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L Tessarollo

Publications and source records attributed to L Tessarollo.

At least 19 recordsLinked to original sources
PubMed2001

Spatial shaping of cochlear innervation by temporally regulated neurotrophin expression.

Previous work suggested qualitatively different effects of neurotrophin 3 (NT-3) in cochlear innervation patterning in different null mutants. We now show that all NT-3 null mutants have a similar phenotype and lose all neurons in the basal turn of the cochlea. To understand these longitudinal deficits in neurotrophin mutants, we have compared the development of the deficit in the NT-3 mutant to the spatial-temporal expression patterns of brain-derived neurotrophic factor (BDNF) and NT-3, using lacZ reporters in each gene and with expression of the specific neurotrophin receptors, trkB and trkC. In the NT-3 mutant, almost normal numbers of spiral ganglion neurons form, but fiber outgrowth to the basal turn is eliminated by embryonic day (E) 13.5. Most neurons are lost between E13.5 and E15.5. During the period preceding apoptosis, NT-3 is expressed in supporting cells, whereas BDNF is expressed mainly in hair cells, which become postmitotic in an apical to basal temporal gradient. During the period of neuronal loss, BDNF is absent from the basal cochlea, accounting for the complete loss of basal turn neurons in the NT-3 mutant. The spatial gradients of neuronal loss in these two mutants appear attributable to spatial-temporal gradients of neurotrophin expression. Our immunocytochemical data show equal expression of their receptors, TrkB and TrkC, in spiral sensory neurons and thus do not relate to the basal turn loss. Mice in which NT-3 was replaced by BDNF show a qualitative normal pattern of innervation at E13.5. This suggests that the pattern of expression of neurotrophins rather than their receptors is essential for the spatial loss of spiral sensory neurons in NT-3 null mutants.

Afferent Pathways↗
PubMed2001

Neurotrophin-3 is required for the survival-differentiation of subsets of developing enteric neurons.

Neurotrophin-3 (NT-3) promotes enteric neuronal development in vitro; nevertheless, an enteric nervous system (ENS) is present in mice lacking NT-3 or TrkC. We thus analyzed the physiological significance of NT-3 in ENS development. Subsets of neurons developing in vitro in response to NT-3 became NT-3 dependent; NT-3 withdrawal led to apoptosis, selectively in TrkC-expressing neurons. Antibodies to NT-3, which blocked the developmental response of enteric crest-derived cells to exogenous NT-3, did not inhibit neuronal development in cultures of isolated crest-derived cells but did so in mixed cultures of crest- and non-neural crest-derived cells; therefore, the endogenous NT-3 that supports enteric neuronal development is probably obtained from noncrest-derived mesenchymal cells. In mature animals, retrograde transport of (125)I-NT-3, injected into the mucosa, labeled neurons in ganglia of the submucosal but not myenteric plexus; injections of (125)I-NT-3 into myenteric ganglia, the tertiary plexus, and muscle, labeled neurons in underlying submucosal and distant myenteric ganglia. The labeling pattern suggests that NT-3-dependent submucosal neurons may be intrinsic primary afferent and/or secretomotor, whereas NT-3-dependent myenteric neurons innervate other myenteric ganglia and/or the longitudinal muscle. Myenteric neurons were increased in number and size in transgenic mice that overexpress NT-3 directed to myenteric ganglia by the promoter for dopamine beta-hydroxylase. The numbers of neurons were regionally reduced in both plexuses in mice lacking NT-3 or TrkC. A neuropoietic cytokine (CNTF) interacted with NT-3 in vitro, and if applied sequentially, compensated for NT-3 withdrawal. These observations indicate that NT-3 is required for the normal development of the ENS.

Animals↗
PubMed2001

Inactivation of LRG-47 and IRG-47 reveals a family of interferon gamma-inducible genes with essential, pathogen-specific roles in resistance to infection.

The cytokine interferon (IFN)-gamma regulates immune clearance of parasitic, bacterial, and viral infections; however, the underlying mechanisms are poorly understood. Recently, a family of IFN-gamma-induced genes has been identified that encode 48-kD GTP-binding proteins that localize to the endoplasmic reticulum of cells. The prototype of this family, IGTP, has been shown to be required for host defense against acute infections with the protozoan parasite Toxoplasma gondii, but not for normal clearance of the bacterium Listeria monocytogenes and murine cytomegalovirus (MCMV). To determine whether other members of the gene family also play important roles in immune defense, we generated mice that lacked expression of the genes LRG-47 and IRG-47, and examined their responses to representative pathogens. After infection with T. gondii, LRG-47-deficient mice succumbed uniformly and rapidly during the acute phase of the infection; in contrast, IRG-47-deficient mice displayed only partially decreased resistance that was not manifested until the chronic phase. After infection with L. monocytogenes, LRG-47-deficient mice exhibited a profound loss of resistance, whereas IRG-47-deficient mice exhibited completely normal resistance. In addition, both strains displayed normal clearance of MCMV. Thus, LRG-47 and IRG-47 have vital, but distinct roles in immune defense against protozoan and bacterial infections.

