An observational study of farmer-reported clinical mastitis in New Zealand dairy ewes

AIMS

To describe the incidence, aetiology, treatment, and outcomes of farmer-reported clinical mastitis on New Zealand dairy sheep farms.

METHODS

A prospective cohort study was conducted on 20 spring-lambing New Zealand sheep milking farms over the 2022-2023 season. Clinical mastitis was defined as a change in the appearance of milk and/or signs of inflammation in the gland. Farmers were required to report all cases of clinical mastitis and collect information on affected ewes' demographics, clinical features, treatments (where applicable), and outcomes. Milk samples from mastitic glands were submitted for microbiological culture and identification by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF).

RESULTS

Partial or complete clinical mastitis data were available for 236 cases from 221 ewes on 18/20 study farms. Clinical mastitis was diagnosed in 0-6% of ewes at the farm level, with an overall incidence of 1.8 (95% CI = 1.0-3.2)% using the study data, or 2.3 (95% CI = 1.6-3.3)% using the study data and farmer estimates that included unreported cases. Cases occurred mostly in early lactation, with 59% detected during the lambing period (August-October), at a median of 7 (IQR 3, 40) days in milk. The majority of cases featured clots in the milk (59%), swelling (55%), and unevenness (71%) of the glands. Pyrexia (rectal temperature ≥ 40.0°C) was diagnosed in 25% of cases and depression (lethargy, inappetence, or inability to stand) in 26% of cases. Treatment was given to 46% of cases, with tylosin being the most commonly used treatment (50% of treated cases). The most common outcome was immediate drying off to be culled without treatment (32%), followed by still milking and recovered but with lasting problems (25%). Nearly half of all the milk samples submitted were culture negative. Streptococcus uberis (14%), non-aureus staphylococci (12%), and Staphylococcus aureus (11%) were the most common isolates, found on 12, 8 and 8 of the 16 farms with microbiological data, respectively.

CONCLUSIONS

Clinical mastitis affected up to 6% of ewes at the farm level. Systemic signs were observed in one quarter of affected ewes, suggesting a role for supportive treatment. Clinical mastitis can be severe and challenging to fully resolve in New Zealand dairy sheep.

CLINICAL RELEVANCE

This is the first systematic study of clinical mastitis in New Zealand dairy ewes. It provides baseline information specific to New Zealand conditions for farmers, veterinarians, and other advisors to guide the management of mastitis for the relatively new dairy sheep industry in New Zealand.

Preclinical Characterization of the Anti-Leukemia Activity of the CD33/CD16a/NKG2D Immune-Modulating TriNKET® CC-96191

Increasing efforts are focusing on natural killer (NK) cell immunotherapies for AML. Here, we characterized CC-96191, a novel CD33/CD16a/NKG2D immune-modulating TriNKET®. CC-96191 simultaneously binds CD33, NKG2D, and CD16a, with NKG2D and CD16a co-engagement increasing the avidity for, and activation of, NK cells. CC-96191 was broadly active against human leukemia cells in a strictly CD33-dependent manner, with maximal efficacy requiring the co-engagement of CD16a and NKG2D. A frequent CD33 single nucleotide polymorphism, R69G, reduced CC-96191 potency but not maximal activity, likely because of reduced CD33 binding. Similarly, the potency, but not the maximal activity, of CC-96191 was reduced by high concentrations of soluble CD33; in contrast, the soluble form of the NKG2D ligand MICA did not impact activity. In the presence of CD33+ AML cells, CC-96191 activated NK cells but not T cells; while maximum anti-AML efficacy was similar, soluble cytokine levels were 10- to >100-fold lower than with a CD33/CD3 bispecific antibody. While CC-96191-mediated cytolysis was not affected by ABC transporter proteins, it was reduced by anti-apoptotic BCL-2 family proteins. Finally, in patient marrow specimens, CC-96191 eliminated AML cells but not normal monocytes, suggesting selectivity of TriNKET-induced cytotoxicity toward neoplastic cells. Together, these findings support the clinical exploration of CC-96191 as in NCT04789655.

An optimized IL-12-Fc expands its therapeutic window, achieving strong activity against mouse tumors at tolerable drug doses

BACKGROUND

Interleukin-12 (IL-12) has emerged as one of the most potent cytokines for tumor immunotherapy due to its ability to induce interferon γ (IFNγ) and polarize Th1 responses. Clinical use of IL-12 has been limited by a short half-life and narrow therapeutic index.

METHODS

We generated a monovalent, half-life-extended IL-12-Fc fusion protein, mDF6006, engineered to retain the high potency of native IL-12 while significantly expanding its therapeutic window. In vitro and in vivo activity of mDF6006 was tested against murine tumors. To translate our findings, we developed a fully human version of IL-12-Fc, designated DF6002, which we characterized in vitro on human cells and in vivo in cynomolgus monkeys in preparation for clinical trials.

FINDINGS

The extended half-life of mDF6006 modified the pharmacodynamic profile of IL-12 to one that was better tolerated systemically while vastly amplifying its efficacy. Mechanistically, mDF6006 led to greater and more sustained IFNγ production than recombinant IL-12 without inducing high, toxic peak serum concentrations of IFNγ. We showed that mDF6006's expanded therapeutic window allowed for potent anti-tumor activity as single agent against large immune checkpoint blockade-resistant tumors. Furthermore, the favorable benefit-risk profile of mDF6006 enabled effective combination with PD-1 blockade. Fully human DF6002, similarly, demonstrated an extended half-life and a protracted IFNγ profile in non-human primates.

CONCLUSION

An optimized IL-12-Fc fusion protein increased the therapeutic window of IL-12, enhancing anti-tumor activity without concomitantly increasing toxicity.

FUNDING

This research was funded by Dragonfly Therapeutics.

Abstract 1714: Preclinical characterization of DF6002/BMS-986415, a novel differentiated IL-12 Fc-fusion protein with robust antitumor activity as monotherapy or in combination with anti-PD-1

Background: Interleukin 12 (IL-12) is a proinflammatory cytokine that plays a central role in regulating both innate and adaptive antitumor immune responses. Clinically, administration of recombinant human IL-12 (rhIL-12) has been limited by a short half-life (t1/2) requiring frequent dosing, causing tachyphylaxis as well as toxic side effects. DF6002/BMS-986415 is an IL-12 Fc-fusion protein designed to have a prolonged t1/2 while retaining equivalent potency to rhIL-12 and promoting sustained IFN-γ response with reduced toxicity. Here we present the preclinical evaluation of DF6002/BMS-986415 ± anti–PD-1.

Methods: DF6002/BMS-986415 and rhIL-12 stimulation of IFN-γ release from human and cynomolgus macaque (Cyno) peripheral blood mononuclear cells (PBMCs) and in vivo exposure in Cynos was assessed. As rhIL-12 is inactive in mice, pharmacokinetic, pharmacodynamic, and antitumor effects were evaluated with mDF6006, a mouse surrogate of DF6002/BMS-986415, and recombinant mouse IL-12 (rmIL-12). Tumor growth was evaluated in inflamed (CT26 and MC38) and immunosuppressed (4T1 and B16F10) mouse tumor models (staged ≥ 200 mm3).

