Role of novel protein kinase C isoforms in Lyme arthritis

Inflammation caused by Borrelia burgdorferi infection occurs as a result of induction of pro-inflammatory cytokines from activation of multiple signalling pathways. It has previously been shown that mitogen-activated protein kinase (MAPK) and Janus kinase/signal transducer and activator of transcription signalling pathways are activated by B. burgdorferi in cultured human chondrocytes. Protein kinase C (PKC) signalling pathways are potential candidates that may control these downstream signalling pathways. Here we show that B. burgdorferi infection leads to phosphorylation and activation of novel PKC isoforms (PKC delta, epsilon, eta and theta) in a time-dependent manner. A specific inhibitor of novel PKC isoforms blocked the induction of pro-inflammatory molecules in response to B. burgdorferi infection as did transient transfection of novel PKC dominant-negative plasmids into chondrocytes. B. burgdorferi-induced p38 MAPK phosphorylation was also significantly inhibited by an inhibitor of novel PKC isoforms, suggesting that PKC activation occurs upstream of p38 activation. In vivo, administration of an inhibitor of classical and novel PKC isoforms to C3H/HeN mice infected with B. burgdorferi resulted in significantly reduced ankle inflammation and swelling. In conclusion, these data suggest that novel PKC isoforms are specifically activated by B. burgdorferi infection and this can contribute to the regulation of inflammation in vitro and in vivo.

The nonhomologous end joining factor Artemis suppresses multi-tissue tumor formation and prevents loss of heterozygosity

Nonhomologous end joining (NHEJ) is a critical DNA repair pathway, with proposed tumor suppression functions in many tissues. Mutations in the NHEJ factor ARTEMIS cause radiation-sensitive severe combined immunodeficiency in humans and may increase susceptibility to lymphoma in some settings. We now report that deficiency for Artemis (encoded by Dclre1c/Art in mouse) accelerates tumorigenesis in several tissues in a Trp53 heterozygous setting, revealing tumor suppression roles for NHEJ in lymphoid and non-lymphoid cells. We also show that B-lineage lymphomas in these mice undergo loss of Trp53 heterozygosity by allele replacement, but arise by mechanisms distinct from those in Art Trp53 double null mice. These findings demonstrate a general tumor suppression function for NHEJ, and reveal that interplay between NHEJ and Trp53 loss of heterozygosity influences the sequence of multi-hit oncogenesis. We present a model where p53 status at the time of tumor initiation is a key determinant of subsequent oncogenic mechanisms. Because Art deficient mice represent a model for radiation-sensitive severe combined immunodeficiency, our findings suggest that these patients may be at risk for both lymphoid and non-lymphoid cancers.

E2f4 is required for normal development of the airway epithelium

The airway epithelium is comprised of specialized cell types that play key roles in protecting the lungs from environmental insults. The cellular composition of the murine respiratory epithelium is established during development and different cell types populate specific regions along the airway. Here we show that E2f4-deficiency leads to an absence of ciliated cells from the entire airway epithelium and the epithelium of the submucosal glands in the paranasal sinuses. This defect is particularly striking in the nasal epithelium of E2f4-/- mice where ciliated cells are replaced by columnar secretory cells that produce mucin-like substances. In addition, in the proximal lung, E2f4 loss causes a reduction in Clara cell marker expression indicating that Clara cell development is also affected. These defects arise during embryogenesis and, in the nasal epithelium, appear to be independent of any changes in cell proliferation, the principal process regulated by members of the E2f family of transcription factors. We therefore conclude that E2f4 is required to determine the appropriate development of the airway epithelium. Importantly, the combination of no ciliated cells and excess mucous cells can account for the chronic rhinitis and increased susceptibility to opportunistic infections that causes the postnatal lethality of E2f4 mutant mice.

