Defective neuromuscular synapses in mice lacking amyloid precursor protein (APP) and APP-Like protein 2

Biochemical and genetic studies place the amyloid precursor protein (APP) at the center stage of Alzheimer's disease (AD) pathogenesis. Although mutations in the APP gene lead to dominant inheritance of familial AD, the normal function of APP remains elusive. Here, we report that the APP family of proteins plays an essential role in the development of neuromuscular synapses. Mice deficient in APP and its homolog APP-like protein 2 (APLP2) exhibit aberrant apposition of presynaptic marker proteins with postsynaptic acetylcholine receptors and excessive nerve terminal sprouting. The number of synaptic vesicles at presynaptic terminals is dramatically reduced. These structural abnormalities are accompanied by defective neurotransmitter release and a high incidence of synaptic failure. Our results identify APP/APLP2 as key regulators of structure and function of developing neuromuscular synapses.

Neurotransmitter acetylcholine negatively regulates neuromuscular synapse formation by a Cdk5-dependent mechanism

Synapse formation requires interactions between pre- and postsynaptic cells to establish the connection of a presynaptic nerve terminal with the neurotransmitter receptor-rich postsynaptic apparatus. At developing vertebrate neuromuscular junctions, acetylcholine receptor (AChR) clusters of nascent postsynaptic apparatus are not apposed by presynaptic nerve terminals. Two opposing activities subsequently promote the formation of synapses: positive signals stabilize the innervated AChR clusters, whereas negative signals disperse those that are not innervated. Although the nerve-derived protein agrin has been suggested to be a positive signal, the negative signals remain elusive. Here, we show that cyclin-dependent kinase 5 (Cdk5) is activated by ACh agonists and is required for the ACh agonist-induced dispersion of the AChR clusters that have not been stabilized by agrin. Genetic elimination of Cdk5 or blocking ACh production prevents the dispersion of AChR clusters in agrin mutants. Therefore, we propose that ACh negatively regulates neuromuscular synapse formation through a Cdk5-dependent mechanism.

Tuberculous peritonitis in a haemodialysis patient with elevated serum CA 125 and hypercalcaemia

CA 125, a glycoprotein derived from coelomic epithelium, is used primarily as a marker of epithelial ovarian cancer. However, elevated levels of serum CA 125 have also been detected in other benign and malignant disorders. This study describes a haemodialysis patient who contracted tuberculous peritonitis associated with hypercalcaemia, erythropoietin-resistant anaemia and elevated CA 125, which normalised gradually following antituberculosis treatment. Tuberculous peritonitis should be considered in the differential diagnosis of ascites with elevated serum CA 125. Additionally, CA 125 is a useful marker for monitoring response to tuberculous peritonitis treatment.

Granulocytic sarcoma of the small bowel causing intestinal obstruction

Granulocytic sarcomas of the small bowel are rare. They are discrete tumours of leukaemic myeloblasts and partially matured granulocytes that form in any part of the body. This disease is infrequently seen in patients with acute myeloid leukaemia, and rarely seen in patients without leukaemia. Here we report a case of small bowel obstruction due to granulocytic sarcoma of mid-ileum in a non-leukaemic patient. We also review the literature on treatment and prognosis of this condition.

Cholinergic Input Is Required during Embryonic Development to Mediate Proper Assembly of Spinal Locomotor Circuits

Rhythmic limb movements are controlled by pattern-generating neurons within the ventral spinal cord, but little is known about how these locomotor circuits are assembled during development. At early stages of embryogenesis, motor neurons are spontaneously active, releasing acetylcholine that triggers the depolarization of adjacent cells in the spinal cord. To investigate whether acetylcholine-driven activity is required for assembly of the central pattern-generating (CPG) circuit, we studied mice lacking the choline acetyltransferase (ChAT) enzyme. Our studies show that a rhythmically active spinal circuit forms in ChAT mutants, but the duration of each cycle period is elongated, and right-left and flexor-extensor coordination are abnormal. In contrast, blocking acetylcholine receptors after the locomotor network is wired does not affect right-left or flexor-extensor coordination. These findings suggest that the cholinergic neurotransmitter pathway is involved in configuring the CPG during a transient period of development.

