The Sox10(Dom) mouse: modeling the genetic variation of Waardenburg-Shah (WS4) syndrome.
(33/9064)
Hirschsprung disease (HSCR) is a multigenic neurocristopathy clinically recognized by aganglionosis of the distal gastrointestinal tract. Patients presenting with aganglionosis in association with hypopigmentation are classified as Waardenburg syndrome type 4 (Waardenburg-Shah, WS4). Variability in the disease phenotype of WS4 patients with equivalent mutations suggests the influence of genetic modifier loci in this disorder. Sox10(Dom)/+ mice exhibit variability of aganglionosis and hypopigmentation influenced by genetic background similar to that observed in WS4 patients. We have constructed Sox10(Dom)/+ congenic lines to segregate loci that modify the neural crest defects in these mice. Consistent with previous studies, increased lethality of Sox10(Dom)/+ animals resulted from a C57BL/6J locus(i). However, we also observed an increase in hypopigmentation in conjunction with a C3HeB/FeJLe-a/a locus(i). Linkage analysis localized a hypopigmentation modifier of the Dom phenotype to mouse chromosome 10 in close proximity to a previously reported modifier of hypopigmentation for the endothelin receptor B mouse model of WS4. To evaluate further the role of SOX10 in development and disease, we have performed comparative genomic analyses. An essential role for this gene in neural crest development is supported by zoo blot hybridizations that reveal extensive conservation throughout vertebrate evolution and by similar Northern blot expression profiles between mouse and man. Comparative sequence analysis of the mouse and human SOX10 gene have defined the exon-intron boundaries of SOX10 and facilitated mutation analysis leading to the identification of two new SOX10 mutations in individuals with WS4. Structural analysis of the HMG DNA-binding domain was performed to evaluate the effect of human mutations in this region. (+info)
Mice transgenic for an expanded CAG repeat in the Huntington's disease gene develop diabetes.
(34/9064)
The autosomal dominant neurological syndrome of Huntington's disease has been modeled in transgenic mice by the expression of a portion of the human huntingtin gene together with 140 CAG repeats (the R6/2 strain). The mice develop progressive chorea with onset at approximately 9 weeks of age and with death at approximately 13 weeks. Associated symptoms include weight loss and polyuria in the absence of eating or drinking deficits. We have found that these mice have insulin-responsive diabetes. Fasting glucose was 211 + 19 mg/dl in R6/2 mice compared with 93 + 5 mg/dl in C57/B6 controls (n = 12, both groups; P < 0.01). Administration of insulin intraperitoneally led to a reduction in blood glucose. At 12.5 weeks, animals were killed and pancreas weighed and analyzed for insulin and glucagon. Pancreatic mass in R6/2 mice was the same as controls, and islets appeared normal in morphology without lymphocytic infiltration. Immunohistochemical staining showed dramatic reductions in glucagon in the alpha-cells and in insulin in the beta-cells. Direct tissue assays showed glucagon and insulin content were reduced to only 10 and 15% of controls, respectively. Diabetes has been reported as being more common in Huntington's disease and other triplet repeat disorders. The R6/2 mouse should prove useful for elucidating the mechanism of diabetes in these genetic diseases. (+info)
A conserved sequence block in the murine and human TCR J alpha region: assessment of regulatory function in vivo.
(35/9064)
Temporal control of rearrangement at the TCR alpha/delta locus is crucial for development of the gamma delta and alpha beta T cell lineages. Because the TCR delta locus is embedded within the alpha locus, rearrangement of any V alpha-J alpha excises the delta locus, precluding expression of a functional gamma delta TCR. Approximately 100 kb spanning the C delta-C alpha region has been sequenced from both human and mouse, and comparison has revealed an unexpectedly high degree of conservation between the two. Of interest in terms of regulation, several highly conserved sequence blocks (> 90% over > 50 bp) were identified that did not correspond to known regulatory elements such as the TCR alpha and delta enhancers or to coding regions. One of these blocks lying between J alpha 4 and J alpha 3, which appears to be conserved in other vertebrates, has been shown to augment TCR alpha enhancer function in vitro and differentially bind factors from nuclear extracts. To further assess a plausible regulatory role for this element, we have created mice in which this conserved sequence block is either deleted or replaced with a neomycin resistance gene driven by the phosphoglycerate kinase promoter (pgk-neor). Deletion of this conserved sequence block in vivo did have a local effect on J alpha usage, echoing the in vitro data. However, its replacement with pgk-neor had a much more dramatic, long range effect, perhaps underscoring the importance of maintaining overall structure at this locus. (+info)
A novel receptor tyrosine kinase, Mer, inhibits TNF-alpha production and lipopolysaccharide-induced endotoxic shock.
(36/9064)
The regulation of monocyte function and the inhibition of TNF-alpha production during bacterial sepsis are critical in attenuating adverse host responses to endotoxemia. To study the function of a novel receptor tyrosine kinase, mer, that is expressed in monocytes, we generated mice (merkd) that lack the signaling tyrosine kinase domain. Upon LPS challenge, merkd animals died of endotoxic shock (15/17, 88.2%), whereas control wild-type mice survived (1/15, 6.7% died). Susceptible merkd mice exhibited edema, leukocyte infiltration, and signs of endotoxic shock that correlated with higher levels of TNF-alpha found in the serum of merkd mice as compared with wild-type control animals. Death due to LPS-induced endotoxic shock in merkd mice was blocked by administration of anti-TNF-alpha Ab, suggesting that overproduction of this cytokine was principally responsible for the heightened suseptibility. The increase in TNF-alpha production appeared to be the result of a substantial increase in the LPS-dependent activation of NF-kappa B nuclear translocation resulting in greater TNF-alpha production by macrophages from merkd mice. Thus, Mer receptor tyrosine kinase signaling participates in a novel inhibitory pathway in macrophages important for regulating TNF-alpha secretion and attenuating endotoxic shock. (+info)
Abnormal photoresponses and light-induced apoptosis in rods lacking rhodopsin kinase.
