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1.  A Differential Dielectric Affinity Glucose Sensor 
Lab on a chip  2013;14(2):294-301.
A continuous glucose monitor with a differential dielectric sensor implanted within the subcutaneous tissue that determines the glucose in the interstitial fluid is presented. The device, created using microelectromechanical systems (MEMS) technology, consists of sensing and reference modules that are identical in design and placed in close proximity. Each module contains a microchamber housing a pair of capacitive electrodes residing on the device substrate and embedded in a suspended, perforated polymer diaphragm. The microchambers, enclosed in semi-permeable membranes, are filled with either a polymer solution that has specific affinity to glucose or a glucose-insensitive reference solution. To accurately determine the glucose concentration, changes in the permittivity of the sensing and the reference solutions induced by changes in glucose concentration are measured differentially. In vitro characterization demonstrated the sensor capable of measuring glucose concentrations from 0 to 500 mg/dL with resolution and accuracy of ∼1.7 μg/dL and ∼1.74 mg/dL, respectively. In addition, device drift was reduced to 1.4% (uncontrolled environment) and 11% (5 °C of temperature variation) of that from non-differential measurements, indicating significant stability improvements. Preliminary animal testing demonstrated that the differential sensor accurately tracks glucose concentration in blood. This sensor can potentially be used clinically as a subcutaneously implanted continuous monitoring device in diabetic patients.
PMCID: PMC3893139  PMID: 24220675
2.  Effects of a novel MC4R agonist on maintenance of reduced body weight in diet induced obese mice 
Obesity (Silver Spring, Md.)  2014;22(5):1287-1295.
The physiology of the weight reduced (WR) state suggests that pharmacologic agents affecting energy homeostasis may have greater efficacy in WR individuals. Our aim was to establish a protocol that allows for evaluation of efficacy of weight maintenance agents and to assess the effectiveness of AZD2820, a novel melanocortin 4 receptor agonist in such a paradigm.
Design and Methods
MC4R agonist was administered in stratified doses to mice who were either fed high fat diet ad libitum (AL) throughout the study; or stabilized at a 20% reduced body weight (BW), administered the drug for four weeks, and thereafter released from caloric restriction while continuing to receive the drug (WR).
After release of WR mice to AL feeding, the high-dose group (53.4nmol/day) regained 12.4% less BW than their vehicle-treated controls. In WR mice, 10.8nmol/day of the agonist was sufficient to maintain these animals at 95.1% of initial BW vs 53.4nmol/day required to maintain the BW of AL animals (94.5%).
In the WR state, the MC4R agonist was comparably efficacious to a 5-fold higher dose in the AL state. This protocol provides a model for evaluating the mechanisms and quantitative efficacy of weight-maintenance strategies and agents.
PMCID: PMC4008720  PMID: 24318934
3.  Genetic Variants Associated with Breast Cancer Risk for Ashkenazi Jewish Women with Strong Family Histories but No Identifiable BRCA1/2 Mutation 
Human genetics  2013;132(5):523-536.
The ability to establish genetic risk models is critical for early identification and optimal treatment of breast cancer. For such a model to gain clinical utility, more variants must be identified beyond those discovered in previous genome wide association studies (GWAS). This is especially true for women at high risk because of family history, but without BRCA1/2 mutations.
This study incorporates three datasets in a GWAS analysis of women with Ashkenazi Jewish (AJ) homogeneous ancestry. Two independent discovery cohorts were comprised of 239 and 238 AJ women with invasive breast cancer or preinvasive ductal carcinoma in situ and strong family histories of breast cancer, but lacking the three BRCA1/2 founder mutations, along with 294 and 230 AJ controls, respectively. An independent, third cohort of 203 AJ cases with familial breast cancer history and 263 healthy controls of AJ women was used for validation.
A total of 19 SNPs were identified as associated with familial breast cancer risk in AJ women. Among these SNPs, 13 were identified from a panel of 109 discovery SNPs, including an FGFR2 haplotype. Additionally, 6 previously identified breast cancer GWAS SNPs were confirmed in this population. Seven of the 19 markers were significant in a multivariate predictive model of familial breast cancer in AJ women, 3 novel SNPs [rs17663555(5q13.2), rs566164(6q21), and rs11075884(16q22.2)], the FGFR2 haplotype, and 3 previously published SNPs [rs13387042(2q35), rs2046210(ESR1), and rs3112612(TOX3)], yielding moderate predictive power with an area under the curve (AUC) of the ROC (receiver-operator characteristic curve) of 0.74.