ErbB2 is required for ductal morphogenesis of the mammary gland

The ERBB2/HER2/NEU receptor tyrosine kinase gene is amplified in up to 30% of human breast cancers. The frequent and specific selection of this receptor kinase gene for amplification in breast cancer implies that it has important normal functions in the mammary gland. To investigate the functions of ErbB2 during normal mouse mammary gland development, we transplanted mammary buds from genetically rescued ErbB2(-/-) embryos that express ErbB2 in the cardiac muscle. ErbB2(-/-) mammary buds transplanted to a wild-type mammary fat pad support outgrowth of an epithelial tree that advances only slowly through the mammary fat pad at puberty. This penetration defect is associated with structural defects in terminal end buds, characterized by a decrease in body cell number, an increased presence of cap-like cells in the prelumenal compartment, and the presence of large luminal spaces. Lobuloalveolar development was not affected in glands that developed from ErbB2(-/-) transplanted tissue. The results may have implications for the aggressive phenotypes associated with ERBB2-overexpressing mammary carcinomas.

Embryotrophic factor-3 from human oviductal cells enhances proliferation, suppresses apoptosis and stimulates the expression of the β1 subunit of sodium–potassium ATPase in mouse embryos

BACKGROUND

Embrytrophic factor-3 (ETF-3) from human oviductal cells enhanced the development of mouse preimplantation embryos. This report studied the embryotrophic mechanisms of the molecule.

METHODS AND RESULTS

Mouse embryos were incubated with ETF-3 for 24 h at different stages of development. ETF-3 treatment between 96 and 120 h post-HCG increased the cell count of blastocysts, whilst treatment between 72 and 96 h post-HCG enhanced the expansion and hatching of the blastocysts. ETF-3 increased the cell number of the embryos by suppressing apoptosis and increasing proliferation as determined by TUNEL and bromodeoxyuridine uptake assays, respectively. Real-time quantitative PCR showed that the in vivo developed and ETF-3-treated blastocysts had a significantly higher mRNA copy number of Na/K-ATPase-beta1, but not of hepsin, than that of blastocysts cultured in medium alone. The former gene was associated with cavitation of blastocysts while the latter was related to hatching of blastocyst. The beneficial effect of ETF-3 on blastocyst hatching was also seen when ETF-3-supplemented commercially available sequential culture medium for human embryo culture was used to culture mouse embryos.

CONCLUSIONS

ETF-3 improves embryo development by enhancing proliferation, suppressing apoptosis and stimulating expression of genes related to blastocyst cavitation. Supplementating human embryo culture medium with ETF-3 may improve the success rate in clinical assisted reproduction.

Neural crest stem cells undergo multilineage differentiation in developing peripheral nerves to generate endoneurial fibroblasts in addition to Schwann cells

Neural crest stem cells (NCSCs) persist in peripheral nerves throughout late gestation but their function is unknown. Current models of nerve development only consider the generation of Schwann cells from neural crest, but the presence of NCSCs raises the possibility of multilineage differentiation. We performed Cre-recombinase fate mapping to determine which nerve cells are neural crest derived. Endoneurial fibroblasts, in addition to myelinating and non-myelinating Schwann cells, were neural crest derived, whereas perineurial cells, pericytes and endothelial cells were not. This identified endoneurial fibroblasts as a novel neural crest derivative, and demonstrated that trunk neural crest does give rise to fibroblasts in vivo, consistent with previous studies of trunk NCSCs in culture. The multilineage differentiation of NCSCs into glial and non-glial derivatives in the developing nerve appears to be regulated by neuregulin, notch ligands, and bone morphogenic proteins, as these factors are expressed in the developing nerve, and cause nerve NCSCs to generate Schwann cells and fibroblasts, but not neurons, in culture. Nerve development is thus more complex than was previously thought, involving NCSC self-renewal, lineage commitment and multilineage differentiation.