Results: DF6002/BMS-986415 induced IFN-γ production in human (EC50, 3.35 pM) and Cyno (EC50, 3.09 pM) PBMCs comparable to rhIL-12. DF6002/BMS-986415 was well tolerated at doses yielding greater exposure vs equimolar rhIL-12 in Cynos. In mice, the mouse surrogate mDF6006 vs rmIL-12 yielded a 5-fold increase in t1/2 and a 40-fold greater serum IFN-γ exposure. In contrast to rmIL-12, mDF6006 achieved protracted IFN-γ levels without peak effects associated with increased toxicity; serum IFN-γ Cmax occurred after day 6 and subsided by day 8. mDF6006 was efficacious across mouse tumor models tested. In the CT26 tumor model, mDF6006 (1 µg IP QW) monotherapy showed greater antitumor activity vs equimolar doses of rmIL-12 and led to complete regression (CR) in mice with large tumors (> 800 mm3); immunological memory response was observed in responders rechallenged with fresh tumor cells. In the B16F10 tumor model, mDF6006 (0.5 µg equivalent rmIL-12 SC QW) + anti–PD-1 (10 mg/kg IP Q2W) yielded a higher CR rate (mDF6006 + anti-PD-1, 4 of 10 CR; mDF6006, 1 of 10 CR) and increased survival vs either agent alone. An increase in the number and activation of CD4+ and CD8+ T cells as well as NK cells was observed 4 days after administration of mDF6006 (0.5 µg) in the B16F10 model.

Conclusions: DF6002/BMS-986415, a novel IL-12 Fc-fusion protein, retained the full potency of rhIL-12 and showed improved exposure and tolerability; mDF6006 exhibited greater antitumor activity than rmIL-12. These data support the ongoing first-in-human phase 1/2 study evaluating DF6002/BMS-986415 as a novel therapeutic for the treatment of solid tumors in combination with nivolumab (NCT04423029).

Citation Format: Eva Gutierrez, Mitchell Bigelow, Colin LaCroix, Patrick Kirby, Lynn Markowitz, Michael Naill, Steve O'Neil, Philip Ansumana Hull, John Engelhardt, Jean-Marie Cuillerott, Ann Cheung, Asya Grinberg, Nicolai Wagtmann. Preclinical characterization of DF6002/BMS-986415, a novel differentiated IL-12 Fc-fusion protein with robust antitumor activity as monotherapy or in combination with anti-PD-1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1714.

0475 Reducing Dysfunctional Sleep-Related Cognitions Improves Nighttime Sleep and Daytime Consequences in Older Adults with Insomnia

Introduction

The long-term impact of addressing sleep-related cognitions, which is an important component of cognitive behavioral therapy for insomnia (CBTI), has not been established, particularly in older adults. We examined whether specific changes in sleep-related cognitions predicted long-term changes in sleep and other outcomes following CBTI in older adults.

Methods

We analyzed data from a randomized controlled trial testing CBTI in older veterans with insomnia (N=159, mean age 72 years). Sleep-related cognitions were assessed with the Dysfunctional Beliefs and Attitudes about Sleep scale (DBAS, subscales: Consequences, Worry/Helplessness, Sleep Expectations, Medication). Outcome measures included the Pittsburgh Sleep Quality Index (PSQI), Insomnia Severity Index (ISI), Epworth Sleepiness Scale (ESS), sleep diary variables, Flinders Fatigue Scale (FFS), and Short Form-12 health-related quality of life (QOL). Analyses completed slope of change in DBAS subscales (baseline to post-treatment: T1) between CBTI and control with respect to slope of change in sleep and other outcomes from post-treatment to 6-months (T2).

Results

Compared to controls, the CBTI group had significantly stronger associations between improvement (T1) in DBAS-Consequences and subsequent (T2) improvement in PSQI (difference in slopes [DIS]=0.9, 95%CI=[.29, 1.43], p=0.004), ISI (DIS=1.1, 95%CI=[.18, 2.0], p=0.019), ESS (DIS=0.6, 95%CI=[.10, 1.18], p=0.020), and FFS (DIS=1.9, 95%CI=[.76, 3.09], p=0.001). The CBTI group also had significantly stronger associations between improvement in DBAS-Worry/Helplessness and subsequent improvements in PSQI, ISI, and FFS; improvement in DBAS-Medication and PSQI and ISI; and improvement in DBAS-Sleep Expectations and improved FFS. Slopes were not different between groups for sleep diary variables or QOL.

Conclusion

Significant improvements in sleep-related cognitions with CBTI across DBAS subscales in older adults predicted improvement in several outcomes of nighttime sleep and daytime consequences. These findings suggest the importance of addressing dysfunctional sleep-related cognitions for sustained improvement with CBTI in older adults

Support

The study was supported by VA Health Services, Research and Development (Alessi, IIR 08-295), National Institute on Aging (K23AG055668, Song), National Heart, Lung, and Blood Institute (K24HL 143055, Martin) of the National Institutes of Health and VA Greater Los Angeles Healthcare System, Geriatric Research, Education and Clinical Center.

Volumetric MRI Study of the Brain in Fetuses with Intrauterine Cytomegalovirus Infection and Its Correlation to Neurodevelopmental Outcome

BACKGROUND AND PURPOSE

In recent years, effort has been made to study 3D biometry as a method for fetal brain assessment. In this study, we aimed to compare brain volumes of fetuses with cytomegalovirus infection and noninfected controls. Also, we wanted to assess whether there is a correlation to their neurodevelopmental outcome as observed after several years.

MATERIALS AND METHODS

A retrospective cohort study examined MR imaging brain scans of 42 fetuses (at 30-34 weeks' gestational age) that were diagnosed with intrauterine cytomegalovirus infection. Volumetric measurements of 6 structures were assessed using a semiautomated designated program and were compared with a control group of 50 fetuses. Data collected included prenatal history and MR imaging and sonographic and neurodevelopmental follow-up.

RESULTS

We found that all brain volumes measured were smaller in the cytomegalovirus-infected group and that there was a correlation between smaller cerebellar volume and lower Vineland II Adaptive Behavior Scales questionnaire scores, especially in the fields of daily living and communication skills.

CONCLUSIONS

In this study, we found that brain volumes are affected by intrauterine cytomegalovirus infection and that it has a developmental prognostic meaning. Such information, which should be supported by further research, may help clinicians further analyze imaging data to treat and make a better assessment of these fetuses.