Population-specific genetic variants in addition to variants shared with populations of European ancestry may improve breast cancer risk prediction among AJ women from high-risk families without founder BRCA1/2 mutations.
PMCID: PMC4072456  PMID: 23354978
Ashkenazi Jewish; breast cancer; genome-wide association study; SNP; risk model; AUC
4.  A MEMS differential viscometric sensor for affinity glucose detection in continuous glucose monitoring 
Micromachined viscometric affinity glucose sensors have been previously demonstrated using vibrational cantilever and diaphragm. These devices featured a single glucose detection module that determines glucose concentrations through viscosity changes of glucose-sensitive polymer solutions. However, fluctuations in temperature and other environmental parameters might potentially affect the stability and reliability of these devices, creating complexity in their applications in subcutaneously implanted continuous glucose monitoring (CGM). To address these issues, we present a MEMS differential sensor that can effectively reject environmental disturbances while allowing accurate glucose detection. The sensor consists of two magnetically driven vibrating diaphragms situated inside microchambers filled with a boronic-acid based glucose-sensing solution and a reference solution insensitive to glucose. Glucose concentrations can be accurately determined by characteristics of the diaphragm vibration through differential capacitive detection. Our in-vitro and preliminary in-vivo experimental data demonstrate the potential of this sensor for highly stable subcutaneous CGM applications.
PMCID: PMC3743269  PMID: 23956499
Viscometric glucose sensor; differential measurement; affinity detection
5.  Responses of Gut Microbiota to Diet Composition and Weight Loss in Lean and Obese Mice 
Obesity (Silver Spring, Md.)  2011;20(4):10.1038/oby.2011.111.
Maintenance of a reduced body weight is accompanied by a decrease in energy expenditure beyond that accounted for by reduced body mass and composition, as well as by an increased drive to eat. These effects appear to be due— in part—to reductions in circulating leptin concentrations due to loss of body fat. Gut microbiota have been implicated in the regulation of body weight. The effects of weight loss on qualitative aspects of gut microbiota have been studied in humans and mice, but these studies have been confounded by concurrent changes in diet composition, which influence microbial community composition. We studied the impact of 20% weight loss on the microbiota of diet-induced obese (DIO: 60% calories fat) mice on a high-fat diet (HFD). Weight-reduced DIO (DIO-WR) mice had the same body weight and composition as control (CON) adlibitum (AL) fed mice being fed a control diet (10% calories fat), allowing a direct comparison of diet and weight-perturbation effects. Microbial community composition was assessed by pyrosequencing 16S rRNA genes derived from the ceca of sacrificed animals. There was a strong effect of diet composition on the diversity and composition of the microbiota. The relative abundance of specific members of the microbiota was correlated with circulating leptin concentrations and gene expression levels of inflammation markers in subcutaneous white adipose tissue in all mice. Together, these results suggest that both host adiposity and diet composition impact microbiota composition, possibly through leptin-mediated regulation of mucus production and/or inflammatory processes that alter the gut habitat.
PMCID: PMC3871199  PMID: 21593810
6.  Continuous Monitoring of Glucose in Subcutaneous Tissue Using Microfabricated Differential Affinity Sensors 
We describe miniaturized differential glucose sensors based on affinity binding between glucose and a synthetic polymer. The sensors possess excellent resistance to environmental disturbances and can potentially allow wireless measurements of glucose concentrations within interstitial fluid in subcutaneous tissue for long-term, stable continuous glucose monitoring (CGM).
The sensors are constructed using microelectromechanical systems (MEMS) technology and exploit poly(N-hydroxy-ethyl acrylamide-ran-3-acrylamidophenylboronic acid) (PHEAA-ran-PAAPBA), a glucose-binding polymer with excellent specificity, reversibility, and stability. Two sensing approaches have been investigated, which respectively, use a pair of magnetically actuated diaphragms and perforated electrodes to differentially measure the glucose-binding-induced changes in the viscosity and permittivity of the PHEAA-ran-PAAPBA solution with respect to a reference, glucose-unresponsive polymer solution.
In vivo characterization of the MEMS affinity sensors were performed by controlling blood glucose concentrations of laboratory mice by exogenous glucose and insulin administration. The sensors experienced an 8–30 min initialization period after implantation and then closely tracked commercial capillary glucose meter readings with time lags ranging from 0–15 min during rapid glucose concentration changes. Clarke error grid plots obtained from sensor calibration suggest that, for the viscometric and dielectric sensors, respectively, approximately 95% (in the hyperglycemic range) and 84% (ranging from hypoglycemic to hyperglycemic glucose concentrations) of measurement points were clinically accurate, while 5% and 16% of the points were clinically acceptable.
