Interrupting sequence variants and age of onset in Huntington's disease: clinical implications and emerging therapies

BACKGROUND

Huntington's disease is a fatal neurodegenerative disorder that is caused by CAG-CAA repeat expansion, encoding polyglutamine, in the huntingtin (HTT) gene. Current age-of-clinical-onset prediction models for Huntington's disease are based on polyglutamine length and explain only a proportion of the variability in age of onset observed between patients. These length-based assays do not interrogate the underlying genetic variation, because known genetic variants in this region do not alter the protein coding sequence. Given that individuals with identical repeat lengths can present with Huntington's disease decades apart, the search for genetic modifiers of clinical age of onset has become an active area of research.

RECENT DEVELOPMENTS

Results from three independent genetic studies of Huntington's disease have shown that glutamine-encoding CAA variants that interrupt DNA CAG repeat tracts, but do not alter polyglutamine length or polyglutamine homogeneity, are associated with substantial differences in age of onset of Huntington's disease in carriers. A variant that results in the loss of CAA interruption is associated with early onset and is particularly relevant to individuals that carry alleles in the reduced penetrance range (ie, CAG 36-39). Approximately a third of clinically manifesting carriers of reduced penetrance alleles, defined by current diagnostics, carry this variant. Somatic repeat instability, modified by interrupted CAG tracts, is the most probable cause mediating this effect. This relationship is supported by genome-wide screens for disease modifiers, which have revealed the importance of DNA-repair genes in Huntington's disease (ie, FAN1, LIG1, MLH1, MSH3, PMS1, and PMS2). WHERE NEXT?: Focus needs to be placed on refining our understanding of the effect of the loss-of-interruption and duplication-of-interruption variants and other interrupting sequence variants on age of onset, and assessing their effect in disease-relevant brain tissues, as well as in diverse population groups, such as individuals from Africa and Asia. Diagnostic tests should be augmented or updated, since current tests do not assess the underlying DNA sequence variation, especially when assessing individuals that carry alleles in the reduced penetrance range. Future studies should explore somatic repeat instability and DNA repair as new therapeutic targets to modify age of onset in Huntington's disease and in other repeat-mediated disorders. Disease-modifying therapies could potentially be developed by therapeutically targeting these processes. Promising approaches include therapeutically targeting the expanded repeat or directly perturbing key DNA-repair genes (eg, with antisense oligonucleotides or small molecules). Targeting the CAG repeat directly with naphthyridine-azaquinolone, a compound that induces contractions, and altering the expression of MSH3, represent two viable therapeutic strategies. However, as a first step, the capability of such novel therapeutic approaches to delay clinical onset in animal models should be assessed.

Length of Uninterrupted CAG, Independent of Polyglutamine Size, Results in Increased Somatic Instability, Hastening Onset of Huntington Disease

Huntington disease (HD) is caused by a CAG repeat expansion in the huntingtin (HTT) gene. Although the length of this repeat is inversely correlated with age of onset (AOO), it does not fully explain the variability in AOO. We assessed the sequence downstream of the CAG repeat in HTT [reference: (CAG)n-CAA-CAG], since variants within this region have been previously described, but no study of AOO has been performed. These analyses identified a variant that results in complete loss of interrupting (LOI) adenine nucleotides in this region [(CAG)n-CAG-CAG]. Analysis of multiple HD pedigrees showed that this LOI variant is associated with dramatically earlier AOO (average of 25 years) despite the same polyglutamine length as in individuals with the interrupting penultimate CAA codon. This LOI allele is particularly frequent in persons with reduced penetrance alleles who manifest with HD and increases the likelihood of presenting clinically with HD with a CAG of 36-39 repeats. Further, we show that the LOI variant is associated with increased somatic repeat instability, highlighting this as a significant driver of this effect. These findings indicate that the number of uninterrupted CAG repeats, which is lengthened by the LOI, is the most significant contributor to AOO of HD and is more significant than polyglutamine length, which is not altered in these individuals. In addition, we identified another variant in this region, where the CAA-CAG sequence is duplicated, which was associated with later AOO. Identification of these cis-acting modifiers have potentially important implications for genetic counselling in HD-affected families.

The Super-Seniors Study: Phenotypic characterization of a healthy 85+ population

Background

To understand why some people live to advanced age in good health and others do not, it is important to study not only disease, but also long-term good health. The Super-Seniors Study aims to identify factors associated with healthy aging.

Methods

480 healthy oldest-old ‘Super-Seniors’ aged 85 to 105 years and never diagnosed with cancer, cardiovascular disease, diabetes, dementia, or major pulmonary disease, were compared to 545 mid-life controls aged 41–54, who represent a group that is unselected for survival from late-life diseases. Health and lifestyle information, personal and family medical history, and blood samples were collected from all participants. Super-Seniors also underwent four geriatric tests.

Results

Super-Seniors showed high cognitive (Mini-Mental State Exam mean = 28.3) and functional capacity (Instrumental Activities of Daily Living Scale mean = 21.4), as well as high physical function (Timed Up and Go mean = 12.3 seconds) and low levels of depression (Geriatric Depression Scale mean = 1.5). Super-Seniors were less likely to be current smokers than controls, but the frequency of drinking alcohol was the same in both groups. Super-Seniors were more likely to have 4 or more offspring; controls were more likely to have no children. Female Super-Seniors had a mean age of last fertility 1.9 years older than controls, and were 2.3 times more likely to have had a child at ≥ 40 years. The parents of Super-Seniors had mean ages of deaths of 79.3 years for mothers, and 74.5 years for fathers, each exceeding the life expectancy for their era by a decade.

Conclusions

Super-Seniors are cognitively and physically high functioning individuals who have evaded major age-related chronic diseases into old age, representing the approximately top 1% for healthspan. The familiality of long lifespan of the parents of Super-Seniors supports the hypothesis that heritable factors contribute to this desirable phenotype.

The molecular epidemiology of Huntington disease is related to intermediate allele frequency and haplotype in the general population

Huntington disease (HD) is the most common monogenic neurodegenerative disorder in populations of European ancestry, but occurs at lower prevalence in populations of East Asian or black African descent. New mutations for HD result from CAG repeat expansions of intermediate alleles (IAs), usually of paternal origin. The differing prevalence of HD may be related to the rate of new mutations in a population, but no comparative estimates of IA frequency or the HD new mutation rate are available. In this study, we characterize IA frequency and the CAG repeat distribution in fifteen populations of diverse ethnic origin. We estimate the HD new mutation rate in a series of populations using molecular IA expansion rates. The frequency of IAs was highest in Hispanic Americans and Northern Europeans, and lowest in black Africans and East Asians. The prevalence of HD correlated with the frequency of IAs by population and with the proportion of IAs found on the HD-associated A1 haplotype. The HD new mutation rate was estimated to be highest in populations with the highest frequency of IAs. In European ancestry populations, one in 5,372 individuals from the general population and 7.1% of individuals with an expanded CAG repeat in the HD range are estimated to have a molecular new mutation. Our data suggest that the new mutation rate for HD varies substantially between populations, and that IA frequency and haplotype are closely linked to observed epidemiological differences in the prevalence of HD across major ancestry groups in different countries.

