Homozygosity mapping of achromatopsia to chromosome 2 using DNA pooling

Achromatopsia is an autosomal recessive disease of the retina, characterized clinically by an inability to distinguish colors, impaired visual acuity, nystagmus and photophobia. A genome-wide search for linkage was performed using an inbred Jewish kindred from Iran. To facilitate the genome-wide search, we utilized a DNA pooling strategy which takes advantage of the likelihood that the disease in this inbred kindred is inherited by all affected individuals from a common founder. Equal molar amounts of DNA from all affected individuals were pooled and used as the PCR template for short tandem repeat polymorphic markers (STRPs). Pooled DNA from unaffected members of the kindred was used as a control. A reduction in the number of alleles in the affected versus control pool was observed at several loci. Upon genotyping of individual family members, significant linkage was established between the disease phenotype and markers localized on chromosome 2. The highest LOD score observed was 5.4 (theta = 0). When four additional small unrelated families were genotyped, the combined peak LOD score was 8.2. Analysis of recombinant chromosomes revealed that the disease gene lies within a 30 cM interval which spans the centromere. Additional fine-mapping studies identified a region of homozygosity in all affected individuals, narrowing the region to 14 cM. A candidate gene for achromatopsia was excluded from this disease interval by radiation hybrid mapping. Linkage of achromatopsia to chromosome 2 is an essential first step in the identification of the disease-causing gene.      

Reduced endocannabinoid immune modulation by a common cannabinoid 2 (CB2) receptor gene polymorphism: possible risk for autoimmune disorders

Immune system responsiveness results from numerous factors, including endogenous cannabinoid signaling in immunocytes termed the "immunocannabinoid" system. This system can be an important signaling pathway for immune modulation. To assess the immunomodulating role of the cannabinoid 2 (CB2) receptor, we sought polymorphisms in the human gene, identified a common dinucleotide polymorphism, and investigated its effect on endocannabinoid-induced inhibition of T lymphocyte proliferation. The CB2 cDNA 188-189 GG/GG polymorphism predicts the substitution of glutamine at amino acid position 63 by arginine. T lymphocytes from CB2 188-189 GG/GG homozygotes had approximately twofold reduction of endocannabinoid-induced inhibition of proliferation compared with cells from CB2 188-189 AA/AA homozygotes. In GG/GG subjects, the reduced endocannabinoid inhibitory response was highly significant for N-arachidonylglycine and nearly significant for 2-arachidonylglycerol, and a specific CB2 receptor antagonist partially blocked these effects. Also, patients with autoimmune diseases had an increased prevalence of the homozygous GG/GG genotype. Collectively, these results demonstrate reduced endogenous fatty acid amide immunomodulatory responses in individuals with the CB2 188-189 GG/GG genotype and suggest that this CB2 gene variation may be a risk factor for autoimmunity. The results also support the proposition that the CB2 receptor may represent a novel pharmacological target for selective agonists designed to suppress autoreactive immune responses while avoiding CB1 receptor-mediated cannabinoid adverse effects.     

Severe Maternal Morbidity in Canada: Temporal Trends and Regional Variations, 2003-2016

ObjectiveThis study sought to quantify temporal trends and provincial and territorial variations in severe maternal morbidity (SMM) in Canada.MethodsThe study used data on all hospital deliveries in Canada (excluding Québec) from 2003 to 2016 to examine temporal trends and from 2012 to 2016 to study regional variations. SMM was identified using diagnosis and intervention codes. Contrasts among periods and regions were quantified using rate ratios (RRs) and 95% confidence intervals (CIs). Temporal changes were also assessed using chi-square tests for trend (Canadian Task Force Classification II-1).ResultsThe study population included 3 882 790 deliveries between 2003 and 2016 and 1 418 545 deliveries between 2012 and 2016. Severe hemorrhage rates increased from 44.8 in 2003 to 62.4 per 10 000 deliveries in 2012 (P for trend <0.0001) and then declined to 41.8 per 10 000 deliveries in 2016 (P for trend <0.0001). Maternal intensive care unit admission and sepsis rates decreased between 2003 and 2016, whereas rates of stroke, severe uterine rupture, hysterectomy, obstetric embolism, shock, and assisted ventilation increased. Rates of composite SMM in 2012-2016 were higher in Newfoundland and Labrador (RR 1.15; 95% CI 1.04–1.26), Nova Scotia (RR 1.11; 95% CI 1.03–1.19), New Brunswick (RR1.22; 95% CI 1.13–1.32), Manitoba (RR 1.09; 95% CI 1.03–1.15), Saskatchewan (RR 1.15; 95% CI 1.09–1.22), the Yukon (RR 1.74; 95% CI 1.35–2.25), and Nunavut (RR 1.76; 95% CI 1.46–2.11) compared with the rest of Canada, whereas rates were lower in Alberta and British Columbia.ConclusionThis surveillance report helps inform clinical practice and public health policy for improving maternal health in Canada.     

Characteristics of primary biliary cirrhosis in British Columbia's First Nations population.