The miniaturized MEMS sensors explore differential measurements of affinity glucose recognition. In vivo testing demonstrated excellent accuracy and stability, suggesting that the devices hold the potential to enable long-term and reliable CGM in clinical applications.
PMCID: PMC3570886  PMID: 23294791
animal experiment; capacitive detection; continuous glucose monitoring; dielectric sensor; differential measurement; viscometric sensor
7.  Novel Association of Early Onset Hepatocellular Carcinoma with Transaldolase Deficiency 
JIMD Reports  2013;12:121-127.
We evaluated a family with a 16-month-old boy with cirrhosis and hepatocellular carcinoma and his 30-month-old brother with cirrhosis. After failing to identify a diagnosis after routine metabolic evaluation, we utilized a combination of RNA-Seq and whole exome sequencing to identify a novel homozygous p.Ser171Phe Transaldolase (TALDO1) variant in the proband, his brother with cirrhosis, as well as a clinically asymptomatic older 8-year-old brother. Metabolite analysis and enzymatic testing of TALDO1 demonstrated elevated ribitol, sedoheptitol, and sedoheptulose-7P, and lack of activity of TALDO1 in the three children homozygous for the p.Ser171Phe mutation. Our findings expand the phenotype of transaldolase deficiency to include early onset hepatocellular carcinoma in humans and demonstrate that, even within the same family, individuals with the same homozygous mutation demonstrate a wide range of phenotypes.
PMCID: PMC3897795  PMID: 24097415
8.  De novo copy number variants are associated with congenital diaphragmatic hernia 
Journal of medical genetics  2012;49(10):650-659.
Congenital diaphragmatic hernia (CDH) is a common birth defect with significant morbidity and mortality. Although the etiology of CDH remains poorly understood, studies from animal models and patients with CDH suggest that genetic factors play an important role in the development of CDH. Chromosomal anomalies have been reported in CDH.
In this study, the authors investigate the frequency of chromosomal anomalies and copy number variants in 256 parent-child trios of CDH using clinical conventional cytogenetic and microarray analysis. The authors also selected a set of CDH related training genes to prioritize the genes in those segmental aneuploidies and identified the genes and gene sets that may contribute to the etiology of CDH.
The authors identified chromosomal anomalies in 16 patients (6.3 %) of the series including 3 aneuploidies, 2 unbalanced translocation, and 11 patients with de novo CNVs ranging in size from 95 kb to 104.6 Mb. The authors prioritized the genes in the CNV segments and identified KCNA2, LMNA, CACNA1S, MYOG, HLX, LBR, AGT, GATA4, SOX7, HYLS1, FOXC1, FOXF2, PDGFA, FGF6, COL4A1, COL4A2, HOMER2, BNC1, BID, and TBX1 as genes that may be involved in diaphragm development. Gene enrichment analysis identified the most relevant gene ontology (GO) categories as those involved in tissue development (p=4.4×10−11) or regulation of multicellular organismal processes (p=2.8×10−10) and “receptor binding” (p = 8.7×10−14) and “DNA binding transcription factor activity” (p= 4.4×10−10).
Our findings support the role of chromosomal anomalies in CDH and provide a set of candidate genes including FOXC1, FOXF2, PDGFA, FGF6, COL4A1, COL4A2, SOX7,BNC1, BID, and TBX1 for further analysis in CDH.
PMCID: PMC3696999  PMID: 23054247
Congenital diaphragmatic hernia (CDH); copy number variant (CNV); chromosomal anomalies; gene priority; gene enrichment
9.  Flavopiridol Synergizes with Sorafenib to Induce Cytotoxicity and Potentiate Antitumorigenic Activity in EGFR/HER-2 and Mutant RAS/RAF Breast Cancer Model Systems12 
Neoplasia (New York, N.Y.)  2013;15(8):939-951.