A novel somatic mouse model to survey tumorigenic potential applied to the Hedgehog pathway

We report a novel mouse model for the generation of sporadic tumors and show the efficiency of this approach by surveying Hedgehog (Hh)-related tumors. Up-regulation of the Hh pathway is achieved by conditionally regulated expression of an activated allele of Smoothened (R26-SmoM2) using either sporadic leakage or global postnatal induction of a ubiquitously expressed inducible Cre transgene (CAGGS-CreER). Following postnatal tamoxifen induction, CAGGS-CreER; R26-SmoM2 mice developed tumors with short latency and high penetrance. All mice exhibited rhabdomyosarcoma and basal cell carcinoma; 40% also developed medulloblastoma. In addition, mice showed a novel pancreatic lesion resembling low-grade mucinous cystic neoplasms in humans. In contrast, widespread activation of SmoM2 in the postnatal prostate epithelium results in no detectable morphologic outcome in 12-month-old mice. Comparison of gene expression profiles among diverse tumors identified several signature genes, including components of platelet-derived growth factor and insulin-like growth factor pathways, which may provide a common mechanistic link to the Hh-related malignancies. This experimental model provides a robust tool for exploring the process of Hh-dependent tumorigenesis and the treatment of such tumors. More generally, this approach provides a genetic platform for identifying tumorigenic potential in putative oncogenes and tumor suppressors and for more effective modeling of sporadic cancers in mice.

p25/cyclin-dependent kinase 5 induces production and intraneuronal accumulation of amyloid beta in vivo

Aberrant processing of the amyloid precursor protein (APP) and the subsequent accumulation of amyloid beta (Abeta) peptide has been widely established as a central event in Alzheimer's disease (AD) pathogenesis. The sequential cleavage steps required for the generation of Abeta are well outlined; however, there is a relative dearth of knowledge pertaining to signaling pathways and molecular mechanisms that can modulate this process. Here, we demonstrate a novel role for p25/cyclin-dependent kinase 5 (Cdk5) in regulating APP processing, Abeta peptide generation, and intraneuronal Abeta accumulation in inducible p25 transgenic and compound PD-APP transgenic mouse models that demonstrate deregulated Cdk5 activity and a neurodegenerative phenotype. Induction of p25 resulted in enhanced forebrain Abeta levels before any evidence of neuropathology in these mice. Intracellular Abeta accumulated in perinuclear regions and distended axons within the forebrains of these mice. Evidence for modulations in axonal transport or beta-site APP cleaving enzyme 1 protein levels and activity are presented as mechanisms that may account for the Abeta accumulation caused by p25/Cdk5 deregulation. Collectively, these findings delineate a novel pathological mechanism involving aberrant APP processing by p25/Cdk5 and have important implications in AD pathogenesis.

p63 protects the female germ line during meiotic arrest

Meiosis in the female germ line of mammals is distinguished by a prolonged arrest in prophase of meiosis I between homologous chromosome recombination and ovulation. How DNA damage is detected in these arrested oocytes is poorly understood, but it is variably thought to involve p53, a central tumour suppressor in mammals. While the function of p53 in monitoring the genome of somatic cells is clear, a consensus for the importance of p53 for germ line integrity has yet to emerge. Here we show that the p53 homologue p63 (refs 5, 6), and specifically the TAp63 isoform, is constitutively expressed in female germ cells during meiotic arrest and is essential in a process of DNA damage-induced oocyte death not involving p53. We also show that DNA damage induces both the phosphorylation of p63 and its binding to p53 cognate DNA sites and that these events are linked to oocyte death. Our data support a model whereby p63 is the primordial member of the p53 family and acts in a conserved process of monitoring the integrity of the female germ line, whereas the functions of p53 are restricted to vertebrate somatic cells for tumour suppression. These findings have implications for understanding female germ line fidelity, the regulation of fertility and the evolution of tumour suppressor mechanisms.