Molecular detection of Bartonella coopersplainsensis and B. henselae in rats from New Zealand

AIM To identify Bartonella spp. in rats from New Zealand using molecular methods. METHODS DNA was extracted from the spleens of 143 black rats (Rattus rattus) captured in the Tongariro National Park, New Zealand. PCR was performed using Bartonella genus-specific primers amplifying segments of the 16S-23S rRNA internal transcribed spacer and citrate synthase (gltA) and beta subunit of the RNA polymerase (rpoB) genes. PCR products were sequenced and compared online with sequences stored in the database of the National Center for Biotechnology Information of the United States of America. RESULTS DNA sequences matching Bartonella coopersplainsensis and B. henselae were detected in samples from 22/143 (15.4%) and 3/143 (2.1%) rats, respectively. Co-occurrence of B. coopersplainsensis and B. henselae sequences was observed in the sample from one rat. CONCLUSIONS AND CLINICAL RELEVANCE Gram-negative fastidious bacteria belonging to the genus Bartonella are associated with a range of human diseases. Rodents play an important role as reservoirs of a broad range of Bartonella species. To our knowledge, this is the first report of a molecular detection of Bartonella spp. DNA in rodents from New Zealand, and the first identification of B. henselae DNA in rats, worldwide. Whereas the public health significance of B. coopersplainsensis remains undefined, B. henselae is the agent of cat scratch disease, and the presence of this bacterium in rats may have public health implications. Our results are preliminary and additional analyses of larger samples, preferably by bacterial culture, would provide more information on the prevalence and diversity of Bartonella spp., in particular B. henselae, in rats.

The Effect of Urine Concentration and pH on the Growth of Escherichia Coli in Canine Urine In Vitro

Background

Lower urinary tract infections are common in dogs, and Escherichia coli is the most common bacterial pathogen isolated. The literature has conflicting evidence regarding the inhibitory effects of urine concentration and pH on E. coli growth.

Hypothesis/Objectives

To determine the effect of different pH and urine concentrations on E. coli growth in vitro.

Animals

Voided urine samples from 10 apparently healthy spayed female dogs were used.

Methods

A matrix of 9 urine specific gravity (USG; 1.010, 1.020, and 1.030) and pH (5.5, 7.0, and 8.5) combinations was prepared by diluting and titrating filtered voided urine samples. Three E. coli isolates were obtained from urine of female dogs with signs of lower urinary tract infection and cultured at different urine pH and USG combinations in wells of a microtiter plate. The number of E. coli colony‐forming units (CFU) per mL of urine was calculated after aerobic incubation of the urine at 37°C for 18 hours, and statistically compared.

Results

Significant differences were identified in the mean log CFU/mL among different combinations of pH and USG. The lowest log CFU/mL were observed in alkaline concentrated urine (pH 8.5 and USG 1.030).

Conclusions and Clinical Importance

Escherichia coli in vitro growth was higher in neutral to acidic and diluted urine compared to alkaline and concentrated urine. The impact of non‐alkalizing diluting diets on the incidence of E. coli lower urinary tract infections should be further explored.

Subclinical Bacteriuria in Older Cats and its Association with Survival

Background

Bacterial urinary tract infections are uncommon in cats in general but the prevalence increases to 29% in older cats with comorbidities (Veterinary Clinical Pathology 2008, 37, 317; Journal of Feline Medicine & Surgery 2007, 9, 124; Veterinary Microbiology 2009, 136, 130). Frequently, the infections are subclinical. The clinical relevance of subclinical bacteriuria (SB) is uncertain, and the optimal treatment requires clarification.

Objective

Prospective, observational study to: (i) identify the prevalence and incidence count of SB in older (≥7 years), nonazotemic cats, (ii) evaluate specific risk factors for SB, and (iii) investigate the potential relationship between untreated SB and survival.

Animals

Sixty‐seven, nonazotemic cats were tested on 5 occasions over 3 years.

Methods

Urine samples were obtained by cystocentesis for quantitative urine culture and blood samples for measurement of serum creatinine concentration. Episodes of SB were not treated. Serum creatinine concentration, body weight, urine specific gravity, sex, and age were evaluated as potential risk factors for a positive urine culture. The association between urine culture results and survival was evaluated with Cox's proportional hazard model.

Results

A total of 256 urine samples was obtained. The prevalence of SB varied between 10 and 13%, and incident infections were uncommon. Female cats were 21 times more likely to have a positive urine culture than were male cats (odds ratio [OR], 21.2; confidence interval [CI], 4.1–110; P = .00028). Subclinical bacteriuria was not significantly associated with survival.

Conclusion and clinical importance

Subclinical bacteriuria is common in nonazotemic, older cats. Although antimicrobial treatment was withheld, the presence of SB was not adversely associated with survival.

Characterisation of extended-spectrum β-lactamase and AmpC β-lactamase-producing Enterobacteriaceae isolated from companion animals in New Zealand

AIMS

To assess the occurrence of, and characterise, extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase (AmpC)-producing Enterobacteriaceae isolated by veterinary diagnostic laboratories from infection sites in companion animals in New Zealand.

METHODS

Selected Enterobacteriaceae isolates were submitted by seven New Zealand veterinary diagnostic laboratories. They were isolated from infection sites in companion animals between June 2012 and June 2013, and were resistant to amoxicillin-clavulanic acid, fluoroquinolones, or any combination of two or more antimicrobials. Based on disk diffusion test results, the isolates were phenotypically categorised according to production of ESBL and AmpC. Genes for ESBL and AmpC production were amplified by PCR and sequenced. Escherichia coli isolates were also typed by multilocus sequence typing.

RESULTS

A total of 115 isolates matching the inclusion criteria were obtained from the participating laboratories, of which 74 (64%) originated from dogs and 29 (25%) from cats. Seven bacterial species were identified, of which E. coli was the most common (87/115, 76%). Of the 115 isolates, 10 (9%) expressed the ESBL phenotype, 43 (37%) the AmpC phenotype, and seven (6%) both ESBL and AmpC phenotypes. Of the 60 ESBL and AmpC-producing isolates, 36 (60%) were E. coli. Amongst these isolates, 27/60 (45%) were classified as multidrug resistant, compared with 15/55 (27%) non-ESBL or AmpC-producing isolates (p<0.01). Ninety five isolates were resistant to amoxicillin-clavulanic acid and 58 (61%) of these were ESBL or AmpC-producing. The predominant ESBL genes were bla_CTX-M-14 and bla_CTX-M-15, and the dominant plasmid-encoded AmpC gene was bla_CMY-2. Thirty-eight E. coli multilocus sequence types (ST) were identified, and the most prevalent were ST12 (12/89, 13%), ST131 (6/89, 7%) and ST648 (6/89, 7%). ESBL and AmpC-producing isolates accounted for 35/1,082 (3.2%) of the Enterobacteriaceae isolated by one laboratory network over the study period.

CONCLUSIONS AND CLINICAL RELEVANCE

ESBL and AmpC-producing Enterobacteriaceae were associated with clinical infections in companion animals in New Zealand, and were often multidrug resistant. In this study, these organisms accounted for <5% of all Enterobacteriaceae isolated from infection sites by one laboratory network, but their prevalence among isolates resistant to amoxicillin-clavulanic acid was 61%. Therefore routine secondary testing for ESBL and AmpC production by Enterobacteriaceae that are resistant to amoxicillin-clavulanic acid in primary testing could improve the accuracy of definitive antimicrobial therapy in companion animals in New Zealand.

Characterisation of methicillin-resistant Staphylococcus aureus clinical isolates from animals in New Zealand, 2012-2013, and subclinical colonisation in dogs and cats in Auckland

AIMS

To characterise methicillin-resistant Staphylococcus aureus (MRSA) isolates from infection sites in animals in New Zealand and assess the prevalence of subclinical MRSA colonisation in dogs and cats attending veterinary clinics in Auckland.