(37/9064)
Phosphorylation is thought to be an essential first step in the prompt deactivation of photoexcited rhodopsin. In vitro, the phosphorylation can be catalyzed either by rhodopsin kinase (RK) or by protein kinase C (PKC). To investigate the specific role of RK, we inactivated both alleles of the RK gene in mice. This eliminated the light-dependent phosphorylation of rhodopsin and caused the single-photon response to become larger and longer lasting than normal. These results demonstrate that RK is required for normal rhodopsin deactivation. When the photon responses of RK-/- rods did finally turn off, they did so abruptly and stochastically, revealing a first-order backup mechanism for rhodopsin deactivation. The rod outer segments of RK-/- mice raised in 12-hr cyclic illumination were 50% shorter than those of normal (RK+/+) rods or rods from RK-/- mice raised in constant darkness. One day of constant light caused the rods in the RK-/- mouse retina to undergo apoptotic degeneration. Mice lacking RK provide a valuable model for the study of Oguchi disease, a human RK deficiency that causes congenital stationary night blindness. (+info)
Immunomodulation of experimental autoimmune encephalomyelitis by oral administration of copolymer 1.
(38/9064)
The activity of copolymer 1 (Cop 1, Copaxone, glatiramer acetate) in suppressing experimental autoimmune encephalomyelitis (EAE) and in the treatment of multiple sclerosis patients when injected parenterally has been extensively demonstrated. In the present study we addressed the question of whether Cop 1 can induce oral tolerance to EAE similar to myelin basic protein (MBP). We now have demonstrated that oral Cop 1 inhibited EAE induction in both rats and mice. Furthermore, oral Cop 1 was more effective than oral MBP in suppressing EAE in rats. The beneficial effect of oral Cop 1 was found to be associated with specific inhibition of the proliferative and Th1 cytokine secretion responses to MBP of spleen cells from Cop 1-fed mice and rats. In all of these assays, oral Cop 1 was more effective than oral MBP. The tolerance induced by Cop 1 could be adoptively transferred with spleen cells from Cop 1-fed animals. Furthermore, Cop 1-specific T cell lines, which inhibit EAE induction in vivo, could be isolated from the above spleen cells. These T cell lines secrete the anti-inflammatory cytokines IL-10 and transforming growth factor type beta, but not IL-4, in response to both Cop 1 and MBP. In conclusion, oral Cop 1 has a beneficial effect on the development of EAE that is associated with down-regulation of T cell immune responses to MBP and is mediated by Th2/3 type regulatory cells. These results suggest that oral administration of Cop 1 may modulate multiple sclerosis as well. (+info)
Neurotrophic factors [activity-dependent neurotrophic factor (ADNF) and basic fibroblast growth factor (bFGF)] interrupt excitotoxic neurodegenerative cascades promoted by a PS1 mutation.
(39/9064)
Although an excitotoxic mechanism of neuronal injury has been proposed to play a role in chronic neurodegenerative disorders such as Alzheimer's disease, and neurotrophic factors have been put forward as potential therapeutic agents, direct evidence is lacking. Taking advantage of the fact that mutations in the presenilin-1 (PS1) gene are causally linked to many cases of early-onset inherited Alzheimer's disease, we generated PS1 mutant knock-in mice and directly tested the excitotoxic and neurotrophic hypotheses of Alzheimer's disease. Primary hippocampal neurons from PS1 mutant knock-in mice exhibited increased production of amyloid beta-peptide 42/43 and increased vulnerability to excitotoxicity, which occurred in a gene dosage-dependent manner. Neurons expressing mutant PS1 exhibited enhanced calcium responses to glutamate and increased oxyradical production and mitochondrial dysfunction. Pretreatment with either basic fibroblast growth factor or activity-dependent neurotrophic factor protected neurons expressing mutant PS1 against excitotoxicity. Both basic fibroblast growth factor and activity-dependent neurotrophic factor stabilized intracellular calcium levels and abrogated the increased oxyradical production and mitochondrial dysfunction otherwise caused by the PS1 mutation. Our data indicate that neurotrophic factors can interrupt excitotoxic neurodegenerative cascades promoted by PS1 mutations. (+info)
Identification of mutations that cause cell migration defects in mosaic clones.
(40/9064)
Cell movement is an important feature of animal development, wound healing and tumor metastasis; however, the mechanisms underlying cell motility remain to be elucidated. To further our understanding, it would be useful to identify all of the proteins that are essential for a cell to migrate, yet such information is not currently available for any cell type. We have carried out a screen for mutations affecting border cell migration in Drosophila. Mutations that cause defects in mosaic clones were identified, so that genes that are also required for viability could be detected. From 6000 mutagenized lines, 20 mutations on chromosome 2R were isolated that cause defects in border cell position. One of the mutations was dominant while all of the recessive mutations appeared to be homozygous lethal. This lethality was used to place the mutations into 16 complementation groups. Many of the mutations failed to complement cytologically characterized deficiencies, allowing their rapid mapping. Mutations in three loci altered expression of a marker gene in the border cells, whereas the remaining mutations did not. One mutation, which caused production of supernumerary border cells, was found to disrupt the costal-2 locus, indicating a role for Hedgehog signaling in border cell development. This screen identified many new loci required for border cell migration and our results suggest that this is a useful approach for elucidating the mechanisms involved in cell motility. (+info)