Diminished lifespan and acute stress-induced death in DNA-PKcs-deficient mice with limiting telomeres

An adequate and appropriate response to physiological and pathophysiological stresses is critical for long-term homeostasis and viability of the aging organism. Previous work has pointed to the immune system, telomeres and DNA repair pathways as important and distinct determinants of a normal healthy lifespan. In this study, we explored the genetic interactions of telomeres and DNA-PKcs, a protein involved in non-homologous end-joining (NHEJ) and immune responses, in the context of a key aspect of aging and lifespan--the capacity to mount an acute and appropriate immune-mediated stress response. We observed that the combination of DNA-PKcs deficiency and telomere dysfunction resulted in a shortened lifespan that was reduced further following viral infection or experimental activation of the innate immune response. Analysis of the innate immune response in the DNA-PKcs-deficient mice with short dysfunctional telomeres revealed high basal serum levels of tumor necrosis factor alpha (TNFalpha) and hyper-active cytokine responses upon challenge with polyinosinic-polycytidylic acid (poly-IC). We further show that serum cytokine levels become elevated in telomere dysfunctional mice as a function of age. These results raise speculation that these genetic factors may contribute to misdirected immune responses of the aged under conditions of acute and chronic stress.

Ability of herpes simplex virus vectors to boost immune responses to DNA vectors and to protect against challenge by simian immunodeficiency virus

The immunogenicity and protective capacity of replication-defective herpes simplex virus (HSV) vector-based vaccines were examined in rhesus macaques. Three macaques were inoculated with recombinant HSV vectors expressing Gag, Env, and a Tat-Rev-Nef fusion protein of simian immunodeficiency virus (SIV). Three other macaques were primed with recombinant DNA vectors expressing Gag, Env, and a Pol-Tat-Nef-Vif fusion protein prior to boosting with the HSV vectors. Robust anti-Gag and anti-Env cellular responses were detected in all six macaques. Following intravenous challenge with wild-type, cloned SIV239, peak and 12-week plasma viremia levels were significantly lower in vaccinated compared to control macaques. Plasma SIV RNA in vaccinated macaques was inversely correlated with anti-Rev ELISPOT responses on the day of challenge (P value<0.05), anti-Tat ELISPOT responses at 2 weeks post challenge (P value <0.05) and peak neutralizing antibody titers pre-challenge (P value 0.06). These findings support continued study of recombinant herpesviruses as a vaccine approach for AIDS.

Adenomatous polyposis coli (APC) is required for normal development of skin and thymus

The tumor suppressor gene Apc (adenomatous polyposis coli) is a member of the Wnt signaling pathway that is involved in development and tumorigenesis. Heterozygous knockout mice for Apc have a tumor predisposition phenotype and homozygosity leads to embryonic lethality. To understand the role of Apc in development we generated a floxed allele. These mice were mated with a strain carrying Cre recombinase under the control of the human Keratin 14 (K14) promoter, which is active in basal cells of epidermis and other stratified epithelia. Mice homozygous for the floxed allele that also carry the K14-cre transgene were viable but had stunted growth and died before weaning. Histological and immunochemical examinations revealed that K14-cre-mediated Apc loss resulted in aberrant growth in many ectodermally derived squamous epithelia, including hair follicles, teeth, and oral and corneal epithelia. In addition, squamous metaplasia was observed in various epithelial-derived tissues, including the thymus. The aberrant growth of hair follicles and other appendages as well as the thymic abnormalities in K14-cre; Apc(CKO/CKO) mice suggest the Apc gene is crucial in embryonic cells to specify epithelial cell fates in organs that require epithelial-mesenchymal interactions for their development.

K-ras activation generates an inflammatory response in lung tumors

Activating mutations in K-ras are one of the most common genetic alterations in human lung cancer. To dissect the role of K-ras activation in bronchial epithelial cells during lung tumorigenesis, we created a model of lung adenocarcinoma by generating a conditional mutant mouse with both Clara cell secretory protein (CC10)-Cre recombinase and the Lox-Stop-Lox K-ras(G12D) alleles. The activation of K-ras mutant allele in CC10 positive cells resulted in a progressive phenotype characterized by cellular atypia, adenoma and ultimately adenocarcinoma. Surprisingly, K-ras activation in the bronchiolar epithelium is associated with a robust inflammatory response characterized by an abundant infiltration of alveolar macrophages and neutrophils. These mice displayed early mortality in the setting of this pulmonary inflammatory response with a median survival of 8 weeks. Bronchoalveolar lavage fluid from these mutant mice contained the MIP-2, KC, MCP-1 and LIX chemokines that increased significantly with age. Cell lines derived from these tumors directly produced MIP-2, LIX and KC. This model demonstrates that K-ras activation in the lung induces the elaboration of inflammatory chemokines and provides an excellent means to further study the complex interactions between inflammatory cells, chemokines and tumor progression.

