α-Synuclein Conformations in Plasma Distinguish Parkinson's Disease from Dementia with Lewy Bodies

Spread and aggregation of misfolded α-synuclein (aSyn) within the brain is the pathologic hallmark of Lewy body diseases (LBD), including Parkinson's disease (PD) and dementia with Lewy bodies (DLB). While evidence exists for multiple aSyn protein conformations, often termed "strains" for their distinct biological properties, it is unclear whether PD and DLB result from aSyn strain differences, and biomarkers that differentiate PD and DLB are lacking. Moreover, while pathological forms of aSyn have been detected outside the brain ( e.g., in skin, gut, blood), the functional significance of these peripheral aSyn species is unclear. Here, we developed assays using monoclonal antibodies selective for two different aSyn species generated in vitro - termed Strain A and Strain B - and used them to evaluate human brain tissue, cerebrospinal fluid (CSF), and plasma, through immunohistochemistry, enzyme-linked immunoassay, and immunoblotting. Surprisingly, we found that plasma aSyn species detected by these antibodies differentiated individuals with PD vs. DLB in a discovery cohort (UPenn, n=235, AUC 0.83) and a multi-site replication cohort (Parkinson's Disease Biomarker Program, or PDBP, n=200, AUC 0.72). aSyn plasma species detected by the Strain A antibody also predicted rate of cognitive decline in PD. We found no evidence for aSyn strains in CSF, and ability to template aSyn fibrillization differed for species isolated from plasma vs. brain, and in PD vs. DLB. Taken together, our findings suggest that aSyn conformational differences may impact clinical presentation and cortical spread of pathological aSyn. Moreover, the enrichment of these aSyn strains in plasma implicates a non-central nervous system source.

Novel THAP1 missense variant with incomplete penetrance in a case of generalized young onset dystonia showing good response to deep brain stimulation

We describe a case of young onset generalized dystonia, harboring a previously unreported likely pathogenic THAP1 missense variant (c.109 G > A; p.Glu37Lys) that was inherited from her unaffected father. Moreover, we report a positive effect of deep brain stimulation, particularly on the cervical component of dystonia.

Whole Clinic Research Enrollment in Parkinson's Disease: The Molecular Integration in Neurological Diagnosis (MIND) Study

BACKGROUND

Observational studies in Parkinson's disease (PD) have focused on relatively small numbers of research participants who are studied extensively. The Molecular Integration in Neurological Diagnosis Initiative at the University of Pennsylvania aims to characterize molecular and clinical features of PD in every patient in a large academic center.

OBJECTIVE

To determine the feasibility and interest in a global-capture biomarker research protocol. Additionally, to describe the clinical characteristics and GBA and LRRK2 variant carrier status among participants.

METHODS

All patients at UPenn with a clinical diagnosis of PD were eligible. Informed consent included options for access to the medical record, future recontact, and use of biosamples for additional studies. A blood sample and a completed questionnaire were obtained from participants. Targeted genotyping for four GBA and eight LRRK2 variants was performed, with plasma and DNA banked for future research.

RESULTS

Between September 2018 and December 2019, 704 PD patients were approached for enrollment; 652 (92.6%) enrolled, 28 (3.97%) declined, and 24 (3.41%) did not meet eligibility criteria. Median age was 69 (IQR 63_75) years, disease duration was 5.41 (IQR 2.49_9.95) years, and 11.10%of the cohort was non-white. Disease risk-associated variants in GBA were identified in 39 participants (5.98%) and in LRRK2 in 16 participants (2.45%).

CONCLUSIONS

We report the clinical and genetic characteristics of PD patients in an all-comers, global capture protocol from an academic center. Patient interest in participation and yield for identification of GBA and LRRK2 mutation carriers is high, demonstrating feasibility of PD clinic-wide molecular characterization.

Subjective Cognitive Complaint in Parkinson's Disease Patients With Normal Cognition: Canary in the Coal Mine?

OBJECTIVE

The objective of this study was to determine the frequency and impact of subjective cognitive complaint (SCC) in Parkinson's disease (PD) patients with normal cognition.