Somatic mutation of p53 leads to estrogen receptor alpha-positive and -negative mouse mammary tumors with high frequency of metastasis

Approximately 70% of human breast cancers are estrogen receptor alpha (ERalpha)-positive, but the origins of ERalpha-positive and -negative tumors remain unclear. Hormonal regulation of mammary gland development in mice is similar to that in humans; however, most mouse models produce only ERalpha-negative tumors. In addition, these mouse tumors metastasize at a low rate relative to human breast tumors. We report here that somatic mutations of p53 in mouse mammary epithelial cells using the Cre/loxP system leads to ERalpha-positive and -negative tumors. p53 inactivation under a constitutive active WAPCre(c) in prepubertal/pubertal mice, but not under MMTVCre in adult mice, leads to the development of ERalpha-positive tumors, suggesting that target cells or developmental stages can determine ERalpha status in mammary tumors. Importantly, these tumors have a high rate of metastasis. An inverse relationship between the number of targeted cells and median tumor latency was also observed. Median tumor latency reaches a plateau when targeted cell numbers exceed 20%, implying the existence of saturation kinetics for breast carcinogenesis. Genetic alterations commonly observed in human breast cancer including c-myc amplification and Her2/Neu/erbB2 activation were seen in these mouse tumors. Thus, this tumor system reproduces many important features of human breast cancer and provides tools for the study of the origins of ERalpha-positive and -negative breast tumors in mice.

Establishment of a capillary-cumulus model to study the selection of sperm for fertilization by the cumulus oophorus

BACKGROUND

Spermatozoa have to traverse the cumulus oophorus before fertilization in vivo. Evidence suggests that the cumulus oophorus plays an important role in the fertilization process. We describe the establishment of a capillary-cumulus oophorus model with which to study the action of cumulus mass on the function of human spermatozoa.

METHODS

Human cumulus oophorus was aspirated into a glass capillary. Spermatozoa were allowed to pass through the cumulus mass in the capillary from one end of the capillary. The spermatozoa that had traversed the mass were collected at the other end of the capillary and underwent sperm function analyses.

RESULTS

Compared with those spermatozoa cultured in medium alone, spermatozoa exposed to the cumulus mass were more likely to have normal morphology, be capacitated and acrosome reacted, with a distinct motility pattern and better zona-binding capacity.

CONCLUSION

A novel in vitro model for spermatozoa penetration through the cumulus oophorus was established. The model can be applied to investigate the effect of the cumulus oophorus on sperm functions.

The Contribution of d-Mannose, l-Fucose, N-Acetylglucosamine, and Selectin Residues on the Binding of Glycodelin Isoforms to Human Spermatozoa1

Previous data showed that glycodelin-A from amniotic fluid and glycodelin-F from follicular fluid inhibited sperm-zona pellucida binding. Solubilized zona pellucida reduced the binding of glycodelin-F to sperm extract dose dependently. This study demonstrated that the zona pellucida proteins also reduced the binding of glycodelin-A to sperm extract. Ionophore-induced acrosome reaction reduced the binding of iodinated glycodelin-A and -F to sperm, indicating that the glycodelin-binding sites are on the outer acrosomal membrane or on the sperm plasma membrane overlying the acrosome. While the binding of glycodelin-A to sperm was suppressed by mannose and fucose neoglycoproteins, that of glycodelin-F was also reduced by acetylglucosamine neoglycoprotein. Pretreatment of sperm with inhibitors of mannosidase and acetylglucosaminidase reduced the binding of glycodelin-F to sperm. On the other hand, inhibitor of mannosidase but not of acetylglucosaminidase inhibited the binding of glycodelin-A. In a competition binding assay, mannosidase reduced both glycodelin-A and -F binding whereas acetylglucosaminidase reduced only glycodelin-F binding. While fucosidase reduced the binding of both glycodelins, fucosidase inhibitor was marginally active in suppressing the binding of glycodelins to human sperm. Among the selectins tested, only E-selectin had a slight inhibitory effect on the binding of glycodelin-A to sperm. The binding of glycodelin-F was unaffected by selectins and their antibodies. In conclusion, the binding of glycodelin-A to sperm involves mannose, fucose, and possibly E- selectin residues, while that of glycodelin-F involves mannose, fucose, and N-acetylglucosamine but not the selectin residue.

