-administered without apparent loss of efficacy.

Evidence for cystic fibrosis transmembrane conductance regulator-dependent sodium reabsorption in kidney, using Cftr(tm2cam) mice

The aims of this study were to investigate (a) if renal Na(+) handling was normal in Cftr(tm2cam) delta F508 cystic fibrosis mice, (b) whether adaptation to dietary salt depletion was preserved and (c) whether Cftr(tm2cam) delta F508 mice exhibited enhanced amiloride-sensitive Na(+) absorption. In Na(+)-replete animals (maintained on a 0.32 % NaCl diet) given a 150 mM NaCl i.v. maintenance infusion, there was no difference in fractional Na(+) excretion (FE(Na)) between wild-type (0. 42 +/- 0.06 %, n = 12) and Cftr(tm2cam) delta F508 mice (0.47 +/- 0.13 %, n = 7). Amiloride infusion significantly increased FE(Na) in both wild-type (3.14 +/- 0.83 %, n = 6) and Cftr(tm2cam) delta F508 mice (3. 47 +/- 0.63 %, n = 9), though with no significant difference between genotypes. A 14 day dietary salt restriction (animals maintained on a 0.03 % NaCl diet) and maintenance infusion with a 15 mM NaCl vehicle caused a reduction in FE(Na) to 0.14 +/- 0.05 %, n = 8 in wild-type mice and 0.14 +/- 0.04 %, n = 8 in Cftr(tm2cam) delta F508 mice. No significant difference in the ability to adapt to low salt conditions was apparent comparing the two genotypes. Treatment of salt-restricted mice with amiloride resulted in a blunted natriuresis in both wild-type mice (FE(Na) = 1.10 +/- 0.16 %, n = 7) and Cftr(tm2cam) delta F508 mice (FE(Na) = 1.97 +/- 0.29 %, n = 9). The natriuresis induced by amiloride was significantly greater in Cftr(tm2cam) delta F508 mice than in wild-type controls. In conclusion, Cftr(tm2cam) delta F508 mice exhibit normal renal salt excretion when either salt replete or salt restricted. Enhanced amiloride-sensitive FE(Na) is consistent with increased Na(+) absorption via the amiloride-sensitive sodium channel ENaC, in cystic fibrosis kidney, but this was only observed during salt restriction.

A murine tracheal culture system to investigate parameters affecting gene therapy for cystic fibrosis

Cystic fibrosis (CF) is a life-threatening condition caused by mutations in the cystic fibrosis transmembrane conductance regulator gene (CFTR). Delivery of the CFTR gene to the airways offers a potential treatment for CF but requires improvement in efficiency to obtain clinical benefit. We have developed a murine tracheal culture system that maintains tissue integrity as judged by normal histological appearance, high transepithelial resistance and electrophysiological responses similar to fresh tissue. This ex vivo system allows precise control of gene delivery parameters to a structure that retains the in vivo cellular architecture. We have demonstrated correction of CFTR-dependent Cl- secretion following ex vivo delivery of the CFTR gene to tracheas from CF null mice. We have used this system to examine parameters affecting liposome-mediated gene delivery to the upper airway such as plasmid dose. We have also found that a contact time of 1 min for the transfection mixture is sufficient to achieve significant DNA binding and maximal reporter gene expression.

Eomesodermin is required for mouse trophoblast development and mesoderm formation

The earliest cell fate decision in the mammalian embryo separates the extra-embryonic trophoblast lineage, which forms the fetal portion of the placenta, from the embryonic cell lineages. The body plan of the embryo proper is established only later at gastrulation, when the pluripotent epiblast gives rise to the germ layers ectoderm, mesoderm and endoderm. Here we show that the T-box gene Eomesodermin performs essential functions in both trophoblast development and gastrulation. Mouse embryos lacking Eomesodermin arrest at the blastocyst stage. Mutant trophoectoderm does not differentiate into trophoblast, indicating that Eomesodermin may be required for the development of trophoblast stem cells. In the embryo proper, Eomesodermin is essential for mesoderm formation. Although the specification of the anterior-posterior axis and the initial response to mesoderm-inducing signals is intact in mutant epiblasts, the prospective mesodermal cells are not recruited into the primitive streak. Our results indicate that Eomesodermin defines a conserved molecular pathway controlling the morphogenetic movements of germ layer formation and has acquired a new function in mammals in the differentiation of trophoblast.