METHODS

Patients with PD with expert consensus-determined normal cognition at baseline were asked a single question regarding the presence of SCC. Baseline (N = 153) and longitudinal (up to 4 follow-up visits during a 5-year period; N = 121) between-group differences in patients with PD with (+SCC) and without (-SCC) cognitive complaint were examined, including cognitive test performance and self-rated and informant-rated functional abilities.

RESULTS

A total of 81 (53%) participants reported a cognitive complaint. There were no between-group differences in global cognition at baseline. Longitudinally, the +SCC group declined more than the -SCC group on global cognition (Mattis Dementia Rating Scale-2 total score, F_1,431 = 5.71, P = 0.02), processing speed (Symbol Digit Modalities Test, F_1,425 = 7.52, P = 0.006), and executive function (Trail Making Test Part B, F_1,419 = 4.48, P = 0.04), although the results were not significant after correction for multiple testing. In addition, the +SCC group was more likely to progress to a diagnosis of cognitive impairment over time (hazard ratio = 2.61, P = 0.02). The +SCC group also demonstrated significantly lower self-reported and knowledgeable informant-reported cognition-related functional abilities at baseline, and declined more on an assessment of global functional abilities longitudinally.

CONCLUSIONS

Patients with PD with normal cognition, but with SCC, report poorer cognition-specific functional abilities, and are more likely to be diagnosed with cognitive impairment and experience global functional ability decline long term. These findings suggest that SCC and worse cognition-related functional abilities may be sensitive indicators of initial cognitive decline in PD. © 2020 International Parkinson and Movement Disorder Society.

Cognitive and Pathological Influences of Tau Pathology in Lewy Body Disorders

OBJECTIVE

To use digital histology in a large autopsy cohort of Lewy body disorder (LBD) patients with dementia to test the hypotheses that co-occurring Alzheimer disease (AD) pathology impacts the anatomic distribution of α-synuclein (SYN) pathology and that co-occurring neocortical tau pathology in LBDs associates with worse cognitive performance and occurs in a pattern differing from AD.

METHODS

Fifty-five autopsy-confirmed LBD (Parkinson disease with dementia, n = 36; dementia with Lewy bodies, n = 19) patients and 25 AD patients were studied. LBD patients were categorized as having moderate/severe AD copathology (SYN + AD = 20) or little/no AD copathology (SYN-AD = 35). Digital measures of tau, β-amyloid (Aβ), and SYN histopathology in neocortical and subcortical/limbic regions were compared between groups and related to antemortem cognitive testing.

RESULTS

SYN burden was higher in SYN + AD than SYN-AD in each neocortical region (F_{1, 54} = 5.6-6.0, p < 0.02) but was equivalent in entorhinal cortex and putamen (F_{1, 43-49} = 0.7-1.7, p > 0.2). SYN + AD performed worse than SYN-AD on a temporal lobe-mediated naming task (t₂₇ = 2.1, p = 0.04). Antemortem cognitive test scores inversely correlated with tau burden (r = -0.39 to -0.68, p < 0.05). AD had higher tau than SYN + AD in all regions (F_{1, 43} = 12.8-97.2, p < 0.001); however, SYN + AD had a greater proportion of tau in the temporal neocortex than AD (t₄₁ = 2.0, p < 0.05), whereas AD had a greater proportion of tau in the frontal neocortex than SYN + AD (t₄₁ = 3.3, p < 0.002). SYN + AD had similar severity and distribution of neocortical Aβ compared to AD (F_{1, 40-43} = 1.6-2.0, p > 0.1).

INTERPRETATION

LBD patients with AD copathology harbor greater neocortical SYN pathology. Regional tau pathology relates to cognitive performance in LBD dementia, and its distribution may diverge from pure AD. Tau copathology contributes uniquely to the heterogeneity of cognitive impairment in LBD. Ann Neurol 2018; 1-13 ANN NEUROL 2019;85:259-271.