The targetable A1 Huntington disease haplotype has distinct Amerindian and European origins in Latin America

Huntington disease (HD) is a dominant neurodegenerative disorder caused by a CAG repeat expansion in the Huntingtin (HTT) gene. HD occurs worldwide, but the causative mutation is found on different HTT haplotypes in distinct ethnic groups. In Latin America, HD is thought to have European origins, but indigenous Amerindian ancestry has not been investigated. Here, we report dense HTT haplotypes in 62 mestizo Peruvian HD families, 17 HD families from across Latin America, and 42 controls of defined Peruvian Amerindian ethnicity to determine the origin of HD in populations of admixed Amerindian and European descent. HD in Peru occurs most frequently on the A1 HTT haplotype (73%), as in Europe, but on an unexpected indigenous variant also found in Amerindian controls. This Amerindian A1 HTT haplotype predominates over the European A1 variant among geographically disparate Latin American controls and in HD families from across Latin America, supporting an indigenous origin of the HD mutation in mestizo American populations. We also show that a proportion of HD mutations in Peru occur on a C1 HTT haplotype of putative Amerindian origin (14%). The majority of HD mutations in Latin America may therefore occur on haplotypes of Amerindian ancestry rather than on haplotypes resulting from European admixture. Despite the distinct ethnic ancestry of Amerindian and European A1 HTT, alleles on the parent A1 HTT haplotype allow for development of identical antisense molecules to selectively silence the HD mutation in the greatest proportion of patients in both Latin American and European populations.

Pancreatic Cytopathology

Pancreatic cytopathology, particularly through the use of endoscopic ultrasound-guided fine-needle aspiration (FNA), has excellent specificity and sensitivity for the diagnosis of pancreatic lesions. Such diagnoses can help guide preoperative management of patients, provide prognostic information, and confirm diagnoses in patients who are not surgical candidates. Furthermore, FNA can be used to obtain cyst fluid for ancillary tests that can improve the diagnosis of cystic lesions. In this article, we describe the cytomorphological features and differential diagnoses of the most commonly encountered pancreatic lesions on FNA.

Carcinoma Showing Thymus-Like Differentiation (CASTLE): Cytopathological Features and Differential Diagnosis

BACKGROUND

CASTLE (carcinoma showing thymus-like differentiation) is a rare tumor (accounting for less than 0.15% of thyroid neoplasms) with most of the reported cases from Asia. Although this tumor is rare, distinguishing it from more aggressive neoplasms is critical because of its improved prognosis. To date, there have been limited studies on its cytomorphological features. Herein, we review the cytomorphological features of 10 fine-needle aspiration (FNA) cases of histologically confirmed CASTLE and discuss the findings in light of the current literature.

METHODS

We retrospectively (1989-2016) identified 10 cases of CASTLE from 17,415 surgical cases of thyroid carcinoma from The Johns Hopkins Hospital and Fudan University Shanghai Cancer Center. The cases were reviewed for discrete cytomorphological characteristics.

RESULTS

All of the cases displayed predominantly single (dishesive) epithelial cell populations, high nuclear/cytoplasmic ratios, hyperchromatic to open/vesicular nuclei and macronucleoli. The majority of cases additionally showed hypercellular, three-dimensional fragments in a background of lymphocytes. The fragments displayed syncytial architecture without molding and rarely squamous differentiation. All cases lacked follicular differentiation, intranuclear inclusions, nuclear molding, or neuroendocrine-type chromatin.

CONCLUSIONS

Cytopathological features alone do not appear to be distinctive or definitive of CASTLE but rather allow for the inclusion of CASTLE within the differential diagnosis. Procurement of cell block material is important and resulted in the single case of CASTLE accurately diagnosed on FNA. Cytopathological features that favored CASTLE included syncytial fragments of malignant cells with pleomorphic large nuclei, vesicular chromatin, and prominent nucleoli in a background of lymphocytes. These cytopathological findings in the appropriate clinicoradiological context warrant its inclusion in the reported differential diagnosis in order to be able to implement appropriate clinical management.

Well-differentiated fetal adenocarcinoma of the lung mimicking adenoid cystic carcinoma on fine needle aspiration: A case report

Well-differentiated fetal adenocarcinoma (WDFA) of the lung is a rare variant of adenocarcinoma with an unusual morphology. Although the histologic features of this rare neoplasm have been well established, there is a deficit in the literature with regards to its discrete cytomorphologic features. We report the fine needle aspiration (FNA) findings of a case of this unusual malignancy in a 44-year-old man with an incidental lung nodule. FNA revealed three-dimensional clusters of epithelial cells with scant cytoplasm, hyperchromatic nuclei that are associated with an extracellular metachromatic matrix. The original cytology report was signed out as an epithelial neoplasm favor adenoid cystic carcinoma. Consequently, a wedge resection of the lung was done and the histologic diagnosis was WDFA of the lung. The findings of minimal nuclear atypia in association with focally abundant spheres of extracellular matrix can mimic adenoid cystic carcinoma. WDFA has good prognosis and therefore, pre-operative cytologic diagnosis is critical to clinical management. We present the cytomorphologic features of this neoplasm with particular emphasis on a potential diagnostic pitfall of this rare entity. Diagn. Cytopathol. 2016;44:917-920. © 2016 Wiley Periodicals, Inc.

Huntington disease reduced penetrance alleles occur at high frequency in the general population

OBJECTIVE

To directly estimate the frequency and penetrance of CAG repeat alleles associated with Huntington disease (HD) in the general population.

METHODS

CAG repeat length was evaluated in 7,315 individuals from 3 population-based cohorts from British Columbia, the United States, and Scotland. The frequency of ≥36 CAG alleles was assessed out of a total of 14,630 alleles. The general population frequency of reduced penetrance alleles (36-39 CAG) was compared to the prevalence of patients with HD with genetically confirmed 36-39 CAG from a multisource clinical ascertainment in British Columbia, Canada. The penetrance of 36-38 CAG repeat alleles for HD was estimated for individuals ≥65 years of age and compared against previously reported clinical penetrance estimates.

RESULTS

A total of 18 of 7,315 individuals had ≥36 CAG, revealing that approximately 1 in 400 individuals from the general population have an expanded CAG repeat associated with HD (0.246%). Individuals with CAG 36-37 genotypes are the most common (36, 0.096%; 37, 0.082%; 38, 0.027%; 39, 0.000%; ≥40, 0.041%). General population CAG 36-38 penetrance rates are lower than penetrance rates extrapolated from clinical cohorts.

CONCLUSION

HD alleles with a CAG repeat length of 36-38 occur at high frequency in the general population. The infrequent diagnosis of HD at this CAG length is likely due to low penetrance. Another important contributing factor may be reduced ascertainment of HD in those of older age.

Targeted next-generation sequencing to diagnose disorders of HDL cholesterol

A low level of HDL cholesterol (HDL-C) is a common clinical scenario and an important marker for increased cardiovascular risk. Many patients with very low or very high HDL-C have a rare mutation in one of several genes, but identification of the molecular abnormality in patients with extreme HDL-C is rarely performed in clinical practice. We investigated the accuracy and diagnostic yield of a targeted next-generation sequencing (NGS) assay for extreme levels of HDL-C. We developed a targeted NGS panel to capture the exons, intron/exon boundaries, and untranslated regions of 26 genes with highly penetrant effects on plasma lipid levels. We sequenced 141 patients with extreme HDL-C levels and prioritized variants in accordance with medical genetics guidelines. We identified 35 pathogenic and probably pathogenic variants in HDL genes, including 21 novel variants, and performed functional validation on a subset of these. Overall, a molecular diagnosis was established in 35.9% of patients with low HDL-C and 5.2% with high HDL-C, and all prioritized variants identified by NGS were confirmed by Sanger sequencing. Our results suggest that a molecular diagnosis can be identified in a substantial proportion of patients with low HDL-C using targeted NGS.