METHODS

MRSA isolates from clinical specimens obtained by the main New Zealand veterinary diagnostic laboratories between June 2012 and June 2013, were genotypically characterised by DNA microarray hybridisation analysis and spa typing. In addition, nasal or perineal skin swabs collected from a cross-sectional sample of dogs (n=361) and cats (n=225) attending 29 veterinary clinics in Auckland during the same period were analysed for MRSA by culture.

RESULTS

Eight MRSA clinical isolates were submitted for characterisation by the participating laboratories. The isolates originated from five dogs, including two isolates from the same dog, one foal, and one isolate had no identification of the source. The strain-types identified were AK3 (ST-5 SCCmecIV t045; n=1), USA500 (ST8 SCCmecIV t064; n=1), WSPP (ST30 SCCmecIV t019; n=1), Rhine Hesse (ST5 SCCmecII t002; n=2), and EMRSA-15 (ST22 SCCmecIV t032; n=3). No MRSA were isolated from 586 cultured swabs. Methicillin-susceptible S. aureus were detected in 9/257 (3.5%) swabs and non-aureus staphylococci in 22/257 (8.5%) swabs. The estimated true MRSA subclinical colonisation prevalence was 0%, with an upper 95% CI boundary of 1.9% for cats and 1.4% for dogs.

CONCLUSIONS

The modest number of MRSA isolates submitted for this study by the participating laboratories suggests clinical MRSA infection in animals in New Zealand continues to be sporadic. The wide variety of strain-types found mirrored the evolving strain-type diversity observed in humans. We cannot rule out bias due to the non-random sampling of dogs and cats, but the apparent colonisation prevalence of 0% was consistent with the low prevalence of subclinical colonisation in humans in New Zealand. These similarities indicate the epidemiology of animal and human MRSA infections are linked.

CLINICAL RELEVANCE

In the last decade, the prevalence of human MRSA infections in New Zealand has steadily increased. This is the second published study of MRSA in animals in New Zealand. The results indicate clinical MRSA infection in animals remains sporadic, but the diversification of the strain-types may pose new therapeutic challenges to veterinarians, due to their diverse resistome.

Susceptibility to antimicrobials of mastitis-causing Staphylococcus aureus, Streptococcus uberis and Str. dysgalactiae from New Zealand and the USA as assessed by the disk diffusion test

OBJECTIVE

To compare the antimicrobial susceptibility patterns of three common mastitis pathogens (Staphylococcus aureus, Streptococcus uberis and Str. dysgalactiae) isolated from milk samples from New Zealand and the USA.

METHODS

A total of 182 S. aureus, 126 Str. uberis and 89 Str. dysgalactiae isolates from New Zealand (107, 106 and 41, respectively) and the USA (75, 20 and 48, respectively) were assessed using the disk diffusion test.

RESULTS

Susceptibility varied among the bacterial species. All isolates were susceptible to the amoxicillin-clavulanic acid combination. Resistance to lincomycin was most frequent (susceptibility of 8.6%) across all species. Non-susceptible (i.e. resistant or intermediate) isolates of S. aureus were identified for the three non-isoxazolyl penicillins (amoxicillin, ampicillin and penicillin: 20.6% and 36.0%) and lincomycin (99.9% and 94.6%) for NZ and the USA, respectively. Resistance to erythromycin (5.3%) and tetracyclines (6.7%) was detected only in isolates from the USA. There were differences in susceptibility between Str. uberis and Str. dysgalactiae; all streptococcal isolates demonstrated resistance to aminoglycosides (neomycin 52.4% and streptomycin 27.9%) and enrofloxacin (28%). Resistance of Str. dysgalactiae to tetracycline was almost 100.0% and to oxytetracycline 89.9%.

CONCLUSION AND CLINICAL RELEVANCE

Most of the isolates tested were susceptible to most of the antimicrobials commonly used for treatment of bovine mastitis, with the exception of the lincosamides. Susceptibility to a selected class-representative antimicrobial and at the genus level should be interpreted with caution. Differences between NZ and the USA confirm the value of national surveys to determine the susceptibility patterns of mastitis pathogens.

Prevalence of endemic enteropathogens of calves in New Zealand dairy farms

AIM

To conduct a country-wide prevalence study of bovine group A rotavirus, coronavirus, Cryptosporidium parvum, Salmonella spp. and enterotoxigenic K99(+) Escherichia coli (K99) in calves on New Zealand dairy farms.

METHODS

Faecal samples (n=1,283) were collected during the 2011 calving season from calves that were 1-5 and 9-21 days-old on 97 dairy farms, and were analysed for the presence of bovine group A rotavirus, coronavirus, Cryptosporidium and Salmonella spp., and K99. Farm-level prevalences were calculated and relationships between demographic variables and the presence of enteropathogens were examined using logistic regression models.

RESULTS

Of the 97 farms, 93 (96%) had at least one sample infected with enteropathogens. The standardised farm prevalences of bovine group A rotavirus, bovine coronavirus and C. parvum were 46, 14 and 18%, respectively, in calves that were 1-5 days-old, and 57, 31 and 52%, respectively, in calves that were 9-21 days-old. The farm-level prevalence of K99 was 11% in calves that were 1-5 days-old. Salmonella spp. were found in three and four samples, from calves that were 1-5 and 9-21 days-old, respectively. No associations between explanatory variables and the presence of the enteropathogens were identified at the farm level. At the calf level, the odds of C. parvum shedding and of co-infection with any combination of pathogens were greater in calves that were 9-21 than 1-5 days-old.

CONCLUSIONS AND CLINICAL RELEVANCE

This study provides epidemiological estimates of the prevalence of calves' enteropathogens in New Zealand, which could be used for infection risk assessment or estimation of the environmental loads of pathogens shed in cattle faeces.

Risk factors for neonatal calf diarrhoea and enteropathogen shedding in New Zealand dairy farms

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A cross sectional study of neonatal calf diarrhoea was performed on 97 New Zealand dairy farms.

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Infectious and environmental risk factors for neonatal calf diarrhoea were identified using multivariable analysis.

To investigate the risk factors for neonatal calf diarrhoea, a cross-sectional study was conducted on 97 New Zealand dairy farms. Faecal specimens from 1283 calves were scored as liquid, semi-solid or solid, and analysed for bovine rotavirus (BRV) and coronavirus (BCV), enterotoxigenic K99⁺Escherichia coli (K99), Salmonella spp. and Cryptosporidium parvum. Calf- and farm-level data were collected by means of a questionnaire and the odds of liquid faeces calculated using mixed effects logistic regression models.

