Loss of Neuron Navigator 2 Impairs Brain and Cerebellar Development

Cerebellar hypoplasia and dysplasia encompass a group of clinically and genetically heterogeneous disorders frequently associated with neurodevelopmental impairment. The Neuron Navigator 2 (NAV2) gene (MIM: 607,026) encodes a member of the Neuron Navigator protein family, widely expressed within the central nervous system (CNS), and particularly abundant in the developing cerebellum. Evidence across different species supports a pivotal function of NAV2 in cytoskeletal dynamics and neurite outgrowth. Specifically, deficiency of Nav2 in mice leads to cerebellar hypoplasia with abnormal foliation due to impaired axonal outgrowth. However, little is known about the involvement of the NAV2 gene in human disease phenotypes. In this study, we identified a female affected with neurodevelopmental impairment and a complex brain and cardiac malformations in which clinical exome sequencing led to the identification of NAV2 biallelic truncating variants. Through protein expression analysis and cell migration assay in patient-derived fibroblasts, we provide evidence linking NAV2 deficiency to cellular migration deficits. In model organisms, the overall CNS histopathology of the Nav2 hypomorphic mouse revealed developmental anomalies including cerebellar hypoplasia and dysplasia, corpus callosum hypo-dysgenesis, and agenesis of the olfactory bulbs. Lastly, we show that the NAV2 ortholog in Drosophila, sickie (sick) is widely expressed in the fly brain, and sick mutants are mostly lethal with surviving escapers showing neurobehavioral phenotypes. In summary, our results unveil a novel human neurodevelopmental disorder due to genetic loss of NAV2, highlighting a critical conserved role of the NAV2 gene in brain and cerebellar development across species.

Umbilical cord plasma 25-hydroxyvitamin D concentration and immune function at birth: the Urban Environment and Childhood Asthma study

BACKGROUND

Recent studies have reported conflicting data on the association between maternal intake of vitamin D during pregnancy and asthma.

OBJECTIVE

To assess the influence of prenatal vitamin D status on immune function at birth.

METHODS

In an inner-city birth cohort of 568 newborns, 520 of whom had at least one atopic parent, we measured the umbilical cord (UC) plasma concentration of 25-hydroxyvitamin D (25(OH)D) and the cytokine responses of UC blood mononuclear cells (UCMCs) to stimuli including phytohaemagglutinin (PHA), lipopolysaccharide (LPS), and peptidoglycan. In a subset, the UCMC expression of regulatory T cell markers and the suppressive activity of CD4(+) CD25(+) UCMCs were measured. Results The 25th, 50th, and 75th percentiles of UC plasma 25(OH)D level were 15.0, 20.2, and 25.6 ng/mL, respectively. Most cytokine responses of UCMC were not correlated with UC 25(OH)D concentration; however, IFN-γ release after LPS stimulation was weakly positively correlated with UC 25(OH)D concentration (r=0.11, P=0.01). PHA responses were not significantly correlated with 25(OH)D concentration. The UC plasma 25(OH)D concentration was inversely related to the number of CD25(+) (r=-0.20, P=0.06), CD25(Bright) (r=-0.21, P=0.05), and CD25(+) FoxP3 (r=-0.29, P=0.06) cells as a proportion of CD4(+) T cells in UC blood (r=-0.26, P=0.04) but not to the suppressive activity of CD4(+) CD25(+) cells (r=0.17, P=0.22).

CONCLUSION AND CLINICAL RELEVANCE

UC 25(OH)D concentration was not correlated with most UCMC cytokine responses to multiple stimuli. There was a suggestion of a weakly positive correlation with IFN-γ release after LPS stimulation. The proportions of CD25(+) , CD25(Bright) , and CD25(+) FoxP3 cells to total CD4(+) T cells were inversely correlated with UC 25(OH)D concentration. Our findings suggest that higher vitamin D levels at birth may be associated with a lower number of T-regulatory cells. Vitamin D status in utero may influence immune regulation in early life.

