Postmortem Material Research Articles

Paracingulate asymmetry in anterior and midcingulate cortex: sex differences and the effect of measurement technique

Many structural brain asymmetries accompany left hemisphere language dominance. For example, the cingulate sulcus is larger in the medial cortex of the right hemisphere, while the more dorsal paracingulate sulcus is larger on the left. The functional significance of these asymmetries is unknown because fMRI studies rarely attempt to localize activation to specific sulci, possibly due to difficulties in consistent sulcal identification. In medial cortex, for example, there are many regions of partial sulcal overlap where MRI images do not provide sufficient information to unambiguously distinguish a paracingulate sulcus from a displaced anterior cingulate segment. As large samples of postmortem material are rarely available for cytoarchitectural studies of sulcal variation, we have investigated the effect of variation in boundary and sulcal definition on paracingulate asymmetry in the MRI scans of 200 healthy adults (100 men, 100 women). Although women displayed a reliable asymmetry in the size of the paracingulate sulcus, regardless of boundary definition or technique, asymmetry was greatest when (1) the measurement was limited to the midcingulate region between the genu and the anterior commissure; and (2) the more dorsal of two overlapping sulci was always classified as a paracingulate sulcus (rather than as a displaced cingulate segment). The fact that paracingulate asymmetry is maximal in the midcingulate region suggests that this region may play a particular role in hemispheric specialization for language. Future work should investigate the structural and functional correlates of sulcal variation in this region.

Subcortical oligodendrocyte- and astrocyte-associated gene expression in subjects with schizophrenia, major depression and bipolar disorder

Deficits in the expression of oligodendrocyte and myelin genes have been described in numerous cortical regions in schizophrenia and affective disorders; however, relatively little attention has been paid to subcortical structures. Here we employed quantitative real time PCR to examine the mRNA expression of 17 genes that are expressed by oligodendrocyte precursors (OLPs) and their derivatives, including astrocytes. Four subcortical regions were examined (the anteroventral (AV) and mediodorsal thalamic nuclei (MDN), internal capsule (IC) and putamen (Put)) in postmortem material from subjects (age 25–68 at time of death) with no known psychiatric history (NCs) as well as in subjects with schizophrenia (SZ), major depressive disorder (MDD), and bipolar disorder (BPD). In all regions examined, genes expressed after the terminal differentiation of oligodendrocytes tended to have lower levels of mRNA expression in subjects with SZ compared to NCs. These differences were statistically significant across regions for four genes (CNP, GALC, MAG and MOG) and approached significance for TF. No genes were under expressed in MDD. Only TF was under expressed in BPD and only in the IC. In contrast, two astrocyte-associated genes (GFAP and ALDH1L1) had higher mean expression levels across regions in all psychiatric groups relative to NCs. These differences reached statistical significance for SZ and MDD relative to NCs. There were no age by diagnosis interactions. The majority of age regressions had negative slopes for the expression of oligodendrocyte-associated genes. GFAP but not ALDH1L1 expression was significantly and positively correlated with age in the MDN, AV and Put. Across subject groups the expression of both astrocyte genes was highly correlated with cumulative neuroleptic exposure in all regions except the Put. Significant positive correlations were also observed in some regions between cumulative neuroleptic exposure and the expression of genes associated with mature oligodendrocytes as well as with bipotential OLPs. Multiple negative correlations were observed between the mRNA expression of astrocyte genes and genes expressed by terminally differentiated oligodendrocytes. These data are discussed in the context of myelin turnover and potential effects of psychiatric illness as well as medications on the developmental fate of OLPs.

The posterosuperior quadrant of the tympanic membrane

Objective To document the anatomic relationship of the posterosuperior segment of the tympanic membrane. Study Design Point-prevalence study of postmortem material. Subjects and Materials One hundred seventy temporal bones from adults without history of otologic pathology were studied. The anatomic details of the tympanic membrane were observed, histology was documented on 30 sectioned bones, and, with the use of the scanning electron microscope, lamina propria was studied in 40 bones. Results We established that the posterosuperior quadrant was the largest, representing 28.7 percent of the total area of the eardrum. This feature implies that this quadrant is more likely than are the other quadrants to exhibit changes prompted by pressure challenges. We also verified that the posterosuperior part of tympanic sulcus, above the chorda tympanic nerve, lost its depth in an unexpected way in 60 percent of the cases. In association, we established that at this level there was a decrease in annulus caliber. In 25 percent of cases, by the absence of the circular fibers of lamina propria, the posterosuperior quadrant had only the radial fiber layer. Conclusions Anatomic and morphologic details in posterosuperior quadrant were newly described and may explain the greater incidence of retraction pockets and marginal perforations that provide origin for the cholesteatoma.

Investigation of calcium and sodium in postmortem material as biochemical markers defining the cause of death from hypothermia

The present investigation was undertaken to evaluate the usefulness of calcium and sodium measurements in the heart, liver, and muscle autopsy samples as biochemical markers defining the cause of death from hypothermia. The concentration of electrolytes in selected internal organ tissues of persons who died from hypothermia ( n = 26) was compared with element concentrations in analogous tissues of persons that died due to other causes (control group, n = 26). Our study showed no significant differences in the calcium content of tissues in persons who died from hypothermia, over those who died in normothermic conditions. The concentration of sodium was significantly ( p < 0.001) increased in the skeletal muscle of subjects who died from hypothermia.