Huntingtin Haplotypes Provide Prioritized Target Panels for Allele-specific Silencing in Huntington Disease Patients of European Ancestry

Huntington disease (HD) is a dominant neurodegenerative disorder caused by a CAG repeat expansion in the Huntingtin gene (HTT). Heterozygous polymorphisms in cis with the mutation allow for allele-specific suppression of the pathogenic HTT transcript as a therapeutic strategy. To prioritize target selection, precise heterozygosity estimates are needed across diverse HD patient populations. Here we present the first comprehensive investigation of all common target alleles across the HTT gene, using 738 reference haplotypes from the 1000 Genomes Project and 2364 haplotypes from HD patients and relatives in Canada, Sweden, France, and Italy. The most common HD haplotypes (A1, A2, and A3a) define mutually exclusive sets of polymorphisms for allele-specific therapy in the greatest number of patients. Across all four populations, a maximum of 80% are treatable using these three target haplotypes. We identify a novel deletion found exclusively on the A1 haplotype, enabling potent and selective silencing of mutant HTT in approximately 40% of the patients. Antisense oligonucleotides complementary to the deletion reduce mutant A1 HTT mRNA by 78% in patient cells while sparing wild-type HTT expression. By suppressing specific haplotypes on which expanded CAG occurs, we demonstrate a rational approach to the development of allele-specific therapy for a monogenic disorder.

A SNP in the HTT promoter alters NF-κB binding and is a bidirectional genetic modifier of Huntington disease

Cis-regulatory variants that alter gene expression can modify disease expressivity, but none have previously been identified in Huntington disease (HD). Here we provide in vivo evidence in HD patients that cis-regulatory variants in the HTT promoter are bidirectional modifiers of HD age of onset. HTT promoter analysis identified a NF-κB binding site that regulates HTT promoter transcriptional activity. A non-coding SNP, rs13102260:G > A, in this binding site impaired NF-κB binding and reduced HTT transcriptional activity and HTT protein expression. The presence of the rs13102260 minor (A) variant on the HD disease allele was associated with delayed age of onset in familial cases, whereas the presence of the rs13102260 (A) variant on the wild-type HTT allele was associated with earlier age of onset in HD patients in an extreme case-based cohort. Our findings suggest a previously unknown mechanism linking allele-specific effects of rs13102260 on HTT expression to HD age of onset and have implications for HTT silencing treatments that are currently in development.

Clinical, Biochemical, and Molecular Characterization of Novel Mutations in ABCA1 in Families with Tangier Disease

Tangier disease is a rare, autosomal recessive disorder caused by mutations in the ABCA1 gene and is characterized by near absence of plasma high-density lipoprotein cholesterol, accumulation of cholesterol in multiple tissues, peripheral neuropathy, and accelerated atherosclerosis. Here we report three new kindreds with Tangier disease harboring both known and novel mutations in ABCA1. One patient was identified to be homozygous for a nonsense mutation, p.Gln1038*. In a remarkably large Tangier disease pedigree with four affected siblings, we identified compound heterozygosity for previously reported missense variants, p.Arg937Val and p.Thr940Met, and show that both of these mutations result in significantly impaired cholesterol efflux in transfected cells. In a third pedigree, the proband was identified to be compound heterozygous for two novel mutations, a frameshift (p.Ile1200Hisfs*4) and an intronic variant (c.4176-11T>G), that lead to the creation of a cryptic splice site acceptor and premature truncation, p.Ser1392Argfs*6. We demonstrate that this mutation arose de novo, the first demonstration of a pathogenic de novo mutation in ABCA1 associated with Tangier disease. We also report results of glucose tolerance testing in a Tangier disease kindred for the first time, showing a gene-dose relationship between ABCA1 activity and glucose tolerance and suggesting that Tangier disease patients may have substantially impaired islet function. Our findings provide insight into the diverse phenotypic manifestations of this rare disorder, expand the list of pathogenic mutations in ABCA1, and increase our understanding of how specific mutations in this gene lead to abnormal cellular and physiological phenotypes.

Pathologic findings in native infective endocarditis

BACKGROUND

There are few studies on the histologic findings in native infective endocarditis, especially regarding mimics of autoimmune valvulitis.

METHODS

We prospectively studied 106 surgical specimens from 95 patients with a clinical diagnosis of infective endocarditis on native valves, and compared gross and histologic findings with culture results, underlying valve disease, risk factors and time interval from symptom onset to surgical intervention.

RESULTS

There were 41 (39%) aortic, 33 (31%) mitral, 9 (9%) tricuspid, 1(.9%) pulmonic and 11 (10%) multiple valve replacements. Underlying valve disease was present in 26 (27%) patients (non-calcified bicuspid aortic valve, 10 (38%) cases; mitral valve prolapse, 5 (19%) cases; calcified trileaflet aortic valve, 5 (19%) cases; calcified bicuspid aortic valve, 2 (8%) cases; post-rheumatic mitral valve disease, 2 (8%) cases; hypertrophic cardiomyopathy-related mitral valve disease, 1 (4%) case, trileaflet aortic insufficiency 1 (4%) case) and associated with streptococcal infection (p = .001). Absence of underlying valve disease was associated with intravenous drug abuse (p = .01) and dialysis dependent renal disease (p = .006). Intravenous drug abuse was associated with staphylococcal infection (p = .03). Vegetations were present in 80 (75%) of cases, and on the nonflow surface of the valve in 65 (81%) of these. Gram-stain positivity and neutrophilic microabscesses were associated with staphylococcal infection (p = .03). Epithelioid macrophages with palisading features mimicking necrobiotic granulomas were seen in 42 (40%) valves and more frequently associated with streptococcal infection (p=.03). As expected, the presence of valve necrosis and acute inflammation decreased with an increase in time with respect to symptomatic onset.

CONCLUSION

Histologic findings that mimic autoimmune inflammation are frequent in infective endocarditis and associated with streptococcal infection. Risk factors for infective endocarditis include calcific valve disease.

U. S. consumer perceptions of U. S. and Canadian beef quality grades

A U.S. consumer (n = 642) study (Baltimore, MD; Phoenix, AZ; and Lubbock, TX) was conducted to compare consumer sensory scores of U.S. beef (83 USDA Choice [Choice] and 96 USDA Select [Select]) and Canadian beef (77 AAA and 82 AA) strip loins. Strip loins (n = 338) were obtained from beef processors in Canada and the United States and were wet aged until 21 d postmortem at 2°C. Marbling scores were assigned at 21 d and loins were paired according to quality grades and marbling score. Strip loins were fabricated into 2.54-cm thick steaks; steaks were vacuum packaged and frozen until further evaluations. Proximate analysis was performed to compare fat, moisture, and protein. Choice and Canadian AAA had similar marbling scores and intramuscular fat. Both Choice and Canadian AAA had greater (P < 0.05) marbling scores and intramuscular fat than Canadian AA, but Select strip loins had intermediate values that were not different from any of the other grades (P > 0.05). Consumers' opinions did not differ when comparing equivalent grades (Choice with Canadian AAA and Select with Canadian AA), but they rated Choice and Canadian AAA more palatable than Select and Canadian AA for all sensory attributes (P < 0.05). Regarding percentage of acceptability and likelihood to buy score, consumers indicated a preference and greater probability to buy (P = 0.001 and P = 0.004, respectively) strip loin steaks from higher quality grade carcasses (Choice and Canadian AAA) than lower quality grade carcasses (Select and Canada AA). Additionally, consumers gave their opinion of Canadian beef, where its quality and safety were rated as "good" to "excellent" for both attributes (76.72% and 88.36%, respectively; P < 0.05), feeling confident in beef that is imported from Canada. In the same way, consumers indicated that country-of-origin labeling was a minimal factor influencing their beef steak purchasing decisions. Results from this consumer study indicated U.S. consumers could not differentiate between U.S. and Canadian beef within comparable quality grades; however, strip loin steaks from higher quality grades were more palatable than lower quality grades according to consumer scores for eating quality traits.

Performance characteristics of ultrasound-guided fine-needle aspiration of axillary lymph nodes for metastatic breast cancer employing rapid on-site evaluation of adequacy: analysis of 136 cases and review of the literature

BACKGROUND

It has been demonstrated that axillary ultrasound-guided fine-needle aspiration (US-FNA) has excellent positive predictive value for the axillary lymph node status of patients with breast cancer before surgery or neoadjuvant therapy and, thus, can obviate the need for sentinel lymph node biopsy in FNA-positive patients. However, US-FNA has only moderate sensitivity, in part because of the collection of nondiagnostic or equivocal specimens. Rapid on-site evaluation for adequacy (ROSE) can improve definitive diagnosis rates but has not been well characterized in this setting.