Topical H2 antagonist prevents periodontitis in a rabbit model

Cimetidine is a powerful H2 receptor antagonist that eliminates histamine's effects on chemotaxis, phagocytosis, and superoxide anion production by phagocytes. The purpose of this study was to analyze the clinical and histopathological changes associated with experimental periodontitis in rabbits in response to topically applied cimetidine. Experimental periodontitis was induced in 21 New Zealand White rabbits using Porphyromonas gingivalis (10(9) CFU) topically applied three times a week for a 6-week period to previously ligatured teeth. Topical application of cimetidine in a liposome carrier for the prevention of periodontitis was evaluated in four groups of four animals each: 1, 10, and 100 mg/ml and no treatment (positive control). In addition, there was a vehicle group (n = 3) that received liposome preparation (carrier) only, and two animals with ligature application alone served as negative controls. Periodontal disease was quantified by direct visualization and radiographical evaluation of bone loss on defleshed skulls and by histological analyses of sections stained with hematoxylin-eosin and tartrate-resistant acid phosphatase. In the no-treatment (positive control) and liposome (vehicle) groups, direct visualization and radiological measurements revealed statistically significant bone loss compared to the negative control. Application of cimetidine at all concentrations tested inhibited inflammation and bone loss by >90%. Histological findings revealed that ligated sites of the positive control and vehicle groups showed significant reduction in bone level (P < 0.05) compared to the three cimetidine groups, with a marked decrease in inflammation. The findings of this study provide morphological and histological evidence that topically active cimetidine is a potent inhibitor of P. gingivalis-elicited periodontal inflammation, arresting and/or preventing tissue destruction and influencing cell populations present in the inflammatory cell infiltrate.

Factors related to the use of bone densitometry: survey responses of 494 primary care physicians in New England

Large population-based surveys have shown that approximately 30% of people over age 65 years have osteoporosis and that 17% of the population over 65 years will sustain a fracture during their lifetime. Many people with osteoporosis are never being evaluated even though effective treatments are available. We examined why primary care physicians order few bone mineral density scans. We conducted a cross-sectional survey of primary care physicians practicing in any of the six New England states. Target physician specialties included internal medicine, general practitioners/family physicians, and obstetrician-gynecologists who had a facsimile number listed with the American Medical Association. Demographics, practice characteristics, use of bone densitometry, and attitudes regarding osteoporosis, bone densitometry and health maintenance were assessed by questionnaire. Twelve percent (n=494) of the physicians responded to the questionnaire. Respondents were similar to non-respondents with respect to years of practice, training and geographical state, though they were more likely to be female (p < or =0.05). Respondents had a mean age of 51 years, and 51% were trained in internal medicine, 25% in general practice/family practice and 24% in obstetrics-gynecology. The mean number of self-reported bone densitometry referrals per month was 10+/-11, and 25% of respondents reported that they referred fewer than 4 patients per month. In adjusted logistic models, factors significantly associated with referring fewer than 4 patients per month were: training in internal medicine (odds ratio (OR) 2.0, 95% confidence interval (CI) 1.0-3.9) or general practice/family practice (OR 2.6, 95% CI 1.3-5.2) versus obstetrics-gynecology; practicing in an urban setting (OR 2.5, 95% CI 1.3-4.9) or rural/small town setting (OR 2.2, 95% CI 1.2-4.1) versus a suburban setting; spending less than 50% of professional time in patient care (OR 4.0, 95% CI 1.7-9.5); seeing the lowest proportion of postmenopausal women (OR 2.5., 95% CI 1.2-5.3); the belief that calcium and vitamin D are adequate to treat osteoporosis (OR 2.1, 95% CI 1.0-4.5); and the belief that osteoporosis treatment should not be based on bone density results (OR 3.2, 95% CI 1.7-6.1). Potentially modifiable physician beliefs and a number of practice characteristics are associated with low referral rates for bone densitometry. Educational strategies aimed at improving the use of bone density testing should consider these factors.

Atrichia caused by mutations in the vitamin D receptor gene is a phenocopy of generalized atrichia caused by mutations in the hairless gene

Generalized atrichia with papules is a rare disorder characterized by loss of hair shortly after birth and development of cutaneous cysts. Mutations in the hairless gene (HR) cause this phenotype in both mouse and human. Here we present a case of atrichia with papules in a patient with a normal HAIRLESS gene but with mutations in both alleles of the VITAMIN D RECEPTOR. The patient exhibited vitamin D resistant rickets, which was confirmed by an absent response of her fibroblasts to 1,25-dihydroxyvitamin D3 in vitro. Similar to individuals with HAIRLESS mutations, her skin showed an absence of normal hair follicles and the presence of follicular remnants and cysts. The cyst epithelium contained keratin-15- and keratin-17-positive cells suggesting derivation from the hair follicle bulge and the presence of epithelial stem cells. Although hair loss has been reported in association with hereditary vitamin D resistant rickets, we now characterize this alopecia as clinically and pathologically indistinguishable from generalized atrichia with papules, which was previously thought to be caused only by mutations in HAIRLESS. These findings suggest that VDR and HR, which are both zinc finger proteins, may be in the same genetic pathway that controls postnatal cycling of the hair follicle.

