Ectopic localization of putative AII amacrine cells in the outer plexiform layer of the developing FVB/N mouse retina

The FVB/N mouse is a model of retinitis pigmentosa which shows a rapid loss of photoreceptors during early postnatal (P) life. We investigated the cellular localization of glycine transporter 1 (GlyT-1) in the developing FVB/N mouse retina. In control retinas, the developmental pattern of GlyT-1-immunoreactive amacrine cells was well in accordance with a previous report. However, in the FVB/N mouse retina, some GlyT-1-labeled amacrine cells sent their processes into the outer plexiform layer (OPL) from P14 onward. From P21 onward, GlyT-1-labeled cells were visible in the OPL. These cells were further characterized by double-label immunofluorescence experiments with an antiserum against disabled 1 (Dab-1), and showed Dab-1 immunoreactivity, indicating that these cells are putative AII amacrine cells. These results clearly demonstrate that AII amacrine cells have the potential capacity to respond to photoreceptor degeneration by migrating or sprouting their processes into the OPL in the developing FVB/N mouse retina.This study was supported by a Korea Research Foundation Grant (2001, PF0005) from the Ministry of Education     

Squamous cell carcinomas of the skin at ear tag sites in aged FVB/N mice

We report the development of squamous cell carcinomas (SCCs) of the skin at or near the site of ear tags composed of a nickel-copper alloy and used for identification during the course of a long-term study of incipient congenic FVB/N mice containing the human BCL6 transgene (FVB.Cg-Tg[tetO-BCL6]Bbn Tg[EmicroSR-tTa]83Bop), their littermate controls, and wild-type FVB/N. Of a total population of 160 mice, 14 (8.8%) developed SCCs in the tagged (right) ear after a median observation period of 25 months, but none of the animals developed tumors in the opposite ear (P = 0.0001). Nine of the fourteen mice with SCCs had to be euthanized because they were thought to be in distress from the ear condition, but the remaining five died or were euthanized for other reasons related to the research study. These animals ranged in age from 331 to 921 days at the time of death. Five of the tumors were well-differentiated (grade 1) SCCs; the remainder were grade 3 and tended to be deeply invasive neoplasms with undifferentiated areas containing a spindle cell component. One of these metastasized to kidney. When using the FVB/N mouse strain for long-term studies, it is necessary to consider that nearly 9% of the population may develop SCCs at or near ear-tag sites that may necessitate early removal of the animal.     

Sequencing and characterisation of the FVB/NJ mouse genome

ABSTRACT: BACKGROUND: The FVB/NJ mouse strain has its origins in a colony of outbred Swiss mice established in 1935 at the National Institutes of Health. Mice derived from this source were selectively bred for sensitivity to histamine diphosphate and the B strain of Friend leukemia virus. This led to the establishment of the FVB/N inbred strain, which was subsequently imported to the Jackson Laboratory and designated FVB/NJ. The FVB/NJ mouse has several distinct characteristics, such as large pronuclear morphology, vigorous reproductive performance, and consistently large litters that make it highly desirable for transgenic strain production and general purpose use. RESULTS: Using next-generation sequencing technology, we have sequenced the genome of FVB/NJ to approximately 50-fold coverage, and have generated a comprehensive catalog of single nucleotide polymorphisms, small insertion/deletion polymorphisms, and structural variants, relative to the reference C57BL/6J genome. We have examined a previously identified quantitative trait locus for atherosclerosis susceptibility on chromosome 10 and identify several previously unknown candidate causal variants. CONCLUSION: The sequencing of the FVB/NJ genome and generation of this catalog has increased the number of known variant sites in FVB/NJ by a factor of four, and will help accelerate the identification of the precise molecular variants that are responsible for phenotypes observed in this widely-used strain.     