MyD88 deficiency results in tissue-specific changes in cytokine induction and inflammation in interleukin-18-independent mice infected with Borrelia burgdorferi

Toll-like receptors (TLRs) play an important role in the control of infection with Borrelia burgdorferi. Deficiencies in TLR-2 or the shared TLR adapter molecule MyD88 have been shown to result in greatly increased bacterial burdens in mice. However, although in vitro studies have shown that the activation of TLR pathways by B. burgdorferi results in the release of inflammatory cytokines, studies in deficient mice have shown either no change or increased rather than decreased inflammation in infected animals. In this study, we looked at mechanisms to explain the increase in inflammation in the absence of MyD88. We found that MyD88-deficient mice infected with B. burgdorferi did not show increased inflammation at sites typically associated with Lyme disease (joints and heart). However, there was markedly increased inflammation in the muscles, kidneys, pancreas, and lungs of deficient animals. Muscle inflammation was typically seen perivascularly and perineuronally similar to that seen in infected humans. Chemotactic chemokines and cytokines were greatly increased in the muscle and kidneys of MyD88-deficient animals but not in the joints or heart tissue, suggesting that MyD88-independent pathways for recognizing B. burgdorferi and inducing these chemokines are present in the muscle and kidneys. Interleukin-18 signaling through MyD88 does not appear to play a role in either control of infection or inflammation.

The impact of human EGFR kinase domain mutations on lung tumorigenesis and in vivo sensitivity to EGFR-targeted therapies

To understand the role of human epidermal growth factor receptor (hEGFR) kinase domain mutations in lung tumorigenesis and response to EGFR-targeted therapies, we generated bitransgenic mice with inducible expression in type II pneumocytes of two common hEGFR mutants seen in human lung cancer. Both bitransgenic lines developed lung adenocarcinoma after sustained hEGFR mutant expression, confirming their oncogenic potential. Maintenance of these lung tumors was dependent on continued expression of the EGFR mutants. Treatment with small molecule inhibitors (erlotinib or HKI-272) as well as prolonged treatment with a humanized anti-hEGFR antibody (cetuximab) led to dramatic tumor regression. These data suggest that persistent EGFR signaling is required for tumor maintenance in human lung adenocarcinomas expressing EGFR mutants.

Inactivation of conditional Rb by Villin-Cre leads to aggressive tumors outside the gastrointestinal tract

We have crossed mice carrying the conditional Rb(tm2Brn) allele with a constitutive Villin-Cre transgenic mouse. The Villin promoter in these animals is highly expressed in adult intestine and kidney proximal tubules and is expressed in the gut and nephros anlagen during embryogenesis. We report here that these mice develop tumors between 12 and 17 months old outside the gastrointestinal (GI) tract. A high penetrance of pituitary tumors and medullar carcinoma of the thyroid is observed with a lower incidence of hyperplasia of pulmonary neuroendocrine cells and aggressive liver, bile duct, stomach, oral cavity tumors, and lipomas. Rb rearrangement due to ectopic Villin promoter activity in neural crest or neural crest stem cells during embryogenesis is most likely responsible for the medullar carcinoma of the thyroid phenotype. The aggressive nature of the medullar carcinoma of the thyroid and its ability to metastasize to unusual sites make the model suitable for the study of tumor progression and mechanism of metastasis. Observed sites of metastasis include the stomach, small intestine, liver, lung, kidney, pancreas, spleen, bone marrow, salivary gland, fat, lymph nodes, and dorsal root ganglion. Because the Villin promoter is highly active throughout the GI and in the nephros anlagen during development, we find that Rb inactivation is not sufficient to initiate tumorigenesis in the GI or kidneys in mice.