Differential cellular localization of estrogen receptor alpha in uterine and mammary cells

The classical alpha isoform of the estrogen receptor (ER) has been reported to localize almost exclusively in the nucleus. However, studies on non-genomic steroid effects have also suggested the existence of ERs residing at the cell surface. In this work, we present immunological data supporting extra-nuclear ERalpha localization in uterine (SHM) and mammary (MCF-7) cell lines. Immunocytological studies performed on SHM cells revealed that native ERs mainly localize as a perinuclear cytoplasmic ring. The receptors were rapidly translocated to the nucleus by 17beta-estradiol. In addition to nuclear ERs, a peripheral reservoir of ERalpha immunoreactivity, most probably associated with the plasma membrane, was detected in MCF-7 cells. These results were confirmed by the detection of membrane estrogen binding sites using fluorescent estrogen-BSA derivatives and ligand binding assays to intact cells, where [3H]-estradiol could be partly displaced by impeded estrogen conjugates. Partial inhibition of radioligand binding by an antibody against the steroid binding domain of the ERalpha suggests that the isoform faces the extracellular media in MCF-7 cells. Moreover, ERalpha-like proteins ( approximately 67 kDa) were found to be associated in isolated membrane subfractions from the cells. However, immunocytology of COS-1 (ER-negative) and SHM cells transfected with the complete cDNA coding for the cloned ERalpha and beta isoforms showed exclusive nuclear localization of the overexpressed ERs. The non-classical distribution of native ERalpha-like proteins in each cell line, suggests an alternative mode of ERalpha cellular localization/function. Cell type-dependent processing may account for the differential localization shown by native and expressed receptors in the systems considered.

Administration of DAB389IL-2 to patients with recalcitrant psoriasis: a double-blind, phase II multicenter trial

BACKGROUND

Current therapies for recalcitrant psoriasis focus on immunoregulation and targeting of activated T-lymphocytes rather than keratinocytes. Previous studies with low doses of the lymphocyte-selective fusion protein DAB389IL-2 have shown benefit to patients with psoriasis.

OBJECTIVE

We examined the safety and efficacy of DAB389IL-2 in 41 volunteers receiving more frequent and higher doses than in a previous trial.

METHODS

Patients were randomized to receive either placebo or 5, 10, or 15 microg/kg daily of DAB389IL-2 intravenously for 3 consecutive days each week for 4 consecutive weeks with a subsequent 4-week observation period.

RESULTS

Of the placebo group, 17% (2 of 12) exhibited at least 50% improvement from baseline Psoriasis Area and Severity Index scores at the end of the study, whereas 24% of all treated patients (7 of 29) showed the same improvement. Overall, 3 of 12 (25%) patients given placebo as opposed to 12 of 29 (41%) patients treated with DAB389IL-2 improved to this same extent at some point during the study. The rate of improvement for treated patients was significantly greater than for placebo patients (p = 0.04; repeated measures ANOVA). Among treated patients, decreases in Psoriasis Area and Severity Index scores were paralleled by changes in the Physician's Global Assessment and the Dermatology Life Quality Index. Treatment in ten patients was discontinued because of adverse events. Flu-like symptoms were the most common with severity increasing at the two higher doses. Only one serious adverse event was reported. This occurred in a patient receiving 5 microg/kg daily who experienced vasospasm and a coagulopathy resulting in arterial thrombosis.

CONCLUSION

Our findings are consistent with the potential antipsoriatic activity of DAB389IL-2 demonstrated in an earlier study. However, DAB389IL-2 was less well tolerated at this dosing regimen, particularly at the highest dose, and it was too toxic at these doses and schedules to be considered in the routine treatment of psoriasis.