Sequencing and characterization of the FVB/NJ mouse genome

Background

The FVB/NJ mouse strain has its origins in a colony of outbred Swiss mice established in 1935 at the National Institutes of Health. Mice derived from this source were selectively bred for sensitivity to histamine diphosphate and the B strain of Friend leukemia virus. This led to the establishment of the FVB/N inbred strain, which was subsequently imported to the Jackson Laboratory and designated FVB/NJ. The FVB/NJ mouse has several distinct characteristics, such as large pronuclear morphology, vigorous reproductive performance, and consistently large litters that make it highly desirable for transgenic strain production and general purpose use.

Results

Using next-generation sequencing technology, we have sequenced the genome of FVB/NJ to approximately 50-fold coverage, and have generated a comprehensive catalog of single nucleotide polymorphisms, small insertion/deletion polymorphisms, and structural variants, relative to the reference C57BL/6J genome. We have examined a previously identified quantitative trait locus for atherosclerosis susceptibility on chromosome 10 and identify several previously unknown candidate causal variants.

Conclusion

The sequencing of the FVB/NJ genome and generation of this catalog has increased the number of known variant sites in FVB/NJ by a factor of four, and will help accelerate the identification of the precise molecular variants that are responsible for phenotypes observed in this widely used strain.     

Local nonuniformities in the horizontal cell syncytium of the turtle retina

Electrical coupling between horizontal cells of the turtle retina was investigated by means of two microelectrodes, stimulating and recording, inserted into neighboring cells at a fixed horizontal distance apart. Morphological coupling was estimated by studying the flow of the luminescent dye Lucifer yellow. The presence of electrical coupling was confirmed between structures of the same type (L₁ with axon terminals, L₂ withcell bodies, R/G with cells of color type) and absence of coupling between cells of different types was confirmed, although L₁ and L₂ are connected with each other directly by thin axons. The degree of electrical coupling in the syncytium of axon terminals (L₁), with a short (50 µ or less) but fixed distance between the electrodes, may vary by several times depending on the position of the microelectrodes. This local nonuniformity of coupling can be explained by the structural nonuniformity of the network of interconnected axon terminals. Local structural nonuniformities can hardly affect the functional properties of the horizontal cell syncytium under the conditions of photic stimulation of the retina.Institute of Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 2, pp. 239–245, March–April, 1985.     

No effect of NGAL/lipocalin-2 on aggressiveness of cancer in the MMTV-PyMT/FVB/N mouse model for breast cancer

NGAL/lipocalin-2 is a siderophore-binding protein that is highly expressed in several cancers. It is suggested to confer a proliferative advantage to cancer cells. Its expression has been correlated with aggressiveness of breast cancer as determined both in patients and in mouse breast cancer models. This was recently confirmed in two mouse models of spontaneous breast cancer in wild-type and lipocalin-2-deficient mice. We used a similar strategy using a different mouse strain. Lipocalin-2-deficient mice and mouse mammary tumor virus-polyoma middle T antigen (MMTV-PyMT) mice were crossed into the same FVB/N background. All mice developed tumors by week 8. The mice were sacrificed on week 13 and tissue was processed for biochemical and histological analysis. The total tumor volume and number of metastases were quantitated in 26 lipocalin-2-deficient mice and 34 wild-type controls. Lipocalin-2 expression in tumors of MMTV-PyMT-positive and wild-type mice was assessed by quantitative real-time PCR and by immunohistochemistry. The expression of the lipocalin-2 receptors 24p3R and megalin and of Mmp-9, transferrin receptor, and Bdh2 (a producer of a mammalian siderophore) were quantitated by real-time PCR. No significant difference was observed between wild-type and lipocalin-2-deficient mice. Lipocalin-2 was highly expressed in tumors from wild-type mice, but the expression did not correlate with tumor size. No effect of lipocalin-2 was observed with respect to time to tumor appearance, total tumor volume, or to the number of metastases. Histology and gelatinolytic activity of the mammary tumors did not differ between wild-type and lipocalin-2-deficient mice. We conclude that NGAL/lipocalin-2 does not invariably affect the aggressiveness of breast cancers as assessed in mouse models, thus questioning the role of lipocalin-2 in cancer development.     