Amino Acid Sequence↗
PubMed2001

Mutations in Cdh23 cause nonsyndromic hearing loss in waltzer mice.

Mutations at the waltzer (v) locus result in deafness and vestibular dysfunction due to degeneration of the neuroepithelium within the inner ear. Here, we use a positional cloning approach to show that waltzer encodes a novel cadherin (Cdh23), which is most closely related to the Drosophila Fat protein. A single nucleotide deletion in the v(J) allele and a single nucleotide insertion in the v allele are predicted to truncate each protein near the N-terminus and produce a functional null allele. In situ hybridization analysis showed that Cdh23 is expressed in the sensory hair cells of the inner ear, where it has been suggested to be a molecule critical for crosslinking of the stereocilia. In addition, Cdh23 is expressed in the urticulo-saccular foramen,the ductus reuniens, and Reissner's membrane, suggesting that Cdh23 may also be involved in maintaining the ionic composition of the endolymph. Finally, mutations in human CDH23 have recently been described for two loci, DFNB12 and USH1D, which cause nonsyndromic deafness, identifying waltzer as a mouse model for human hearing loss.

Alleles↗
PubMed2001

Lsh, a SNF2 family member, is required for normal murine development.

Lsh is a member of the SNF2 family of chromatin remodelers, that regulate diverse biological processes such as replication, repair and transcription. Although expression of Lsh is highly tissue specific in adult animals, Lsh mRNA is detectable in multiple tissues during embryogenesis. In order to determine the physiologic role of Lsh during murine development and to assess its unique function in adult mice, we performed targeted deletion of the Lsh gene using homologous recombination in murine embryonic stem cells. Lsh-/- embryos occurred with the expected Mendelian frequency after implantation and during embryogenesis. However, Lsh-/- mice died within a few hours after birth. Furthermore, newborn mice were 22% lower in weight in comparison with their littermates and showed renal lesions. Thus Lsh is a non-redundant member of the SNF2 family and is essential for normal murine development and survival.

Animals↗
PubMed2001

A highly efficient Escherichia coli-based chromosome engineering system adapted for recombinogenic targeting and subcloning of BAC DNA.

Recently, a highly efficient recombination system for chromosome engineering in Escherichia coli was described that uses a defective lambda prophage to supply functions that protect and recombine a linear DNA targeting cassette with its substrate sequence (Yu et al., 2000, Proc. Natl. Acad. Sci. USA 97, 5978-5983). Importantly, the recombination is proficient with DNA homologies as short as 30-50 bp, making it possible to use PCR-amplified fragments as the targeting cassette. Here, we adapt this prophage system for use in bacterial artificial chromosome (BAC) engineering by transferring it to DH10B cells, a BAC host strain. In addition, arabinose inducible cre and flpe genes are introduced into these cells to facilitate BAC modification using loxP and FRT sites. Next, we demonstrate the utility of this recombination system by using it to target cre to the 3' end of the mouse neuron-specific enolase (Eno2) gene carried on a 250-kb BAC, which made it possible to generate BAC transgenic mice that specifically express Cre in all mature neurons. In addition, we show that fragments as large as 80 kb can be subcloned from BACs by gap repair using this recombination system, obviating the need for restriction enzymes or DNA ligases. Finally, we show that BACs can be modified with this recombination system in the absence of drug selection. The ability to modify or subclone large fragments of genomic DNA with precision should facilitate many kinds of genomic experiments that were difficult or impossible to perform previously and aid in studies of gene function in the postgenomic era.

Animals↗
PubMed2001

Targeted disruption of the Nijmegen breakage syndrome gene NBS1 leads to early embryonic lethality in mice.

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive human disease whose clinical features include growth retardation, immunodeficiency, and increased susceptibility to lymphoid malignancies. Cells from NBS patients exhibit gamma-irradiation sensitivity, S-phase checkpoint defects, and genomic instability. Recently, it was demonstrated that this chromosomal breakage syndrome is caused by mutations in the NBS1 gene that result in a total loss of full-length NBS1 expression. Here we report that in contrast to the viability of NBS patients, targeted inactivation of NBS1 in mice leads to early embryonic lethality in utero and is associated with poorly developed embryonic and extraembryonic tissues. Mutant blastocysts showed greatly diminished expansion of the inner cell mass in culture, and this finding suggests that NBS1 mediates essential functions during proliferation in the absence of externally induced damage. Together, our results indicate that the complex phenotypes observed in NBS patients and cell lines may not result from a complete inactivation of NBS1 but may instead result from hypomorphic truncation mutations compatible with cell viability.

