African-American and Caucasian participation in postmortem human brain donation for neuropsychiatric research.

Increased African-American research participation is critical to the applicability and generalizability of biomedical research, as population diversity continues to increase both domestically and abroad. Yet numerous studies document historical origins of mistrust, as well as other barriers that may contribute to resistance in the African-American community towards participation in biomedical research. However, a growing body of more recent scientific evidence suggests that African-Americans value research and are willing to participate when asked. In the present study, we set out to determine factors associated with research participation of African-American families in postmortem human brain tissue donation for neuropsychiatric disorders as compared with Caucasian families, from same-day medical examiner autopsy referrals. We retrospectively reviewed brain donation rates, as well as demographic and clinical factors associated with donation in 1,421 consecutive referrals to three medical examiner's offices from 2010-2015. Overall, 69.7% of all next-of-kin contacted agreed to brain donation. While Caucasian families consented to donate brain tissue at a significantly higher rate (74.1%) than African-American families (57.0%) (p<0.001), African-American brain donation rates were as high as 60.5% in referrals from Maryland. Neither African-American nor Caucasian donors differed significantly from non-donors on any demographic or clinical factors ascertained, including age, sex, diagnosis of the donor, or in the relationship of the next-of-kin being contacted (p>0.05). However, Caucasian donors were significantly older, had more years of education, were more likely to be referred for study due to a psychiatric diagnosis, more likely to have comorbid substance abuse, and more likely to have died via suicide, as compared with African-American donors (p<0.05). When African-American participants are identified and approached, African-American families as well as Caucasian families are indeed willing to donate brain tissue on the spot for neuropsychiatric research, which supports the belief that African-American attitudes towards biomedical research may be more favorable than previously thought.

Brain donation at autopsy: clinical characterization and toxicologic analyses.

The study of postmortem human brain tissue is central to the advancement of neurobiologic studies of psychiatric and neurologic illnesses, particularly the study of brain-specific isoforms and molecules. Due to tissue demands, especially pertaining to brain regions strongly implicated in the pathophysiology of neuropsychiatric disorders, the success and future of this research depend on the availability of high-quality brain specimens from large numbers of subjects, including nonpsychiatric controls, both of which may be obtained from brain banks. In this chapter, we elaborate on the need for and acquisition of well-curated and properly diagnosed postmortem human brains, relying upon our experience with the Human Brain and Tissue Repository located at the Lieber Institute for Brain Development in Baltimore, MD. We explain the advantages of sourcing postmortem human tissue from medical examiner offices, which provide access to cases of all ages, both with and without central nervous system disorders. Neuropathology analyses and toxicologic screenings, along with autopsy reports and extensive interviews with family members and treating physicians, are invaluable to the diagnoses of postmortem cases. Ultimately, the study of psychiatric and neurologic disorders is the study of brain disease, and accordingly, there is no substitution for human brain tissue.

Genetic risk mechanisms of posttraumatic stress disorder in the human brain.

Posttraumatic stress disorder (PTSD) follows exposure to a traumatic event in susceptible individuals. Recently, genome-wide association studies have identified a number of genetic sequence variants that are associated with the risk of developing PTSD. To follow up on identifying the molecular mechanisms of these risk variants, we performed genotype to RNA sequencing-derived quantitative expression (whole gene, exon, and exon junction levels) analysis in the dorsolateral prefrontal cortex (DLPFC) of normal postmortem human brains. We further investigated genotype-gene expression associations within the amygdala in a smaller independent RNA sequencing (Genotype-Tissue Expression [GTEx]) dataset. Our DLPFC analyses identified significant expression quantitative trait loci (eQTL) associations for a "candidate" PTSD risk SNP rs363276 and the expression of two genes: SLC18A2 and PDZD8, where the PTSD risk/minor allele T was associated with significantly lower levels of gene expression for both genes, in the DLPFC. These eQTL associations were independently confirmed in the amygdala from the GTEx database. Rs363276 "T" carriers also showed significantly increased activity in the amygdala during an emotional face-matching task in healthy volunteers. Taken together, our preliminary findings in normal human brains represent a tractable approach to identify mechanisms by which genetic variants potentially increase an individual's risk for developing PTSD. © 2016 Wiley Periodicals, Inc.