Essential roles of Her2/erbB2 in cardiac development and function

The tyrosine kinase receptor erbB2, also known in humans as Her2, is a member of the epidermal growth factor receptor (EGFR or erbB1) family, which also includes erbB3 and erbB4. The erbBs were discovered in an avian erythroblastosis tumor virus and exhibited similarities to human EGFR (Yarden and Sliwkowski, 2001). Her2/erbB2 is highly expressed in many cancer types. Its overexpression is correlated with a poor prognosis for breast and ovarian cancer patients. ErbB receptors bind to a family of growth factors, termed neuregulins/heregulin (NRG/HRG), which comprise NRG-1, -2, -3, and -4 and include multiple isoforms. ErbB2/Her2 is an orphan receptor that does not bind ligand alone but heterodimerizes with the other erbB receptors for NRG signaling. ErbB2 is expressed in multiple neuronal and non-neuronal tissues in embryos and adult animals, including the heart. Genetic data demonstrated that erbB2 is required for normal embryonic development of neural crest-derived cranial sensory neurons. ErbB2/Her2-null mutant embryos of a trabeculation defect die before embryonic day (E) 11. To study its role at later stages of development, we generated a transgenic mouse line that specifically expresses the rat erbB2 cDNA in the heart under the control of the cardiac-specific alpha-myosin heavy chain promoter. When crossed into the null background, the expression of the rat erbB2 cDNA rescued the cardiac phenotype in the erbB2-null mutant mice that survive until birth but display an absence of Schwann cells and a severe loss of both motor and spinal sensory neurons. To study the role of erbB2 in the adult heart, we generated conditional mutant mice carrying a cardiac-restricted deletion of erbB2. These erbB2 conditional mutants exhibited multiple independent parameters of dilated cardiomyopathy, including chamber dilation, wall thinning, and decreased contractility. Interestingly, treatment of breast cancers overexpressing erbB2 with Herceptin (Trastuzumab), a humanized monoclonal antibody specific to the extracellular domain of erbB2, results in some patients developing cardiac dysfunction. The adverse effect is increased significantly in those patients who also receive the chemotherapeutical agent anthracycline. We found that erbB2-deficient cardiac myocytes are more susceptible to anthracycline-induced cytotoxicity. These results suggest that erbB2 signaling in the heart is essential for the prevention of dilated cardiomyopathy. These lines of mice provide models with which to elucidate the molecular and cellular mechanisms by which erbB2 signaling regulates cardiac functions. These mice also will provide important information for devising strategies to mitigate the cardiotoxic effects of Herceptin treatment, allowing for the potential expanded use of this drug to treat all cancers overexpressing erbB2.

The cardiovascular physiologic actions of urocortin II: acute effects in murine heart failure

Corticotropin-releasing factor (CRF) and its paralogues urocortin (Ucn)I, -II, and -III signal by activating their receptors, CRF receptors (CRFR)1 and -2, to maintain homeostasis through endocrine, autonomic, and behavioral responses. CRFR2 is found in cardiomyocytes and in endothelial and smooth muscle cells of the systemic vasculature. Echocardiography and cardiac catheterization were used in mice to assess the physiologic effects of i.v. UcnII and CRFR2 deficiency on left ventricular function and the systemic vasculature. UcnII treatment augmented heart rate, exhibited potent inotropic and lusitropic actions on the left ventricle, and induced a downward shift of the diastolic pressure-volume relation. UcnII also reduced systemic arterial pressure, associated with a lowering of systemic arterial elastance (end-systolic pressure/stroke volume) and systemic vascular resistance. CRFR2-deficient mice showed no alteration in cardiac contractility or blood pressure in response to UcnII administration, suggesting that the effects of UcnII are specific to CRFR2 function. Pretreatment with a beta-adrenergic receptor antagonist, esmalol, had no effect on the inotropic or lusitropic effects of UcnII in vivo, indicating that its actions are independent of beta-adrenergic receptors. Single i.v. bolus administration of UcnII to a heart failure model (muscle-specific LIM protein-deficient mice) produced significant enhancement of inotropic and lusitropic effects on left ventricular function and improved cardiac output. These results demonstrate the potent cardiovascular physiologic actions of UcnII in both wild-type and cardiomyopathic mice and support a potential beneficial use of this peptide in therapy of congestive heart failure.