Oncogenic receptor tyrosine kinase (RTK) signaling through the Ras-Raf-Mek-Erk (Ras-MAPK) pathway is implicated in a wide array of carcinomas, including those of the breast. The cyclin-dependent kinases (CDKs) are implicated in regulating proliferative and survival signaling downstream of this pathway. Here, we show that CDK inhibitors exhibit an order of magnitude greater cytotoxic potency than a suite of inhibitors targeting RTK and Ras-MAPK signaling in cell lines representative of clinically recognized breast cancer (BC) subtypes. Drug combination studies show that the pan-CDK inhibitor, flavopiridol (FPD), synergistically potentiated cytotoxicity induced by the Raf inhibitor, sorafenib (SFN). This synergy was most pronounced at sub-EC50 SFN concentrations in MDA-MB-231 (KRAS-G13D and BRAF-G464V mutations), MDA-MB-468 [epidermal growth factor receptor (EGFR) overexpression], and SKBR3 [ErbB2/EGFR2 (HER-2) overexpression] cells but not in hormone-dependent MCF-7 and T47D cells. Potentiation of SFN cytotoxicity by FPD correlated with enhanced apoptosis, suppression of retinoblastoma (Rb) signaling, and reduced Mcl-1 expression. SFN and FPD were also tested in an MDA-MB-231 mammary fat pad engraftment model of tumorigenesis. Mice treated with both drugs exhibited reduced primary tumor growth rates and metastatic tumor load in the lungs compared to treatment with either drug alone, and this correlated with greater reductions in Rb signaling and Mcl-1 expression in resected tumors. These findings support the development of CDK and Raf co-targeting strategies in EGFR/HER-2-overexpressing or RAS/RAF mutant BCs.
PMCID: PMC3730045  PMID: 23908594
10.  Estimating Energy Expenditure in mice using an Energy Balance Technique 
To compare, in mice, the accuracy of estimates of energy expenditure using an energy balance technique (TEEbal : food energy intake and body composition change) versus indirect calorimetry (TEEIC).
In 32 male C57BL/6J mice energy expenditure was estimated using an energy balance (caloric intake minus change in body energy stores) method over a 37 day period. Energy expenditure was also measured in the same animals by indirect calorimetry. These measures were compared.
The two methods were highly correlated (r2 = 0.87: TEEbal = 1.07 * TEEIC − 0.22, p < 0.0001). By Bland-Altman analysis, TEEbal estimates were slightly higher (4.6±1.5%; p < 0.05) than TEEIC estimates (Bias = 0.55 kcal/24h).
TEEbal can be performed in “home cages” and provides an accurate integrated long-term measurement of energy expenditure while minimizing potentially confounding stress that may accompany the use of indirect calorimetry systems. The technique can also be used to assess long term energy intake.
PMCID: PMC3697837  PMID: 22751256
Obesity; Indirect Calorimetry; Metabolism
11.  ILDR2: An Endoplasmic Reticulum Resident Molecule Mediating Hepatic Lipid Homeostasis 
PLoS ONE  2013;8(6):e67234.
Ildr2, a modifier of diabetes susceptibility in obese mice, is expressed in most organs, including islets and hypothalamus, with reduced levels in livers of diabetes-susceptible B6.DBA mice congenic for a 1.8 Mb interval of Chromosome 1. In hepatoma and neuronal cells, ILDR2 is primarily located in the endoplasmic reticulum membrane. We used adenovirus vectors that express shRNA or are driven by the CMV promoter, respectively, to knockdown or overexpress Ildr2 in livers of wild type and ob/ob mice. Livers in knockdown mice were steatotic, with increased hepatic and circulating triglycerides and total cholesterol. Increased circulating VLDL, without reduction in triglyceride clearance suggests an effect of reduced hepatic ILDR2 on hepatic cholesterol clearance. In animals that overexpress Ildr2, hepatic triglyceride and total cholesterol levels were reduced, and strikingly so in ob/ob mice. There were no significant changes in body weight, energy expenditure or glucose/insulin homeostasis in knockdown or overexpressing mice. Knockdown mice showed reduced expression of genes mediating synthesis and oxidation of hepatic lipids, suggesting secondary suppression in response to increased hepatic lipid content. In Ildr2-overexpressing ob/ob mice, in association with reduced liver fat content, levels of transcripts related to neutral lipid synthesis and cholesterol were increased, suggesting “relief” of the secondary suppression imposed by lipid accumulation. Considering the fixed location of ILDR2 in the endoplasmic reticulum, we investigated the possible participation of ILDR2 in ER stress responses. In general, Ildr2 overexpression was associated with increases, and knockdown with decreases in levels of expression of molecular components of canonical ER stress pathways. We conclude that manipulation of Ildr2 expression in liver affects both lipid homeostasis and ER stress pathways. Given these reciprocal interactions, and the relatively extended time-course over which these studies were conducted, we cannot assign causal primacy to either the effects on hepatic lipid homeostasis or ER stress responses.
