Rare recurrent copy number variations in metabotropic glutamate receptor interacting genes in children with neurodevelopmental disorders.

BACKGROUND: Neurodevelopmental disorders (NDDs), such as attention deficit hyperactivity disorder (ADHD) and autism spectrum disorder (ASD), are examples of complex and partially overlapping phenotypes that often lack definitive corroborating genetic information. ADHD and ASD have complex genetic associations implicated by rare recurrent copy number variations (CNVs). Both of these NDDs have been shown to share similar biological etiologies as well as genetic pleiotropy. METHODS: Platforms aimed at investigating genetic-based associations, such as high-density microarray technologies, have been groundbreaking techniques in the field of complex diseases, aimed at elucidating the underlying disease biology. Previous studies have uncovered CNVs associated with genes within shared candidate genomic networks, including glutamate receptor genes, across multiple different NDDs. To examine shared biological pathways across two of the most common NDDs, we investigated CNVs across 15,689 individuals with ADHD (n = 7920), ASD (n = 4318), or both (n = 3,416), as well as 19,993 controls. Cases and controls were matched by genotype array (i.e., Illumina array versions). Three case-control association studies each calculated and compared the observed vs. expected frequency of CNVs across individual genes, loci, pathways, and gene networks. Quality control measures of confidence in CNV-calling, prior to association analyses, included visual inspection of genotype and hybridization intensity. RESULTS: Here, we report results from CNV analysis in search for individual genes, loci, pathways, and gene networks. To extend our previous observations implicating a key role of the metabotropic glutamate receptor (mGluR) network in both ADHD and autism, we exhaustively queried patients with ASD and/or ADHD for CNVs associated with the 273 genomic regions of interest within the mGluR gene network (genes with one or two degrees protein-protein interaction with mGluR 1-8 genes). Among CNVs in mGluR network genes, we uncovered CNTN4 deletions enriched in NDD cases (P = 3.22E - 26, OR = 2.49). Additionally, we uncovered PRLHR deletions in 40 ADHD cases and 12 controls (P = 5.26E - 13, OR = 8.45) as well as clinically diagnostic relevant 22q11.2 duplications and 16p11.2 duplications in 23 ADHD + ASD cases and 9 controls (P = 4.08E - 13, OR = 15.05) and 22q11.2 duplications in 34 ADHD + ASD cases and 51 controls (P = 9.21E - 9, OR = 3.93); those control samples were not with previous 22qDS diagnosis in their EHR records. CONCLUSION: Together, these results suggest that disruption in neuronal cell-adhesion pathways confers significant risk to NDDs and showcase that rare recurrent CNVs in CNTN4, 22q11.2, and 16p11.2 are overrepresented in NDDs that constitute patients predominantly suffering from ADHD and ASD. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02286817 First Posted: 10 November 14, ClinicalTrials.gov Identifier: NCT02777931 first posted: 19 May 2016, ClinicalTrials.gov Identifier: NCT03006367 first posted: 30 December 2016, ClinicalTrials.gov Identifier: NCT02895906 first posted: 12 September 2016.

Returning integrated genomic risk and clinical recommendations: The eMERGE study.

PURPOSE: Assessing the risk of common, complex diseases requires consideration of clinical risk factors as well as monogenic and polygenic risks, which in turn may be reflected in family history. Returning risks to individuals and providers may influence preventive care or use of prophylactic therapies for those individuals at high genetic risk. METHODS: To enable integrated genetic risk assessment, the eMERGE (electronic MEdical Records and GEnomics) network is enrolling 25,000 diverse individuals in a prospective cohort study across 10 sites. The network developed methods to return cross-ancestry polygenic risk scores, monogenic risks, family history, and clinical risk assessments via a genome-informed risk assessment (GIRA) report and will assess uptake of care recommendations after return of results. RESULTS: GIRAs include summary care recommendations for 11 conditions, education pages, and clinical laboratory reports. The return of high-risk GIRA to individuals and providers includes guidelines for care and lifestyle recommendations. Assembling the GIRA required infrastructure and workflows for ingesting and presenting content from multiple sources. Recruitment began in February 2022. CONCLUSION: Return of a novel report for communicating monogenic, polygenic, and family history-based risk factors will inform the benefits of integrated genetic risk assessment for routine health care.