METHODS

One hundred thirty-three patients with breast carcinoma were identified who underwent 136 US-FNAs of axillary lymph nodes, all with ROSE, and the results were correlated with the diagnosis on a subsequent surgical procedure.

RESULTS

The adequacy rate was 95.6% (130 of 136 FNAs), and a definitive diagnosis was made in 91.2% (124 of 136 FNAs). Among definite diagnoses, sensitivity was 75%, specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 79%. Sources of false-negative and potential false-positive diagnoses were evaluated among these cases and in the literature.

CONCLUSIONS

Small metastasis size is the most common cause of false-negative results, whereas interpretation errors by pathologists are quite rare. ROSE appears to improve adequacy and definitive diagnosis rates and, thus, can more accurately triage patients to appropriate care.

High frequency of intermediate alleles on Huntington disease-associated haplotypes in British Columbia's general population

Intermediate alleles (27-35 CAG, IAs) for Huntington disease (HD) usually do not confer the disease phenotype but are prone to CAG repeat instability. Consequently, offspring are at-risk of inheriting an expanded allele in the HD range (≥36 CAG). IAs that expand into a new mutation have been hypothesized to be more susceptible to instability compared to IAs identified on the non-HD side of a family from the general population. Frequency estimates for IAs are limited and have largely been determined using clinical samples of HD or related disorders, which may result in an ascertainment bias. This study aimed to establish the frequency of IAs in a sample of a British Columbia's (B.C.) general population with no known association to HD and examine the haplotype of new mutation and general population IAs. CAG sizing was performed on 1,600 DNA samples from B.C.'s general population. Haplotypes were determined using 22 tagging SNPs across the HTT gene. 5.8% of individuals were found to have an IA, of which 60% were on HD-associated haplotypes. There was no difference in the haplotype distribution of new mutation and general population IAs. These findings suggest that IAs are relatively frequent in the general population and are often found on haplotypes associated with expanded CAG lengths. There is likely no difference in the propensity of new mutation and general population IAs to expand into the disease range given that they are both found on disease-associated haplotypes. These findings have important implications for clinical practice.

Cytotechnologists and on-site evaluation of adequacy

While fine needle aspiration (FNA) is certainly not a new biopsy technique, recent developments in advanced imaging techniques, molecular testing, and targeted therapies have coincided with a rapid increase in the number of FNA procedures being performed. Concurrently, the demand for on-site evaluation of adequacy (OSEA) has also increased, outstripping the capacity of available cytopathologists at some institutions. Among the several alternatives to cytopathologist-performed OSEA, cytotechnologist-attended OSEA stands out because it preserves the representation of the pathology service at the time of the procedure. Herein, we review the current literature about OSEA and the necessity of cytotechnologists to expand access of this useful pathology service to a broader patient population. We also examine how cytotechnologists are likely to fit into the emerging practice of telecytology.

CAG size-specific risk estimates for intermediate allele repeat instability in Huntington disease

INTRODUCTION

New mutations for Huntington disease (HD) occur due to CAG repeat instability of intermediate alleles (IA). IAs have between 27 and 35 CAG repeats, a range just below the disease threshold of 36 repeats. While they usually do not confer the HD phenotype, IAs are prone to paternal germline CAG repeat instability. Consequently, they may expand into the HD range upon transmission to the next generation, producing a new mutation. Quantified risk estimates for IA repeat instability are extremely limited but needed to inform clinical practice.

METHODS

Using small-pool PCR of sperm DNA from Caucasian men, we examined the frequency and magnitude of CAG repeat instability across the entire range of intermediate CAG sizes. The CAG size-specific risk estimates generated are based on the largest sample size ever examined, including 30 IAs and 18 198 sperm.

RESULTS

Our findings demonstrate a significant risk of new mutations. While all intermediate CAG sizes demonstrated repeat expansion into the HD range, alleles with 34 and 35 CAG repeats were associated with the highest risk of a new mutation (2.4% and 21.0%, respectively). IAs with ≥33 CAG repeats showed a dramatic increase in the frequency of instability and a switch towards a preponderance of repeat expansions over contractions.

CONCLUSIONS

These data provide novel insights into the origins of new mutations for HD. The CAG size-specific risk estimates inform clinical practice and provide accurate risk information for persons who receive an IA predictive test result.

Huntington disease in the South African population occurs on diverse and ethnically distinct genetic haplotypes

Huntington disease (HD) is a neurodegenerative disorder resulting from the expansion of a CAG trinucleotide repeat in the huntingtin (HTT) gene. Worldwide prevalence varies geographically with the highest figures reported in populations of European ancestry. HD in South Africa has been reported in Caucasian, black and mixed subpopulations, with similar estimated prevalence in the Caucasian and mixed groups and a lower estimate in the black subpopulation. Recent studies have associated specific HTT haplotypes with HD in distinct populations. Expanded HD alleles in Europe occur predominantly on haplogroup A (specifically high-risk variants A1/A2), whereas in East Asian populations, HD alleles are associated with haplogroup C. Whether specific HTT haplotypes associate with HD in black Africans and how these compare with haplotypes found in European and East Asian populations remains unknown. The current study genotyped the HTT region in unaffected individuals and HD patients from each of the South African subpopulations, and haplotypes were constructed. CAG repeat sizes were determined and phased to haplotype. Results indicate that HD alleles from Caucasian and mixed patients are predominantly associated with haplogroup A, signifying a similar European origin for HD. However, in black patients, HD occurs predominantly on haplogroup B, suggesting several distinct origins of the mutation in South Africa. The absence of high-risk variants (A1/A2) in the black subpopulation may also explain the reported low prevalence of HD. Identification of haplotypes associated with HD-expanded alleles is particularly relevant to the development of population-specific therapeutic targets for selective suppression of the expanded HTT transcript.

A fully humanized transgenic mouse model of Huntington disease

Silencing the mutant huntingtin gene (muHTT) is a direct and simple therapeutic strategy for the treatment of Huntington disease (HD) in principle. However, targeting the HD mutation presents challenges because it is an expansion of a common genetic element (a CAG tract) that is found throughout the genome. Moreover, the HTT protein is important for neuronal health throughout life, and silencing strategies that also reduce the wild-type HTT allele may not be well tolerated during the long-term treatment of HD. Several HTT silencing strategies are in development that target genetic sites in HTT that are outside of the CAG expansion, including HD mutation-linked single-nucleotide polymorphisms and the HTT promoter. Preclinical testing of these genetic therapies has required the development of a new mouse model of HD that carries these human-specific genetic targets. To generate a fully humanized mouse model of HD, we have cross-bred BACHD and YAC18 on the Hdh(-/-) background. The resulting line, Hu97/18, is the first murine model of HD that fully genetically recapitulates human HD having two human HTT genes, no mouse Hdh genes and heterozygosity of the HD mutation. We find that Hu97/18 mice display many of the behavioral changes associated with HD including motor, psychiatric and cognitive deficits, as well as canonical neuropathological abnormalities. This mouse line will be useful for gaining additional insights into the disease mechanisms of HD as well as for testing genetic therapies targeting human HTT.

Use of qualitative methods to identify solutions to selected equine welfare problems in Ireland

This paper explores the views of those in the Irish equine industry, organisations and government regarding necessary improvements to equine welfare in Ireland at unregulated gatherings and during the disposal process. Three qualitative research methods were employed, namely semistructured interviews, focus groups and a structured, facilitated workshop. Representatives from industry, welfare societies, socially disadvantaged groupings and government engaged with this process and shared their views regarding horse welfare and implementable solutions with merit to address welfare problems. A consensus was achieved that equine welfare in Ireland could be improved by the development of a comprehensive identification system, a Code of Practice for horse gatherings, a horse licensing scheme, ring-fenced funding to promote responsible, humane horse disposal and better means of raising awareness of the value of safeguarding horse welfare for the benefit of all parties.