Differentiating between orchiectomized rats and controls using measurements of trabecular bone density: a comparison among DXA, histomorphometry, and peripheral quantitative computerized tomography

In studies of rat bone metabolism, trabecular bone density should be measured. Three established methods of measuring trabecular bone include trabecular bone volume by histomorphometry (BV/TV%), trabecular bone density by peripheral quantitative computerized tomography (pQCT), and areal bone density of trabecular-rich regions by dual x-ray absorptiometry (DXA). We compared the ability of these three methods to discriminate between orchiectomized (orchidectomized) rats and controls. Sixteen male Sprague-Dawley rats (400-425 g) were orchiectomized, and 16 others were controls. In vivo spine bone mineral density (BMD) was measured at the beginning of the study and again after 11 weeks. Rats were sacrificed, and ex vivo BMDs of the right femur and tibia were measured by DXA, followed by trabecular bone density of the right proximal tibia by pQCT. BT/TV% of the left proximal tibia was measured by histomorphometry. Differences between groups were detected by all three methods, but both the magnitude of the difference between groups and the variance of the measurements was much greater for histomorphometry and pQCT than for DXA. Consequently, the statistical significance for the difference between groups was comparable for all three methods. Of the sites measured with DXA, the proximal tibia had the greatest statistical significance for the difference between groups. In summary, all three methods can demonstrate the effect of orchiectomy on trabecular bone. The large differences between groups seen by histomorphometry are also seen by pQCT but not by DXA. We conclude that trabecular bone density by pQCT may be a reasonable surrogate for measurements by histomorphometry.

1,25-Dihydroxyvitamin D3 increases secretion of insulin-like growth factor binding protein-4 (IGFBP-4) by human osteoblast-like cells in vitro and elevates IGFBP-4 serum levels in vivo

Insulin-like growth factors (IGFs) and IGF-binding proteins (IGFBPs) are thought to play an important role in the regulation of bone metabolism. In the present study, we investigated the effect of 1,25-dihydroxyvitamin D(3) [1,25-(OH)2D3] on the expression and secretion of IGFBPs in human osteoblast-like osteosarcoma cells (MG63) and untransformed human bone-derived cells in vitro. Northern blot analysis revealed that 1,25-(OH)2D3 (10(-8) mol/L) increased IGFBP-4 messenger RNA maximally 11-fold over control level in MG63 cells (after 24 h treatment) and 2.8-fold in human bone-derived cells (at 10(-10) mol/L). 1,25-(OH)2D3 increased secretion of IGFBP-4 2- and 3-fold, respectively, in MG63 cells and in human bone-derived cells. In normal human bone-derived cells, 1,25-(OH)2D3 also stimulated messenger RNA expression (3.9-fold) and the secretion of IGFBP-3 (2.2-fold). 1,25-(OH)2D3 also increased IGFBP-4 expression in skin fibroblasts but not in hepatocellular carcinoma cells. Consistent with these in vitro findings, treatment of human subjects with high doses of oral 1,25-(OH)2D3 (2-3 micrograms/day) for psoriasis resulted in a significant increase in serum IGFBP-4 concentration compared with pretreatment levels. Our observations present direct evidence that 1,25-(OH)2D3 plays an important role in the regulation of IGFBP secretion in vitro and in vivo.

Therapy with parenteral pamidronate prevents thyroid hormone-induced bone turnover in humans

Bisphosphonates have been shown to decrease bone turnover in a variety of high turnover states. We postulated that pamidronate (APD), a bisphosphonate, could prevent the increased bone turnover caused by thyroid hormone excess. Twenty-two male subjects were randomized to receive either placebo (group 1) or APD (30 mg, iv, daily for 2 days; group 2). Subsequently, all subjects received T3 (50 micrograms, twice daily, for 8 days). Biochemical indices of bone turnover were measured in blood and urine at baseline, after treatment with APD/placebo, and after treatment with T3. The urinary calcium/creatinine ratio (Uca/cr) fell significantly after treatment with APD, but not after treatment with placebo (group 1, 0.131 +/- 0.021; group 2, 0.040 +/- 0.013 mmol Ca/mmol Cr; P < 0.002). After treatment with T3, Uca/cr rose significantly in group 1, but not in group 2 (group 1, 0.275 +/- 0.042; group 2, 0.065 +/- 0.025 mmol Ca/mmol Cr; P < 0.05). Thus, APD prevented the rise in Uca/cr caused by treatment with T3. Similar results were obtained with urinary hydroxyproline and urinary pyridinoline cross-links. We conclude that 8 days of mild thyroid hormone excess in normal men increases bone turnover, and prior administration of APD prevents thyroid hormone-induced increases in bone resorption. APD may be useful in the prevention of thyroid hormone-induced osteopenia.