Measurements of auto-antibodies to α-synuclein in the serum and cerebral spinal fluids of patients with Parkinson's disease

Biomarkers for α-synuclein are needed for diagnosis and prognosis in Parkinson's disease (PD). Endogenous auto-antibodies to α-synuclein could serve as biomarkers for underlying synucleinopathy, but previous assessments of auto-antibodies have shown variability and inconsistent clinical correlations. We hypothesized that auto-antibodies to α-synuclein could be diagnostic for PD and explain its clinical heterogeneity. To test this hypothesis, we developed an enzyme-linked immunosorbent assay for measuring α-synuclein auto-antibodies in human samples. We evaluated 69 serum samples (16 healthy controls (HC) and 53 PD patients) and 145 CSF samples (52 HC and 93 PD patients) from our Institution. Both serum and CSF were available for 24 participants. Males had higher auto-antibody levels than females in both fluids. CSF auto-antibody levels were significantly higher in PD patients as compared with HC, whereas serum levels were not significantly different. CSF auto-antibody levels did not associate with amyloid-β_1-42 , total tau, or phosphorylated tau. CSF auto-antibody levels correlated with performance on the Montreal Cognitive Assessment, even when controlled for CSF amyloidβ_1-42 . CSF hemoglobin levels, as a proxy for contamination of CSF by blood during lumbar puncture, did not influence these observations. Using recombinant α-synuclein with N- and C-terminal truncations, we found that CSF auto-antibodies target amino acids 100 through 120 of α-synuclein. We conclude that endogenous CSF auto-antibodies are significantly higher in PD patients as compared with HC, suggesting that they could indicate the presence of underlying synucleinopathy. These auto-antibodies associate with poor cognition, independently of CSF amyloidβ_1-42 , and target a select C-terminal region of α-synuclein. Read the Editorial Highlight for this article on page 433.

CSF tau and β-amyloid predict cerebral synucleinopathy in autopsied Lewy body disorders

OBJECTIVE

To test the association of antemortem CSF biomarkers with postmortem pathology in Lewy body disorders (LBD).

METHODS

Patients with autopsy-confirmed LBD (n = 24) and autopsy-confirmed Alzheimer disease (AD) (n = 23) and cognitively normal (n = 36) controls were studied. In LBD, neuropathologic criteria defined Lewy body α-synuclein (SYN) stages with medium/high AD copathology (SYN + AD = 10) and low/no AD copathology (SYN - AD = 14). Ordinal pathology scores for tau, β-amyloid (Aβ), and SYN pathology were averaged across 7 cortical regions to obtain a global cerebral score for each pathology. CSF total tau (t-tau), phosphorylated tau at threonine181, and Aβ1-42 levels were compared between LBD and control groups and correlated with global cerebral pathology scores in LBD with linear regression. Diagnostic accuracy for postmortem categorization of LBD into SYN + AD vs SYN - AD or neocortical vs brainstem/limbic SYN stage was tested with receiver operating curves.

RESULTS

SYN + AD had higher CSF t-tau (mean difference 27.0 ± 8.6 pg/mL) and lower Aβ1-42 (mean difference -84.0 ± 22.9 g/mL) compared to SYN - AD (p < 0.01, both). Increasing global cerebral tau and plaque scores were associated with higher CSF t-tau (R2 = 0.15-0.16, p < 0.05, both) and lower Aβ1-42 (R2 = 0.43-0.49, p < 0.001, both), while increasing cerebral SYN scores were associated with lower CSF Aβ1-42 (R2 = 0.31, p < 0.001) and higher CSF t-tau/Aβ1-42 ratio (R2 = 0.27, p = 0.01). CSF t-tau/Aβ1-42 ratio had 100% specificity and 90% sensitivity for SYN + AD, and CSF Aβ1-42 had 77% specificity and 82% sensitivity for neocortical SYN stage.

CONCLUSIONS

Higher antemortem CSF t-tau/Aβ1-42 and lower Aβ1-42 levels are predictive of increasing cerebral AD and SYN pathology. These biomarkers may identify patients with LBD vulnerable to cortical SYN pathology who may benefit from both SYN and AD-targeted disease-modifying therapies.