Among the infectious agents, only C. parvum (odds ratio [OR] = 2.6; 95% confidence interval [CI], 1.3–5.6; P = 0.02), BRV (OR = 2.7; 95% CI, 1.3–5.9; P = 0.01) and co-infection with more than one agent (compared with mono-infection: OR = 2.5; 95% CI, 1.3–4.8; P = 0.01) were associated with increased odds of liquid faeces in calves which were 9 to 21 days old. Housing of calves in open barns so exposing them to the weather was also associated with increased odds of liquid faeces compared with closed barns (OR = 2.1; 95% CI, 1.1–12.2; P = 0.03). Vaccinating cows against calf enteropathogens (OR = 0.2; 95% CI, 0.1–0.9; P = 0.03), administering waste milk (from mastitis and/or containing antibiotics; OR = 0.4; 95% CI, 0.1–0.8; P = 0.01), the sex of calves (females compared to males OR = 0.2, 95% CI, 0.07–0.7; P < 0.01), and the use of straw for bedding (OR = 0.2; 95% CI, 0.03–0.9; P = 0.03) decreased the odds of liquid faeces. Conversely, in calves that were 1 to 5 days old, only K99 was associated with liquid faeces (OR = 4.6; 95% CI, 1.2–16.1; P = 0.02). In this age group, the odds of liquid faeces were smaller on farms where females took care of the calves, compared with males (OR = 0.4; 95% CI, 0.01–0.9; P = 0.04).

Cardiovascular responses to lower body negative pressure before and after 4 h of head-down bed rest and seated control in men and women

Cardiovascular deconditioning after a 4-h head-down bed rest (HDBR) might be a consequence of the time of day relative to pre-HDBR testing, or simply 4 h of confinement and inactivity rather than the posture change. Ten men and 11 women were studied during lower body negative pressure (LBNP) before and after 4-h HDBR and 4-h seated posture (SEAT) as a control for time of day and physical inactivity effects to test the hypotheses that cardiovascular deconditioning was a consequence of the HDBR posture, and that women would have a greater deconditioning response. Following HDBR, men and women had lower blood volume, higher heart rate with a greater increase during LBNP, a greater decrease of stroke volume during LBNP, lower central venous pressure, smaller inferior vena cava diameter, higher portal vein resistance index with a greater increase during LBNP, but lower forearm vascular resistance, lower norepinephrine, and lower renin. Women had lower vasopressin and men had higher vasopressin after HDBR, and women had lower pelvic impedance and men higher pelvic impedance. Following SEAT, brachial vascular resistance was reduced, thoracic impedance was elevated, the reduction of central venous pressure during LBNP was changed, women had higher angiotensin II whereas men had lower levels, and pelvic impedance increased in women and decreased in men. Cardiovascular deconditioning was greater after 4-h HDBR than after SEAT. Women and men had similar responses for most cardiovascular variables in the present study that tested the responses to LBNP after short-duration HDBR compared with a control condition.

A soluble activin type IIB receptor improves function in a mouse model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurologic disease characterized by progressive weakness that results in death within a few years of onset by respiratory failure. Myostatin is a member of the TGF-beta superfamily that is predominantly expressed in muscle and acts as a negative regulator of muscle growth. Attenuating myostatin has previously been shown to produce increased muscle mass and strength in normal and disease animal models. In this study, a mouse model of ALS (SOD1(G93A) transgenic mice) was treated with a soluble activin receptor, type IIB (ActRIIB.mFc) which is a putative endogenous signaling receptor for myostatin in addition to other ligands of the TGF-beta superfamily. ActRIIB.mFc treatment produces a delay in the onset of weakness, an increase in body weight and grip strength, and an enlargement of muscle size whether initiated pre-symptomatically or after symptom onset. Treatment with ActRIIB.mFc did not increase survival or neuromuscular junction innervation in SOD1(G93A) transgenic mice. Pharmacologic treatment with ActRIIB.mFc was superior in all measurements to genetic deletion of myostatin in SOD1(G93A) transgenic mice. The improved function of SOD1(G93A) transgenic mice following treatment with ActRIIB.mFc is encouraging for the development of TGF-beta pathway inhibitors to increase muscle strength in patients with ALS.

A global benchmark study using affinity-based biosensors

To explore the variability in biosensor studies, 150 participants from 20 countries were given the same protein samples and asked to determine kinetic rate constants for the interaction. We chose a protein system that was amenable to analysis using different biosensor platforms as well as by users of different expertise levels. The two proteins (a 50-kDa Fab and a 60-kDa glutathione S-transferase [GST] antigen) form a relatively high-affinity complex, so participants needed to optimize several experimental parameters, including ligand immobilization and regeneration conditions as well as analyte concentrations and injection/dissociation times. Although most participants collected binding responses that could be fit to yield kinetic parameters, the quality of a few data sets could have been improved by optimizing the assay design. Once these outliers were removed, the average reported affinity across the remaining panel of participants was 620 pM with a standard deviation of 980 pM. These results demonstrate that when this biosensor assay was designed and executed appropriately, the reported rate constants were consistent, and independent of which protein was immobilized and which biosensor was used.

Host-shaped segregation of the Cryptosporidium parvum multilocus genotype repertoire

Cattle are among the major reservoirs of Cryptosporidium parvum in nature. However, the relative contribution of C. parvum oocysts originating from cattle to human disease burden is difficult to assess, as various transmission pathways -- including the human to human route -- can co-occur. In this study, multilocus genotype richness of representative samples of human and bovine C. parvum are compared statistically using analytical rarefaction and non-parametric taxonomic richness estimators. Results suggest that in the time and space frames underlying the analysed data, humans were infected with significantly wider spectra of C. parvum genotypes than cattle, and consequently, a significant fraction of human infections may not have originated from the regional bovine reservoirs. This study provides statistical support to the emerging idea of the existence of distinct anthroponotic C. parvum cycles that do not involve cattle.

Prediction of penicillin resistance in Staphylococcus aureus isolates from dairy cows with mastitis, based on prior test results

AIM

To gauge how well prior laboratory test results predict in vitro penicillin resistance of Staphylococcus aureus isolates from dairy cows with mastitis.

METHODS

Population-based data on the farm of origin (n=79), genotype based on pulsed-field gel electrophoresis (PFGE) results, and the penicillin-resistance status of Staph. aureus isolates (n=115) from milk samples collected from dairy cows with mastitis submitted to two diagnostic laboratories over a 6-month period were used. Data were mined stochastically using the all-possible-pairs method, binomial modelling and bootstrap simulation, to test whether prior test results enhance the accuracy of prediction of penicillin resistance on farms.

RESULTS

Of all Staph. aureus isolates tested, 38% were penicillin resistant. A significant aggregation of penicillin-resistance status was evident within farms. The probability of random pairs of isolates from the same farm having the same penicillin-resistance status was 76%, compared with 53% for random pairings of samples across all farms. Thus, the resistance status of randomly selected isolates was 1.43 times more likely to correctly predict the status of other isolates from the same farm than the random population pairwise concordance probability (p=0.011). This effect was likely due to the clonal relationship of isolates within farms, as the predictive fraction attributable to prior test results was close to nil when the effect of within-farm clonal infections was withdrawn from the model.

CONCLUSIONS

Knowledge of the penicillin-resistance status of a prior Staph. aureus isolate significantly enhanced the predictive capability of other isolates from the same farm. In the time and space frame of this study, clinicians using previous information from a farm would have more accurately predicted the penicillin-resistance status of an isolate than they would by chance alone on farms infected with clonal Staph. aureus isolates, but not on farms infected with highly genetically heterogeneous bacterial strains.