PMCID: PMC3691114  PMID: 23826244
12.  iPSC-derived β cells model diabetes due to glucokinase deficiency 
The Journal of Clinical Investigation  2013;123(7):3146-3153.
Diabetes is a disorder characterized by loss of β cell mass and/or β cell function, leading to deficiency of insulin relative to metabolic need. To determine whether stem cell–derived β cells recapitulate molecular-physiological phenotypes of a diabetic subject, we generated induced pluripotent stem cells (iPSCs) from subjects with maturity-onset diabetes of the young type 2 (MODY2), which is characterized by heterozygous loss of function of the gene encoding glucokinase (GCK). These stem cells differentiated into β cells with efficiency comparable to that of controls and expressed markers of mature β cells, including urocortin-3 and zinc transporter 8, upon transplantation into mice. While insulin secretion in response to arginine or other secretagogues was identical to that in cells from healthy controls, GCK mutant β cells required higher glucose levels to stimulate insulin secretion. Importantly, this glucose-specific phenotype was fully reverted upon gene sequence correction by homologous recombination. Our results demonstrate that iPSC-derived β cells reflect β cell–autonomous phenotypes of MODY2 subjects, providing a platform for mechanistic analysis of specific genotypes on β cell function.
PMCID: PMC3696557  PMID: 23778137
13.  Whole Exome Sequencing to Identify a Novel Gene (Caveolin-1) Associated with Human Pulmonary Arterial Hypertension 
Heritable and idiopathic pulmonary arterial hypertension (PAH) are phenotypically identical and associated with mutations in several genes related to TGF beta signaling, including bone morphogenetic protein receptor type 2 (BMPR2), activin receptor-like kinase 1 (ALK1), endoglin (ENG), and mothers against decapentaplegic 9 (SMAD9). Approximately 25% of heritable cases lack identifiable mutations in any of these genes.
Methods and Results
We used whole exome sequencing to study a three generation family with multiple affected family members with PAH but no identifiable TGF beta mutation. We identified a frameshift mutation in Caveolin-1 (CAV1), which encodes a membrane protein of caveolae abundant in the endothelium and other cells of the lung. An independent de novo frameshift mutation was identified in a child with idiopathic PAH. Western blot analysis demonstrated a reduction in caveolin-1 protein, while lung tissue immunostaining studies demonstrated a reduction in normal caveolin-1 density within the endothelial cell layer of small arteries.
Our study represents successful elucidation of a dominant Mendelian disorder using whole exome sequencing. Mutations in CAV1 are associated in rare cases with PAH. This may have important implications for pulmonary vascular biology as well as PAH-directed therapeutic development.
PMCID: PMC3380156  PMID: 22474227
bioinfomatics genes; genetics; BMPR2; caveolae; pulmonary hypertension
14.  Reproducibility and accuracy of body composition assessments in mice by dual energy x-ray absorptiometry and time domain nuclear magnetic resonance 
To assess the accuracy and reproducibility of dual-energy absorptiometry (DXA; PIXImus™) and time domain nuclear magnetic resonance (TD-NMR; Bruker Optics) for the measurement of body composition of lean and obese mice.
Subjects and measurements
Thirty lean and obese mice (body weight range 19–67 g) were studied. Coefficients of variation for repeated (x 4) DXA and NMR scans of mice were calculated to assess reproducibility. Accuracy was assessed by comparing DXA and NMR results of ten mice to chemical carcass analyses. Accuracy of the respective techniques was also assessed by comparing DXA and NMR results obtained with ground meat samples to chemical analyses. Repeated scans of 10–25 gram samples were performed to test the sensitivity of the DXA and NMR methods to variation in sample mass.
In mice, DXA and NMR reproducibility measures were similar for fat tissue mass (FTM) (DXA coefficient of variation [CV]=2.3%; and NMR CV=2.8%) (P=0.47), while reproducibility of lean tissue mass (LTM) estimates were better for DXA (1.0%) than NMR (2.2%) (

DXA and NMR provide comparable levels of reproducibility in measurements of body composition lean and obese mice. While DXA and NMR measures are highly correlated with chemical analysis measures, DXA consistently overestimates LTM and FTM (by ~8% and ~46%, respectively), while NMR only slightly underestimates LTM (by ~0.2%) and overestimates FTM (~15%.) The NMR method also has practical advantages compared to DXA, such as speed of measurement and the ability to scan unanesthetized animals.
PMCID: PMC3169293  PMID: 21909234
DXA; NMR; adiposity; obesity
Genes, brain, and behavior  2010;9(6):575-582.