Epidermal growth factor receptor variant III mutations in lung tumorigenesis and sensitivity to tyrosine kinase inhibitors

The tyrosine kinase inhibitors gefitinib (Iressa) and erlotinib (Tarceva) have shown anti-tumor activity in the treatment of non-small cell lung cancer (NSCLC). Dramatic and durable responses have occurred in NSCLC tumors with mutations in the tyrosine kinase domain of the epidermal growth factor receptor (EGFR). In contrast, these inhibitors have shown limited efficacy in glioblastoma, where a distinct EGFR mutation, the variant III (vIII) in-frame deletion of exons 2-7, is commonly found. In this study, we determined that EGFRvIII mutation was present in 5% (3/56) of analyzed human lung squamous cell carcinoma (SCC) but was not present in human lung adenocarcinoma (0/123). We analyzed the role of the EGFRvIII mutation in lung tumorigenesis and its response to tyrosine kinase inhibition. Tissue-specific expression of EGFRvIII in the murine lung led to the development of NSCLC. Most importantly, these lung tumors depend on EGFRvIII expression for maintenance. Treatment with an irreversible EGFR inhibitor, HKI-272, dramatically reduced the size of these EGFRvIII-driven murine tumors in 1 week. Similarly, Ba/F3 cells transformed with the EGFRvIII mutant were relatively resistant to gefitinib and erlotinib in vitro but proved sensitive to HKI-272. These findings suggest a therapeutic strategy for cancers harboring the EGFRvIII mutation.

Pten deficiency activates distinct downstream signaling pathways in a tissue-specific manner

PTEN deficiency predisposes to a subset of human cancers, but the mechanism that underlies such selectivity is unknown. We have generated a mouse line that conditionally deletes Pten in urogenital epithelium. These mice develop carcinomas at high frequency in the prostate but at relatively low frequency in the bladder, despite early and complete penetrance of hyperplasia in both organs. Cell proliferation is initially high in the bladder of newborn Pten-deficient mice but within days is inhibited by p21 induction. In contrast, proliferation remains elevated in Pten-deficient prostate, where p21 is never induced, suggesting that p21 induction is a bladder-specific compensatory mechanism to inhibit proliferation caused by Pten deletion. Furthermore, the AKT/mammalian target of rapamycin growth pathway, which is highly activated in Pten-deficient prostate, is not activated in bladder epithelium. Our results reveal alternative downstream signaling pathways activated by Pten deficiency that lead to tissue-specific susceptibilities to tumorigenesis.

The fibrinolytic system facilitates tumor cell migration across the blood-brain barrier in experimental melanoma brain metastasis

BACKGROUND

Patients with metastatic tumors to the brain have a very poor prognosis. Increased metastatic potential has been associated with the fibrinolytic system. We investigated the role of the fibrinolytic enzyme plasmin in tumor cell migration across brain endothelial cells and growth of brain metastases in an experimental metastatic melanoma model.

METHODS

Metastatic tumors to the brain were established by direct injection into the striatum or by intracarotid injection of B16F10 mouse melanoma cells in C57Bl mice. The role of plasminogen in the ability of human melanoma cells to cross a human blood-brain barrier model was studied on a transwell system.

RESULTS

Wild type mice treated with the plasmin inhibitor epsilon-aminocaproic acid (EACA) and plg-/- mice developed smaller tumors and survived longer than untreated wild type mice. Tumors metastasized to the brain of wild type mice treated with EACA and plg-/- less efficiently than in untreated wild type mice. No difference was observed in the tumor growth in any of the three groups of mice. Human melanoma cells were able to cross the human blood-brain barrier model in a plasmin dependent manner.

CONCLUSION

Plasmin facilitates the development of tumor metastasis to the brain. Inhibition of the fibrinolytic system could be considered as means to prevent tumor metastasis to the brain.