Sodium channel blockers and uridine triphosphate: effects on nasal potential difference in cystic fibrosis mice

Sodium channel inhibitors block the enhanced Na+ reabsorption in cystic fibrosis (CF). Extracellular nucleotides facilitate Cl- secretion via Ca2+ gated Cl- channels. A combination of these effects may produce less viscid secretions in CF which are easier to expectorate. This study examined the effects of combining sodium channel blockers with uridine triphosphate (UTP) on nasal membrane potential difference (PD) in CF insertional null mutant mice (cftr(tm1HGU)), deltaF508 homozygous mice (cftr(tm1Cam)) and matched control animals. Median basal PD in the insertional CF mice and deltaF508 CF mice were -28 and -34 mV respectively. These values were significantly different to the control animals (-20 mV). Amiloride and loperamide reduced the PD in cftr(tm1HGU) CF mice (deltaPD 13 mV & 15 mV respectively) suggesting Na+ blockade. The subsequent addition of UTP in a chloride-free vehicle increased the PD (deltaPD -8- -12.5 mV). DeltaF508 mice showed significantly greater responses compared with CF insertional null mutant mice (p<0.05). The action of UTP was brief and not prolonged by the addition alpha-beta-methylene-adenosine 5' diphosphate. Suramin, a competitive antagonist of P2 purinoceptors blocked the action of UTP. In conclusion, this study demonstrated dose dependant nasal membrane potential changes in differences mice with uridine triphosphate in the presence of sodium channel blockers suggestive of chloride secretion. More stable analogues of uridine triphosphate in combination with long acting sodium channel blockers such as loperamide may have therapeutic potential in cystic fibrosis.

A retroviral gene trap insertion into the histone 3.3A gene causes partial neonatal lethality, stunted growth, neuromuscular deficits and male sub-fertility in transgenic mice

Spermatogenesis is a complex developmental pro-cess involving cell division and differentiation. Approximately half of all sterile males have defects in spermatogenesis or sperm function. An insight into the molecular control points regulating this process might help in treating male infertility. Gene trapping in embryonic stem cells and the generation of transgenic mice represents one route to identify genes expressed during spermatogenesis. The trapped gene is tagged with a lacZ reporter gene so that the expression pattern of the gene can be visualized by staining for beta-galactosidase activity. We have screened transgenic mouse lines for expression of trapped genes in the gonads. One such trap event was shown to be in the replacement histone 3.3A gene ( H3.3A ). This gene was expressed ubiquitously during embryonic development until 13.5 days post-coitum and in the adult heart, kidney, brain, testes and ovaries. This mutation resulted in postnatal death of 50% of homozygous mutants. Surviving mutants displayed reduced growth rates when competing with wild-type siblings for food. Mutant mice also had a neuro-muscular deficit and males displayed reduced copulatory activity. When copulations did occur, these resulted in very few pregnancies, suggesting that mutations in the H3.3A gene may contribute to some cases of impaired fertility in man.