Animals↗
PubMed2001

Human BRCA1 gene rescues the embryonic lethality of Brca1 mutant mice.

Half of all familial breast cancers are due to mutation in the BRCA1 gene. However, despite its importance, attempts to model BRCA1-induced disease in the mouse have been disappointing. Heterozygous Brca1 knockout mice do not develop mammary tumors and homozygous knockout mice die during embryogenesis from ill-defined causes. Sequence analysis has shown that the coding region, genomic organization, and regulatory sequences of the human and mouse genes are not well conserved. This has raised the question of whether the mouse can serve as an effective model for functional analysis of the human BRCA1 gene. To address this question we have introduced a bacterial artificial chromosome containing the human BRCA1 gene into the germline of Brca1 knockout mice. Surprisingly, we have found that the embryonic lethality of Brca1 knockout mice is rescued by the human transgene. We also show that expression of human BRCA1 transgene mirrors the endogenous murine gene. Our "humanized" transgenic mice can serve as a model system for functional analyses of the human BRCA1 gene. Published 2001 Wiley-Liss, Inc.

Animals↗
PubMed2001

Neurotrophin-3 modulates noradrenergic neuron function and opiate withdrawal.

Somatic symptoms and aversion of opiate withdrawal, regulated by noradrenergic signaling, were attenuated in mice with a CNS-wide conditional ablation of neurotrophin-3. This occurred in conjunction with altered cAMP-mediated excitation and reduced upregulation of tyrosine hydroxylase in A6 (locus coeruleus) without loss of neurons. Transgene-derived NT-3 expressed by noradrenergic neurons of conditional mutants restored opiate withdrawal symptoms. Endogenous NT-3 expression, strikingly absent in noradrenergic neurons of postnatal and adult brain, is present in afferent sources of the dorsal medulla and is upregulated after chronic morphine exposure in noradrenergic projection areas of the ventral forebrain. NT-3 expressed by non-catecholaminergic neurons may modulate opiate withdrawal and noradrenergic signalling.

Aging↗
PubMed2001

Cse1l is essential for early embryonic growth and development.

The CSE1L gene, the human homologue of the yeast chromosome segregation gene CSE1, is a nuclear transport factor that plays a role in proliferation as well as in apoptosis. CSE1 and CSE1L are essential genes in Saccharomyces cerevisiae and mammalian cells, as shown by conditional yeast mutants and mammalian cell culture experiments with antisense-mediated depletion of CSE1L. To analyze whether CSE1L is also essential in vivo and whether its absence can be compensated for by other genes or mechanisms, we have cloned the murine CSE1L gene (Cse1l) and analyzed its tissue- and development-specific expression: Cse1l was detected at embryonic day 7.0 (E7.0), E11.0, E15.0, and E17.0, and in adults, high expression was observed in proliferating tissues. Subsequently, we inactivated the Cse1l gene in embryonic stem cells to generate heterozygous and homozygous knockout mice. Mice heterozygous for Cse1l appear normal and are fertile. However, no homozygous pups were born after interbreeding of heterozygous mice. In 30 heterozygote interbreeding experiments, 50 Cse1l wild-type mice and 100 heterozygotes were born but no animal with both Cse1l alleles deleted was born. Embryo analyses showed that homozygous mutant embryos were already disorganized and degenerated by E5.5. This implicates with high significance (P < 0.0001, Pearson chi-square test) an embryonically lethal phenotype of homozygous murine CSE1 deficiency and suggests that Cse1l plays a critical role in early embryonic development.

Active Transport, Cell Nucleus↗
PubMed2001

Dissection of NT3 functions in vivo by gene replacement strategy.

The development of the peripheral nervous system is governed in part by a family of neurotrophic factors that signal through Trk tyrosine kinase receptors. Neurotrophin 3 (NT3) ablation in mice causes a more severe neuronal phenotype than deletion of its receptor TrkC, suggesting that NT3 acts also through other non-preferred Trk receptors. To study the role of low-affinity ligand receptor interactions in vivo, we have replaced the Nt3 gene with the gene for brain-derived neurotrophic factor (BDNF), a TrkB ligand. As in NT3 and TrkC null mice, the proprioception system of these mutants failed to assemble. However, sensory fiber projections in the embryonic spinal cord suggest chemotropic effects of BDNF in vivo. In the dorsal root ganglia, the developmental dynamic of neuron numbers demonstrates that NT3 is required for activation of TrkB during neurogenesis and that TrkA is required during target tissue innervation. In the inner ear, the ectopic BDNF rescued the severe neuronal deficits caused by NT3 absence, indicating that TrkB and TrkC activate equivalent pathways to promote survival of cochlear neurons. However, specific increased innervation densities suggest unique functions for BDNF and NT3 beyond promoting neuronal survival. This mouse model has allowed the dissection of specific spatiotemporal Trk receptor activation by NT3. Our analysis provides examples of how development can be orchestrated by complex high- and low-affinity interactions between ligand and receptor families.