Epigenetic mechanisms may moderate genetic and environmental risk (G × E) for mood disorders. We used an experimental rhesus macaque model of early life stress to test whether epigenetic regulation of serotonin transporter (5-HTT) may contribute to G× E interactions that influence behavior and emotion. We hypothesized that peripheral blood mononuclear cell (PBMC) DNA methylation within an 800 bp CpG island that overlaps with the5-HTT transcription initiation start site, a hypothesized model of the same genomic region in brain tissue, would mediate or moderate the effects of early life stress and a functional5-HTT promoter polymorphism (rh5-HTTLPR) on two outcomes: PBMC5-HTT expression; and behavioral stress reactivity. Eighty-seven infant rhesus macaques (3–4 months of age) were either mother-reared in large social groups (n= 70) or nursery-reared (n= 17). During a maternal/social separation, infants’ blood was sampled and behavioral stress reactivity recorded. PBMC DNA and RNA samples were used to determine:rh5-HTTLPR genotype;5-HTT mRNA expression using qRT-PCR; and5-HTT CpG methylation status using sodium bisulfite pyrosequencing. Consistent with human data, carriers of the low expressingrh5-HTTLPR alleles exhibited higher mean5-HTT CpG methylation, which was associated with lower PBMC5-HTT expression. Higher5-HTT CpG methylation, but not rh5-HTTLPR genotype, exacerbated the effects of early life stress on behavioral stress reactivity in infants.5-HTT CpG methylation may be an important regulator of 5-HTT expression early in development, and may contribute to the risk for mood disorders observed in “high-risk”5-HTTLPR carriers.
PMCID: PMC2921011  PMID: 20398062
Serotonin transporter; rhesus macaque; DNA methylation; rh5-HTTLPR genotype; behavior; development
The Journal of Clinical Investigation  2011;121(3):1191-1198.
Malnutrition substantially increases susceptibility to Entamoeba histolytica in children. Leptin is a hormone produced by adipocytes that inhibits food intake, influences the immune system, and is suppressed in malnourished children. Therefore we hypothesized that diminished leptin function may increase susceptibility to E. histolytica infection. We prospectively observed a cohort of children, beginning at preschool age, for infection by the parasite E. histolytica every other day over 9 years and evaluated them for genetic variants in leptin (LEP) and the leptin receptor (LEPR). We found increased susceptibility to intestinal infection by this parasite associated with an amino acid substitution in the cytokine receptor homology domain 1 of LEPR. Children carrying the allele for arginine (223R) were nearly 4 times more likely to have an infection compared with those homozygous for the ancestral glutamine allele (223Q). An association of this allele with amebic liver abscess was also determined in an independent cohort of adult patients. In addition, mice carrying at least 1 copy of the R allele of Lepr were more susceptible to infection and exhibited greater levels of mucosal destruction and intestinal epithelial apoptosis after amebic infection. These findings suggest that leptin signaling is important in mucosal defense against amebiasis and that polymorphisms in the leptin receptor explain differences in susceptibility of children in the Bangladesh cohort to amebiasis.
PMCID: PMC3049405  PMID: 21393862
Neurobiology of disease  2008;33(3):499-508.
Analysis of naturally occurring mutations that cause seizures in rodents has advanced understanding of the molecular mechanisms underlying epilepsy. Abnormalities of Ih and h channel expression have been found in many animal models of absence epilepsy. We characterized a novel spontaneous mutant mouse, apathetic (ap/ap), and identified the ap mutation as a 4 base pair insertion within the coding region of Hcn2, the gene encoding the h channel subunit 2 (HCN2). We demonstrated that Hcn2ap mRNA is reduced by 90% compared to wild type, and the predicted truncated HCN2ap protein is absent from the brain tissue of mice carrying the ap allele. ap/ap mice exhibited ataxia, generalized spike-wave absence seizures, and rare generalized tonic-clonic seizures. ap/+ mice had a normal gait, occasional absence seizures and an increased severity of chemoconvulsant-induced seizures. These findings help elucidate basic mechanisms of absence epilepsy and suggest HCN2 may be a target for therapeutic intervention.
PMCID: PMC2643333  PMID: 19150498
Obesity (Silver Spring, Md.)  2008;17(1):126-135.