Restoration by intratracheal gene transfer of bicarbonate secretion in cystic fibrosis mouse gallbladder

Gallbladders from cystic fibrosis (CF) mice (Cftrtm1Cam and Cftrtm2Cam) were examined with the short-circuit current technique. The tissues failed to show any electrogenic anion transport in response to forskolin (cAMP stimulus) but responded to the Ca2+ ionophore ionomycin. Administration of the plasmid pTrial10-CFTR2 complexed with cationic liposomes (3beta-[N-(dimethylaminoethane)-carbamoyl]cholesterol and L-alpha-phosphatidylethanolamine dioleolyl) to the airways restored the phenotype of CF gallbladders to that of the wild type, but did not do so when given orally. Formation of human CFTR mRNA in gallbladders of transfected CF null mice was demonstrated. Using the reporter genes pCMV-luc and pCMV-LacZ, we showed that 1) the intratracheal route was more effective than the oral,intravenous, intramuscular, subcutaneous, or intraperitoneal routes in expressing luciferase activity in the gallbladder and 2) beta-galactosidase staining after pCMV-LacZ was confined to the columnar epithelium lining the gallbladder without any discernible activity in it smooth muscle. The discovery of an unusual route for gene transfer to the biliary system may give useful insight into counteracting the consequences of biliary fibrosis in human CF patients.

Crouzon-like craniofacial dysmorphology in the mouse is caused by an insertional mutation at the Fgf3/Fgf4 locus

Retroviral insertional mutagenesis by means of ES cells has resulted in a new autosomal dominant mutation causing craniofacial dysmorphology in the mouse (Bulgy-eye, Bey). Heterozygous Bey mice are viable and fertile but show facial shortening with increased interorbital distance and precocious closure of several cranial sutures (craniosynostosis). These features provide a murine phenocopy for a large class of human craniofacial dysmorphology syndromes associated with craniosynostosis, particularly Crouzon syndrome. The retroviral vector integration responsible for the Bey mutation is inserted in the intragenic region between Fgf3 and Fgf4. Transcript analysis demonstrates that expression of both Fgf3 and Fgf4 is up-regulated in the cranial sutures of Bey mice. Many of these human craniosynostosis syndromes are caused by mutations in the extracellular domain of receptors for fibroblast growth factors that result in constitutive receptor activation. Our data confirm that fibroblast growth factor signalling pathways are involved in craniofacial development and suggest that some human malformation pedigrees or sporadic craniosynostosis may be caused by mutations that deregulate expression of the Fgf ligands.

Disruption of murine alpha-enolase by a retroviral gene trap results in early embryonic lethality

Gene trapping with the retroviral ROSA beta geo vector was used to generate lines of mice carrying disrupted genes. Both cDNA and genomic flanks have been cloned from a number of these lines. One mutation has been shown to disrupt the alpha-enolase gene by insertion of the splice-trap vector into the first intron. In adult mice, lacZ expression was detected only in testes. Embryonic expression was detected from 10.5-day postcoitum embryos and was seen as a diffuse staining pattern over much of the embryo, consistent with the housekeeping gene function of alpha-enolase. This mutation results in an early recessive embryonic lethality. Mice heterozygous for the mutation have no obvious phenotype. Mutations of this gene in humans are reported to be associated with rare autosomal-dominant, non-spherocytic haemolytic anaemia. This phenotype is not reproduced in mice heterozygous for this mutation.

Salmonella typhi uses CFTR to enter intestinal epithelial cells

Homozygous mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) cause cystic fibrosis (CF). In the heterozygous state, increased resistance to infectious diseases may maintain mutant CFTR alleles at high levels in selected populations. Here we investigate whether typhoid fever could be one such disease. The disease is initiated when Salmonella typhi enters gastrointestinal epithelial cells for submucosal translocation. We found that S. typhi, but not the related murine pathogen S. typhimurium, uses CFTR for entry into epithelial cells. Cells expressing wild-type CFTR internalized more S. typhi than isogenic cells expressing the most common CFTR mutation, a phenylalanine deleted at residue 508 (delta508). Monoclonal antibodies and synthetic peptides containing a sequence corresponding to the first predicted extracellular domain of CFTR inhibited uptake of S. typhi. Heterozygous deltaF508 Cftr mice translocated 86% fewer S. typhi into the gastrointestinal submucosa than wild-type Cftr mice; no translocation occurred in deltaF508 Cftr homozygous mice. The Cftr genotype had no effect on the translocation of S. typhimurium. Immunoelectron microscopy revealed that more CFTR bound to S. typhi in the submucosa of Cftr wild-type mice than in deltaF508 heterozygous mice. We conclude that diminished levels of CFTR in heterozygotes may decrease susceptibility to typhoid fever.