Regional brain amyloid-β accumulation associates with domain-specific cognitive performance in Parkinson disease without dementia

Parkinson disease patients develop clinically significant cognitive impairment at variable times over their disease course, which is often preceded by milder deficits in memory, visuo-spatial, and executive domains. The significance of amyloid-β accumulation to these problems is unclear. We hypothesized that amyloid-β PET imaging by 18F-florbetapir, a radiotracer that detects fibrillar amyloid-β plaque deposits, would identify subjects with global cognitive impairment or poor performance in individual cognitive domains in non-demented Parkinson disease patients. We assessed 61 non-demented Parkinson disease patients with detailed cognitive assessments and 18F-florbetapir PET brain imaging. Scans were interpreted qualitatively (positive or negative) by two independent nuclear medicine physicians blinded to clinical data, and quantitatively by a novel volume-weighted method. The presence of mild cognitive impairment was determined through an expert consensus process using Level 1 criteria from the Movement Disorder Society. Nineteen participants (31.2%) were diagnosed with mild cognitive impairment and the remainder had normal cognition. Qualitative 18F-florbetapir PET imaging was positive in 15 participants (24.6%). Increasing age and presence of an APOE ε4 allele were associated with higher composite 18F-florbetapir binding. In multivariable models, an abnormal 18F-florbetapir scan by expert rating was not associated with a diagnosis of mild cognitive impairment. However, 18F-florbetapir retention values in the posterior cingulate gyrus inversely correlated with verbal memory performance. Retention values in the frontal cortex, precuneus, and anterior cingulate gyrus retention values inversely correlated with naming performance. Regional cortical amyloid-β amyloid, as measured by 18F-florbetapir PET, may be a biomarker of specific cognitive deficits in non-demented Parkinson disease patients.

Novel conformation-selective alpha-synuclein antibodies raised against different in vitro fibril forms show distinct patterns of Lewy pathology in Parkinson's disease

AIMS

The aim of this study was to test the hypothesis that different conformations of misfolded α-synuclein (α-syn) are present in Parkinson's disease (PD) brain.

METHODS

Using two previously characterized conformations of α-syn fibrils, we generated new conformation-selective α-syn monoclonal antibodies (mAbs). We then interrogated multiple brain regions in a well-characterized autopsy cohort of PD patients (n = 49) with these mAbs, Syn7015 and Syn9029.

RESULTS

Syn7015 detects Lewy bodies (LBs) and Lewy neurites (LNs) formed by pathological α-syn in all brain regions tested, and is particularly sensitive to LNs and small Lewy dots, inclusions believed to form early in the disease. Further, we observed colocalization between Syn7015 and an early marker of α-syn pathology formation, phospho-Ser129-α-syn, and a lack of extensive colocalization with markers of more mature pathology. In comparison, Syn9029 detects Lewy pathology in all regions examined, but indicates significantly fewer LNs than Syn7015. In addition, colocalization of Syn9029 with later markers of α-syn pathology maturation (ubiquitin and P62) suggests that the pathology detected by Syn9029 is older. Semiquantitative scoring of both LN and LB pathology in nine brain regions further established this trend, with Syn7015 LN scores consistently higher than Syn9029 LN scores.

CONCLUSIONS

Our data indicate that different conformations of α-syn pathology are present in PD brain and correspond to different stages of maturity for Lewy pathology. Regional analysis of Syn7015 and Syn9029 immunostaining also provides support for the Braak hypothesis that α-syn pathology advances through the brain.

Amyloid-Beta Positron Emission Tomography Imaging of Alzheimer's Pathology in Parkinson's Disease Dementia

BACKGROUND

Neuronal loss and α-synuclein (α-syn) pathology are diagnostic of PD in the appropriate clinical context. However, some PD patients have co-morbid Alzheimer's disease (AD) pathology on autopsy, including amyloid-β (Aβ) plaques and neurofibrillary tangles. Florbetapir(¹⁸F) is a PET ligand that detects Aβ pathology. We hypothesized that florbetapir(¹⁸F) imaging could detect Aβ pathology in Parkinson disease dementia (PDD) patients prior to death.