Analysis of selected anticonvulsants by high performance liquid chromatography-tandem mass spectrometry

A method for the analysis of the basic antiepileptic compounds felbamate, lamotrigine, carbamazepine, carbamazepine-10,11-epoxide, gabapentin, pregabalin, levetiracetam, and oxcarbazepine monohydroxy derivative (oxcarb MHD) in human plasma is described. This protocol incorporates a simplified sample preparation step followed by quantitative high performance chromatography-tandem mass spectrometry detection of commonly prescribed and monitored anticonvulsant drugs. Since polytherapy is common in epilepsy patients, use of a multiconstituent assay can improve laboratory efficiency and reduce required analytical time.

Caveolae compartmentalise β2-adrenoceptor signals by curtailing cAMP production and maintaining phosphatase activity in the sarcoplasmic reticulum of the adult ventricular myocyte

Inotropy and lusitropy in the ventricular myocyte can be efficiently induced by activation of β1-, but not β2-, adrenoceptors (ARs). Compartmentation of β2-AR-derived cAMP-dependent signalling underlies this functional discrepancy. Here we investigate the mechanism by which caveolae (specialised sarcolemmal invaginations rich in cholesterol and caveolin-3) contribute to compartmentation in the adult rat ventricular myocyte. Selective activation of β2-ARs (with zinterol/CGP20712A) produced little contractile response in control cells but pronounced inotropic and lusitropic responses in cells treated with the cholesterol-depleting agent methyl-β-cyclodextrin (MBCD). This was not linked to modulation of L-type Ca²⁺ current, but instead to a discrete PKA-mediated phosphorylation of phospholamban at Ser¹⁶. Application of a cell-permeable inhibitor of caveolin-3 scaffolding interactions mimicked the effect of MBCD on phosphorylated phospholamban (pPLB) during β2-AR stimulation, consistent with MBCD acting via caveolae. Biosensor experiments revealed β2-AR mobilisation of cAMP in PKA II signalling domains of intact cells only after MBCD treatment, providing a real-time demonstration of cAMP freed from caveolar constraint. Other proteins have roles in compartmentation, so the effects of phosphodiesterase (PDE), protein phosphatase (PP) and phosphoinositide-3-kinase (PI3K) inhibitors on pPLB and contraction were compared in control and MBCD treated cells. PP inhibition alone was conspicuous in showing robust de-compartmentation of β2-AR-derived signalling in control cells and a comparatively diminutive effect after cholesterol depletion. Collating all evidence, we promote the novel concept that caveolae limit β2-AR-cAMP signalling by providing a platform that not only attenuates production of cAMP but also prevents inhibitory modulation of PPs at the sarcoplasmic reticulum. This article is part of a Special Issue entitled “Local Signaling in Myocytes”.

Are patient characteristics associated with the accuracy of hysterosalpingography in diagnosing tubal pathology? An individual patient data meta-analysis

BACKGROUND

Conventional meta-analysis has estimated the sensitivity and specificity of hysterosalpingography (HSG) to be 65% and 83%. The impact of patient characteristics on the accuracy of HSG is unknown. The aim of this study was to assess by individual patient data meta-analysis whether the accuracy of HSG is associated with different patient characteristics.

METHODS

We approached authors of primary studies reporting on the accuracy of HSG using findings at laparoscopy as the reference. We assessed whether patient characteristics such as female age, duration of subfertility and a clinical history without risk factors for tubal pathology were associated with the accuracy of HSG, using a random intercept logistic regression model.

RESULTS

We acquired data of seven primary studies containing data of 4521 women. Pooled sensitivity and specificity of HSG were 53% and 87% for any tubal pathology and 46% and 95% for bilateral tubal pathology. In women without risk factors, the sensitivity of HSG was 38% for any tubal pathology, compared with 61% in women with risk factors (P = 0.005). For bilateral tubal pathology, these rates were 13% versus 47% (P = 0.01). For bilateral tubal pathology, the sensitivity of HSG decreased with age [factor 0.93 per year (P = 0.05)]. The specificity of HSG was very stable across all subgroups.

CONCLUSIONS

The accuracy of HSG in detecting tubal pathology was similar in all subgroups, except for women without risk factors in whom sensitivity was lower, possibly due to false-positive results at laparoscopy. HSG is a useful tubal patency screening test for all infertile couples.

Harvestman (Opiliones) fauna associated with Maine lowbush blueberry fields in the major production areas of Washington and Hancock counties

Over a period of 19 yr, the harvestman (Opiliones) community associated with the lowbush blueberry agro-ecosystem in Maine was studied. Eight species representing five genera, four subfamilies, and two families of harvestmen belonging to the suborder Eupnoi were collected. The harvestman community was dominated by two introduced, synanthropic species: Phalangium opilio in all but 1 yr (that year dominated by Rilaena triangularis). Rilaena was recorded for the first time from eastern North America. Relative abundance of harvestman adults increases throughout the season and the temporal pattern of trap capture does not refute speculated life cycles of the harvestmen being univoltine with overwintering eggs. Some blueberry management practices were found to affect trap capture. We did find that on average (with opposite results 1 yr) trap captures are greater in pruned fields than in fruit-bearing fields. Organic fields were found to have higher relative abundance of harvestmen than conventionally managed fields. Conventionally managed fields with reduced-risk insecticides showed no difference in harvestmen relative abundance compared with those conventionally managed fields using the older more persistent organophosphate insecticides. Insecticide trials with common insecticides used in blueberry insect pest management showed that the organophosphate insecticide, phosmet, and the pyrethroid insecticide, esfenvalerate, were detrimental to P. opilio adults when exposed to leaf residues, whereas the reduced-risk insecticide, spinosad, showed no negative effects compared with nonsprayed foliage.

Unstable familial transmissions of Huntington disease alleles with 27-35 CAG repeats (intermediate alleles)

There are inconsistent reports regarding the likelihood of repeat instability for alleles with 27-35 CAG repeats in the Huntington disease (HD) gene. We have examined the intergenerational stability of such intermediate alleles in 51 families from the University of British Columbia's DNA and Tissue Bank for Huntington Disease Research (UBC-HD Databank). A total of 181 transmissions were identified, with 30% (n = 54/181) of the alleles being unstable upon transmission. The unstable transmissions included both expansions (n = 37) and contractions (n = 17) of CAG size. Of the expanded alleles, 68% (n = 25/37) expanded into the HD range (>36 CAG). Therefore, 14% (n = 25/181) of the 27-35 CAG allele transmissions examined expanded into the disease-associated range resulting in a new mutation for HD. Significantly, of these new mutations, 40% (n = 10/25) originated from an allele with 35 CAG repeats with CAG repeat expansions ranging from +1 CAG to +23 CAG. The proportion of new mutations in the UBC-HD Databank is consistent with the most recent new mutation rate for HD, estimated to be at least 10%. The observed difference in the stability of HD intermediate allele transmissions in this data set and in other studies may be a reflection of a small sample size. Alternately, these inconsistencies may indicate an underlying difference in genetic factors which influence repeat instability between the different populations examined. Additional studies determining the frequency and magnitude of repeat instability in this CAG repeat range and factors that influence instability are urgently needed. Until we understand the clinical implications of HD alleles with 27-35 CAG repeats and establish reliable risks of instability, we should exercise caution when translating these results to the clinic.