An imprinted locus epistatically influences Nstr1 and Nstr2 to control resistance to nerve sheath tumors in a neurofibromatosis type 1 mouse model

Cancer is a complex disease in which cells acquire many genetic and epigenetic alterations. We have examined how three types of alterations, mutations in tumor suppressor genes, changes in an imprinted locus, and polymorphic loci, interact to affect tumor susceptibility in a mouse model of neurofibromatosis type 1 (NF1). Mutations in tumor suppressor genes such as TP53 and in oncogenes such as KRAS have major effects on tumorigenesis due to the central roles of these genes in cell proliferation and cell survival. Imprinted genes expressed from only one parental chromosome affect tumorigenesis if their monoallelic expression is lost or duplicated. Because imprinted loci are within regions deleted or amplified in cancer, the parental origin of genomic rearrangements could affect tumorigenesis. Gene polymorphisms can vary tumor incidence by affecting rate-limiting steps in tumorigenesis within tumor cells or surrounding stroma. In our mouse model of NF1, the incidence of tumors mutant for the tumor suppressor genes Nf1 and Trp53 is strongly modified by a linked imprinted locus acting epistatically on two unlinked polymorphic loci, Nstr1 and Nstr2. This interaction of an imprinted locus and polymorphic susceptibility loci has profound implications for human mapping studies where the parental contribution of alleles is often unknown.

Increased susceptibility to UV-induced skin carcinogenesis in polymerase eta-deficient mice

Xeroderma pigmentosum variant (XPV) patients with mutations in the DNA polymerase eta (pol eta) gene are hypersensitive to sunlight and have greatly increased susceptibility to sunlight-induced skin cancer. Consistent with the ability of Pol eta to efficiently bypass UV light-induced cyclobutane pyrimidine dimers, XPV cells lacking Pol eta have diminished capacity to replicate UV-damaged DNA and are sensitive to UV light-induced killing and mutagenesis. To better understand these and other Pol eta functions, we generated Pol eta-deficient mice. Mice homozygous for a null mutation in pol eta are viable, fertile, and do not show any obvious spontaneous defects during the first year of life. However, fibroblasts derived from these mutant mice are sensitive to killing by exposure to UV light, and all Pol eta-deficient mice develop skin tumors after UV irradiation, in contrast to the wild-type littermate controls that did not develop such tumors. These results and biochemical studies of translesion synthesis by mouse Pol eta indicate that Pol eta-dependent bypass of cyclobutane pyrimidine dimers suppresses UV light-induced skin cancer in mice. Moreover, 37.5% of pol eta heterozygous mice also developed skin cancer during 5 months after a 5-month exposure to UV light, suggesting that humans who are heterozygous for mutations in pol eta may also have an increased risk of skin cancer.

A direct test of potential roles for beta3 and beta5 integrins in growth and metastasis of murine mammary carcinomas

alphavbeta3 or alphavbeta5 integrins are widely expressed on blood and endothelial cells. Inhibition of the functions of these integrins has been reported to suppress neovascularization and tumor growth, suggesting that they may be critical modulators of angiogenesis. However, mice lacking these integrins exhibit extensive angiogenesis. Tumors arising from s.c. injections of tumor cells into mice lacking one or both integrins show enhanced tumor growth compared with growth in control mice due to both increased angiogenesis and to altered innate immune response. Other data suggest additional roles for these integrins, on either platelets or the tumor cells themselves, in enhancing tumor progression and metastasis. Here, we investigate the involvement of beta3 and beta5 integrins in the development and progression of mammary carcinomas. We intercrossed mouse mammary tumor virus (MMTV)-c-neu transgenic mice with beta3 or beta5 or beta3beta5 integrin-deficient mice and observed that multiple, large mammary tumors developed in 100% of mice on all genetic backgrounds. A statistically significant earlier onset of tumor growth was observed in the MMTV-c-neu/beta3beta5 integrin-null females compared with control mice. No major differences were observed in tumor size or number, vessel number or vessel structure and lung metastases were observed with similar frequency and size in all strains. MMTV-c-neu/beta3beta5 integrin-null mice had higher numbers of mammary acini, which may account for the earlier onset of tumors in this strain. These data indicate that alphavbeta3 or alphavbeta5 integrins are not essential for tumor growth and progression, although they might play some role in mammary gland development.