Attitudes among Parents towards Return of Disease-Related Polygenic Risk Scores (PRS) for Their Children.

The electronic MEdical Records and GEnomics (eMERGE) consortium will return risk reports pertaining to specific diseases, a key component of which will be polygenic risk scores (PRS), to 25,000 participants, including 5000 children. Understanding comprehension and the perceived value of these PRS-based reports among parents will be critical for effective return of results in children. To address this issue, we conducted semi-structured interviews with 40 African American and Hispanic parents at The Children's Hospital of Philadelphia and Boston Children's Hospital. Each participant received a hypothetical risk report identifying their child as high risk for either type 2 diabetes or asthma. Participants were assessed on their comprehension of absolute versus relative risk framing, likelihood of following risk-reduction recommendations, perceived value of the information, psychosocial impact, education/support needed, and suggestions to improve the PRS-based report to make it more accessible. Results demonstrated high perceived value in receiving PRS-based reports but also draws attention to important shortfalls in comprehension due to factors including the health of the child, family history, and how the risk was framed. This study provides an insight into implementing the return of genomic risk scores in a pediatric setting.

An electronic health record (EHR) phenotype algorithm to identify patients with attention deficit hyperactivity disorders (ADHD) and psychiatric comorbidities.

BACKGROUND: In over half of pediatric cases, ADHD presents with comorbidities, and often, it is unclear whether the symptoms causing impairment are due to the comorbidity or the underlying ADHD. Comorbid conditions increase the likelihood for a more severe and persistent course and complicate treatment decisions. Therefore, it is highly important to establish an algorithm that identifies ADHD and comorbidities in order to improve research on ADHD using biorepository and other electronic record data. METHODS: It is feasible to accurately distinguish between ADHD in isolation from ADHD with comorbidities using an electronic algorithm designed to include other psychiatric disorders. We sought to develop an EHR phenotype algorithm to discriminate cases with ADHD in isolation from cases with ADHD with comorbidities more effectively for efficient future searches in large biorepositories. We developed a multi-source algorithm allowing for a more complete view of the patient's EHR, leveraging the biobank of the Center for Applied Genomics (CAG) at Children's Hospital of Philadelphia (CHOP). We mined EHRs from 2009 to 2016 using International Statistical Classification of Diseases and Related Health Problems (ICD) codes, medication history and keywords specific to ADHD, and comorbid psychiatric disorders to facilitate genotype-phenotype correlation efforts. Chart abstractions and behavioral surveys added evidence in support of the psychiatric diagnoses. Most notably, the algorithm did not exclude other psychiatric disorders, as is the case in many previous algorithms. Controls lacked psychiatric and other neurological disorders. Participants enrolled in various CAG studies at CHOP and completed a broad informed consent, including consent for prospective analyses of EHRs. We created and validated an EHR-based algorithm to classify ADHD and comorbid psychiatric status in a pediatric healthcare network to be used in future genetic analyses and discovery-based studies. RESULTS: In this retrospective case-control study that included data from 51,293 subjects, 5840 ADHD cases were discovered of which 46.1% had ADHD alone and 53.9% had ADHD with psychiatric comorbidities. Our primary study outcome was to examine whether the algorithm could identify and distinguish ADHD exclusive cases from ADHD comorbid cases. The results indicate ICD codes coupled with medication searches revealed the most cases. We discovered ADHD-related keywords did not increase yield. However, we found including ADHD-specific medications increased our number of cases by 21%. Positive predictive values (PPVs) were 95% for ADHD cases and 93% for controls. CONCLUSION: We established a new algorithm and demonstrated the feasibility of the electronic algorithm approach to accurately diagnose ADHD and comorbid conditions, verifying the efficiency of our large biorepository for further genetic discovery-based analyses. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02286817 . First posted on 10 November 2014. CLINICALTRIALS: gov, NCT02777931 . First posted on 19 May 2016. CLINICALTRIALS: gov, NCT03006367 . First posted on 30 December 2016. CLINICALTRIALS: gov, NCT02895906 . First posted on 12 September 2016.