Primary biliary cirrhosis (PBC) is a rare, autoimmune liver disorder characterized by progressive destruction of intrahepatic bile ducts, that results in portal inflammation, scarring, cirrhosis and, eventually, liver failure. Although considered rare in Canadian populations, it is the leading indication for referral for liver transplantation in British Columbia's First Nations population. Previously, an expanded review of all cases referred to the British Columbia Transplant Society for PBC was carried out comparing the demographics of those of First Nations descent with those not of First Nations descent. The review suggested that the rate of referral for transplantation was eight times higher for those of First Nations descent compared with those of other descent (P=0.0001), and a disproportionate number of the First Nations cases lived on Vancouver Island (48% of cases versus 18% expected, P<0.05). Additionally, the age of referral was significantly younger (45.9 versus 54.3 years) for those of First Nations descent and there are fewer First Nations men referred (1:34) than expected. For the purpose of the present report, 28 symptomatic cases were ascertained separately and reviewed in a clinical study to delineate the features of this population. RESULTS: Although available liver biopsy reports were consistent with PBC, not all cases were antimitochondrial antibody-positive (18% negative). There was a family history of PBC confirmed by medical records in 33% of cases. There were five multiplex families identified, one with seven affected individuals. Detailed family histories revealed a recurrence risk of 4% for PBC for all first-degree relatives older than 21 years of age, but 10% when considering only women. Other autoimmune conditions coexisted in PBC patients in 79% of all cases. Arthritis was most frequent (60%), with thyroid disease (16%) and systemic lupus erythematosus (12%) also present. Additionally, a history of autoimmune diseases (arthritis, systemic lupus erythematosus and thyroid disease) was present in 21% of first-degree relatives. A strong genetic predisposition to PBC and other autoimmune diseases, combined with common environmental factors, is postulated in this population. Further study is underway to identify these factors.     

Proposed model for interaction between residents and residency training programs,and pharmaceutical industry

Medical residents in training are as much targets of pharmaceutical-industry marketing as are physicians in practice. This interaction is often subtle and takes the form of sponsorship of meals at academic events, support for conference travel, books, and items such as pens and notepads. Most residency programs direct little time towards training in ethics and the critical analysis of pharmaceutical-industry marketing. We propose a model for the relationship between residents and residency programs, and the pharmaceutical industry that addresses the need for such interaction to be viewed in light of the patient-centered ethic of professional conduct and the ideal of unbiased medical practice. A committee of residents at different levels of training and two staff physicians received the mandate to examine this issue. The committee developed a set of guidelines and a proposed schema for the handling of funds from pharmaceutical companies (still not implemented). Each residency program would develop a common fund for money donated by pharmaceutical companies. This fund would be administered by a committee with defined priorities. The presence of residents on this committee under staff preceptorship would serve as a springboard for education on the subject. Guidelines for acknowledgement of sponsorship, solicitation of funds, gifts for care of patients, ongoing education, and the wider applicability of these proposals were also developed. Residents' interaction with the pharmaceutical industry during training could have lifelong influence on medical practice. We hope that our model will promote critical appraisal of the potential risks and benefits of this interaction.     

A new approach for evaluating antigen-specific T cell responses to myelin antigens during the course of multiple sclerosis

We used a flow cytometry assay to measure proliferation and cytokine production of self-antigen-specific T cells in individual patients during the clinical course of multiple sclerosis (MS). Myelin-associated oligodendrocytic basic protein (MOBP) was selected for proof of principles in the assay, along with myelin basic protein (MBP) to assess specific activated T cells in 10 MS patients over an 18-month period, in parallel with brain magnetic resonance imaging (MRI) scans and clinical rating scale. A positive correlation occurred between antigen-specific T cell proliferation and interferon-gamma production with clinical relapses and MRI lesion activity that was absent when the same patients were in remission.     

Discordant measures of androgen-binding kinetics in two mutant androgen receptors causing mild or partial androgen insensitivity, respectively

We have characterized two different mutations of the human androgen receptor (hAR) found in two unrelated subjects with androgen insensitivity syndrome (AIS): in one, the external genitalia were ambiguous (partial, PAIS); in the other, they were male, but small (mild, MAIS). Single base substitutions have been found in both individuals: E772A in the PAIS subject, and R871G in the MAIS patient. In COS-1 cells transfected with the E772A and R871G hARs, the apparent equilibrium dissociation constants (Kd) for mibolerone (MB) and methyltrienolone are normal. Nonetheless, the mutant hAR from the PAIS subject (E772A) has elevated nonequilibrium dissociation rate constants (k(diss)) for both androgens. In contrast, the MAIS subject's hAR (R871G) has k(diss) values that are apparently normal for MB and methyltrienolone; in addition, the R871G hAR's ability to bind MB resists thermal stress better than the hAR from the PAIS subject. The E772A and R871G hARs, therefore, confer the same pattern of discordant androgen-binding parameters in transfected COS-1 cells as observed previously in the subjects' genital skin fibroblasts. This proves their pathogenicity and correlates with the relative severity of the clinical phenotype. In COS-1 cells transfected with an androgen-responsive reporter gene, trans-activation was 50% of normal in cells containing either mutant hAR. However, mutant hAR-MB binding is unstable during prolonged incubation with MB, whereas normal hAR-MB binding increases. Thus, normal equilibrium dissociation constants alone, as determined by Scatchard analysis, may not be indicative of normal hAR function. An increased k(diss) despite a normal Kd for a given androgen suggests that it not only has increased egress from a mutant ligand-binding pocket, but also increased access to it. This hypothesis has certain implications in terms of the three-dimensional model of the ligand-binding domain of the nuclear receptor superfamily.