Digital detection of genetic mutations using SPC-sequencing

Deletion or insertion mutations lead to a frameshift that causes misalignment between wild-type and mutated allele sequences, making it difficult to identify such mutations unambiguously by using electrophoresis-based DNA sequencing. We have previously established the feasibility of an accurate DNA sequencing method using solid-phase capturable (SPC) dideoxynucleotides and MALDI-TOF mass spectrometry on synthetic templates, an approach we refer to as SPC-sequencing. Here, we report the application of SPC-sequencing in characterizing frameshift mutations by using the detection of the BRCA1 gene mutations 185delAG and 5382insC as examples. In this method, Sanger DNA sequencing fragments are generated in one tube by using biotinylated dideoxynucleotides. The sequencing fragments carrying a biotin moiety at the 3' end are captured on a streptavidin-coated solid phase to eliminate excess primer, primer dimers, and false stops. Only correctly terminated DNA fragments are captured, subsequently released, and analyzed by mass spectrometry to obtain digital DNA sequencing data. This method produces distinct doublet mass peaks at each point in the mass spectrum beyond the mutation site, facilitating the accurate characterization of the mutation. We have compared SPC-sequencing with electrophoresis-based sequencing in characterizing the above BRCA1 mutations, demonstrating the significant advantage offered by SPC-sequencing for the accurate identification of frameshift mutations.     

Common and Dissociable Dysfunction of the Reward System in Bipolar and Unipolar Depression

Unipolar and bipolar depressive episodes have a similar clinical presentation that suggests common dysfunction of the brain’s reward system. Here, we evaluated the relationship of both dimensional depression severity and diagnostic category to reward system function in both bipolar and unipolar depression. In total, 89 adults were included, including 27 with bipolar depression, 25 with unipolar depression, and 37 healthy comparison subjects. Subjects completed both a monetary reward task and a resting-state acquisition during 3T BOLD fMRI. Across disorders, depression severity was significantly associated with reduced activation for wins compared with losses in bilateral ventral striatum, anterior cingulate cortex, posterior cingulate cortex, and right anterior insula. Resting-state connectivity within this reward network was also diminished in proportion to depression severity, most notably connectivity strength in the left ventral striatum. In addition, there were categorical differences between patient groups: resting-state connectivity at multiple reward network nodes was higher in bipolar than in unipolar depression. Reduced reward system task activation and resting-state connectivity therefore appear to be a brain phenotype that is dimensionally related to depression severity in both bipolar and unipolar depression. In contrast, categorical differences in reward system resting connectivity between unipolar and bipolar depression may reflect differential risk of mania. Reward system dysfunction thus represents a common brain mechanism with relevance that spans categories of psychiatric diagnosis.     

Amotivation in Schizophrenia: Integrated Assessment With Behavioral,Clinical, and Imaging Measures

Motivational deficits play a central role in disability caused by schizophrenia and constitute a major unmet therapeutic need. Negative symptoms have previously been linked to hypofunction in ventral striatum (VS), a core component of brain motivation circuitry. However, it remains unclear to what extent this relationship holds for specific negative symptoms such as amotivation, and this question has not been addressed with integrated behavioral, clinical, and imaging measures. Here, 41 individuals with schizophrenia and 37 controls performed a brief, computerized progressive ratio task (PRT) that quantifies effort exerted in pursuit of monetary reward. Clinical amotivation was assessed using the recently validated Clinical Assessment Interview for Negative Symptoms (CAINS). VS function was probed during functional magnetic resonance imaging using a monetary guessing paradigm. We found that individuals with schizophrenia had diminished motivation as measured by the PRT, which significantly and selectively related to clinical amotivation as measured by the CAINS. Critically, lower PRT motivation in schizophrenia was also dimensionally related to VS hypofunction. Our results demonstrate robust dimensional associations between behavioral amotivation, clinical amotivation, and VS hypofunction in schizophrenia. Integrating behavioral measures such as the PRT will facilitate translational efforts to identify biomarkers of amotivation and to assess response to novel therapeutic interventions.Key words: motivation, progressive ratio, ventral striatum, fMRI, negative symptoms     

Synchronous splenectomy during cholecystectomy for hereditary spherocytosis: Is it really necessary?

Background/Purpose

Expert guidelines recommend performing synchronous splenectomy in patients with mild hereditary spherocytosis (HS) and symptoms of gallstone disease. This recommendation has not been widely explored in the literature. The aim of this study is to determine if our data support expert opinion and if different practice patterns should exist.

Methods

This is an IRB-approved retrospective study. All HS patients under 18 years of age who underwent cholecystectomy for symptomatic gallstones at a single institution between 1981 and 2009 were identified. Patients who underwent cholecystectomy without concurrent splenectomy were reviewed retrospectively for future need for splenectomy and evidence of recurrent gallstone disease.

Results

Of the 32 patients identified, 27 underwent synchronous splenectomy. The remaining 5 patients underwent cholecystectomy without splenectomy and had a mean age of 9.4 years. One of the 5 patients eventually required splenectomy for left upper quadrant pain. None of the remaining 4 required hospitalization for symptoms related to hemolysis or hepatobiliary disease. Median follow-up is 15.6 years.

Conclusion

The need for splenectomy in patients with mild HS and symptomatic cholelithiasis should be assessed on a case by case basis. Our recommendation is to not perform synchronous splenectomy in conjunction with cholecystectomy for these patients if no indication for splenectomy exists.     

Telling truth from lie in individual subjects with fast event-related fMRI

Deception is a clinically important behavior with poorly understood neurobiological correlates. Published functional MRI (fMRI) data on the brain activity during deception indicates that, on a multisubject group level, lie is distinguished from truth by increased prefrontal and parietal activity. These findings are theoretically important; however, their applied value will be determined by the accuracy of the discrimination between single deceptive and truthful responses in individual subjects. This study presents the first quantitative estimate of the accuracy of fMRI in conjunction with a formal forced-choice paradigm in detecting deception in individual subjects. We used a paradigm balancing the salience of the target cues to elicit deceptive and truthful responses and determined the accuracy of this model in the classification of single lie and truth events. The relative salience of the task cues affected the net activation associated with lie in the superior medial and inferolateral prefrontal cortices. Lie was discriminated from truth on a single-event level with an accuracy of 78%, while the predictive ability expressed as the area under the curve (AUC) of the receiver operator characteristic curve (ROC) was 85%. Our findings confirm that fMRI, in conjunction with a carefully controlled query procedure, could be used to detect deception in individual subjects. Salience of the task cues is a potential confounding factor in the fMRI pattern attributed to deception in forced choice deception paradigms.