Perturbations in the functional integrity of the leptin axis are obvious candidates for mediation of altered adiposity. In a large number of genetic association studies in humans, the non-conservative LEPR Q223R allele has been inconsistently associated with adiposity. Subtle, long term effects of such genetic variants can be obscured by effects of the environment and other confounders that render definitive inferences difficult to reach. We directly assessed the biological effects of this variant in 129P3/J mice segregating for the humanized Lepr allele at codon 223. No effects of this allele were detected on body weight, composition, or energy expenditure in animals fed diets of varying fat content over periods as long as 235 days. In vitro, Q223R did not affect leptin signaling as reflected by activation of STAT3. We conclude that Q223R is unlikely to play a significant role in regulation of human adiposity. This approach to vetting of human allelic variation might be more widely employed.
PMCID: PMC2808713  PMID: 18997673
genetics; obesity; leptin; mouse models
Two recent, large GWAS in European populations have associated a ∼47 Kb region that contains part of the FTO gene with high BMI. The functions of FTO and adjacent FTM in human biology are not clear. We examined expression of these genes in organs of mice segregating for monogenic obesity mutations, exposed to under/over feeding, and to 4 °C. Fto/Ftm expression was reduced in mesenteric adipose tissue of mice segregating for the Ay, Lepob, Leprdb, Cpefat or tub mutations and there was a similar trend in other tissues. These effects were not due to adiposity per se. Hypothalamic Fto and Ftm expression were decreased by fasting in lean and obese animals and by cold exposure in lean mice. The fact that responses of Fto and Ftm expression to these manipulations were almost indistinguishable suggested that the genes might be co-regulated. The putative overlapping regulatory region contains at least 2 canonical CUTL1 binding sites. One of these nominal CUTL1 sites includes rs8050136, a SNP associated with high body mass. The A allele of rs8050136 – associated with lower body mass than the C allele – preferentially bound CUTL1 in human fibroblast DNA. 70% knockdown of CUTL1 expression in human fibroblasts decreased FTO and FTM expression by 90 and 65 %, respectively. Animals and humans with various genetic interruptions of FTO or FTM have phenotypes reminiscent of aspects of the Bardet-Biedl obesity syndrome, a confirmed “ciliopathy”. FTM has recently been shown to be a ciliary basal body protein.
PMCID: PMC2808712  PMID: 18256137
obesity; hypothalamus; adipose tissue; CUTL1
Prenatal diagnosis  2009;29(6):560-569.
Walker-Warburg syndrome (WWS) is a genetically heterogeneous congenital muscular dystrophy caused by abnormal glycosylation of α-dystroglycan (α-DG) that is associated with brain malformations and eye anomalies. The Fukutin (FKTN) gene, which causes autosomal recessively inherited WWS is most often associated with Fukuyama congenital muscular dystrophy in Japan. We describe the clinical features of four nonconsanguinous Ashkenazi Jewish families with WWS and identify the underlying genetic basis for WWS.
We screened for mutations in POMGnT1, POMT1, POMT2, and FKTN, genes causing WWS, by dideoxy sequence analysis.
We identified an identical homozygous c.1167insA mutation in the FKTN gene on a common haplotype in all four families and identified 2/299 (0.7%) carriers for the c.1167insA mutation among normal American Ashkenazi Jewish adults.
These data suggest that the c.1167insA FKTN mutation described by us is a founder mutation that can be used to target diagnostic testing and carrier screening in the Ashkenazi Jewish population.
PMCID: PMC2735827  PMID: 19266496
genetic screening; muscle-eye-brain disease
PLoS Genetics  2008;4(7):e1000137.
In 404 Lepob/ob F2 progeny of a C57BL/6J (B6) x DBA/2J (DBA) intercross, we mapped a DBA-related quantitative trait locus (QTL) to distal Chr1 at 169.6 Mb, centered about D1Mit110, for diabetes-related phenotypes that included blood glucose, HbA1c, and pancreatic islet histology. The interval was refined to 1.8 Mb in a series of B6.DBA congenic/subcongenic lines also segregating for Lepob. The phenotypes of B6.DBA congenic mice include reduced β-cell replication rates accompanied by reduced β-cell mass, reduced insulin/glucose ratio in blood, reduced glucose tolerance, and persistent mild hypoinsulinemic hyperglycemia. Nucleotide sequence and expression analysis of 14 genes in this interval identified a predicted gene that we have designated “Lisch-like” (Ll) as the most likely candidate. The gene spans 62.7 kb on Chr1qH2.3, encoding a 10-exon, 646–amino acid polypeptide, homologous to Lsr on Chr7qB1 and to Ildr1 on Chr16qB3. The largest isoform of Ll is predicted to be a transmembrane molecule with an immunoglobulin-like extracellular domain and a serine/threonine-rich intracellular domain that contains a 14-3-3 binding domain. Morpholino knockdown of the zebrafish paralog of Ll resulted in a generalized delay in endodermal development in the gut region and dispersion of insulin-positive cells. Mice segregating for an ENU-induced null allele of Ll have phenotypes comparable to the B.D congenic lines. The human ortholog, C1orf32, is in the middle of a 30-Mb region of Chr1q23-25 that has been repeatedly associated with type 2 diabetes.