OBJECTIVE

To determine the utility of florbetapir(¹⁸F) PET imaging in detecting Aβ pathology in patients with autopsy-confirmed PDD.

METHODS

Five participants with PDD had florbetapir(¹⁸F) PET imaging prior to death as a part of a longitudinal research study of cognitive decline in PD. PET scans were evaluated by expert raters blinded to clinical and neuropathological information. At autopsy, all five participants underwent semi-quantitative assessments of regional Aβ and tau immunohistochemistry.

RESULTS

All participants met neuropathological criteria for PD. Two had both positive florbetapir(¹⁸F) scans and Aβ-positive plaques in multiple brain regions. Regional florbetapir(¹⁸F) binding correlated with regional semi-quantitative Aβ pathology in these cases. Three cases had negative florbetapir(¹⁸F) scans. Two of these had significant tau pathology without Aβ pathology, consistent with progressive supranuclear palsy (PSP) in one case and argyrophilic grain disease (AGD) in the other. The last case had a low level of AD neuropathological change.

CONCLUSIONS

Florbetapir(¹⁸F) Aβ imaging can detect the presence of Aβ neuropathology in patients with PDD. This imaging technique may aid the clinical evaluation of PDD patients to determine if cognitive decline is occurring in the setting of Aβ accumulation.

Longitudinal study of normal cognition in Parkinson disease

OBJECTIVE

To report the rates and predictors of progression from normal cognition to either mild cognitive impairment (MCI) or dementia using standardized neuropsychological methods.

METHODS

A prospective cohort of patients diagnosed with Parkinson disease (PD) and baseline normal cognition was assessed for cognitive decline, performance, and function for a minimum of 2 years, and up to 6. A panel of movement disorders experts classified patients as having normal cognition, MCI, or dementia, with 55/68 (80.9%) of eligible patients seen at year 6. Kaplan-Meier curves and Cox proportional hazard models were used to examine cognitive decline and its predictors.

RESULTS

We enrolled 141 patients, who averaged 68.8 years of age, 63% men, who had PD on average for 5 years. The cumulative incidence of cognitive impairment was 8.5% at year 1, increasing to 47.4% by year 6. All incident MCI cases had progressed to dementia by year 5. In a multivariate analysis, predictors of future decline were male sex (p = 0.02), higher Unified Parkinson's Disease Rating Scale motor score (p ≤ 0.001), and worse global cognitive score (p < 0.001).

CONCLUSIONS

Approximately half of patients with PD with normal cognition at baseline develop cognitive impairment within 6 years and all new MCI cases progress to dementia within 5 years. Our results show that the transition from normal cognition to cognitive impairment, including dementia, occurs frequently and quickly. Certain clinical and cognitive variables may be useful in predicting progression to cognitive impairment in PD.

Cytoplasmic p53 and activated Bax regulate p53-dependent, transcription-independent neural precursor cell apoptosis

The prodeath effects of p53 are typically mediated via its transcriptional upregulation of proapoptotic Bcl-2 family members, including PUMA, Noxa, and/or Bax. We previously reported that staurosporine (STS), a broad-spectrum kinase inhibitor and prototypical apoptosis-inducing agent, produced p53-dependent, Bax-dependent, neural precursor cell (NPC) apoptosis, but that this effect occurred independently of new gene transcription and PUMA expression. To further characterize the mechanism by which p53 regulates NPC death, we used primary cerebellar NPCs derived from wild-type, p53-deficient, and Bax-deficient neonatal mice and the mouse cerebellar neural stem cell line, C17.2. We found that STS rapidly increased p53 cytoplasmic immunoreactivity in neuritic-like processes in C17.2 cells, which preceded Bax activation and caspase-3 cleavage. Confocal microscopy analysis of STS-treated cells revealed partial colocalization of p53 with the mitochondrial marker pyruvate dehydrogenase as well as with conformationally altered "activated" Bax, suggesting an interaction between these proapoptotic molecules in triggering apoptotic death. Nucleophosmin (NPM), a CRM1-dependent nuclear chaperone, also exhibited partial colocalization with both activated Bax and p53 following STS treatment. These observations suggest that cytoplasmic p53 can trigger transcription-independent NPC apoptosis through its potential interaction with NPM and activated Bax.