Mutation analysis of the c-mos proto-oncogene in human ovarian teratomas

Female transgenic mice lacking a functional c-mos proto-oncogene develop ovarian teratomas, indicating that c-mos may behave as a tumour-suppressor gene for this type of tumour. We have analysed the entire coding region of the c-MOS gene in a series of human ovarian teratomas to determine whether there are any cancer-causing alterations. DNA from twenty teratomas was analysed by single-strand conformational analysis (SSCA) and heteroduplex analysis (HA) to screen for somatic and germline mutations. In nine of these tumours the entire gene was also sequenced. A previously reported polymorphism and a single new sequence variant were identified, neither of which we would predict to be disease-causing alterations. These results suggest that mutations in the coding region of the c-MOS gene do not play a significant role in the genesis of human ovarian teratomas.

Mice deficient for the secreted glycoprotein SPARC/osteonectin/BM40 develop normally but show severe age-onset cataract formation and disruption of the lens

SPARC (secreted protein acidic and rich in cysteine, also known as osteonectin/BM40) is a secreted Ca2+-binding glycoprotein that interacts with a range of extracellular matrix molecules, including collagen IV. It is widely expressed during embryogenesis, and in vitro studies have suggested roles in the regulation of cell adhesion and proliferation, and in the modulation of cytokine activity. In order to analyse the function of this protein in vivo, the endogenous Sparc locus was disrupted by homologous recombination in murine embryonic stem cells. SPARC-deficient mice (Sparctm1Cam) appear normal and fertile until around 6 months of age, when they develop severe eye pathology characterized by cataract formation and rupture of the lens capsule. The first sign of lens pathology occurs in the equatorial bow region where vacuoles gradually form within differentiating epithelial cells and fibre cells. The lens capsule, however, shows no qualitative changes in the major basal lamina proteins laminin, collagen IV, perlecan or entactin. These mice are an excellent resource for further studies on how SPARC affects cell behaviour in vivo.

Thymic lymphomas in mice with a truncating mutation in Brca2

Inherited mutations in the BRCA2 gene predispose women to breast and ovarian cancer. We created a mutation in the mouse Brca2 gene that terminates translation in exon 11 at 45% of the normal transcript length. Ninety % of Brca2(tm1Cam) homozygous mutant mice die prenatally or perinatally. The location of the Brca2(tm1Cam) mutation differs from those reported previously, and this phenotype suggests a correlation with genotype analogous to that previously reported in humans. Although heterozygote mice have remained free of tumors for 10 months, Brca2(tm1Cam) homozygous mutants that survived to adulthood died with thymic lymphomas between 12 and 14 weeks of age.

Basal chloride currents in murine airway epithelial cells: modulation by CFTR

We have isolated ciliated respiratory cells from the nasal epithelium of wild-type and cystic fibrosis (CF) null mice and used the patch-clamp technique to investigate their basal conductances. Current-clamp experiments on unstimulated cells indicated the presence of K+ and Cl- conductances and, under certain conditions, a small Na+ conductance. Voltage-clamp experiments revealed three distinct Cl- conductances. Itv-indep was time and voltage independent with a linear current-voltage (I-V) plot; Iv-act exhibited activation at potentials greater than +/- 50 mV, giving an S-shaped I-V plot; and Ihyp-act was activated by hyperpolarizing potentials and had an inwardly rectified I-V plot. The current density sequence was Ihyp-act = Iv-act >> Itv-indep. These conductances had Cl(-)-to-N-methyl-D-glucamine cation permeability ratios of between 2.8 and 10.3 and were unaffected by tamoxifen, flufenamate, glibenclamide, DIDS, and 5-nitro-2-(3-phenylpropylamino) benzoic acid but were inhibited by Zn2+ and Gd3+. Itv-indep and Iv-act were present in wild-type and CF cells at equal density and frequency. However, Ihyp-act was detected in only 3% of CF cells compared with 26% of wild-type cells, suggesting that this conductance may be modulated by cystic fibrosis transmembrane conductance regulator (CFTR).