Author Summary
Type 2 diabetes (T2D) accounts for over 90% of instances of diabetes and is a leading cause of medical morbidity and mortality. Twin studies indicate a strong polygenic contribution to susceptibility within the context of obesity. Although approximately ten genes making important contributions to individual risk have been identified, it is clear that others remain to be identified. In this study, we intercrossed obese, diabetes-resistant and diabetes-prone mouse strains to implicate a genetic interval on mouse Chr1 associated with reduced β-cell numbers and elevated blood glucose. We narrowed the region using molecular genetics and computational approaches to identify a novel gene we designated “Lisch-like” (Ll). The orthologous human genetic interval has been repeatedly implicated in T2D. Mice with an induced mutation that reduces Ll expression are impaired in both β-cell development and glucose metabolism, and reduced expression of the homologous gene in zebrafish disrupts islet development. Ll is expressed in organs implicated in the pathophysiology of T2D (hypothalamus, islets, liver, and skeletal muscle) and is predicted to encode a transmembrane protein that could mediate cholesterol transport and/or convey signals related to cell division. Either mechanism could mediate effects on β-cell mass that would predispose to T2D.
PMCID: PMC2464733  PMID: 18654634
The Journal of Clinical Investigation  2002;110(10):1449-1459.
The mouse coat color mutant mahoganoid (md) darkens coat color and decreases the obesity of Ay mice that ectopically overexpress agouti-signaling protein. The phenotypic effects of md are similar to those of the recently identified coat color mutant mahogany (Atrnmg). We report the positional cloning of mahoganoid, encoding a novel 494–amino acid protein containing a C3HC4 RING (really interesting new gene) domain that may function as an E3 ubiquitin ligase. The mutations in the mahoganoid allelic series (md, md2J, md5J) are all due to large retroviral insertions. In md and md2J, the result is minimal expression of the normal size transcripts in all tissues examined. Unlike Atrnmg/Atrnmg animals, we observe no evidence of neurological deficit or neuropathology in md/md mice. Body weight and body mass index (a surrogate for adiposity) measurements of B6.C3H-md-A md/+ and md/md animals on 9% and 45% kcal fat diets indicate that mahoganoid does not suppress body weight in B6.C3H animals in a gene dose-dependent fashion.
PMCID: PMC151815  PMID: 12438443
Paediatrics & Child Health  2001;6(8):536-539.
To evaluate the value of signs and symptoms in children for the radiological diagnosis of acute sinusitis.
Prospective cohort study.
University-affiliated tertiary care hospital.
All children presenting with symptoms suggestive of acute sinusitis for whom sinus radiographs were ordered.
Data were collected on the presence of specific symptoms and the initial probability of sinusitis. Criterion-based radiological diagnoses were made.
Three hundred ninety-two consecutive children were seen; 257 children had a radiological diagnosis of acute sinusitis (66%), 128 patients (33%) presented with complete opacity of at least one sinus and 14 (4%) children had an air-fluid level. Sensitivity, specificity, predictive values and likelihood ratios were measured for clinical findings. Classical symptoms (rhinorrhea lasting more than 10 days and purulent rhinorrhea) increased the likelihood ratios the most (1.3 and 1.34, respectively). Logistic regression showed two independent predictors: purulent rhinorrhea (odds ratio 2.0) and the presence of acute otitis media (odds ratio 2.6). The initial clinical probability was more accurate than any other single finding: high probability (likelihood ratio 2.0), intermediate probability (likelihood ratio 1.1) and low probability (likelihood ratio 0.6).
Classical symptoms are predictive of the presence of acute sinusitis as diagnosed on sinus radiographs. The physician’s overall clinical impression, expressed as an initial probability, was superior to any single historical or examination finding in the diagnosis of acute sinusitis.
PMCID: PMC2805589  PMID: 20084123
Diagnosis; Sinusitis
24.  Editor's notes 
PMCID: PMC2277772
25.  Editor's notes 
PMCID: PMC2277921

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