Oligogenic basis of isolated gonadotropin-releasing hormone deficiency

Between the genetic extremes of rare monogenic and common polygenic diseases lie diverse oligogenic disorders involving mutations in more than one locus in each affected individual. Elucidating the principles of oligogenic inheritance and mechanisms of genetic interactions could help unravel the newly appreciated role of rare sequence variants in polygenic disorders. With few exceptions, however, the precise genetic architecture of oligogenic diseases remains unknown. Isolated gonadotropin-releasing hormone (GnRH) deficiency caused by defective secretion or action of hypothalamic GnRH is a rare genetic disease that manifests as sexual immaturity and infertility. Recent reports of patients who harbor pathogenic rare variants in more than one gene have challenged the long-held view that the disorder is strictly monogenic, yet the frequency and extent of oligogenicity in isolated GnRH deficiency have not been investigated. By systematically defining genetic variants in large cohorts of well-phenotyped patients (n = 397), family members, and unaffected subjects (n = 179) for the majority of known disease genes, this study suggests a significant role of oligogenicity in this disease. Remarkably, oligogenicity in isolated GnRH deficiency was as frequent as homozygosity/compound heterozygosity at a single locus (2.5%). Among the 22% of patients with detectable rare protein-altering variants, the likelihood of oligogenicity was 11.3%. No oligogenicity was detected among controls (P < 0.05), even though deleterious variants were present. Viewing isolated GnRH deficiency as an oligogenic condition has implications for understanding the pathogenesis of its reproductive and nonreproductive phenotypes; deciphering the etiology of common GnRH-related disorders; and modeling the genetic architecture of other oligogenic and multifactorial diseases.     