Implementation and clinical characteristics of a posttraumatic stress disorder brain collection.

A postmortem human brain collection to study posttraumatic stress disorder (PTSD) is critical for uncovering the molecular mechanisms that contribute to this psychiatric disorder. We describe here the PTSD brain collection at the Lieber Institute for Brain Development in Baltimore, Maryland, consisting of postmortem brain donations acquired between 2012 and 2017. Thus far, 87 brains from individuals meeting DSM-5 criteria for PTSD were collected after consent was obtained from legal next-of-kin, and subsequently clinically characterized for molecular studies. PTSD brain donors had high rates of comorbid diagnoses, including depression (62.1%), substance abuse (74.7%), drug-related death (69.0%), and suicide completion (17.2%). PTSD cases were subdivided into two categories: combat-related PTSD (n = 24) and noncombat/domestic PTSD (n = 63). The major differences between the combat-related and domestic PTSD cohorts were sex, drug-related death, and the prevalence of bipolar disorder (BPD) comorbidity. The combat-related group was entirely male, with only one BPD subject (4.2%), and had significantly fewer drug-related deaths (45.8%) in contrast to the domestic group (31.8% male, 36.5% bipolar, and 77.8% drug-related deaths). Medical examiners' offices, particularly in areas with higher military populations, are an excellent source for PTSD brain donations of both combat-related and domestic PTSD.

Deficits in the activity of presynaptic γ-aminobutyric acid type B receptors contribute to altered neuronal excitability in fragile X syndrome.

The behavioral and anatomical deficits seen in fragile X syndrome (FXS) are widely believed to result from imbalances in the relative strengths of excitatory and inhibitory neurotransmission. Although modified neuronal excitability is thought to be of significance, the contribution that alterations in GABAergic inhibition play in the pathophysiology of FXS are ill defined. Slow sustained neuronal inhibition is mediated by γ-aminobutyric acid type B (GABAB) receptors, which are heterodimeric G-protein-coupled receptors constructed from R1a and R2 or R1b and R2 subunits. Via the activation of Gi/o, they limit cAMP accumulation, diminish neurotransmitter release, and induce neuronal hyperpolarization. Here we reveal that selective deficits in R1a subunit expression are seen in Fmr1 knock-out mice (KO) mice, a widely used animal model of FXS, but the levels of the respective mRNAs were unaffected. Similar trends of R1a expression were seen in a subset of FXS patients. GABAB receptors (GABABRs) exert powerful pre- and postsynaptic inhibitory effects on neurotransmission. R1a-containing GABABRs are believed to mediate presynaptic inhibition in principal neurons. In accordance with this result, deficits in the ability of GABABRs to suppress glutamate release were seen in Fmr1-KO mice. In contrast, the ability of GABABRs to suppress GABA release and induce postsynaptic hyperpolarization was unaffected. Significantly, this deficit contributes to the pathophysiology of FXS as the GABABR agonist (R)-baclofen rescued the imbalances between excitatory and inhibitory neurotransmission evident in Fmr1-KO mice. Collectively, our results provided evidence that selective deficits in the activity of presynaptic GABABRs contribute to the pathophysiology of FXS.

Strong Components of Epigenetic Memory in Cultured Human Fibroblasts Related to Site of Origin and Donor Age.