Do research participants share genomic screening results with family members?

The public health impact of genomic screening can be enhanced by cascade testing. However, cascade testing depends on communication of results to family members. While the barriers and facilitators of family communication have been researched following clinical genetic testing, the factors impacting the dissemination of genomic screening results are unknown. Using the pragmatic Electronic Medical Records and Genomics Network-3 (eMERGE-3) study, we explored the reported sharing practices of participants who underwent genomic screening across the United States. Six eMERGE-3 sites returned genomic screening results for mostly dominant medically actionable disorders and surveyed adult participants regarding communication of results with first-degree relatives. Across the sites, 279 participants completed a 1-month and/or 6-month post-results survey. By 6 months, only 34% of the 156 respondents shared their results with all first-degree relatives and 4% did not share with any. Over a third (39%) first-degree relatives were not notified of the results. Half (53%) of participants who received their results from a genetics provider shared them with all first-degree relatives compared with 11% of participants who received their results from a non-genetics provider. The most frequent reasons for sharing were a feeling of obligation (72%) and that the information could help family members make medical decisions (72%). The most common reasons indicated for not sharing were that the family members were too young (38%), or they were not in contact (25%) or not close to them (25%). These data indicate that the professional returning the results may impact sharing patterns, suggesting that there is a need to continue to educate healthcare providers regarding approaches to facilitate sharing of genetic results within families. Finally, these data suggest that interventions to increase sharing may be universally effective regardless of the origin of the genetic result.

JAK/STAT inhibitor therapy partially rescues the lipodystrophic autoimmune phenotype in Clec16a KO mice.

CLEC16A is implicated in multiple autoimmune diseases. We generated an inducible whole-body knockout (KO), Clec16aΔUBC mice to address the role of CLEC16A loss of function. KO mice exhibited loss of adipose tissue and severe weight loss in response to defective autophagic flux and exaggerated endoplasmic reticulum (ER) stress and robust cytokine storm. KO mice were glucose tolerant and displayed a state of systemic inflammation with elevated antibody levels, including IgM, IgA, Ig2b and IgG3, significantly reduced circulating insulin levels in the presence of normal food consumption. Metabolic analysis revealed disturbances in the lipid profile, white adipose decreasing concomitantly with enhanced inflammatory response, and energy wasting. Mechanistically, endoplasmic reticulum (ER) stress triggers excessive hormone sensitive lipases (HSL) mediated lipolysis which contributes to adipose inflammation via activation of JAK-STAT, stress kinases (ERK1/2, P38, JNK), and release of multiple proinflammatory mediators. Treatment with a JAK-STAT inhibitor (tofacitinib) partially rescued the inflammatory lipodystrophic phenotype and improved survival of Clec16aΔUBC mice by silencing cytokine release and modulating ER stress, lipolysis, mitophagy and autophagy. These results establish a mechanistic link between CLEC16A, lipid metabolism and the immune system perturbations. In summary, our Clec16aΔUBC mouse model highlights multifaceted roles of Clec16a in normal physiology, including a novel target for weight regulation and mutation-induced pathophysiology.

Inducible knockout of Clec16a in mice results in sensory neurodegeneration.

CLEC16A has been shown to play a role in autophagy/mitophagy processes. Additionally, genetic variants in CLEC16A have been implicated in multiple autoimmune diseases. We generated an inducible whole-body knockout, Clec16aΔUBC mice, to investigate the loss of function of CLEC16A. The mice exhibited a neuronal phenotype including tremors and impaired gait that rapidly progressed to dystonic postures. Nerve conduction studies and pathological analysis revealed loss of sensory axons that are associated with this phenotype. Activated microglia and astrocytes were found in regions of the CNS. Several mitochondrial-related proteins were up- or down-regulated. Upregulation of interferon stimulated gene 15 (IGS15) were observed in neuronal tissues. CLEC16A expression inversely related to IGS15 expression. ISG15 may be the link between CLEC16A and downstream autoimmune, inflammatory processes. Our results demonstrate that a whole-body, inducible knockout of Clec16a in mice results in an inflammatory neurodegenerative phenotype resembling spinocerebellar ataxia.