Involvement of Brca2 in DNA repair

Abnormalities precipitated by a targeted truncation in the murine gene Brca2 define its involvement in DNA repair. In culture, cells harboring truncated Brca2 exhibit a proliferative impediment that worsens with successive passages. Arrest in the G1 and G2/M phases is accompanied by elevated p53 and p21 expression. Increased sensitivity to genotoxic agents, particularly ultraviolet light and methylmethanesulfonate, shows that Brca2 function is essential for the ability to survive DNA damage. But checkpoint activation and apoptotic mechanisms are largely unaffected, thereby implicating Brca2 in repair. This is substantiated by the spontaneous accumulation of chromosomal abnormalities, including breaks and aberrant chromatid exchanges. These findings define a function of Brca2 in DNA repair, whose loss precipitates replicative failure, mutagen sensitivity, and genetic instability reminiscent of Bloom syndrome and Fanconi anemia.

A functional CFTR protein is required for mouse intestinal cAMP-, cGMP- and Ca(2+)-dependent HCO3- secretion

1. Most segments of the gastrointestinal tract secrete HCO3-, but the molecular nature of the secretory mechanisms has not been identified. We had previously speculated that the regulator for intestinal electrogenic HCO3- secretion is the cystic fibrosis transmembrane regulator (CFTR) channel. To prove this hypothesis, we have now measured HCO3- secretion by pH-stat titration, and recorded the electrical parameters of in vitro duodenum, jejunum and ileum of mice deficient in the gene for the CFTR protein ('CF-mice') and their normal littermates. 2. Basal HCO3- secretory rates were reduced in all small intestinal segments of CF mice. Forskolin, PGE2, 8-bromo-cAMP and VIP (cAMP-dependent agonists), heat-stable enterotoxin of Escherichia coli (STa), guanylin and 8-bromo-cGMP (cGMP-dependent agonists) and carbachol (Ca2+ dependent) stimulated both the short-circuit current (Isc) and the HCO3- secretory rate (JHCO3-) in all intestinal segments in normal mice, whereas none of these agonists had any effect on JHCO3- in the intestine of CF mice. 3. To investigate whether Cl(-)-HCO3- exchangers, which have been implicated in mediating the response to some of these agonists in the intestine, were similarly active in the small intestine of normal and CF mice, we studied Cl- gradient-driven 36Cl- uptake into brush-border membrane (BBM) vesicles isolated from normal and CF mouse small intestine. Both the time course and the peak value for 4,4'-diisothiocyanostilbene-2',2-disulphonic acid (DIDS)-inhibited 36Cl- uptake was similar in normal and CF mice BBM vesicles. 4. In summary, the results demonstrate that the presence of the CFTR channel is necessary for agonist-induced stimulation of electrogenic HCO3- secretion in all segments of the small intestine, and all three intracellular signal transduction pathways stimulate HCO3- secretion exclusively via activation of the CFTR channel.