Loss of BH3-only protein Bim inhibits apoptosis of hemopoietic cells in the fetal liver and male germ cells but not neuronal cells in bcl-x-deficient mice

Members of the Bcl-2 family include pro- and antiapoptotic proteins that regulate programmed cell death of developing tissues and death in response to cellular damage. In developing mice, the antiapoptotic Bcl-x(L) is necessary for survival of neural and hematopoietic cells, and consequently, bcl-x-deficient mice die around Day 13.5 of embryogenesis. Furthermore, adult bcl-x(+/-) heterozygous male mice have reduced fertility because of testicular degeneration. Bax, a multi-BH (Bcl-2 homology) domain proapoptotic member of the Bcl-2 family, is regulated by Bcl-x(L) and is required for the neuropathological abnormalities seen in bcl-x-deficient embryos. The BH3 domain only subgroup of the Bcl-2 family includes proapoptotic members that are essential for the initiation of apoptotic signaling. In this study, we investigated the role for Bim, a BH3 domain only protein, in the embryonic lethality and increased developmental cell death in bcl-x-deficient animals and the perturbed testicular function in bcl-x(+/-) adults. Our studies show that bim deficiency attenuates hematopoietic cell death in the fetal liver of bcl-x-deficient animals, indicating that Bim contributes to programmed cell death in this cell population. In addition, we found that testicular degeneration of adult bcl-x(+/-) males was rescued by concomitant Bim deficiency. However, concomitant Bim deficiency had no effect on the embryonic lethality and widespread nervous system abnormalities caused by bcl-x deficiency. Our work identifies Bim as an important regulator of bcl-x deficiency-induced cell death during hematopoiesis and testicular development.

Immunohistochemical detection with quantum dots

Quantum dot (QD) conjugates have many immunohistochemical applications. The optical, excitation/emission, and photostable properties of QDs offer several advantages over the use of chromogens or organic fluorophores in these applications. Here, we describe the use of QD conjugates to detect primary antibody binding in fixed tissue sections. We also describe the use of QDs in simultaneous and sequential multilabeling procedures and in combination with enzyme-based signal amplification techniques. QD conjugates expand the arsenal of the immunohistochemist and increase experimental flexibility in many applications.

p53 Transcription-Dependent and -Independent Regulation of Cerebellar Neural Precursor Cell Apoptosis

Regulation of cerebellar neural precursor cell (NPC) death is important for both normal brain development and prevention of brain tumor formation. The tumor suppressor p53 is an important regulator of NPC apoptosis, but the precise mechanism of p53-regulated cerebellar NPC death remains largely unknown. Here, by using primary cerebellar NPCs and a mouse cerebellar NPC line, we compared the molecular regulation of cerebellar NPC death produced by staurosporine (STS), a broad-spectrum kinase inhibitor, with that caused by genotoxic agents. We found that both STS- and genotoxin-induced cerebellar NPC death were markedly inhibited by p53 or Bax deficiency. Genotoxin-induced cerebellar NPC death required new protein synthesis and PUMA, a p53 transcriptionally regulated BH3-only molecule. In contrast, STS caused cerebellar NPC death without requiring new protein synthesis or PUMA expression. In addition, genotoxic agents increased nuclear p53 immunoreactivity, whereas STS produced rapid cytoplasmic p53 accumulation. Interestingly, STS-induced death of cerebellar granule neurons was p53-independent, indicating a differentiation-dependent feature of neuronal apoptotic regulation. These results suggest that STS-induced cerebellar NPC death requires a direct effect of p53 on cytoplasmic apoptotic mediators, whereas genotoxin-induced death requires p53-dependent gene transcription of PUMA. Thus, p53 has multiple death promoting mechanisms in cerebellar NPCs.