Reduced Phosphoinositide 3-Kinase (p110α) Activation Increases the Susceptibility to Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia presenting at cardiology departments. A limited understanding of the molecular mechanisms responsible for the development of AF has hindered treatment strategies. The purpose of this study was to assess whether reduced activation of phosphoinositide 3-kinase (PI3K, p110α) makes the compromised heart susceptible to AF. Risk factors for AF, including aging, obesity, and diabetes, have been associated with insulin resistance that leads to depressed/defective PI3K signaling. However, to date, there has been no link between PI3K(p110α) and AF. To address this question, we crossed a cardiac-specific transgenic mouse model of dilated cardiomyopathy (DCM) with a cardiac-specific transgenic mouse expressing a dominant negative mutant of PI3K (dnPI3K; reduces PI3K activity). Adult (∼4.5 months) double-transgenic (dnPI3K-DCM), single-transgenic (DCM-Tg, dnPI3K-Tg), and nontransgenic mice were subjected to morphological, functional/ECG, microarray, and biochemical analyses. dnPI3K-DCM mice developed AF and had depressed cardiac function as well as greater atrial enlargement and fibrosis than DCM-Tg mice. AF was not detected in other groups. Aged DCM-Tg mice (∼15 months) with a similar phenotype to dnPI3K-DCM mice (4.5 months) did not develop AF, suggesting loss of PI3K activity directly contributed to the AF phenotype. Furthermore, increasing PI3K activity reduced atrial fibrosis and improved cardiac conduction in DCM-Tg mice. Finally, in atrial appendages from patients with AF, PI3K activation was lower compared with tissue from patients in sinus rhythm. These results suggest a link between PI3K(p110α) and AF.Atrial fibrillation (AF) is a cardiac disorder characterized by uncoordinated atrial activation. It is the most common sustained arrhythmia presenting in cardiology departments worldwide and is associated with substantially increased mortality and morbidity from heart failure, stroke, and thromboembolism.¹ With a growing aging population the incidence of AF is increasing, adding considerably to health care costs.^1,2,3,4 The multifactorial nature of AF and a limited understanding of the molecular mechanisms responsible for the development of AF have greatly limited treatment strategies.Genetically modified mouse models offer a powerful approach to define molecular mechanisms. The very small size of mouse atria, together with the high heart rate (HR), make finding murine AF models difficult, as the potential for re-entry circuits is restricted. Despite these limitations, there are some genetically modified mouse models that are susceptible to AF. These include gene disruption/mutation of connexin40, KCNE1, or nuclear core component NUP155,^5,6,7 overexpression of RhoA,⁸ basic leucine zipper inhibitor protein: JDP2,⁹ angiotensin converting enzyme,¹⁰ tumor necrosis factor α,¹¹ Rac1,¹² and MURC.¹³AF often occurs in combination with heart failure, although the factors that precipitate the onset of AF in patients with (or without) pre-existing heart disease remain unclear.^14,15 We previously demonstrated that phosphoinositide 3-kinase (PI3K, p110α) is a critical regulator of adaptive physiological heart growth,^16,17,18 and that inhibiting PI3K(p110α) accelerates heart failure in a setting of dilated cardiomyopathy (DCM).¹⁹ However, due to the severity of the disease progression in this mouse model (average life span of approximately 40 days¹⁹) it was not possible to perform functional or electrocardiogram (ECG) analyses. The rationale for hypothesizing a link between AF and reduced PI3K(p110α) activity came from multiple lines of evidence. First, we previously demonstrated that decreasing PI3K activation alters gene expression of ion channels in ventricular tissue. Second, several classes of drugs have been reported to induce AF in patients.²¹ The mechanisms considered responsible include adrenergic stimulation and cardiotoxicity.²¹ PI3K(p110α) is a cardioprotective protein that has been shown to inhibit pathological signaling cascades downstream of G protein coupled receptors,¹⁹ thus loss of PI3K(p110α) would be expected to increase the likelihood of cardiotoxicity and activation of signaling proteins downstream of G protein coupled receptors. Third, we previously reported that heat shock protein 70 (Hsp70) expression is elevated in hearts of mice with increased PI3K(p110α) activity and decreased in hearts of mice with decreased PI3K(p110α) activity.²⁰ A number of reports have linked Hsp70 to AF. Patients with high Hsp70 expression levels have a lower incidence of postoperative AF, and an M439T substitution in Hsp70 was associated with an increased risk of postoperative AF.^22,23,24,25 Finally, advanced age and possibly obesity and diabetes are risk factors for the development of AF.^26,27,28 These factors are typically associated with reduced physical activity and insulin resistance. Since PI3K(p110α) is activated in the heart in response to exercise,²⁹ and is a critical molecular signal for insulin, one would predict that PI3K(p110α) activity is generally lower in hearts of obese patients, diabetics, and the elderly.It was also of interest to examine electrical activity in the heart under conditions of reduced PI3K(p110α) activity because of the recent enthusiasm surrounding the development of PI3K(p110α) inhibitors as anticancer agents.^30,31 Uncontrolled activation of the PI3K(p110α) pathway is a critical molecular mechanism by which cancer cells bypass normal growth-limiting controls. However, a challenge in targeting PI3K(p110α) relates to its diverse actions in numerous cell types.³² As noted earlier, PI3K(p110α) is a critical regulator of adaptive physiological heart growth^16,17,18 and we recently demonstrated that inhibiting PI3K(p110α) accelerates heart failure in the compromised heart.¹⁹To reduce PI3K(p110α) activity in a setting of cardiac stress, we genetically crossed a cardiac-specific transgenic (Tg) mouse model of DCM,³³ with a cardiac-specific transgenic mouse expressing a dominant negative mutant of the p110α isoform of PI3K (dnPI3K).¹⁶ Expression of the dnPI3K transgene reduces PI3K activity in cardiac myocytes by approximately 77%.¹⁶ We report here that reduced PI3K(p110α) activity increases the susceptibility to AF in a mouse model of DCM and that PI3K activity is also reduced in atrial appendages from patients with AF compared with those in sinus rhythm.     

Torsion dystonia in israel

A country-wide search for idiopathic torsion dystonia (ITD) in Israel between 1969 and 1975 revealed 42 patients (41 Jewish and 1 Druze Arab). Prevalence of ITD per million population, age-adjusted to the United States population in 1970, was 10.8 in the total Jewish population (22.0 among Jews of European extraction contrasted with 1.5 among Jews with Afro-Asian forebears). Among Europeans, the highest prevalence was among Jews from Eastern Europe. The average age-adjusted annual incidence rates per million population were 0.43 in the total Jewish population, 0.98 in the Europeans, and 0.11 in the Afro-Asians. Among the 40 patients for whom familial data were available, the majority of cases (26) were sporadic. The other 14 belonged to four unrelated European families, all of Russian-Polish origin. The pattern of inheritance in these four families fits an autosomal dominant model with incomplete penetrance.     