Genetic variation in healthy oldest-old

Individuals who live to 85 and beyond without developing major age-related diseases may achieve this, in part, by lacking disease susceptibility factors, or by possessing resistance factors that enhance their ability to avoid disease and prolong lifespan. Healthy aging is a complex phenotype likely to be affected by both genetic and environmental factors. We sequenced 24 candidate healthy aging genes in DNA samples from 47 healthy individuals aged eighty-five years or older (the 'oldest-old'), to characterize genetic variation that is present in this exceptional group. These healthy seniors were never diagnosed with cancer, cardiovascular disease, pulmonary disease, diabetes, or Alzheimer disease. We re-sequenced all exons, intron-exon boundaries and selected conserved non-coding sequences of candidate genes involved in aging-related processes, including dietary restriction (PPARG, PPARGC1A, SIRT1, SIRT3, UCP2, UCP3), metabolism (IGF1R, APOB, SCD), autophagy (BECN1, FRAP1), stem cell activation (NOTCH1, DLL1), tumor suppression (TP53, CDKN2A, ING1), DNA methylation (TRDMT1, DNMT3A, DNMT3B) Progeria syndromes (LMNA, ZMPSTE24, KL) and stress response (CRYAB, HSPB2). We detected 935 variants, including 848 single nucleotide polymorphisms (SNPs) and 87 insertion or deletions; 41% (385) were not recorded in dbSNP. This study is the first to present a comprehensive analysis of genetic variation in aging-related candidate genes in healthy oldest-old. These variants and especially our novel polymorphisms are valuable resources to test for genetic association in models of disease susceptibility or resistance. In addition, we propose an innovative tagSNP selection strategy that combines variants identified through gene re-sequencing- and HapMap-derived SNPs.

CAG expansion in the Huntington disease gene is associated with a specific and targetable predisposing haplogroup

Huntington disease (HD) is an autosomal-dominant disorder that results from >or=36 CAG repeats in the HD gene (HTT). Approximately 10% of patients inherit a chromosome that underwent CAG expansion from an unaffected parent with <36 CAG repeats. This study is a comprehensive analysis of genetic diversity in HTT and reveals that HD patients of European origin (n = 65) have a significant enrichment (95%) of a specific set of 22 tagging single nucleotide polymorphisms (SNPs) that constitute a single haplogroup. The disease association of many SNPs is much stronger than any previously reported polymorphism and was confirmed in a replication cohort (n = 203). Importantly, the same haplogroup is also significantly enriched (83%) in individuals with 27-35 CAG repeats (intermediate alleles, n = 66), who are unaffected by the disease, but have increased CAG tract sizes relative to the general population (n = 116). These data support a stepwise model for CAG expansion into the affected range (>or=36 CAG) and identifies specific haplogroup variants in the general population associated with this instability. The specific variants at risk for CAG expansion are not present in the general population in China, Japan, and Nigeria where the prevalence of HD is much lower. The current data argue that cis-elements have a major predisposing influence on CAG instability in HTT. The strong association between specific SNP alleles and CAG expansion also provides an opportunity of personalized therapeutics in HD where the clinical development of only a small number of allele-specific targets may be sufficient to treat up to 88% of the HD patient population.

What is the most valid comparison treatment in trials of intrauterine insemination, timed or uninfluenced intercourse? A systematic review and meta-analysis of indirect evidence

BACKGROUND

Timed intercourse (TI), which is the usual control treatment in trials of intrauterine insemination (IUI), is not a typical coital activity and could impair fertility. This review summarizes the trials of IUI of male partner's prepared semen among subfertile couples according to whether the control group had TI or expectant management.

METHODS

A search of relevant databases and bibliographies until February 2008 yielded 150 citations of which 31 were potentially relevant and 11 met all criteria. The total estimates of the differences in pregnancy rates per couple were calculated with weights equal to the inverse variance. The primary analysis was a categorical meta-analysis by the type of control treatment (TI or expectant management).

RESULTS

In 11 trials with 13 comparisons of IUI and intercourse among 1329 couples with subfertility, the average difference in pregnancy rate between IUI and controls was 6.1% in trials with TI and 3.9% in trials with expectant management, as the control. The adjusted indirect estimate of the difference between the types of control groups was 2.8% (95% CI -6.3, 10.7). The difference by type of control treatment was not significant, neither in the 11 most relevant trials (P = 0.82), nor in a broader group of 19 trials and 2512 patients (P = 0.20).

CONCLUSIONS

The additional benefit accruing to IUI, where TI is the control, is not significant, but it is consistent with the possibility that pregnancy may be less likely in TI controls than in expectant management controls.

Mechanism of mRNA destabilization by the glmS ribozyme

An array of highly structured domains that function as metabolite-responsive genetic switches has been found to reside within noncoding regions of certain bacterial mRNAs. In response to intracellular fluctuations of their target metabolite ligands, these RNA elements exert control over transcription termination or translation initiation. However, for a particular RNA class within the 5' untranslated region (UTR) of the glmS gene, binding of glucosamine-6-phosphate stimulates autocatalytic site-specific cleavage near the 5' of the transcript in vitro, resulting in products with 2'-3' cyclic phosphate and 5' hydroxyl termini. The sequence corresponding to this unique natural ribozyme has been subjected to biochemical and structural scrutiny; however, the mechanism by which self-cleavage imparts control over gene expression has yet to be examined. We demonstrate herein that metabolite-induced self-cleavage specifically targets the downstream transcript for intracellular degradation. This degradation pathway relies on action of RNase J1, a widespread ribonuclease that has been proposed to be a functional homolog to the well-studied Escherichia coli RNase E protein. Whereas RNase E only poorly degrades RNA transcripts containing a 5' hydroxyl group, RNase J1 specifically degrades such transcripts in vivo. These findings elucidate key features of the mechanism for genetic control by a natural ribozyme and suggest that there may be fundamental biochemical differences in RNA degradation machinery between E. coli and other bacteria.

The contribution of HIV fitness to the evolution pattern of reverse transcriptase inhibitor resistance

All currently recommended anti-retroviral therapy protocols employ reverse transcriptase inhibitors (RTIs). However, mutations within the reverse transcriptase (RT) domain can lead to resistance to these agents and treatment failure. The contribution of the fitness of drug-resistant species to the evolution of RTI resistance has not been elucidated despite its potential implications for therapeutic strategies. In this study we utilized a competitive fitness assay to assess the relative fitness of 13 drug-resistant HIV-1 mutants in the presence and absence of inhibitor. Among these mutants were thymidine analog mutations (TAMs) such as 41L/210W/215Y and 67N/70R/219Q, as well as single mutants such as 103N and 181C that confer high-level resistance to non-nucleoside reverse transcriptase inhibitors (NNRTIs) such as nevirapine. These studies revealed that 67N/70R and 67N/70R/219Q were fitter than the 70R progenitor species, and the acquisition of 41L by 215Y substantially increased its fitness in the absence of drug. We also observed that 215Y was more fit than 70R and 67N/70R, and that 41L/215Y and 41L/210W/215Y were the most-fit species in the presence of zidovudine. Moreover, 103N was fitter than 181C without nevirapine but less fit with nevirapine. From these studies we conclude that viral fitness contributes substantially to the evolutionary pattern of TAMs suggesting that, as for protease inhibitor resistance, mutations can act in primary (increasing resistance) and secondary (increasing fitness) capacities. We also surmise that drug resistance and fitness are competing forces underlying the emergence of nevirapine resistant mutants 103N and 181C.

Karyotypic analysis of adult pluripotent stem cells

Three categories of precursor cells have been identified in postnatal mammals: tissue-committed progenitor cells, germ layer lineage-committed stem cells and lineage-uncommitted pluripotent stem cells. Progenitor cells are the immediate precursors of differentiated tissues. Germ layer lineage stem cells can be induced to form multiple cell types belonging to their respective ectodermal, mesodermal, and endodermal embryological lineages. Pluripotent stem cells will form somatic cell types from all three primary germ layer lineages. Progenitor cells demonstrate a finite life span before replicative senescence and cell death occur. Both germ layer lineage stem cells and pluripotent stem cells are telomerase positive and display extensive capabilities for self-renewal. Stem cells which undergo such extensive replication have the potential for undergoing mutations that may subsequently alter cellular functions. Gross mutations in the genome may be visualized as chromosomal aneuploidy and/or chromosomes that appear aberrant. This study was designed to determine whether any gross genomic mutations occurred within the adult pluripotent stem cells. Karyotypic analysis was performed using pluripotent stem cells purified from adult male rats using established procedures. Giemsa Banding was used in conjunction with light microscopy to visualize metaphase chromosome spreads. To date over 800 metaphase spreads have been analyzed. We found that the metaphase spreads averaged 42 chromosomes and concluded that these pluripotent stem cells isolated from adult rats have a normal karyotype.