A second dose of a CFTR cDNA-liposome complex is as effective as the first dose in restoring cAMP-dependent chloride secretion to null CF mice trachea

Phase I clinical trials have provided encouraging data suggesting that gene transfer could provide a treatment for cystic fibrosis (CF). However, for all the current viral and nonviral vectors used to deliver the cystic fibrosis transmembrane conductance regulator (CFTR) gene, the duration of CFTR expression is limited, necessitating a repeat dosing regimen to provide a long-term treatment. This study was performed to determine whether a second delivery of a CFTR cDNA-liposome complex could result in a similar level of functional CFTR expression observed after a single delivery and to assess whether the deliveries produced adverse inflammatory responses. CFTR functional expression was assessed by short circuit current measurements of tracheas taken from CF null mice (Cftrtm1Cam) treated with a CFTR cDNA-liposome complex in the upper airways. Mice receiving two deliveries of this complex, the second after the response to the first had declined, showed cAMP-stimulated chloride currents which were not significantly different from normal tracheas or tissues assayed after a single dose of the complex. This double treatment was well tolerated with no discernible inflammation of lung tissue.

The intrinsic Cl- conductance of mouse kidney cortex brush-border membrane vesicles is not related to CFTR

Brush-border membrane vesicles (BBMV) were prepared from whole Balb/c mice kidneys by a Mg2+ precipitation technique. The presence of an intrinsic Cl- conductance co-expressed with Na+/glucose cotransport was inferred by the anion dependence of [14C]glucose uptake and overshoot with inward Na(+)-anion gradients. In Na(+)-equilibrated conditions, an inside-negative membrane potential difference (p.d.) produced by an inward Cl- gradient alone was capable of driving intravesicular [14C]glucose accumulation. The apparent anion conductance had a selectivity of Br- = I- = Cl- > F- > > gluconate, was inhibited by 0.5 mM 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) but was unaffected by 0.5 mM 4,4'-diisothiocyanatostilbene 2,2'-disulphonate (DIDS). BBMV were isolated from mice in which the CFTR gene had been disrupted by a termination mutation (-/-) and compared with normal litter mates (+/+) and heterozygotes (-/+)[18]. [14C]Glucose uptake in NaCl media was significantly greater than glucose uptake in Na gluconate media for all three genotypes measured at 20 s: for homozygous -/- animals [14C]glucose uptake was increased by 2.80 +/- 0.53 fold in Cl- media compared to gluconate media, n = 6; for wild-type +/+, by 2.16 +/- 0.53 fold, n = 8; and for heterozygous +/- animals, by 2.17 +/- 0.45 fold, n = 8. The observation of a Cl-(-)dependent component in BBMV isolated from homozygous -/- mutant animals shows that the chloride conductance in these vesicles cannot be due to CFTR expression.

Normalization of ion transport in murine cystic fibrosis nasal epithelium using gene transfer

The murine nasal epithelium was investigated by the short-circuit current (SCC) technique. Electrogenic sodium absorption was revealed by addition of amiloride and calcium-dependent chloride secretion by the addition of amiloride and calcium-dependent chloride secretion by the addition of 2,5-di-(tert-butyl)-1,4-benzohydroquinone (TBHQ)/ionomycin. In the presence of these agents a further increase in SCC was obtained by addition of forskolin. Epithelia from both cystic fibrosis (CF) null (Cftrtm1Cam) and CF delta F508 (Cftrtm2Cam) mice had enhanced sodium absorption compared with controls, whereas only delta F508 epithelia had increased calcium-dependent chloride secretion. Both strains gave nasal epithelia that showed significantly reduced responses to forskolin, due to the absence of CF transmembrane conductance regulator (CFTR) chloride channels. In Cftrtm2Cam nasal epithelia the forskolin responses were not significantly different from zero. Transfection of these mice with the plasmid pTRIAL10-CFTR2 complexed with cationic liposomes normalized the transporting activity in the nasal epithelium. Basal SCC and calcium-dependent chloride secretion were significantly reduced, whereas CFTR-dependent chloride secretion was increased to normal values. Amiloride-sensitive SCC was reduced by transfection but failed to reach significance. The similarity of murine CF nasal epithelium to that in human CF airways makes the model valuable for gene therapy studies.