Animals↗
PubMed2000

The status of voltage-dependent calcium channels in alpha 1E knock-out mice.

It has been hypothesized that R-type Ca currents result from the expression of the alpha(1E) gene. To test this hypothesis we examined the properties of voltage-dependent Ca channels in mice in which the alpha(1E) Ca channel subunit had been deleted. Application of omega-conotoxin GVIA, omega-agatoxin IVA, and nimodipine to cultured cerebellar granule neurons from wild-type mice inhibited components of the whole-cell Ba current, leaving a "residual" R current with an amplitude of approximately 30% of the total Ba current. A minor portion of this R current was inhibited by the alpha(1E)-selective toxin SNX-482, indicating that it resulted from the expression of alpha(1E). However, the majority of the R current was not inhibited by SNX-482. The SNX-482-sensitive portion of the granule cell R current was absent from alpha(1E) knock-out mice. We also identified a subpopulation of dorsal root ganglion (DRG) neurons from wild-type mice that expressed an SNX-482-sensitive component of the R current. However as with granule cells, most of the DRG R current was not blocked by SNX-482. We conclude that there exists a component of the R current that results from the expression of the alpha(1E) Ca channel subunit but that the majority of R currents must result from the expression of other Ca channel alpha subunits.

Animals↗
PubMed2000

Copper chaperone for superoxide dismutase is essential to activate mammalian Cu/Zn superoxide dismutase.

Recent studies in Saccharomyces cerevisiae suggest that the delivery of copper to Cu/Zn superoxide dismutase (SOD1) is mediated by a cytosolic protein termed the copper chaperone for superoxide dismutase (CCS). To determine the role of CCS in mammalian copper homeostasis, we generated mice with targeted disruption of CCS alleles (CCS(-/-) mice). Although CCS(-/-) mice are viable and possess normal levels of SOD1 protein, they reveal marked reductions in SOD1 activity when compared with control littermates. Metabolic labeling with (64)Cu demonstrated that the reduction of SOD1 activity in CCS(-/-) mice is the direct result of impaired Cu incorporation into SOD1 and that this effect was specific because no abnormalities were observed in Cu uptake, distribution, or incorporation into other cuproenzymes. Consistent with this loss of SOD1 activity, CCS(-/-) mice showed increased sensitivity to paraquat and reduced female fertility, phenotypes that are characteristic of SOD1-deficient mice. These results demonstrate the essential role of any mammalian copper chaperone and have important implications for the development of novel therapeutic strategies in familial amyotrophic lateral sclerosis.

Alleles↗
PubMed2000

Loss of brain-derived neurotrophic factor-dependent neural crest-derived sensory neurons in neurotrophin-4 mutant mice.

Peripheral ganglion neurons confer sensory information including touch, pain, temperature, and proprioception. Sensory modality is linked to specific neurotrophin (NTF) requirements. NT-3 supports survival of neurons that differentiate primarily into proprioceptors whereas nerve growth factor and brain-derived neurotrophic factor (BDNF) support subpopulations that transmit nociception and mechanoreception, respectively. We examined sensory neurons of gene-targeted mouse mutants at the NT-4, BDNF, NT-3, and TrkA loci. We show that NT-4 functions early in gangliogenesis, upstream of BDNF. In the absence of NT-4 function, BDNF-dependent, TrkB-expressing neurons fail to appear. The results are consistent with the model that precursor cells intended to become BDNF-dependent mechanoreceptors instead differentiate into NT-3-dependent proprioceptive neurons.

Animals↗
PubMed2000

Pathogen-specific loss of host resistance in mice lacking the IFN-gamma-inducible gene IGTP.

Interferon-gamma (IFN-gamma) is critical for defense against pathogens, but the molecules that mediate its antimicrobial responses are largely unknown. IGTP is the prototype for a family of IFN-gamma-regulated genes that encode 48-kDa GTP-binding proteins that localize to the endoplasmic reticulum. We have generated IGTP-deficient mice and found that, despite normal immune cell development and normal clearance of Listeria monocytogenes and cytomegalovirus infections, the mice displayed a profound loss of host resistance to acute infections of the protozoan parasite Toxoplasma gondii. By contrast, IFN-gamma receptor-deficient mice have increased susceptibility to all three pathogens. Thus, IGTP defines an IFN-gamma-regulated pathway with a specialized role in antimicrobial resistance.

Animals↗