Urocortin-II and urocortin-III are cardioprotective against ischemia reperfusion injury: an essential endogenous cardioprotective role for corticotropin releasing factor receptor type 2 in the murine heart

Corticotropin-releasing factor (CRF) receptor type 2beta (CRFR2beta) is expressed in the heart. Urocortin (Ucn)-I activation of CRFR2beta is cardioprotective against ischemic reperfusion (I/R) injury by stimulation of the ERKs1/2 p42, 44. However, by binding CRF receptor type 1, Ucn-I can also activate the hypothalamic stress axis. Ucn-II/stresscopin related peptide and Ucn-III/stresscopin are two new members of the CRF/Ucn-I gene family and are selective for CRFR2beta. We propose that CRFR2beta selective Ucn-II or Ucn-III will protect cardiomyocytes and the ex vivo Langendorff perfused rat heart from I/R injury by activation of ERK1/2-p42, 44. Ucn-II is expressed in mouse cardiomyocytes, and Ucn-II or Ucn-III can bind to CRFR2beta, resulting in ERK1/2-p42, p-44 phosphorylation and cAMP stimulation. Phosphorylation of ERK1/2-p42, p-44 is regulated by the Ras/Raf-1 kinase pathway, independent of adenylate cyclase and, therefore, cAMP activation. Ucn-II and Ucn-III protect cardiomyocytes from I/R injury and reduce the percentage of infarct size:risk ratio in Langendorff perfused rat hearts exposed to regional I/R (P<0.001). The CRFR2 selective antagonist astressin2-B and an ERK1/2-p42, 44 inhibitor abolish the cardioprotective actions of Ucn-II and Ucn-III in reperfusion. Cardiomyocytes isolated from CRFR2-null mice are less resistant to I/R injury, compared with wild-type cardiomyocytes. We propose the use of CRFR2 selective agonists, Ucn-II and Ucn-III, to treat ischemic heart disease because of their potent cardioprotective effects in the murine heart and their minimal impact on the hypothalamic stress axis. We emphasize an important endogenous cardioprotective role for CRFR2beta in the murine heart.

Consensus statement on iodine deficiency disorders in Hong Kong

This article reviews the available data on the study of iodine deficiency disorders in Hong Kong and to discuss the approach towards preventing such disorders in Hong Kong. The importance of iodine and iodine deficiency disorders is described, and the available data on the dietary iodine intake and urinary iodine concentration in different populations of Hong Kong are summarised and discussed. Dietary iodine insufficiency among pregnant women in Hong Kong is associated with maternal goitrogenesis and hypothyroxinaemia as well as neonatal hypothyroidism. Borderline iodine deficiency exists in the expectant mothers in Hong Kong. Women of reproductive age, and pregnant and lactating women should be made aware and educated to have an adequate iodine intake, such as iodised salt, as an interim measure. A steering group involving all stakeholders should be formed to advise on the strategy of ensuring adequate iodine intake, including universal iodisation of salt in Hong Kong. Continuous surveillance of iodine status in the Hong Kong population is necessary.

Identification of novel genes expressed during spermatogenesis in stage-synchronized rat testes by differential display

The molecular mechanism regulating spermatogenesis at different developmental stages remains largely unknown. In a vitamin A-deficiency (VAD) rat model, five distinct histologically defined, stage-synchronized testes: (i) resting spermatogonia and preleptotene spermatocytes at Day 0 of post-vitamin A treatment (PVA); (ii) early pachytene spermatocytes at Day 7 PVA; (iii) late pachytene at Day 15 PVA; (iv) round spermatids at Day 25 PVA; and (v) elongated spermatids at Day 35 PVA were used to study gene expression profiles by mRNA differential display. Twenty-four differentially expressed cDNA fragments were identified and cloned; oligonucleotide sequence analyses indicated that there are 12 novel gene sequences, half of which share no apparent match in current GenBank/EMBL databases. Other 12 VAD clones share sequence homology to membrane channel and transport, transcription and translation, cell cycle and morphogenesis, inducer and transducer, surface or secreted glycoproteins or enzymes, and other miscellaneous molecules. Semi-quantitative RT-PCR analyses against different stages of VAD testes demonstrated: (i) restricted expression of VAD1.2 and 1.3 (novel) on Day 25 PVA when round spermatids form; (ii) escalating pattern of VAD12 (Cx43) in Sertoli cells; and (iii) relative constant levels of VAD4 (A5D3), VAD26.1 (ribonuclease), and VAD27 (GRP8) in spermatogenesis.