The occurrence of Cryptosporidium parvum, Campylobacter and Salmonella in newborn dairy calves in the Manawatu region of New Zealand

AIM

To determine the occurrence of Cryptosporidium parvum oocysts, Campylobacter spp and Salmonella spp in faecal samples taken from newborn dairy calves on 24 dairy farms in the Manawatu region of New Zealand.

METHODS

A cross-sectional study was conducted during the 2002 calving season. Faecal samples were collected from 185 newborn calves from a convenience sample of 24 dairy farms. The samples were tested microscopically for the presence of C. parvum oocysts, and bacteriologically for the presence of Campylobacter spp and Salmonella spp.

RESULTS

Infections with C. parvum were identified in 33/156 (21.2%) calves from 10 farms. More than 10(6) oocysts/g (OPG) faeces were detected in calves from four farms. Campylobacter spp were isolated from 58/161 (36%) calves from 18 farms; in particular, C. jejuni subsp jejuni was isolated from 11/161 (6.8%) calves from seven farms. Salmonellae were not detected.

CONCLUSIONS

Despite the short and concentrated calving pattern and the long interval between calving seasons characterising most dairy farms in New Zealand, C. parvum is widespread among calves. Campylobacter spp, especially C. jejuni, rapidly colonise the intestinal tract of newborn calves.

RELEVANCE

This study provided an estimate of the ecological impact of newborn dairy calves with regard to the potentially zoonotic enteric pathogens most frequently isolated from human gastrointestinal infections in New Zealand.

Epidemiological and molecular evidence of a monophyletic infection with Staphylococcus aureus causing a purulent dermatitis in a dairy farmer and multiple cases of mastitis in his cows

An epidemiological and molecular investigation of a cutaneous suppurative infection with Staphylococcus aureus in a dairy farmer, occurring concurrently with an outbreak of clinical mastitis in his herd, was carried out. A common aetiology for the diseases in the farmer and his cows was established by combining clinical evidence with a molecular genomic analysis of the bacterial isolates using pulsed field gel electrophoresis of DNA macro-restriction fragments. This case indicates the possibility of the emergence and circulation of anthropozoonotic clones of S. aureus in dairy herds. It also provides further evidence of the severe impact of infection with highly virulent clones on dairy lactating cattle.

Controlling the onset of natural cryptosporidiosis in calves with paromomycin sulphate

A prospective, controlled-blind field trial was conducted to evaluate the efficacy and safety of paromomycin sulphate, given for 10 days from birth, in preventing natural cryptosporidiosis in calves. In the untreated control group, oocyst shedding and diarrhoea followed the pattern that had occurred on the farm before the trial, consistent with a perinatal infection, whereas in the treated group, the prepatent period was significantly longer than in the control group (P < 0.01) and oocyst shedding and diarrhoea started only after the drug was withdrawn. However, the regimen did not reduce the incidence of disease in the treated group.

Regulatory mechanisms at the mouse Igf2/H19 locus

The closely linked H19 and Igf2 genes show highly similar patterns of gene expression but are reciprocally imprinted. H19 is expressed almost exclusively from the maternally inherited chromosome, while Igf2 expression is mostly from the paternal chromosome. In humans, loss of imprinting at this locus is associated with tumors and with developmental disorders. Monoallelic expression at the imprinted Igf2/H19 locus occurs by at least two distinct mechanisms: a developmentally regulated silencing of the paternal H19 promoter, and transcriptional insulation of the maternal Igf2 promoters. Both mechanisms of allele-specific silencing are ultimately dependent on a common cis-acting element located just upstream of the H19 promoter. The coordinated expression patterns and some experimental data support the idea that positive regulatory elements are also shared by the two genes. To clarify the organization and function of positive and negative regulatory elements at the H19/Igf2 locus, we analyzed two mouse mutations. First, we generated a deletion allele to localize enhancers used in vivo for expression of both H19 and Igf2 in mesodermal tissues to sequences downstream of the H19 gene. Coincidentally, we demonstrated that some expression of Igf2 is independent of the shared enhancer element. Second, we used this new information to further characterize an ectopic H19 differentially regulated region and the associated insulator. We demonstrated that its activity is parent-of-origin dependent. In contrast to recent results from Drosophila model systems; we showed that this duplication of a mammalian insulator does not interfere with its normal function. Implications of these findings for current models for monoallelic gene expression at this locus are discussed.

Dickkopf1 is required for embryonic head induction and limb morphogenesis in the mouse

Dickkopf1 (Dkk1) is a secreted protein that acts as a Wnt inhibitor and, together with BMP inhibitors, is able to induce the formation of ectopic heads in Xenopus. Here, we show that Dkk1 null mutant embryos lack head structures anterior of the midbrain. Analysis of chimeric embryos implicates the requirement of Dkk1 in anterior axial mesendoderm but not in anterior visceral endoderm for head induction. In addition, mutant embryos show duplications and fusions of limb digits. Characterization of the limb phenotype strongly suggests a role for Dkk1 both in cell proliferation and in programmed cell death. Our data provide direct genetic evidence for the requirement of secreted Wnt antagonists during embryonic patterning and implicate Dkk1 as an essential inducer during anterior specification as well as a regulator during distal limb patterning.

Knock-in mutation of the distal four tyrosines of linker for activation of T cells blocks murine T cell development

The integral membrane adapter protein linker for activation of T cells (LAT) performs a critical function in T cell antigen receptor (TCR) signal transduction by coupling the TCR to downstream signaling pathways. After TCR engagement, LAT is tyrosine phosphorylated by ZAP-70 creating docking sites for multiple src homology 2-containing effector proteins. In the Jurkat T cell line, the distal four tyrosines of LAT bind PLCgamma-1, Grb2, and Gads. Mutation of these four tyrosine residues to phenylalanine (4YF) blocked TCR-mediated calcium mobilization, Erk activation, and nuclear factor (NF)-AT activation. In this study, we examined whether these four tyrosine residues were essential for T cell development by generating LAT "knock-in" mutant mice that express the 4YF mutant protein under the control of endogenous LAT regulatory sequences. Significantly, the phenotype of 4YF knock-in mice was identical to LAT(-/)- (null) mice; thymocyte development was arrested at the immature CD4(-)CD8(-) stage and no mature T cells were present. Knock-in mice expressing wild-type LAT protein, generated by a similar strategy, displayed a normal T cell developmental profile. These results demonstrate that the distal four tyrosine residues of LAT are essential for preTCR signaling and T cell development in vivo.