BH3-only proapoptotic Bcl-2 family members Noxa and Puma mediate neural precursor cell death

Neural precursor cells (NPCs) are highly sensitive to genotoxic injury, which triggers activation of the intrinsic mitochondria-dependent apoptotic pathway. This pathway is typically initiated by members of the BH3 (Bcl-2 homology 3)-only subgroup of the Bcl-2 (B-cell CLL/lymphoma 2) protein family, which are positioned upstream in the apoptotic pathway to respond to specific death stimuli. We have shown previously that NPCs deficient in the tumor suppressor protein p53 show significantly less death after exposure to genotoxic injury or to staurosporine (STS), a broad kinase inhibitor and potent apoptosis inducer. p53 has been shown to regulate the expression of both Noxa and Puma, two BH3-only proteins, although their involvement in p53-dependent cell death appears to be cell-type and stimulus specific. A systematic comparison of the relative contributions of Noxa and Puma to NPC apoptosis has not yet been performed. We hypothesized that p53-dependent transcription of Noxa and Puma leads to death in telencephalic NPCs exposed to genotoxic stress. We found that genotoxic injury induces a rapid p53-dependent increase in expression of Noxa and Puma mRNA in telencephalic NPCs. Furthermore, deficiency of either Noxa or Puma inhibited DNA damage-induced caspase-3 activation and cell death in telencephalic NPCs in vitro. However, only Puma deficiency protected telencephalic ventricular zone NPCs from death in vivo. In contrast to genotoxic injury, STS produced a p53-independent increase in Noxa and Puma expression, but neither Noxa nor Puma was required for STS-induced NPC death. Together, these experiments identify Noxa and Puma as important regulators of genotoxin-induced telencephalic NPC death.

Neural precursor cells possess multiple p53-dependent apoptotic pathways

Neural precursor cells (NPCs) are markedly sensitive to apoptotic insults. p53-Dependent transcriptional activation of proapoptotic genes has been hypothesized to regulate NPC death in response to DNA damage. Recent studies of non-NPCs have also indicated that p53 may directly interact with Bcl-2 molecules and thereby regulate death independently of transcription. The contribution of transcription-independent p53 activation in NPC death has not been characterized. In this study, we found that apoptosis caused by chemotherapeutic agents in NPCs required p53 expression and new macromolecular synthesis. In contrast, NPC death induced by staurosporine, a broad kinase inhibitor, is regulated by p53 in the absence of macromolecular synthesis. The apoptosis effector molecules Bax and Bak, Apaf-1, and caspase-9 were shown to be downstream of p53 in both pathways. These findings indicate that p53 is in a unique position to regulate at least two distinct signaling portals that activate the intrinsic apoptotic death pathway in NPCs.

Bcl-2 family regulation of neuronal development and neurodegeneration

Neuronal cell death is a key feature of both normal nervous system development and neuropathological conditions. The Bcl-2 family, via its regulation of both caspase-dependent and caspase-independent cell death pathways, is uniquely positioned to critically control neuronal cell survival. Targeted gene disruptions of specific bcl-2 family members and the generation of transgenic mice overexpressing anti- or pro-apoptotic Bcl-2 family members have confirmed the importance of the Bcl-2 family in the nervous system. Data from studies of human brain tissue and experimental animal models of neuropathological conditions support the hypothesis that the Bcl-2 family regulates cell death in the mature nervous system and suggest that pharmacological manipulation of Bcl-2 family action could prove beneficial in the treatment of human neurological conditions such as stroke and neurodegenerative diseases.

Combined tyramide signal amplification and quantum dots for sensitive and photostable immunofluorescence detection

Conventional immunofluorescence detection of biologically relevant proteins and antigens in tissue sections is often limited by relatively weak signals that fade rapidly on illumination. We have developed an immunohistochemical protocol that combines the sensitivity of tyramide signal amplification with the photostability of quantum dots to overcome these limitations. This simple method provides a sensitive and stable fluorescence immunohistochemical alternative to standard chromogen detection.