Further characterization of reproductive abnormalities in mCd59b knockout mice: a potential new function of mCd59 in male reproduction

CD59 is a GPI-linked membrane protein that inhibits formation of the membrane attack complex of complement. We reported recently that mice have two CD59 genes (termed mCd59a and mCd59b), and that the targeted deletion of mCd59b (mCd59b-/-) results in spontaneous hemolytic anemia and progressive loss of male fertility. Further studies of the reproductive abnormalities in mCd59b-/- mice reported in this study revealed the presence of abnormal multinucleated cells and increased apoptotic cells within the walls of the seminiferous tubules, and a decrease in the number, motility, and viability of sperm associated with a significant increase in abnormal sperm morphologies. Both the capacitation-associated tyrosine phosphorylation and the ionophore-induced acrosome reaction as well as luteinizing hormone, follicle-stimulating hormone, and testosterone serum levels were similar in mCd59b-/- and mCd59b+/+. Surprisingly, the functional deficiency of the complement protein C3 did not rescue the abnormal reproductive phenotype of mCd59b-/-, although it was efficient in rescuing their hemolytic anemia. These results indicate that the male reproductive abnormalities in mCd59b-/- are complement-independent, and that mCd59 may have a novel function in spermatogenesis that is most likely unrelated to its function as an inhibitor of membrane attack complex formation.

Influence of caloric restriction on motor behavior, longevity, and brain lipid composition in Sandhoff disease mice

Caloric restriction (CR), which improves health and increases longevity, was studied as a therapy in a hexosaminidase beta knockout mouse model of Sandhoff disease (SD), an incurable neurodegenerative disease involving accumulation of brain ganglioside GM2 and asialo-GM2 (GA2). Adult mice were fed a rodent chow diet either ad libitum (AL) or restricted to reduce body weight by 15-18% (CR). Although GM2 and GA2 were elevated, no significant differences were seen between the Hexb-/- and the Hexb+/- mice for most brain phospholipids and cholesterol. Cerebrosides and sulfatides were reduced in the Hexb-/- mice. In addition, rotorod performance was significantly worse in the Hexb-/- mice than in the Hexb+/- mice. CR, which decreased circulating glucose and elevated ketone bodies, significantly improved rotorod performance and extended longevity in the Hexb-/- mice but had no significant effect on brain lipid composition or on cytoplasmic neuronal vacuoles. The expression of CD68 and F4/80 was significantly less in the CR-fed than in the AL-fed Hexb-/- mice. We suggest that the CR delays disease progression in SD and possibly in other ganglioside storage diseases through anti-inflammatory mechanisms.

Trak1 mutation disrupts GABA(A) receptor homeostasis in hypertonic mice

Hypertonia, which results from motor pathway defects in the central nervous system (CNS), is observed in numerous neurological conditions, including cerebral palsy, stroke, spinal cord injury, stiff-person syndrome, spastic paraplegia, dystonia and Parkinson disease. Mice with mutation in the hypertonic (hyrt) gene exhibit severe hypertonia as their primary symptom. Here we show that hyrt mutant mice have much lower levels of gamma-aminobutyric acid type A (GABA(A)) receptors in their CNS, particularly the lower motor neurons, than do wild-type mice, indicating that the hypertonicity of the mutants is likely to be caused by deficits in GABA-mediated motor neuron inhibition. We cloned the responsible gene, trafficking protein, kinesin binding 1 (Trak1), and showed that its protein product interacts with GABA(A) receptors. Our data implicate Trak1 as a crucial regulator of GABA(A) receptor homeostasis and underscore the importance of hyrt mice as a model for studying the molecular etiology of hypertonia associated with human neurological diseases.