GroEL-assisted refolding of adrenodoxin during chemical cluster insertion

Chemical reconstitution of recombinant bovine adrenal mitochondrial apoadrenodoxin was carried out in the presence of the nonhomologous chaperone protein GroEL and of the cochaperone GroES, both in the presence and in the absence of ATP. The approach used here was different from the one characterizing studies on chaperone activity, as we used an adrenodoxin apoprotein, devoid of the cluster iron and sulfide, rather than a denaturant-unfolded form of the protein, and catalytic amounts of the chaperone proteins. A possible scaffolding role for two bacterial sulfur transferases, namely, rhodanese from Azotobacter vinelandii and a rhodanese-like sulfurtransferase from Escherichia coli, was also investigated in the absence of the enzyme substrates. The extent and the rate of adrenodoxin refolding following cluster insertion was measured by spectroscopy and by monitoring the activity recovery in a NADPH-cytochrome c reduction assay. These measurements were carried out on the unresolved reaction mixture and on the adrenodoxin-containing fraction obtained by HPLC fractionation of the reconstitution mixture at different reaction times. The rate and extent of cluster insertion and activity recovery were substantially improved by addition of GroEL and increased with increasing the GroEL/apoadrenodoxin ratio. GroES and ATP had no effect by themselves, and did not enhance the effect of GroEL. A. vinelandii rhodanese, the E. coli sulfurtransferase, and bovine serum albumin had no effect on the rate and yield of chemical reconstitution. The accelerated chemical reconstitution of apoadrenoxin in the presence of GroEL is therefore attributable to a scaffolding effect of this protein.

Biochemical, phenotypic and neurophysiological characterization of a genetic mouse model of RSH/Smith--Lemli--Opitz syndrome

The RSH/Smith--Lemli--Opitz syndrome (RSH/SLOS) is a human autosomal recessive syndrome characterized by multiple malformations, a distinct behavioral phenotype with autistic features and mental retardation. RSH/SLOS is due to an inborn error of cholesterol biosynthesis caused by mutation of the 3 beta-hydroxysterol Delta(7)-reductase gene. To further our understanding of the developmental and neurological processes that underlie the pathophysiology of this disorder, we have developed a mouse model of RSH/SLOS by disruption of the 3 beta-hydroxysterol Delta(7)-reductase gene. Here we provide the biochemical, phenotypic and neurophysiological characterization of this genetic mouse model. As in human patients, the RSH/SLOS mouse has a marked reduction of serum and tissue cholesterol levels and a marked increase of serum and tissue 7-dehydrocholesterol levels. Phenotypic similarities between this mouse model and the human syndrome include intra-uterine growth retardation, variable craniofacial anomalies including cleft palate, poor feeding with an uncoordinated suck, hypotonia and decreased movement. Neurophysiological studies showed that although the response of frontal cortex neurons to the neurotransmitter gamma-amino-n-butyric acid was normal, the response of these same neurons to glutamate was significantly impaired. This finding provides insight into potential mechanisms underlying the neurological dysfunction seen in this human mental retardation syndrome and suggests that this mouse model will allow the testing of potential therapeutic interventions.

Targeted disruption of the Kcnq1 gene produces a mouse model of Jervell and Lange-Nielsen Syndrome

KCNQ1 encodes KCNQ1, which belongs to a family of voltage-dependent K(+) ion channel proteins. KCNQ1 associates with a regulatory subunit, KCNE1, to produce the cardiac repolarizing current, I(Ks). Loss-of-function mutations in the human KCNQ1 gene have been linked to Jervell and Lange-Nielsen Syndrome (JLNS), a disorder characterized by profound bilateral deafness and a cardiac phenotype. To generate a mouse model for JLNS, we created a line of transgenic mice that have a targeted disruption in the Kcnq1 gene. Behavioral analysis revealed that the Kcnq1(-/-) mice are deaf and exhibit a shaker/waltzer phenotype. Histological analysis of the inner ear structures of Kcnq1(-/-) mice revealed gross morphological anomalies because of the drastic reduction in the volume of endolymph. ECGs recorded from Kcnq1(-/-) mice demonstrated abnormal T- and P-wave morphologies and prolongation of the QT and JT intervals when measured in vivo, but not in isolated hearts. These changes are indicative of cardiac repolarization defects that appear to be induced by extracardiac signals. Together, these data suggest that Kcnq1(-/-) mice are a potentially valuable animal model of JLNS.

Targeted deletion of the gene encoding iron regulatory protein-2 causes misregulation of iron metabolism and neurodegenerative disease in mice

In mammalian cells, regulation of the expression of proteins involved in iron metabolism is achieved through interactions of iron-sensing proteins known as iron regulatory proteins (IRPs), with transcripts that contain RNA stem-loop structures referred to as iron responsive elements (IREs). Two distinct but highly homologous proteins, IRP1 and IRP2, bind IREs with high affinity when cells are depleted of iron, inhibiting translation of some transcripts, such as ferritin, or turnover of others, such as the transferrin receptor (TFRC). IRPs sense cytosolic iron levels and modify expression of proteins involved in iron uptake, export and sequestration according to the needs of individual cells. Here we generate mice with a targeted disruption of the gene encoding Irp2 (Ireb2). These mutant mice misregulate iron metabolism in the intestinal mucosa and the central nervous system. In adulthood, Ireb2(-/-) mice develop a movement disorder characterized by ataxia, bradykinesia and tremor. Significant accumulations of iron in white matter tracts and nuclei throughout the brain precede the onset of neurodegeneration and movement disorder symptoms by many months. Ferric iron accumulates in the cytosol of neurons and oligodendrocytes in distinctive regions of the brain. Abnormal accumulations of ferritin colocalize with iron accumulations in populations of neurons that degenerate, and iron-laden oligodendrocytes accumulate ubiquitin-positive inclusions. Thus, misregulation of iron metabolism leads to neurodegenerative disease in Ireb2(-/-) mice and may contribute to the pathogenesis of comparable human neurodegenerative diseases.

A large upstream region is not necessary for gene expression or hypersensitive site formation at the mouse beta -globin locus

Developmental expression at the beta-globin locus is regulated in part by the locus control region, a region upstream of the genes containing at least five major DNase I hypersensitive sites (HSs) in mammalian erythrocytes. Sequences farther 5' of these HSs are conserved in mouse and human, and both loci are embedded within a cluster of functional odorant receptor genes. In humans, distant upstream sequences have been implicated in regulation of the beta-globin genes. In this study, the role of the 5'-most HSs and their adjacent sequence was investigated by deletion of an 11-kb region from the mouse locus, including 5'HS 4.2, 5'HS 5, 5'HS 6, and the 5'beta1 odorant receptor gene. Mice that were homozygous for this deletion were fully viable, and no significant effect on adult beta-globin gene expression was seen. 5'HSs 1-4, which are located downstream of the deletion, were still present in the mutant mice. In addition, two new upstream HSs, HS -60.7 and HS -62.5, were found in erythroid tissue of both wild-type and mutant mice. Therefore, although the possibility of a minor role still exists, neither the HSs nor the other regions deleted in this study are essential for beta-globin gene expression, and it is unlikely that chromatin structure is affected either upstream or downstream of the deletion. This is the largest deletion at the mouse locus control region to show no apparent phenotype, and focuses attention on the possible contribution of sequences even farther upstream.

