Faculty Bibliography

Dynamic changes of the actin cytoskeleton are instrumental in morphogenetic processes including changes in cell shape and adhesion. Formin proteins regulate actin microfilament assembly and can specifically influence adherens junction formation. Previous studies in our lab have demonstrated remarkable plasticity of formin isoforms during heart development and in vitro cardiomyocyte differentiation. As gap junction stability is dependent on the presences of mechanical junctions we were interested if modulation of cardiac formins influences expression of Cx43 protein and gap junction function. Objective: To investigate the effect of cardiac formin knockdown (KD) on cell-cell contact formation and functional coupling of cardiomyocytes. Methods: Cardiomyocytes were isolated from neonatal rat hearts (NRCM) and cultured as monolayers (d0); NRCM were treated with transfection agent only (TF), control siRNA (Ctr) or formin specific rat siRNAs (Daam1; Fhod1; Fhod3; Dharmacon) (d1); cultures were subjected to high resolution optical mapping or processed for immunofluorescence analysis (d4). Results: KD of Fhod1 or Fhod3 lead to disruption of sarcomers, cell rounding and ultimately resulted in complete dissociation of NRCM. In contrast, Daam1 KD resulted in significant cell elongation without loss of cell-cell contacts (mean cell areas in mum²: 681.8 + 99.1 (Daam1) vs. 594.9 + 67.6 (TF), 564 + 53.3 (Ctr), 455.9 + 47.4 (Fhod1), 339.3 + 14.3 (Fhod3); P: 0.01, ANOVA). As expected, optical mapping data for discontinuous Fhod1 and Fhod3 monolayers were very variable due to areas of complete block of conduction. Optical mapping analysis of Daam1 silenced NRCM demonstrated significant increase in conduction velocity (0.241 + 0.004 m/s; n=4) compared to NRCM treated with TF only (0.197 + 0.010 m/s, n=3) or Ctr (0.207 + 0.005 m/s, n=3; P: 0.003, ANOVA). Average gap junction diameter (0.24 + 0.03 mum (n=489; Daam1) vs. 0.41 + 0.03 mum (n=550; DF), 0.38 + 0.04 mum (n=574; Ctr) P: 0.009, ANOVA), and total !

BACKGROUND: Mutations in either Abeta Precursor protein (APP) or genes that regulate APP processing, such as BRI2/ITM2B and PSEN1/PSEN2, cause familial dementias. Although dementias due to APP/PSEN1/PSEN2 mutations are classified as familial Alzheimer disease (FAD) and those due to mutations in BRI2/ITM2B as British and Danish dementias (FBD, FDD), data suggest that these diseases have a common pathogenesis involving toxic APP metabolites. It was previously shown that FAD mutations in APP and PSENs promote activation of caspases leading to the hypothesis that aberrant caspase activation could participate in AD pathogenesis. RESULTS: Here, we tested whether a similar mechanism applies to the Danish BRI2/ITM2B mutation. We have generated a genetically congruous mouse model of FDD, called FDD(KI), which presents memory and synaptic plasticity deficits. We found that caspase-9 is activated in hippocampal synaptic fractions of FDD(KI) mice and inhibition of caspase-9 activity rescues both synaptic plasticity and memory deficits. CONCLUSION: These data directly implicate caspase-9 in the pathogenesis of Danish dementia and suggest that reducing caspase-9 activity is a valid therapeutic approach to treating human dementias.

Although previous work identified transcription factors crucial for the specification and migration of parvalbumin (PV)-expressing and somatostatin (SST)-expressing interneurons, the intrinsic factors required for the terminal differentiation, connectivity, and survival of these cell types remain uncharacterized. Here we demonstrate that, within subpopulations of cortical interneurons, Satb1 (special AT-rich binding protein) promotes terminal differentiation, connectivity, and survival in interneurons that express PV and SST. We find that conditional removal of Satb1 in mouse interneurons results in the loss of a majority of SST-expressing cells across all cortical layers, as well as some PV-expressing cells in layers IV and VI, by postnatal day 21. SST-expressing cells initially migrate to the cortex in Satb1 mutant mice, but receive reduced levels of afferent input and begin to die during the first postnatal week. Electrophysiological characterization indicates that loss of Satb1 function in interneurons results in a loss of functional inhibition of excitatory principal cells. These data suggest that Satb1 is required for medial ganglionic eminence-derived interneuron differentiation, connectivity, and survival.

How do humans make choices between different types of rewards? Economists have long argued on theoretical grounds that humans typically make these choices as if the values of the options they consider have been mapped to a single common scale for comparison. Neuroimaging studies in humans have recently begun to suggest the existence of a small group of specific brain sites that appear to encode the subjective values of different types of rewards on a neural common scale, almost exactly as predicted by theory. We have conducted a meta analysis using data from thirteen different functional magnetic resonance imaging studies published in recent years and we show that the principle brain area associated with this common representation is a subregion of the ventromedial prefrontal cortex (vmPFC)/orbitofrontal cortex (OFC). The data available today suggest that this common valuation path is a core system that participates in day-to-day decision making suggesting both a neurobiological foundation for standard economic theory and a tool for measuring preferences neurobiologically. Perhaps even more exciting is the possibility that our emerging understanding of the neural mechanisms for valuation and choice may provide fundamental insights into pathological choice behaviors like addiction, obesity and gambling.