Integrative analysis of genome-wide association studies identifies novel loci associated with neuropsychiatric disorders.

Neuropsychiatric disorders, such as autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), schizophrenia (SCZ), bipolar disorder (BIP), and major depressive disorder (MDD) share common clinical presentations, suggesting etiologic overlap. A substantial proportion of SNP-based heritability for neuropsychiatric disorders is attributable to genetic components, and genome-wide association studies (GWASs) focusing on individual diseases have identified multiple genetic loci shared between these diseases. Here, we aimed at identifying novel genetic loci associated with individual neuropsychiatric diseases and genetic loci shared by neuropsychiatric diseases. We performed multi-trait joint analyses and meta-analysis across five neuropsychiatric disorders based on their summary statistics from the Psychiatric Genomics Consortium (PGC), and further carried out a replication study of ADHD among 2726 cases and 16299 controls in an independent pediatric cohort. In the multi-trait joint analyses, we found five novel genome-wide significant loci for ADHD, one novel locus for BIP, and ten novel loci for MDD. We further achieved modest replication in our independent pediatric dataset. We conducted fine-mapping and functional annotation through an integrative multi-omics approach and identified causal variants and potential target genes at each novel locus. Gene expression profile and gene-set enrichment analysis further suggested early developmental stage expression pattern and postsynaptic membrane compartment enrichment of candidate genes at the genome-wide significant loci of these neuropsychiatric disorders. Therefore, through a multi-omics approach, we identified novel genetic loci associated with the five neuropsychiatric disorders which may help to better understand the underlying molecular mechanism of neuropsychiatric diseases.

The Autoimmune Disorder Susceptibility Gene CLEC16A Restrains NK Cell Function in YTS NK Cell Line and Clec16a Knockout Mice.

CLEC16A locus polymorphisms have been associated with several autoimmune diseases. We overexpressed CLEC16A in YTS natural killer (NK) cells and observed reduced NK cell cytotoxicity and IFN-γ release, delayed dendritic cell (DC) maturation, decreased conjugate formation, cell-surface receptor downregulation and increased autophagy. In contrast, siRNA mediated knockdown resulted in increased NK cell cytotoxicity, reversal of receptor expression and disrupted mitophagy. Subcellular localization studies demonstrated that CLEC16A is a cytosolic protein that associates with Vps16A, a subunit of class C Vps-HOPS complex, and modulates receptor expression via autophagy. Clec16a knockout (KO) in mice resulted in altered immune cell populations, increased splenic NK cell cytotoxicity, imbalance of dendritic cell subsets, altered receptor expression, upregulated cytokine and chemokine secretion. Taken together, our findings indicate that CLEC16A restrains secretory functions including cytokine release and cytotoxicity and that a delicate balance of CLEC16A is needed for NK cell function and homeostasis.

CLEC16A regulates splenocyte and NK cell function in part through MEK signaling.

CLEC16A is implicated in multiple autoimmune diseases. We generated Clec16a inducible knockout (KO) mice to examine the functional link between CLEC16A auto-inflammation and autoimmunity. Clec16a KO mice exhibited weight loss and thymic and splenic atrophy. Mitochondrial potential was lowered in KO mice splenocytes resulting in aggregation of unhealthy mitochondria in B, T, and NK cells. In Clec16a KO mice we detected disrupted mitophagy in splenic B and T cells. NK cells from Clec16a KO mice exhibited increased cytotoxicity. Incomplete mitophagy was attenuated with PI3K and/or MEK inhibition in Clec16a KO mice. Our results demonstrate a functional link between CLEC16A and disrupted mitophagy in immune cells and show that incomplete mitophagy predisposes the KO mice to inflammation. Taken together, loss of function variants in CLEC16A that are associated with decreased CLEC16A expression levels may contribute to inflammation in autoimmunity through disrupted mitophagy. Drugs modulating mitophagy reverse the process and may be effective in treating and preventing autoimmunity in individuals with risk associated CLEC16A variants.