Zona-binding inhibitory factor-1 from human follicular fluid is an isoform of glycodelin

Zona-binding inhibitory factor-1 (ZIF-1), a glycoprotein in human follicular fluid, reduces the binding of spermatozoa to the zona pellucida. ZIF-1 has a number of properties similar to those of glycodelin-A from human follicular fluid. The objective of this study was to compare the biochemical characteristics of these two glycoproteins. N-terminal sequencing and protease-digested peptide mapping showed that ZIF-1 and glycodelin-A have the same protein core. However, these glycoproteins differ in their oligosaccharide chains, as demonstrated by fluorophore-assisted carbohydrate electrophoresis, lectin-binding ability, and isoelectric focusing. ZIF-1 inhibited spermatozoa-zona pellucida binding slightly more than did glycodelin-A and significantly suppressed progesterone-induced acrosome reaction of human spermatozoa. Indirect immunofluorescence staining revealed specific binding of glycodelin-A and ZIF-1 to the acrosome region of human spermatozoa, where ZIF-1 produced a stronger signal than did glycodelin-A at the same protein concentration. These data suggest that ZIF-1 is a differentially glycosylated isoform of glycodelin that potently inhibits human sperm-egg interaction. Future study on the function role of ZIF-1 would provide a better understanding of the regulation of fertilization in humans.

Corticotropin-releasing factor receptor-2-deficient mice display abnormal homeostatic responses to challenges of increased dietary fat and cold

Corticotropin-releasing factor (CRF) and its family of ligands are key regulators of energy balance. These ligands function via activation of their two receptors, CRFR1 and CRFR2. CRFR1 has been shown to be the dominant receptor in activation of the hypothalamic-pituitary-adrenal axis in response to stress as well as a key mediator of anxiety in the limbic system. To specifically examine the role of CRFR2 in energy balance, mice deficient for CRFR2 were exposed to physiological perturbations of homeostasis, including high-fat diet, repeated cold stress, and glucose and insulin challenges, and their responses measured. While on a high-fat diet, CRFR2-mutant mice consumed substantially more food and maintaining the same weight but had significantly lower body fat and lower plasma lipids than their wild-type littermates. These mice were also less inclined to develop diet-induced insulin resistance and more sensitive to changes in plasma glucose, indicating increased insulin sensitivity. Following repeated cold stress, mutant mice had significantly lower body fat and a transient reduction in feed efficiency, despite similar body weights, suggesting a possible preference for fat as an energy substrate. Elevated levels of uncoupling protein-1 in brown adipose tissue as well as smaller white and brown adipocytes from CRFR2-mutant mice were indications of possible increased sympathetic tone. These results demonstrate that CRFR2 plays a critical role in regulation of energy expenditure and is important for responses to homeostatic challenges.

Mice lacking methyl-CpG binding protein 1 have deficits in adult neurogenesis and hippocampal function

DNA methylation-mediated epigenetic regulation plays critical roles in regulating mammalian gene expression, but its role in normal brain function is not clear. Methyl-CpG binding protein 1 (MBD1), a member of the methylated DNA-binding protein family, has been shown to bind methylated gene promoters and facilitate transcriptional repression in vitro. Here we report the generation and analysis of MBD1-/- mice. MBD1-/- mice had no detectable developmental defects and appeared healthy throughout life. However, we found that MBD1-/- neural stem cells exhibited reduced neuronal differentiation and increased genomic instability. Furthermore, adult MBD1-/- mice had decreased neurogenesis, impaired spatial learning, and a significant reduction in long-term potentiation in the dentate gyrus of the hippocampus. Our findings indicate that DNA methylation is important in maintaining cellular genomic stability and is crucial for normal neural stem cell and brain functions.