Somatic gene targeting in the developing and adult mouse retina

Retinogenesis is a developmental process that is tightly regulated both temporally and spatially and is therefore an excellent model system for studying the molecular and cellular mechanisms of neurogenesis in the central nervous system. Understanding of these events in vivo is greatly facilitated by the availability of mouse mutant models, including those with natural or targeted mutations and those with conditional knockout or forced expression of genes. This article reviews these genetic modifications and their contribution to the study of retinogenesis in mammals, with special emphasis on conditional gene targeting approaches.     

Destructive Changes in the Neuronal Structure of the FVB/N Mouse Retina

We applied a series of selective antibodies for labeling the various cell types in the mammalian retina. These were used to identify the progressive loss of neurons in the FVB/N mouse, a model of early onset retinal degeneration produced by a mutation in the pde6b gene. The immunocytochemical studies, together with electroretinogram (ERG) recordings, enabled us to examine the time course of the degenerative changes that extended from the photoreceptors to the ganglion cells at the proximal end of the retina. Our study indicates that photoreceptors in FVB/N undergo a rapid degeneration within three postnatal weeks, and that there is a concomitant loss of retinal neurons in the inner nuclear layer. Although the loss of rods was detected at an earlier age during which time M- and S-opsin molecules were translocated to the cone nuclei; by 6 months all cones had also degenerated. Neuronal remodeling was also seen in the second-order neurons with horizontal cells sprouting processes proximally and dendritic retraction in rod-driven bipolar cells. Interestingly, the morphology of cone-driven bipolar cells were affected less by the disease process. The cellular structure of inner retinal neurons, i.e., ChAT amacrine cells, ganglion cells, and melanopsin-positive ganglion cells did not exhibit any gross changes of cell densities and appeared to be relatively unaffected by the massive photoreceptor degeneration in the distal retina. However, Muller cell processes began to express GFAP at their endfeet at p14, and it climbed progressively to the cell’s distal ends by 6 months. Our study indicates that FVB/N mouse provides a useful model with which to assess possible intervention strategies to arrest photoreceptor death in related diseases.     

Novel Leb-like Helicobacter pylori-binding glycosphingolipid created by the expression of human alpha-1,3/4-fucosyltransferase in FVB/N mouse stomach

The Le(b) mouse was established as a model for investigations of the molecular events following Le(b)-mediated adhesion of Helicobacter pylori to the gastric epithelium. By the expression of a human alpha-1,3/4-fucosyltransferase in the gastric pit cell lineage of FVB/N transgenic mice, a production of Le(b) glycoproteins in gastric pit and surface mucous cells was obtained in this Le(b) mouse, as demonstrated by binding of monoclonal anti-Le(b) antibodies. To explore the effects of the human alpha-1,3/4-fucosyltransferase on glycosphingolipid structures, neutral glycosphingolipids were isolated from stomachs of transgenic alpha-1,3/4-fucosyltransferase-expressing mice. A glycosphingolipid recognized by BabA-expressing H. pylori was isolated and characterized by mass spectrometry and proton NMR as Fuc alpha 2Gal beta 3(Fuc alpha 4)GalNAc beta 4 Gal beta 4 Glc beta 1Cer, i.e., a novel Le(b)-like glycosphingolipid on a ganglio core. In addition, two other novel glycosphingolipids were isolated from the mouse stomach epithelium that were found to be nonbinding with regard to H. pylori. The first was a pentaglycosylceramide, GalNAc beta 3 Gal alpha 3(Fuc alpha 2)Gal beta 4 Glc beta 1Cer, in which the isoglobotetrasaccharide has been combined with Fuc alpha 2 to yield an isoglobotetraosylceramide with an internal blood group B determinant. The second one was an elongated fucosyl-gangliotetraosylceramide, GalNAc beta 3(Fuc alpha 2)Gal beta 3GalNAc beta 4Gal beta 4 Glc beta 1Cer.     