Genome-wide association study for acute otitis media in children identifies FNDC1 as disease contributing gene.

Acute otitis media (AOM) is among the most common pediatric diseases, and the most frequent reason for antibiotic treatment in children. Risk of AOM is dependent on environmental and host factors, as well as a significant genetic component. We identify genome-wide significance at a locus on 6q25.3 (rs2932989, Pmeta=2.15 × 10-09), and show that the associated variants are correlated with the methylation status of the FNDC1 gene (cg05678571, P=1.43 × 10-06), and further show it is an eQTL for FNDC1 (P=9.3 × 10-05). The mouse homologue, Fndc1, is expressed in middle ear tissue and its expression is upregulated upon lipopolysaccharide treatment. In this first GWAS of AOM and the largest OM genetic study to date, we identify the first genome-wide significant locus associated with AOM.

The Added Value of Family Material in the Discovery of Multiple Sclerosis Genes.

A mutation in a nuclear receptor (NR1H3) gene was detected in a familial, progressive form of multiple sclerosis (PPMS). Further analyses showed a significant association between a common NR1H3 variant in PPMS patients and loss of function for the encoded protein.

Effect of a Novel, Orally Active Matrix Metalloproteinase-2 and -9 Inhibitor in Spinal and Trigeminal Rat Models of Neuropathic Pain.

AIMS: To study the effects of a novel matrix metalloproteinase-2 (MMP-2) and MMP-9 inhibitor, AQU-118, on mechanical allodynia in the spinal nerve ligation (SNL) model of neuropathic pain and the chronic constriction injury of the infraorbital nerve (CCI-IoN) model of neuropathic orofacial pain. METHODS: Five groups of SNL rats were given daily oral doses of AQU-118 (5, 10, 20 mg/kg), gabapentin (100 mg/kg), or vehicle (0.5% methylcellulose) and then paw withdrawal threshold was measured with von Frey filaments (VF). Three groups of CCI-IoN rats were given daily oral doses of either AQU-118 (40 mg/kg), gabapentin (100 mg/kg), or vehicle (0.5% methylcellulose) and then mechanical allodynia was measured with facial VF and non-reflex-based orofacial stimulation test (OFST) assay. Naïve rats were also tested for the effect of AQU-118 (40 mg/kg) on basal sensitivity to mechanical stimulation/locomotive activity. RESULTS: Mechanical allodynia in SNL rats was attenuated by gabapentin (100 mg/kg) and AQU-118 (in a dose-dependent manner). Mechanical allodynia in CCI-IoN rats was also attenuated (in an equipotent manner) by both AQU-118 (40 mg/ kg) and gabapentin (100 mg/kg) as measured by both facial VF and OFST assay. Upon cessation of either AQU-118 or gabapentin, VF-related responses in both models and OFST assay times reverted to levels observed in vehicle-treated rats. No statistically significant change was observed in locomotive activity/paw withdrawal threshold by AQU-118 (40 mg/kg) in naïve rats. CONCLUSION: The results demonstrated that oral AQU-118 attenuates mechanical allodynia in both neuropathic pain models and with efficacies that mirror gabapentin at the 40 mg/kg dose used in the CCI-IoN model but without effect on basal sensitivity to mechanical stimulation/locomotive activity. These findings support a possible role for MMP-2/-9 in the etiology of neuropathic pain and also suggest that inhibition strategies represent a viable treatment option.

Anticonvulsant activity of pregabalin in the maximal electroshock-induced seizure assay in α2δ1 (R217A) and α2δ2 (R279A) mouse mutants.

