HCFC2 is needed for IRF1- and IRF2-dependent Tlr3 transcription and for survival during viral infections

Sun et al. show that host cell factor C2 (HCFC2) is necessary for basal and induced Tlr3 transcription; deficiency of HCFC2 compromises survival during influenza virus and herpes simplex virus 1 infections in mice.

Transcriptional regulation of numerous interferon-regulated genes, including Toll-like receptor 3 (Tlr3), which encodes an innate immune sensor of viral double-stranded RNA, depends on the interferon regulatory factor 1 (IRF1) and IRF2 transcription factors. We detected specific abrogation of macrophage responses to polyinosinic-polycytidylic acid (poly(I:C)) resulting from three independent N-ethyl-N-nitrosourea–induced mutations in host cell factor C2 (Hcfc2). Hcfc2 mutations compromised survival during influenza virus and herpes simplex virus 1 infections. HCFC2 promoted the binding of IRF1 and IRF2 to the Tlr3 promoter, without which inflammatory cytokine and type I IFN responses to the double-stranded RNA analogue poly(I:C) are reduced in mouse macrophages. HCFC2 was also necessary for the transcription of a large subset of other IRF2-dependent interferon-regulated genes. Deleterious mutations of Hcfc2 may therefore increase susceptibility to diverse infectious diseases.

ENU-induced phenovariance in mice: inferences from 587 mutations

Background

We present a compendium of N-ethyl-N-nitrosourea (ENU)-induced mouse mutations, identified in our laboratory over a period of 10 years either on the basis of phenotype or whole genome and/or whole exome sequencing, and archived in the Mutagenetix database. Our purpose is threefold: 1) to formally describe many point mutations, including those that were not previously disclosed in peer-reviewed publications; 2) to assess the characteristics of these mutations; and 3) to estimate the likelihood that a missense mutation induced by ENU will create a detectable phenotype.

Findings

In the context of an ENU mutagenesis program for C57BL/6J mice, a total of 185 phenotypes were tracked to mutations in 129 genes. In addition, 402 incidental mutations were identified and predicted to affect 390 genes. As previously reported, ENU shows strand asymmetry in its induction of mutations, particularly favoring T to A rather than A to T in the sense strand of coding regions and splice junctions. Some amino acid substitutions are far more likely to be damaging than others, and some are far more likely to be observed. Indeed, from among a total of 494 non-synonymous coding mutations, ENU was observed to create only 114 of the 182 possible amino acid substitutions that single base changes can achieve. Based on differences in overt null allele frequencies observed in phenotypic vs. non-phenotypic mutation sets, we infer that ENU-induced missense mutations create detectable phenotype only about 1 in 4.7 times. While the remaining mutations may not be functionally neutral, they are, on average, beneath the limits of detection of the phenotypic assays we applied.

Conclusions

Collectively, these mutations add to our understanding of the chemical specificity of ENU, the types of amino acid substitutions it creates, and its efficiency in causing phenovariance. Our data support the validity of computational algorithms for the prediction of damage caused by amino acid substitutions, and may lead to refined predictions as to whether specific amino acid changes are responsible for observed phenotypes. These data form the basis for closer in silico estimations of the number of genes mutated to a state of phenovariance by ENU within a population of G3 mice.

Internet Medline providers

Each database in this review has features that will appeal to some users. Each provides a credible interface to information available within the Medline database. The major differences are pricing and interface design. In this context, features that cost more and might seem trivial to the occasional searcher may actually save time and money when used by the professional. Internet Grateful Med is free, but Ms. Coady and I agree the availability of only three ANDable search fields is a major functional limitation. PubMed is also free but much more powerful. The command line interface that permits very sophisticated searches requires a commitment that casual users will find intimidating. Ms. Coady did not believe the feedback currently provided during a search was sufficient for sustained professional use. Paper Chase and Knowledge Finder are mature, modestly priced Medline search services. Paper Chase provides a menu-driven interface that is very easy to use, yet permits the user to search virtually all of Medline's data fields. Knowledge Finder emphasizes the use of natural language queries but fully supports more traditional search strategies. The impact of the tradeoff between fuzzy and Boolean strategies offered by Knowledge Finder is unclear and beyond the scope of this review. Additional software must be downloaded to use all of Knowledge Finders' features. Other providers required no software beyond the basic Internet browser, and this requirement prevented Ms. Coady from evaluating Knowledge Finder. Ovid and Silver Platter offer well-designed interfaces that simplify the construction of complex queries. These are clearly services designed for professional users. While pricing eliminates these for casual use, it should be emphasized that Medline citation access is only a portion of the service provided by these high-end vendors. Finally, we should comment that each of the vendors and government-sponsored services provided prompt and useful feedback to e-mail questions about usage. In conclusion, we would suggest you try the various services, determine which interface suits your style and budget, then perform simple searches until you learn the strengths and weaknesses of the service you select.

Recent developments in the diagnosis, treatment, and prevention of pulmonary embolism

The diagnosis of pulmonary embolism remains enigmatic. Points to look for are: (1) Ninety percent or more of patients with pulmonary embolism have known predisposing factors. (2) Eighty percent or more complain of dyspnea and exhibit hyperpnea (eg, respiratory rate > 20 breaths per minute). (3) Chest roentgenogram abnormalities occur in more than 80% of patients. (4) Seventy percent to 90% of patients complain of chest pain. (5) Either the pCO2 is low or the alveolar-arterial oxygen gradient is high in more than 95% of cases. (6) Twenty percent of patients have normal pO2. (7) Anxiety is present more often than not, and, if present, is no reason to dismiss the cause as "hyperventilation syndrome." Pulmonary arteriography is the "gold standard" for diagnosis, although the combination of ventilation/perfusion scan and noninvasive leg vein studies may decrease its use. An experimental test, the immunosorbent plasma D-dimer assay, seems a promising future screening tool if its reportedly high sensitivity is confirmed. Transthoracic or esophageal echocardiology, if immediately available, may have a place in assessing patients who present with cardiovascular collapse. Early and adequate heparinization coupled with the use of intravenous heparin protocols should lower future mortality rates. Food and Drug Administration approval of low-molecular-weight heparin and heparinoids may revolutionize the management of routine thromboembolism, as these substances are easier to use and less hazardous. A recent British study showed no advantage to anticoagulation beyond 4 weeks for patients with perioperative thrombophlebitis and no other risk factors. In selected cases, thrombolytic therapy, vena caval filters, and invasive embolectomy have been shown to decrease both short- and long-term mortality.

Congestive heart failure

Causes of congestive heart failure include hypertension, coronary artery disease, alcohol abuse and valvular heart disease. Two-dimensional echocardiography with Doppler examination is excellent for identifying valvular heart disease. While noninvasive screening for coronary artery disease may seem cost-effective, the consequences of a missed diagnosis are such that coronary angiography should be strongly considered if there is any suggestion of ischemic heart disease. Medical management primarily consists of vasodilators, diuretics and inotropic agents. Vasodilator therapy may prolong the patient's life. Digoxin and diuretics improve symptoms and hemodynamic abnormalities. With advanced heart failure, adequate control of fluid retention and dyspnea may require diuretic doses associated with azotemia, and systolic blood pressure may have to be maintained at less than 100 mm Hg in spite of postural hypotension.