Polymorphonuclear leukocyte-associated antigenemia in measles: Demonstration and significance

An indirect immunoperoxidase technique was used for the identification of measles virus (MeV) antigen in routinely prepared peripheral blood smears. Characteristic brown immunoperoxidase staining was present in the polymorphonuclear (PMN) leukocytes in 25 of 31 children during the exanthematous stage of measles. No peroxidase staining was seen on peripheral blood smears in any of 9 children convalescing from measles or in 9 children with upper respiratory tract infections (URTI) without exanthema. These findings were confirmed by control studies and were reproduced by immunofluorescent staining. The data suggest that MeV antigen is localized in the PMN leukocytes during the acute stage of measles infection, and may be connected to phagocytosis of viral antigenic material by PMN leukocytes. The technique described has potential for rapid laboratory diagnosis of measles and, possibly, of other viral infections during the acute stage and before measurable amounts of antibodies are produced.     

CD20 is associated with a small mature plasma cell morphology and t(11;14) in multiple myeloma

CD20 has been reinvestigated in 66 patients with multiple myeloma (MM). Twelve of the patients (18%) expressed CD20, including 5 of 50 patients at diagnosis presenting 100% CD20+ cells. Seven (58%) of 12 CD20+ patients with MM had a small mature plasma cell morphology as opposed to 4 (7%) of 54 with CD20- MM (P =.0001). Of note, 10 (83%) of 12 patients with CD20+ MM had t(11;14) as opposed to 5 of 54 (9%) CD20- patients (P <.001). All the patients with 100% CD20+ cells presented with t(11;14) and 4 of 5 with a small mature plasma cell morphology. Thus, 66% of the patients with t(11;14) expressed CD20, whereas only 4% of the 51 patients lacking such translocation expressed CD20 (P <.0001). In conclusion, CD20 expression is associated with small mature plasma cell morphology and with t(11;14) in patients with MM.     

Real-time monitoring of bacterial infection in vivo: development of bioluminescent staphylococcal foreign-body and deep-thigh-wound mouse infection models

Staphylococcal infections associated with catheter and prosthetic implants are difficult to eradicate and often lead to chronic infections. Development of novel antibacterial therapies requires simple, reliable, and relevant models for infection. Using bioluminescent Staphylococcus aureus, we have adapted the existing foreign-body and deep-wound mouse models of staphylococcal infection to allow real-time monitoring of the bacterial colonization of catheters or tissues. This approach also enables kinetic measurements of bacterial growth and clearance in each infected animal. Persistence of infection was observed throughout the course of the study until termination of the experiment at day 16 in a deep-wound model and day 21 in the foreign-body model, providing sufficient time to test the effects of antibacterial compounds. The usefulness of both animal models was assessed by using linezolid as a test compound and comparing bioluminescent measurements to bacterial counts. In the foreign-body model, a three-dose antibiotic regimen (2, 5, and 24 h after infection) resulted in a decrease in both luminescence and bacterial counts recovered from the implant compared to those of the mock-treated infected mice. In addition, linezolid treatment prevented the formation of subcutaneous abscesses, although it did not completely resolve the infection. In the thigh model, the same treatment regimen resulted in complete resolution of the luminescent signal, which correlated with clearance of the bacteria from the thighs.     

Transforming growth factor-beta and its role in asthma

Transforming growth factor-beta (TGF-beta) is an important fibrogenic and immunomodulatory factor that may play a role in the structural changes observed in the asthmatic airways. In vitro as well as in vivo studies have evidenced a dual role for TGF-beta: it can either function as a pro- or anti-inflammatory cytokine on inflammatory cells, participating into the initiation and resultion of inflammatory and immune responses in the airways. TGF-beta is also involved in the remodelling of the airway wall, and has in particular been related to the subepithelial fibrosis. TGF-beta is produced in the airways by inflammatory cells infiltrated in the bronchial mucosa, as well as by structural cells of the airway wall including fibroblasts, epithelial, endothelial and smooth muscle cells. By releasing TGF-beta, these different cell types may then participate into the increased levels of TGF-beta observed in bronchoalveolar lavage fluid from asthmatic patients. Taken together, these results suggest that TGF-beta may play a role in inflammation in asthma. However, as its role is dual in the modulation of inflammation, further studies are needed to elucidate the precise role of TGF-beta in the airways.