Two new prediction rules for spontaneous pregnancy leading to live birth among subfertile couples, based on the synthesis of three previous models

BACKGROUND

Several models have been published for the prediction of spontaneous pregnancy among subfertile patients. The aim of this study was to broaden the empirical basis for these predictions by making a synthesis of three previously published models.

METHODS

We used the original data from the studies of Eimers et al. (1994), Collins et al. (1995) and Snick et al. (1997) on couples consulting for various forms of subfertility. We developed a so-called three-sample synthesis model for predicting spontaneous conception leading to live birth within 1 year after intake based on the three data sets. The predictors used are duration of subfertility, women's age, primary or secondary infertility, percentage of motile sperm, and whether the couple was referred by a general practitioner or by a gynaecologist (referral status). The performance of this model was assessed according to a 'jack-knife' analysis. Because the post-coital test (PCT) was not assessed in one of the samples, a synthesis model including the PCT was based on two samples only.

RESULTS

The ability of the synthesis models to distinguish between women who became pregnant and those who did not was comparable to the ability of the one-sample models when applied in the other samples. The reliability of the predictions by the three-sample synthesis model was somewhat better. Predictions improved considerably by including the PCT.

CONCLUSIONS

The synthesis models performed better and had a broader empirical basis than the original models. They are therefore better suitable for application in other centres.

A comparison of ovulation suppression and ovulation stimulation in the treatment of endometriosis-associated infertility

This study compares ovulation stimulation or suppression with the pregnancy rate among infertile couples with endometriosis. The design is a nonrandomized, prospective, multicentered cohort analytic study. Two hundred and ninety-seven couples with laparoscopy-proven endometriosis were analyzed: 68 received no therapy, 42 received clomiphene and 74 received danazol. Forty patients (22%) conceived and pregnancy rates were similar in each treatment group. The relative likelihood of pregnancy associated with clomiphene was 2.9 (95% confidence limits 1.2-7.1); the relative likelihood of pregnancy with danazol was 1.02 (95% confidence limits 0.5-2.3). This study suggests that pregnancy rates during clomiphene treatment could be superior to expectant therapy, while pregnancy rate after danazol is similar to no treatment.

Unexplained infertility: a review of diagnosis, prognosis, treatment efficacy and management

The dilemma of unexplained infertility posed by Southam in 1960 remains today: despite advances in the diagnostic assessment of infertility, many couples still have no explanation for their infertility. Even the most sophisticated evaluation of semen, ovulation and genital tract competence cannot reveal all of the possible defects in the complex process leading to conception. Because it arises from these shortcomings in our knowledge of fertilization and from our inability to utilize all of the current knowledge, unexplained infertility is a challenge for both biological and clinical research. This paper attempts to summarize some clinical issues in the management of unexplained infertility: the prevalence of the disorder, problems in the definition and possible explanations for the existence of this diagnostic category. It reviews outcome-based clinical publications as a guide to decision-making on what diagnostic tests to use, provides a summary of the untreated prognosis and evaluates study results that may serve as a basis for treatment decisions in this puzzling diagnostic category of infertility.

Control of gene expression by a natural metabolite-responsive ribozyme

Most biological catalysts are made of protein; however, eight classes of natural ribozymes have been discovered that catalyse fundamental biochemical reactions. The central functions of ribozymes in modern organisms support the hypothesis that life passed through an 'RNA world' before the emergence of proteins and DNA. We have identified a new class of ribozymes that cleaves the messenger RNA of the glmS gene in Gram-positive bacteria. The ribozyme is activated by glucosamine-6-phosphate (GlcN6P), which is the metabolic product of the GlmS enzyme. Additional data indicate that the ribozyme serves as a metabolite-responsive genetic switch that represses the glmS gene in response to rising GlcN6P concentrations. These findings demonstrate that ribozyme switches may have functioned as metabolite sensors in primitive organisms, and further suggest that modern cells retain some of these ancient genetic control systems.

Competitive fitness of nevirapine-resistant human immunodeficiency virus type 1 mutants

Determining the fitness of drug-resistant human immunodeficiency virus type 1 (HIV-1) strains is necessary for the development of population-based studies of resistance patterns. For this purpose, we have developed a reproducible, systematic assay to determine the competitive fitness of HIV-1 drug-resistant mutants. To demonstrate the applicability of this assay, we tested the fitness of the five most common nevirapine-resistant mutants (103N, 106A, 181C, 188C, and 190A), with mutations in HIV-1 reverse transcriptase (RT), singly and in combination (for a total of 31 variants) in a defined HIV-1 background. For these experiments, the 27 RT variants that produced viable virus were cocultured with wild-type virus without nevirapine. The ratios of the viral species were determined over time by utilization of a quantitative real-time RT-PCR-based assay. These experiments revealed that all of the viable variants were less fit than the wild type and demonstrated that the order of relative fitness of the single mutants tested was as follows: 103N > 181C > 190A > 188C > 106A. This order correlated with the commonality of these mutants as a result of nevirapine monotherapy. These investigations also revealed that, on average, the double mutants were less fit than the single mutants and the triple mutants were less fit than the double mutants. However, the fitness of the single and double mutants was often not predictive of the fitness of the derivative triple mutants, suggesting the presence of complex interactions between the closely aligned residues that confer nevirapine resistance. This complexity was also evident from the observation that all three of the replication-competent quadruple mutants were fitter than most of the triple mutants, and in some cases, even the double mutants. Our data suggest that, in many cases, viral fitness is the determining factor in the evolution of nevirapine-resistant mutants in vivo, that interactions between the residues that confer nevirapine resistance are complex, and that these interactions substantially affect reverse transcriptase structure and/or function.

Surgery or embolisation for varicocele in subfertile men

BACKGROUND

A varicocele is a meshwork of distended blood vessels in the scrotum, usually left-sided, due to dilatation of the spermatic vein. Although the concept that varicocele causes, and varicocelectomy cures, male subfertility has been around for almost fifty years, the mechanisms by which varicocele would affect fertility have not yet been satisfactorily explained, and neither have the mechanisms by which varicocelectomy would restore fertility. Furthermore, it has been questioned whether a causal relation exists at all between the distension of the pampiniform plexus and impairment of fertility.

OBJECTIVES

To evaluate the effect of varicocele treatment on pregnancy rate in subfertile couples.

SEARCH STRATEGY

We searched the Cochrane Menstrual Disorders and Subfertility Group trials register (searched 12 Sept 2003), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 1, 2004), MEDLINE (January 1966 to May 2004), EMBASE (January 1985 to May 2004) and reference lists of articles. In addition, we hand searched 22 specialist journals in the field from their first issue until 2004. We also checked cross references, references from review articles, and contacted researchers in the field.

SELECTION CRITERIA

RCTs were included if they were relevant to the clinical question posed, if they reported pregnancy rates as an outcome measure, and if they reported data in treated (surgical ligation or radiological embolization of the internal spermatic vein) and untreated groups.