Generation and phenotype of mice harboring a nonsense mutation in the V2 vasopressin receptor gene

The V2 vasopressin receptor (V2R) plays a key role in the maintenance of a normal body water balance. To generate an in vivo model that allows the physiological and molecular analysis of the role of V2Rs in kidney function, we have created mouse lines that lack functional V2Rs by using targeted mutagenesis in mouse embryonic stem cells. Specifically, we introduced a nonsense mutation known to cause X-linked nephrogenic diabetes insipidus (XNDI) in humans (Glu242stop) into the mouse genome. V2R-deficient hemizygous male pups showed a decrease in basal urine osmolalities and were unable to concentrate their urine. These pups also exhibited an enlargement of renal pelvic space, failed to thrive, and died within the first week after birth due to hypernatremic dehydration. Interestingly, female mice heterozygous for the V2R mutation showed normal growth but displayed an XNDI-like phenotype, characterized by reduced urine concentrating ability of the kidney, polyuria, and polydipsia. Western blot analysis and immunoelectron microscopic studies showed that the loss of functional V2Rs had no significant effect on the basal expression levels of aquaporin-2 and the bumetanide-sensitive Na-K-2Cl cotransporter (BSC-1). The V2R mutant mice described here should serve as highly useful tools for the development of novel therapeutic strategies for the treatment of XNDI.

A transcriptional insulator at the imprinted H19/Igf2 locus

Igf2 and H19 exhibit parent-of-origin-specific monoallelic expression. H19 is expressed from the maternal chromosome and Igf2 from the paternal. The two genes share enhancer elements and monoallelic expression of both genes is dependent on cis-acting sequences upstream of the H19 promoter. In this work we examine the mechanisms by which this region silences the maternal Igf2 allele and we demonstrate that deletion of this region can result in high levels of activation of both H19 and Igf2 from a single chromosome. Moreover, by inserting this cis element between a promoter and its enhancer at a heterologous position, we demonstrate that the sequences carry both insulator activity and the ability to be stably imprinted. We also characterize the insulator in vitro and show that it is neither enhancer nor promoter specific.

H19 and Igf2 monoallelic expression is regulated in two distinct ways by a shared cis acting regulatory region upstream of H19

H19 and Igf2 are expressed in a monoallelic fashion from the maternal and paternal chromosomes, respectively. A region upstream of H19 has been shown to regulate such imprinted expression of both genes in cis. We have taken advantage of a loxP/cre recombinase-based strategy to delete this region in mice in a conditional manner to determine the temporal requirement of the upstream region in initiating and maintaining the imprinted expression of H19 and Igf2. Analysis of allele-specific expression of H19 and Igf2 and DNA methylation at the H19 promoter demonstrates that this region controls the monoallelic expression of the two genes in different ways, suggesting that it harbors two functionally distinct regulatory elements. Continued presence of the region is required to silence maternal Igf2 in accordance with its proposed role as an insulator. However, it does not have a direct role in keeping the paternal H19 promoter silenced. Instead, on the paternal chromosome, the upstream element mediates epigenetic modifications of the H19 promoter region during development, leading to transcriptional silencing of H19. Thereafter, its presence is redundant for preventing transcription. Presently, this temporal requirement of the silencing element appears to be a unique cis activity in the mammalian system. However, it is likely that other cis-acting elements, positive and negative, have the ability to effect stable changes in the chromatin structure and are not constantly required to give signals to the transcriptional machinery.

Glial cell line-derived neurotrophic factor receptor alpha1 availability regulates glial cell line-derived neurotrophic factor signaling: evidence from mice carrying one or two mutated alleles

Glial cell line-derived neurotrophic factor receptor alpha1 (GFRalpha1, also known as GDNFR-alpha) is a glycolipid-anchored membrane protein of the GFRalpha family, which binds glial cell line-derived neurotrophic factor [Jing S. et al. (1996) Cell 85, 1113-1124; Treanor J. J. et al. (1996) Nature 382, 80-83], a survival factor for several populations of central and peripheral neurons, including midbrain dopamine neurons [Lin L. F. et al. (1993) Science 260, 1130-1132], and mediates its ligand-induced cell response via a tyrosine kinase receptor called Ret [Takahashi M. et al. (1988) Oncogene 3, 571-578; Takahashi M. and Cooper G. M. (1987) Molec. Cell Biol. 7, 1378-1385]. In this paper, we show that mice with a null mutation of the GFRalpha1 gene manifest epithelial-mesenchymal interaction deficits in kidney and severe disturbances of intestinal tract development similar to those seen with glial cell line-derived neurotrophic factor or Ret null mutations. There is a marked renal dysgenesis or agenesis and the intrinsic enteric nervous system fails completely to develop. We also show that newborn GFRalpha1-deficient mice display no or minimal changes in dorsal root and sympathetic ganglia. This is in contrast to the deficits reported in these neuronal populations in glial cell line-derived neurotrophic factor and Ret null mutations. Mesencephalic dopaminergic neurons in the substantia nigra and ventral tegmental area appear intact at the time of birth of the mutated mice. Mice homozygous for the GFRalpha1 null mutation die within 24 h of birth because of uremia. Heterozygous animals, however, live to adulthood. There is a significantly reduced neuroprotective effect of glial cell line-derived neurotrophic factor in such heterozygous animals, compared with wild-type littermates, after cerebral ischemia. Taken together with previous data on glial cell line-derived neurotrophic factor and Ret, our results strongly suggest that GFRalpha1 is the essential GFRalpha receptor for signaling in the glial cell line-derived neurotrophic factor-Ret pathway in the kidney and enteric nervous system development, and that GFRalpha2 or GFRalpha3 cannot substitute for the absence of GFRalpha1. Moreover, neuroprotective actions of exogenous glial cell line-derived neurotrophic factor also require full GFRalpha1 receptor expression.

Gene dosage affects the cardiac and brain phenotype in nonmuscle myosin II-B-depleted mice

Complete ablation of nonmuscle myosin heavy chain II-B (NMHC-B) in mice resulted in cardiac and brain defects that were lethal during embryonic development or on the day of birth. In this paper, we report on the generation of mice with decreased amounts of NMHC-B. First, we generated B(DeltaI)/B(DeltaI) mice by replacing a neural-specific alternative exon with the PGK-Neo cassette. This resulted in decreased amounts of NMHC-B in all tissues, including a decrease of 88% in the heart and 65% in the brain compared with B(+)/B(+) tissues. B(DeltaI)/B(DeltaI) mice developed cardiac myocyte hypertrophy between 7 months and 11 months of age, at which time they reexpressed the cardiac beta-MHC. Serial sections of B(DeltaI)/B(DeltaI) brains showed abnormalities in neural cell migration and adhesion in the ventricular wall. Crossing B(DeltaI)/B(DeltaI) with B(+)/B(-) mice generated B(DeltaI)/B(-) mice, which showed a further decrease of approximately 55% in NMHC-B in the heart and brain compared with B(DeltaI)/B(DeltaI) mice. Five of 8 B(DeltaI)/B(-) mice were born with a membranous ventricular septal defect. Moreover, 5 of 5 B(DeltaI)/B(-) mice developed myocyte hypertrophy by 1 month; B(DeltaI)/B(-) mice also reexpressed the cardiac beta-MHC. More than 60% of B(DeltaI)/B(-) mice developed overt hydrocephalus and showed more severe defects in neural cell migration and adhesion than did B(DeltaI)/B(DeltaI) mice. These data on B(DeltaI)/B(DeltaI) and B(DeltaI)/B(-) mice demonstrate a gene dosage effect of the amount of NMHC-B on the severity and time of onset of the defects in the heart and brain.