Differentiating pluripotent cells from fibroblast progenitors is a potentially transformative tool in personalized medicine. We previously identified relatively greater success culturing dura-derived fibroblasts than scalp-derived fibroblasts from postmortem tissue. We hypothesized that these differences in culture success were related to epigenetic differences between the cultured fibroblasts by sampling location, and therefore generated genome-wide DNA methylation and transcriptome data on 11 intrinsically matched pairs of dural and scalp fibroblasts from donors across the lifespan (infant to 85 years). While these cultured fibroblasts were several generations removed from the primary tissue and morphologically indistinguishable, we found widespread epigenetic differences by sampling location at the single CpG (N = 101,989), region (N = 697), "block" (N = 243), and global spatial scales suggesting a strong epigenetic memory of original fibroblast location. Furthermore, many of these epigenetic differences manifested in the transcriptome, particularly at the region-level. We further identified 7,265 CpGs and 11 regions showing significant epigenetic memory related to the age of the donor, as well as an overall increased epigenetic variability, preferentially in scalp-derived fibroblasts-83% of loci were more variable in scalp, hypothesized to result from cumulative exposure to environmental stimuli in the primary tissue. By integrating publicly available DNA methylation datasets on individual cell populations in blood and brain, we identified significantly increased inter-individual variability in our scalp- and other skin-derived fibroblasts on a similar scale as epigenetic differences between different lineages of blood cells. Lastly, these epigenetic differences did not appear to be driven by somatic mutation--while we identified 64 probable de-novo variants across the 11 subjects, there was no association between mutation burden and age of the donor (p = 0.71). These results depict a strong component of epigenetic memory in cell culture from primary tissue, even after several generations of daughter cells, related to cell state and donor age.

Myelin, myelin-related disorders, and psychosis.

The neuropathological basis of schizophrenia and related psychoses remains elusive despite intensive scientific investigation. Symptoms of psychosis have been reported in a number of conditions where normal myelin development is interrupted. The nature, location, and timing of white matter pathology seem to be key factors in the development of psychosis, especially during the critical adolescent period of association area myelination. Numerous lines of evidence implicate myelin and oligodendrocyte function as critical processes that could affect neuronal connectivity, which has been implicated as a central abnormality in schizophrenia. Phenocopies of schizophrenia with a known pathological basis involving demyelination or dysmyelination may offer insights into the biology of schizophrenia itself. This article reviews the pathological changes in white matter of patients with schizophrenia, as well as demyelinating diseases associated with psychosis. In an attempt to understand the potential role of dysmyelination in schizophrenia, we outline the evidence from a number of both clinically-based and post-mortem studies that provide evidence that OMR genes are genetically associated with increased risk for schizophrenia. To further understand the implication of white matter dysfunction and dysmyelination in schizophrenia, we examine diffusion tensor imaging (DTI), which has shown volumetric and microstructural white matter differences in patients with schizophrenia. While classical clinical-neuropathological correlations have established that disruption in myelination can produce a high fidelity phenocopy of psychosis similar to schizophrenia, the role of dysmyelination in schizophrenia remains controversial.

Characteristics of the cation cotransporter NKCC1 in human brain: alternate transcripts, expression in development, and potential relationships to brain function and schizophrenia.

Early in development, GABA, an inhibitory neurotransmitter in adults, is excitatory. NKCC1 (SLC12A2) encodes one of two cation chloride cotransporters mediating the conversion of GABA from excitatory to inhibitory. Using 3' and 5' RACE and PCR, we verified previously characterized alternative transcripts of NKCC1a (1-27) and NKCC1b (1-27(Δ21)), identified new NKCC1 transcripts, and explored their expression patterns during human prefrontal cortical development. A novel ultra-short transcript (1-2a) was expressed preferentially in the fetus. Expression of NKCC1b and 1-2a were decreased in schizophrenia compared with controls (NKCC1b: 0.8-fold decrease, p = 0.013; 1-2a: 0.8-fold decrease, p = 0.006). Furthermore, the expression of NKCC1b was associated with NKCC1 polymorphism rs3087889. The minor allele at rs3087889, associated with reduced NKCC1b expression (homozygous for major allele: N = 37; homozygous for minor allele: N = 15; 1.5-fold decrease; p < 0.01), was also associated with a modest increase in schizophrenia risk in a case-control sample (controls: N = 435; cases: N = 397, OR = 1.5). This same allele was then found associated with cognitive (n = 369) and fMRI (n = 313) intermediate phenotypes associated with schizophrenia-working memory (Cohen's d = 0.35), global cognition or g (d = 0.18), and prefrontal inefficiency (d = 0.36) as measured by BOLD fMRI during a working memory task. Together, these preclinical and clinical results suggest that variation in NKCC1 may increase risk for schizophrenia via alterations of mRNA expression at the molecular level and impairment of optimal prefrontal function at the macro or systems level.