DATA COLLECTION AND ANALYSIS

Nine studies met the inclusion criteria for this review. One was an extension of a previously published study (Nieschlag 1995/1998), which left eight studies for analysis (Nilsson 1979; Breznik 1993; Madgar 1995; Yamamoto 1996; Nieschlag 1995/1998; Grasso 2000; Unal 2001; Krause 2002). All eight only included men from couples with subfertility problems, one (Madgar 1995) excluded men with sperm counts <5 mill/mL, one (Krause 2002) men with sperm counts <2 mill/mL and/or progressive motility <10%, two trials involving clinical varicoceles included some men with normal semen analysis (Nilsson 1979; Breznik 1993). Three studies (Yamamoto 1996; Grasso 2000; Unal 2001) specifically addressed only men with subclinical varicoceles. Two authors independently screened potentially relevant trials. Any differences of opinion were resolved by consensus (none occurred for this review). Studies were excluded from meta-analysis if they made comparisons other than those specified above.

MAIN RESULTS

The combined Peto odds ratio (OR) of the eight studies is 1.10 (95%CI 0.73 to 1.68), indicating no benefit of varicocele treatment over expectant management in subfertility couples in whom varicocele in the man is the only abnormal finding.

REVIEWERS' CONCLUSIONS

There is no evidence that treatment of varicocele in men from couples with otherwise unexplained subfertility improves the couple's chance of conception.

Current perspectives on oral contraceptive use

Oral contraceptives are one of the most highly effective forms of contraception and provide many short- and long-term noncontraceptive health benefits. They control menstrual cycle irregularities, such as breakthrough bleeding and amenorrhea, and are effective in treating dysfunctional uterine bleeding. In addition, for decades after oral contraceptive use is discontinued they are associated with substantial decreases in the risk of ovarian cancer (up to 80%) and of endometrial cancer (40%-50%), and nearly eliminate benign functional ovarian cysts. Long-term oral contraceptive use confers protection against benign breast disease and colorectal cancer, may help prevent rheumatoid arthritis, decreases ectopic pregnancy and hospitalizations for pelvic inflammatory disease, and helps preserve bone mineral density to reduce risk of fractures. Large bodies of evidence from extensive research have clarified the perceived association of oral contraceptive use with cardiovascular disease and with breast cancer. Findings indicate that there is no increased risk of myocardial infarction or stroke associated with oral contraceptive use in healthy, nonsmoking, normotensive women. Although there is a 3- to 4-fold increased risk of venous thromboembolism with current oral contraceptive use, the absolute risk is very small and is half that associated with pregnancy. Women of all reproductive ages, including perimenopausal women, can realize many health benefits through oral contraceptive use, including improved health status later in life.

Current perspectives on benefits and risks of hormone replacement therapy

Hormone replacement therapy with estrogen alone or with added progestin relieves menopausal symptoms and physical changes associated with depleted endogenous estrogen levels. Estrogen replacement has also demonstrated a clear benefit in the prevention of osteoporosis. Hormone replacement therapy with added progestin maintains spinal bone density, protects against postmenopausal hip fractures, and provides these benefits even when therapy is started after age 60. More recently, additional benefits have emerged. Current estrogen and hormone replacement therapy users have a 34% reduction in the risk of colorectal cancer and a 20% to 60% reduction in the risk of Alzheimer's disease. Until recently, the body of evidence indicated that hormone replacement therapy with estrogen only reduced cardiovascular disease risk by 40% to 50% in healthy patients; whether the findings of 3 ongoing trials will change this conclusion is pending availability of the final results. The many benefits of estrogen and hormone replacement therapy must be weighed against a slight increase in the risk of breast cancer diagnosis with use for 5 or more years, but which disappears following cessation of therapy. Overall, estrogen and hormone replacement therapy improves the quality of life and increases life expectancy for most menopausal women.

Cost-effectiveness of hysterosalpingography, laparoscopy, and Chlamydia antibody testing in subfertile couples

OBJECTIVE

To evaluate the cost-effectiveness analysis of hysterosalpingography (HSG), laparoscopy, and Chlamydia antibody testing (CAT) in subfertile couples.

DESIGN

Cost-effectiveness analysis.

SETTING

Decision analytic framework.

PATIENT(S)

Data of >2,000 subfertile couples in the Canadian Infertility Treatment Evaluation Study. Results of CA-125 measurement and CAT were simulated from baseline characteristics.

INTERVENTION(S)

Expectant management was considered to be the reference strategy (strategy 1). In strategy 2 and 3, IVF was offered either immediately or after 2.5 years. In strategy 4, the decision to offer or delay treatment was based on the couple's chance of spontaneous conception. Nine strategies incorporated combinations of CAT, CA-125 measurement, HSG, and laparoscopy.

MAIN OUTCOME MEASURE(S)

Expected live birth rates, expected number of IVF cycles, and expected total costs.

RESULT(S)

The strategy starting with CAT was the most cost-effective in couples whose 3-year chance of conception was >14%, whereas the strategy starting with HSG was the most cost-effective in couples with worse fertility prospects.

CONCLUSION(S)

The diagnostic work-up to detect tubal pathology in subfertile couples should start with CAT in couples with relatively good fertility prospects and immediate HSG in couples with relatively poor fertility prospects.

Surgery or embolisation for varicocele in subfertile men

BACKGROUND

A varicocele is an, almost exclusively left-sided, varicosity of the pampiniform plexus of the spermatic cord, forming a tangle of distended blood vessels in the scrotum. Although the concept that varicocele causes male subfertility and therefore varicocelectomy cures male subfertility has been around for almost fifty years now, the mechanisms by which varicocele would affect fertility have not yet been satisfactorily explained, and neither have the mechanisms by which varicocelectomy would resolve subfertility. Furthermore, it has been questioned whether a causal relation exists at all between the distension of the pampiniform plexus and impairment of fertility.

OBJECTIVES

To evaluate the effect of varicocele treatment on pregnancy rate in subfertile couples.

SEARCH STRATEGY

Relevant trials were identified in the Cochrane Menstrual Disorders and Subfertility Group's specialised register of controlled trials. A MEDLINE search, using the group's search strategy, was performed for the period 1966-2000. Also, hand searching was performed of 22 specialist journals in the field from their first issue till 2000. Cross references and references from review articles were checked.

SELECTION CRITERIA

RCTs were included if they were relevant to the clinical question posed, if they reported pregnancy rates as an outcome measure, and if they reported data in treated (surgical ligation or radiological embolization of the internal spermatic vein) and untreated groups.

DATA COLLECTION AND ANALYSIS

Six studies met the inclusion criteria for this review. One (Nieschlag 1995/1998) was an extension of a previously published study (Nieschlag 1995/1998), which left five studies for analysis (Nilsson 1979; Breznik 1993; Madgar 1995; Yamamoto 1996; Nieschlag 1995/1998). The results of a WHO megatrial are awaited but as yet are unavailable. The WHO data will be added if and when they will have become available. All five only included men from couples with subfertility problems, one (Madgar 1995) excluded men with sperm counts <5 mill/mL, three (Nilsson 1979; Breznik 1993; Yamamoto 1996) also included men with normal semen analysis. One study (Yamamoto 1996) specifically addressed only men with subclinical varicoceles as diagnosed by thermography. Potentially relevant trials were screened independently by two authors (JE and JC). Any differences of opinion were resolved by consensus meeting (none occurred for this review). Studies were excluded from meta-analysis if they made comparisons other than those specified above.

MAIN RESULTS

One trial (Madgar 1995) reported a statistically significant improvement in pregnancy rate following high ligation of the left spermatic vein. None of the other four studies showed individually a significant effect on pregnancy rates of varicocele treatment over no-treatment (Nilsson 1979; Breznik 1993; Yamamoto 1996), or over counseling only (Nieschlag 1995/1998). The combined RR (Relative Risk; random effects method) of the five studies is 1.06 (95%CI 0.57-1.94), the Peto OR (Odds Ratio) is 1.15 (95%CI 0.73-1.83).

REVIEWER'S CONCLUSIONS

Insufficient evidence exists that treatment of varicocele in men from couples with otherwise unexplained subfertility does improve the couple's spontaneous pregnancy chances.