Quantification and kinetics of 25-hydroxyvitamin D3 by isotope dilution liquid chromatography/thermospray mass spectrometry

A liquid chromatography/thermospray mass spectrometry method has been developed and used to measure the plasma levels and half-life of 25-hydroxyvitamin D3 in adults. The mean plasma levels of 25-hydroxyvitamin D3 averaged 40 ng ml-1 (n = 4) in summer and 30 ng ml-1 (n = 6) in winter. The method was also used to determine the half-life of serum 25-hydroxyvitamin D3 in subjects maintained on either high or low-fiber diets who had been given an intravenous infusion of (6,19,19-2H3)25-hydroxyvitamin D3 sufficient to label 5% of their estimated body pools. The half-life was determined to be 10.4 days (n = 4), which is approximately 50% of the currently accepted value of 19 days, determined using radiolabeled methods. This difference may be due to kinetic isotope effects arising as a result of the tritiated compounds being labeled at sites that undergo Cyt-P450-catalyzed oxidations.

The 24/25-kDa serum insulin-like growth factor-binding protein is increased in elderly women with hip and spine fractures

Fractures of the hip in elderly women represent a clinical syndrome (age-related osteoporosis) often marked by decreased calcium absorption and secondary hyperparathyroidism. We studied 13 elderly women with fractures of the hip and spine and 18 healthy similarly aged control women to determine whether serum insulin-like growth factor-I (IGF-I) or its carrier binding proteins (IGFBPs) were altered in this syndrome. Serum IGF-I concentrations were not different in the two groups (P = 0.50), but immunoreactive PTH was significantly higher in the fracture group (58.50 +/- 8.20 vs. 13.50 +/- 2.70 ng/L; P less than 0.003). Binding of [125I]IGF-I to IGFBP-3, IGFBP-2, and IGFBP-1, measured by ligand blotting, was not statistically different in the 2 groups, but binding intensities for the serum 24/25-kDa IGFBP were approximately 2.5 times greater in fracture women than control women (P less than 0.0005). In data pooled from both groups, PTH correlated strongly (r = 0.70; P less than 0.0001) with the relative binding intensities for the 24/25-kDa IGFBP. Based on previous work, we speculate that production of the 24/25-kDa IGFBP, which in vitro is known to inhibit IGF-I- and IGF-II-mediated osteoblast function, may be stimulated by PTH in patients with the syndrome of age-related osteoporosis.

Treatment of psoriatic arthritis with oral 1,25-dihydroxyvitamin D3: a pilot study

We conducted a 6-month open-label trial in which 10 patients with active psoriatic arthritis received 2 micrograms of oral 1,25-dihydroxyvitamin D3 daily. Statistically significant improvement was noted in the tender joint count and physician global impression. Of these 10 patients, 4 had substantial (greater than or equal to 50%) improvement, and 3 had moderate (greater than or equal to 25%) improvement in the tender joint count. Two patients were unable to receive therapeutic doses because of hypercalciuria. High-dose vitamin D may be a useful therapeutic agent for psoriatic arthritis.

D-Mannitol dehydrogenase from Absidia glauca. Purification, metabolic role, and subunit interactions

When Absidia glauca was grown in minimal media with D-mannitol as the only source of carbon, an NAD+ specific D-mannitol dehydrogenase (EC 1.1.1.67) was induced. The crude extract also gave evidence of mannitol kinase, mannitol-1-phosphate dehydrogenase, phosphofructokinase, and L-iditol dehydrogenase activity. The heat labile purified preparation was judged enzymically homogeneous based on evidence derived from substrate specificity studies and activity staining, following disc gel electrophoresis. The enzymic monomer, with a weight of about 67000 daltons, slowly polymerizes when stored at -20 degrees C, giving a multiplicity of protein bands on electrophoresis distributed predominantly across a spectrum from dimer to pentamer, with enzymic activity resident predominantly in even multiples of the monomer. Depolymerization occurred rapidly (hours) when a frozen preparation was brought to and held between 4 and 20 degrees C. Aggregate fragmentation with sodium dodecyl sulfate showed a time-temperature dependence, terminating in a subunit component of 13000 daltons. pH optimum for polyol oxidation occurs at 9.6 (NaOH-glycine buffer) while ketose reduction proceeded most rapidly at pH 7.0-7.2 (phosphate buffer). A regulatory role is suggested for this enzyme based on dead-end inhibition by mannitol 1-phosphate, multiple enzyme forms, and its locus at the initiation site for mannitol utilization. The physiological relevance of low-temperature aggregation to regulatory control remains to be established.