Study purposes were to determine the prevalence of persistent pain in the breast; characterize distinct persistent pain classes using growth mixture modeling; and evaluate for differences among these pain classes in demographic, preoperative, intraoperative, and postoperative characteristics. In addition, differences in the severity of common symptoms and quality of life outcomes measured prior to surgery, among the pain classes, were evaluated. Patients (n = 398) were recruited prior to surgery and followed for 6 months. Using growth mixture modeling, patients were classified into no (31.7%), mild (43.4%), moderate (13.3%), and severe (11.6%) pain groups based on ratings of worst breast pain. Differences in a number of demographic, preoperative, intraoperative, and postoperative characteristics differentiated among the pain classes. In addition, patients in the moderate and severe pain classes reported higher preoperative levels of depression, anxiety, and sleep disturbance than the no pain class. Findings suggest that approximately 25% of women experience significant and persistent levels of breast pain in the first 6 months following breast cancer surgery. PERSPECTIVE: Persistent pain is a significant problem for 25% of women following surgery for breast cancer. Severe breast pain is associated with clinically meaningful decrements in functional status and quality of life.

BACKGROUND: Clinical and epidemiological studies suggest an association between cannabis use and psychosis but this relationship remains controversial. METHOD: Clinical high-risk (CHR) subjects (age 12-22 years) with attenuated positive symptoms of psychosis (CHR+, n=101) were compared to healthy controls (HC, n=59) on rates of substance use, including cannabis. CHR+ subjects with and without lifetime cannabis use (and abuse) were compared on prodromal symptoms and social/role functioning at baseline. Participants were followed an average of 2.97 years to determine psychosis conversion status and functional outcome. RESULTS: At baseline, CHR+ subjects had significantly higher rates of lifetime cannabis use than HC. CHR+ lifetime cannabis users (n=35) were older (p=0.015, trend), more likely to be Caucasian (p=0.002), less socially anhedonic (p<0.001) and had higher Global Functioning: Social (GF:Social) scores (p<0.001) than non-users (n=61). CHR+ cannabis users continued to have higher social functioning than non-users at follow-up (p<0.001) but showed no differences in role functioning. A small sample of CHR+ cannabis abusers (n=10) showed similar results in that abusers were older (p=0.008), less socially anhedonic (p=0.017, trend) and had higher baseline GF:Social scores (p=0.006) than non-abusers. Logistic regression analyses revealed that conversion to psychosis in CHR+ subjects (n=15) was not related to lifetime cannabis use or abuse. CONCLUSIONS: The current data do not indicate that low to moderate lifetime cannabis use is a major contributor to psychosis or poor social and role functioning in clinical high-risk youth with attenuated positive symptoms of psychosis.

Since the brain's gray matter (GM) and white matter (WM) metabolite concentrations differ, their partial volumes can vary the voxel's (1) H MR spectroscopy ((1) H-MRS) signal, reducing sensitivity to changes. While single-voxel (1) H-MRS cannot differentiate between WM and GM signals, partial volume correction is feasible by MR spectroscopic imaging (MRSI) using segmentation of the MRI acquired for VOI placement. To determine the magnitude of this effect on metabolic quantification, we segmented a 1-mm(3) resolution MRI into GM, WM and CSF masks that were co-registered with the MRSI grid to yield their partial volumes in approximately every 1 cm(3) spectroscopic voxel. Each voxel then provided one equation with two unknowns: its i- metabolite's GM and WM concentrations C(i) (GM) , C(i) (WM) . With the voxels' GM and WM volumes as independent coefficients, the over-determined system of equations was solved for the global averaged C(i) (GM) and C(i) (WM) . Trading off local concentration differences offers three advantages: (i) higher sensitivity due to combined data from many voxels; (ii) improved specificity to WM versus GM changes; and (iii) reduced susceptibility to partial volume effects. These improvements made no additional demands on the protocol, measurement time or hardware. Applying this approach to 18 volunteered 3D MRSI sets of 480 voxels each yielded N-acetylaspartate, creatine, choline and myo-inositol C(i) (GM) concentrations of 8.5 +/- 0.7, 6.9 +/- 0.6, 1.2 +/- 0.2, 5.3 +/- 0.6mM, respectively, and C(i) (WM) concentrations of 7.7 +/- 0.6, 4.9 +/- 0.5, 1.4 +/- 0.1 and 4.4 +/- 0.6mM, respectively. We showed that unaccounted voxel WM or GM partial volume can vary absolute quantification by 5-10% (more for ratios), which can often double the sample size required to establish statistical significance