Embryotrophic factor-3 from human oviductal cells affects the messenger RNA expression of mouse blastocyst

Our previous results showed that embryotrophic factor-3 (ETF-3) from human oviductal cells increased the size and hatching rate of mouse blastocysts in vitro. The present study investigated the production of ETF-3 by an immortalized human oviductal cell line (OE-E6/E7) and the effects of ETF-3 on the mRNA expression of mouse embryos. The ETF-3 was purified from primary oviductal cell conditioned media using sequential liquid chromatographic systems, and antiserum against ETF-3 was raised. The ETF-3-supplemented Chatot-Ziomek-Bavister medium was used to culture Day 1 MF1 x BALB/c mouse embryos for 4 days. The ETF-3 treatment significantly enhanced the mouse embryo blastulation and hatching rate. The antiserum, at concentrations of 0.03-3%, abolished the embryotrophic effect of ETF-3. Positive ETF-3 immunoreactivity was detected in the primary oviductal cells, OE-E6/E7, and blastocysts derived from ETF-3 treatment. Vero cells (African Green Monkey kidney cell line), fibroblasts, and embryos cultured in control medium did not possess ETF-3 immunoreactivity. The mRNA expression patterns of the treated embryos were studied at the blastocyst stage by mRNA differential display reverse transcription-polymerase chain reaction (DDRT-PCR). The DDRT-PCR showed that some of the mRNAs were differentially expressed after ETF-3 treatment. Twelve of the differentially expressed mRNAs that had high homology with cDNA sequences in the GenBank were selected for further characterization. The differential expression of seven of these mRNAs (ezrin, heat shock 70-kDa protein, cytochrome c oxidase subunit VIIa-L precursor, proteinase-activated receptor 2, eukaryotic translation initiation factor 2beta, cullin 1, and proliferating cell nuclear antigen) was confirmed by semiquantitative RT-PCR. In conclusion, immortalized oviductal cells produce ETF-3, which influences mRNA expression of mouse blastocyst.

Aberrant patterning of neuromuscular synapses in choline acetyltransferase-deficient mice

In this study we examined the developmental roles of acetylcholine (ACh) by establishing and analyzing mice lacking choline acetyltransferase (ChAT), the biosynthetic enzyme for ACh. As predicted, ChAT-deficient embryos lack both spontaneous and nerve-evoked postsynaptic potentials in muscle and die at birth. In mutant embryos, abnormally increased nerve branching occurs on contact with muscle, and hyperinnervation continues throughout subsequent prenatal development. Postsynaptically, ACh receptor clusters are markedly increased in number and occupy a broader muscle territory in the mutants. Concomitantly, the mutants have significantly more motor neurons than normal. At an ultrastructural level, nerve terminals are smaller in mutant neuromuscular junctions, and they make fewer synaptic contacts to the postsynaptic muscle membrane, although all of the typical synaptic components are present in the mutant. These results indicate that ChAT is uniquely essential for the patterning and formation of mammalian neuromuscular synapses.

Colonic epithelial expression of ErbB2 is required for postnatal maintenance of the enteric nervous system

We utilized the Cre-LoxP system to establish erbB2 conditional mutant mice in order to investigate the role of erbB2 in postnatal development of the enteric nervous system. The erbB2/nestin-Cre conditional mutants exhibit retarded growth, distended colons, and premature death, resembling human Hirschsprung's disease. Enteric neurons and glia are present at birth in the colon of erbB2/nestin-Cre mutants; however, a marked loss of multiple classes of enteric neurons and glia occurs by 3 weeks of age. Furthermore, we demonstrate that the requirement for erbB2 in maintaining the enteric nervous system is not cell autonomous, but rather erbB2 signaling in the colonic epithelia is required for the postnatal survival of enteric neurons and glia.

The bound leading the bound: target-derived receptors act as guidance cues

Developing axons are guided to their targets by chemoattractive and chemorepulsive ligands. Ledda et al., in this issue of Neuron, demonstrate that the target-derived receptor glial cell line-derived neurotrophic factor receptor alpha1 (GFRalpha1) can also act in trans as an axon guidance molecule for neurons.