Morphological types of horizontal cell in the retina of the domestic cat.

Two morphologically distinct types of horizontal cell are described from Golgi-stained whole mounts of the cat retina. They are referred to as A-type and B-type cells. The two types differ in their dendritic branching pattern, their overall size and the absence or presence of an axon. At every retinal position the dendrites of B-type cells branch more densely and overlap each other more frequently than do the dendrites of A-type cells. At equivalent retinal positions the dendritic field size of A-type cells is greater than that of B-type cells by a factor of about 1.5. Only B-type cells have an axon, which branches at the end into a large axon terminal system. The axons have no preferred direction of orientation. The stain-ability of horizontal cells by different Golgi methods is discussed.     

Development of electrocardiogram intervals during growth of FVB/N neonate mice

Background  

Electrocardiography remains the best diagnostic tool and therapeutic biomarker for a spectrum of pediatric diseases involving cardiac or autonomic nervous system defects. As genetic links to these disorders are established and transgenic mouse models produced in efforts to understand and treat them, there is a surprising lack of information on electrocardiograms (ECGs) and ECG abnormalities in neonate mice. This is likely due to the trauma and anaesthesia required of many legacy approaches to ECG recording in mice, exacerbated by the fragility of many mutant neonates. Here, we use a non-invasive system to characterize development of the heart rate and electrocardiogram throughout the growth of conscious neonate FVB/N mice.     

Pericentriolar processes of photoreceptor cell basal bodies in the mammalian retina

Pericentriolar processes (arm-like fibers) of the migrating centrioles (diplosome) in differentiating retinal photoreceptor cells were examined in six mammalian species (hamster, vole, rat, rabbit, ferret, cat). These processes emanate in a radial fashion from one end of the centrioles comprising the photoreceptor diplosome. The pericentriolar processes of the basal body are first observed as the diplosome migrates toward the apical plasmalemma, suggesting that centrioles are committed early-on to developing such processes. One pericentriolar process arises from each set of microtubular triplets comprising the centriole and are apicoexternally oriented at an angle of between 30 and 60 degrees with the centriolar axis. Prior to the arrival of one of the centrioles at the apical plasmalemma these processes connect with an electron-dense portion of a centriole-associated vacuole. The diplosome migrates to the apical plasmalemma where one centriole (the presumptive basal body) orients perpendicularly to the apical plasmalemma. The centriole-associated vacuole appears to fuse with the plasmalemma. The pericentriolar processes appear to attach to this fusion site on the plasmalemma which is a region of the membrane characterized by increased electron density (the basilar plate). Invagination of the apical membrane, which occurs at this same site, is accompanied by a lengthening of the microtubules forming a cilium and is observed as an outpouching of the plasmalemma within the aforementioned invagination. The associated vacuole apparently becomes continuous with the apical plasmalemma. These pericentriolar processes appear to be functionally involved in ciliogenesis and offer structural stability between the basal body, the plasmalemma and indirectly the cilium.     

Ionic mechanism for the generation of horizontal cell potentials in isolated axolotl retina

The ionic mechanism of horizontal cell potentials was investigated in the isolated retina of the axolotl Ambystoma mexicanum. The membrane potentials of both receptors and horizontal cells were recorded intracellularly while the ionic composition of the medium flowing over the receptor side of the retina was changed. The membrane potential of the horizontal cell is highly depender side of the retina was changed. The membrane potential of the horizontal cell is highly dependent on the extracellular concentration of sodium. When the external ion concentration of either chloride or potassium was changed independently of the other, there were shifts in the membrane potential of the horizontal cell which could not be explained by changes in the equilibrium potential of these ions. If the external concentrations of both potassium and chloride ions were varied so that the product of their external concentrations did not change, the shift in the membrane potential of the horizontal cell was in the direction predicted by the Nernst equation. The results are consistent with the suggestion that in the dark the receptors release a synaptic transmitter which increases primarily the sodium conductance of the horizontal cell postsynaptic membrane.