Pregabalin has been shown to have anticonvulsant, analgesic, and anxiolytic activity in animal models. Pregabalin binds with high affinity to the α2δ1 and α2δ2 subunits of voltage-gated calcium channels. In order to better understand the relative contribution that binding to either the α2δ1 or α2δ2 subunits confers on the anticonvulsant activity of pregabalin, we characterized the anticonvulsant activity of pregabalin in different wild-type (WT) and mutant mouse strains. Two targeted mouse mutants have been made in which either the α2δ1 subunit was mutated (arginine-to-alanine mutation at amino acid 217; R217A) or the α2δ2 subunit was mutated (arginine-to-alanine mutation at amino acid 279; R279A). These mutations in α2δ1 or α2δ2 render the subunits relatively insensitive to pregabalin binding. The anticonvulsant activity of pregabalin was assessed in these different mouse lines using the maximal electroshock-induced seizure (MES) model. Pregabalin reduced the percentage of seizures and increased the latency to seizure in the MES model in two parental mouse strains used to construct the mutants. Pregabalin also reduced the percentage of seizures and increased latency to seizure similarly in the α2δ2 (R279A) and WT littermate control mice. In contrast, pregabalin's anticonvulsant efficacy was significantly reduced in α2δ1 (R217A) mutants compared with WT littermate control mice. Phenytoin showed anticonvulsant activity across all WT and mutant mice. These data show that the anticonvulsant activity of pregabalin in the MES model requires binding to the α2δ1 subunit.

Possible therapeutic effect of trilostane in rodent models of inflammation and nociception.

BACKGROUND: Trilostane was identified in an in vivo screen of compounds in a lipopolysaccharide model of inflammation to support a repurposing effort. There is no previous documentation of any anti-inflammatory effects of trilostane. OBJECTIVE: The aim of this study was to elucidate the novel pharmacologic activity of trilostane in a series of inflammation and nociception signal-finding models. METHODS: Anti-inflammatory effects of trilostane were evaluated in lipopolysaccharide-induced systemic and lung inflammation models and in a 2,4-dinitrofluorobenzene-induced delayed-type hypersensitivity (DTH) model in the mouse ear. The analgesic activities of trilostane were evaluated in a hot plate nociception model as a function of paw-withdrawal latency and in the formalin-induced nociception model with a behavioral end point. In all studies, trilostane was administered 15 minutes before challenge. In the DTH model, the animals were given a second dose 24 hours after the first dose. RESULTS: Trilostane inhibited tumor necrosis factor-α and monocyte chemoattractant protein-1 production in the lipopolysaccharide-induced systemic and pulmonary inflammation models. It also significantly reduced ear swelling in the 2,4-dinitrofluorobenzene-induced DTH model. In the hot plate nociception model, trilostane increased the latency of paw-licking behavior. Trilostane also significantly reduced the duration of pain behaviors in the late phase of the formalin-induced inflammatory pain model. CONCLUSIONS: These signal-finding studies suggest that trilostane has novel anti-inflammatory and analgesic properties.

Anti-inflammatory and immunomodulatory effects of bortezomib in various in vivo models.

Bortezomib (Velcade®) is a proteasome inhibitor that has been approved for the treatment of multiple myeloma and mantle cell lymphoma. It has been shown to inhibit the expression of cell adhesion molecules, co-stimulatory molecules, and NFκB activation, to deplete alloreactive T lymphocytes, and to decrease Th1 cytokine production. The anti-inflammatory effects of bortezomib were further investigated in this current set of studies. Systemic treatment with bortezomib was efficacious in the thioglycolate-induced MCP-1 production model, and the dinitrofluorobenzene-induced delayed-type hypersensitivity model. Psoriasis is an autoimmune disease that affects about 2% of the world population. Many treatments have been reported with varying degrees of efficacy. A topical bortezomib formulation was developed to minimize systemic exposure. Its tolerability was investigated in a topical imiquimod (IMQ)-induced psoriasis model. Daily application of IMQ on mouse skin induced inflamed scaly skin lesions resembling plaque-type psoriasis. Fatality was observed in the 1-mg/ml dose group. At 0.1 and 0.01 mg/ml, bortezomib potentiated IMQ-induced erythema, scaling, skin thickening, and caused necrotic lesions. Lower doses had no effect on the clinical observations. Histologically, bortezomib dose-dependently increased parakeratosis, hyperkeratosis, acanthosis, and inflammatory cell infiltration. This study demonstrated that topical bortezomib is not suitable for the treatment of psoriasis.

Genomic loci and candidate genes underlying inflammatory nociception.

Heritable genetic factors contribute significantly to inflammatory nociception. To determine candidate genes underlying inflammatory nociception, the current study used a mouse model of abdominal inflammatory pain. BXD recombinant inbred (RI) mouse strains were administered the intraperitoneal acetic acid test, and genome-wide quantitative trait locus (QTL) mapping was performed on the mean number of abdominal contraction and extension movements in 3 distinct groups of BXD RI mouse strains in 2 separate experiments. Combined mapping results detected 2 QTLs on chromosomes (Chr) 3 and 10 across experiments and groups of mice; an additional sex-specific QTL was detected on Chr 16. The results replicate previous findings of a significant QTL, Nociq2, on distal Chr 10 for formalin-induced inflammatory nociception and will aid in identification of the underlying candidate genes. Comparisons of sensitivity to intraperitoneal acetic acid in BXD RI mouse strains with microarray mRNA transcript expression profiles in specific brain areas detected covarying expression of candidate genes that are also found in the detected QTL confidence intervals. The results indicate that common and distinct genetic mechanisms underlie heritable sensitivity to diverse inflammatory insults, and provide a discrete set of high-priority candidate genes to investigate further in rodents and human association studies. Novel genomic regions linked to inflammatory nociception were detected, a previously reported locus was confirmed, and high-priority candidate genes for inflammatory nociception and pain were identified.

An extensive phenotypic characterization of the hTNFalpha transgenic mice.

BACKGROUND: Tumor necrosis factor alpha (TNFalpha) is implicated in a wide variety of pathological and physiological processes, including chronic inflammatory conditions, coronary artery disease, diabetes, obesity, and cachexia. Transgenic mice expressing human TNFalpha (hTNFalpha) have previously been described as a model for progressive rheumatoid arthritis. In this report, we describe extensive characterization of an hTNFalpha transgenic mouse line. RESULTS: In addition to arthritis, these hTNFalpha transgenic mice demonstrated major alterations in body composition, metabolic rate, leptin levels, response to a high-fat diet, bone mineral density and content, impaired fertility and male sexual function. Many phenotypes displayed an earlier onset and a higher degree of severity in males, pointing towards a significant degree of sexual dimorphism in response to deregulated expression of TNFalpha. CONCLUSION: These results highlight the potential usefulness of this transgenic model as a resource for studying the progressive effects of constitutively expressed low levels of circulating TNFalpha, a condition mimicking that observed in a number of human pathological conditions.

Identification of quantitative trait loci for chemical/inflammatory nociception in mice.

Sensitivity to pain is widely variable, and much of this variability is genetic in origin. The specific genes responsible have begun to be identified, but only for thermal nociception. In order to facilitate the identification of polymorphic, pain-related genes with more clinical relevance, we performed quantitative trait locus (QTL) mapping studies of the most common assay of inflammatory nociception, the formalin test. QTL mapping is a technique that exploits naturally occurring variability among inbred strains for the identification of genomic locations containing genes contributing to that variability. An F2 intercross was constructed using inbred A/J and C57BL/6J mice as progenitors, strains previously shown to display resistance and sensitivity, respectively, to formalin-induced nociception. Following phenotypic testing (5% formalin, 25 microl intraplantar injection), mice were genotyped at 90 microsatellite markers spanning the genome. We provide evidence for two statistically significant formalin test QTLs - chromosomal regions whose inheritance is associated with trait variability - on distal mouse chromosomes 9 and 10. Identification of the genes underlying these QTLs may illuminate the basis of individual differences in inflammatory pain, and lead to novel analgesic treatment strategies.