Baccharis Pteronioides Toxicity in Livestock and Hamsters

Baccharis pteronioides DC has been intermittently associated with livestock poisoning in the southwestern United States. In 2004, nearly 100 cows were reported poisoned by B. pteronioides in southern New Mexico. Initial field studies and postmortem examinations found drought conditions, evidence of B. pteronioides consumption, and a reported mortality of nearly 40%. Because postmortem materials were unsuitable for further examination, plant samples were collected for feeding trials and chemical evaluation. Forty-eight Syrian hamsters (8 weeks old) were randomly divided into 4 groups and dosed with 0, 50, 100, and 200 mg of B. pteronioides for 10 days. After dosing, the hamsters were necropsied; sera were analyzed biochemically; and tissues were collected and evaluated histologically. The hamsters treated with 200 mg and several of the 100-mg animals developed anorexia and diarrhea. These animals developed multiple hemorrhagic infarcts in the liver and kidney, with severe hemorrhagic enteritis. Histologically, the higher-dosed animals had severe necrotizing vasculitis with vascular thrombosis of hepatic and renal vessels. Many glomerular capillaries contained fibrin thrombi. The superficial intestinal and colonic mucosa was necrotic, with extensive hemorrhage and proliferation of luminal bacteria. Lower-dosed animals had mild hepatocellular swelling, with proliferation of intestinal and gastric bacteria and yeast. The findings indicate that at high doses, B. pteronioides is toxic to hamsters and produces lesions that are very similar to bacterial endotoxin-produced vasculitis and infarction. Research to purify and identify the toxin, the toxic dose, and mechanism of toxicity are ongoing.

Dopamine D2-receptors in human narcolepsy: a SPECT study with 123I-IBZM.

Increased dopamine D2 receptor binding in basal ganglia has been reported in human narcolepsy. These studies have been based on post-mortem material of 8 patients, most of them also medicated for narcolepsy. We studied six narcoleptics without stimulant or anticataplectic medication. The patients had an unambiguous history of cataplexy, and they were also studied polygraphically. Single photon emission computed tomography (SPECT) imaging was performed. The D2 receptor density was determined by using 123I-iodobenzamide (IBZM). The control subjects were 8 unmedicated Parkinson patients with one-sided (hemiparkinsonian) clinical symptoms. The D2 receptor density in them is known to be normal or somewhat increased compared to healthy normals. The striatum/frontal D2 activity ratio was 1.331 +/- 0.084 (with phantom study correction 2.101 +/- 0.300) in the narcoleptic patients, and in the parkinsonian controls 1.321 +/- 0.052 (2.067 +/- 0.185) for the asymptomatic side and 1.335 +/- 0.025 (2.117 +/- 0.090) for the symptomatic side (i.e. contralateral to the side with the clinical extrapyramidal signs). There was no statistical difference between the groups or between the symptomatic and asymptomatic side in the Parkinson patients. Thus, our results differ from the earlier post-mortem studies.

Death of a female cocaine user due to the serotonin syndrome following moclobemide–venlafaxine overdose

To our knowledge, the majority of evidence supporting the relationship between the serotonin syndrome and medications that effect 5HT is based on case reports. The justification for taking up this subject has been a fatal outcome of a 21 year-old female following an administration of toxic doses of moclobemide (MAOI) and venlafaxine (SNRI). As a result of complex toxicological investigations including antemortem and postmortem material, antemortem clinical observations and postmortem examinations, the cause of death was identified as overdose with antidepressants – moclobemide and venlafaxine – in the mechanism of the clinically fully developed severe toxic serotonin syndrome. The analysis of a hair strand collected from the victim documented the use of the above-mentioned drugs simultaneously with cocaine in the period of at least 20 months preceding death. The fact is a matter of considerable interest in view of the employed pharmacotherapy, giving rise to suspicion that the woman had not developed the serotonin syndrome during the almost 2-year antemortem period until she took toxic doses of both medications.

A sex difference in the hypothalamic uncinate nucleus: relationship to gender identity

Transsexuality is an individual's unshakable conviction of belonging to the opposite sex, resulting in a request for sex-reassignment surgery. We have shown previously that the bed nucleus of the stria terminalis (BSTc) is female in size and neuron number in male-to-female transsexual people. In the present study we investigated the hypothalamic uncinate nucleus, which is composed of two subnuclei, namely interstitial nucleus of the anterior hypothalamus (INAH) 3 and 4. Post-mortem brain material was used from 42 subjects: 14 control males, 11 control females, 11 male-to-female transsexual people, 1 female-to-male transsexual subject and 5 non-transsexual subjects who were castrated because of prostate cancer. To identify and delineate the nuclei and determine their volume and shape we used three different stainings throughout the nuclei in every 15th section, i.e. thionin, neuropeptide Y and synaptophysin, using an image analysis system. The most pronounced differences were found in the INAH3 subnucleus. Its volume in thionin sections was 1.9 times larger in control males than in females (P < 0.013) and contained 2.3 times as many cells (P < 0.002). We showed for the first time that INAH3 volume and number of neurons of male-to-female transsexual people is similar to that of control females. The female-to-male transsexual subject had an INAH3 volume and number of neurons within the male control range, even though the treatment with testosterone had been stopped three years before death. The castrated men had an INAH3 volume and neuron number that was intermediate between males (volume and number of neurons P > 0.117) and females (volume P > 0.245 and number of neurons P > 0.341). There was no difference in INAH3 between pre-and post-menopausal women, either in the volume (P > 0.84) or in the number of neurons (P < 0.439), indicating that the feminization of the INAH3 of male-to-female transsexuals was not due to estrogen treatment. We propose that the sex reversal of the INAH3 in transsexual people is at least partly a marker of an early atypical sexual differentiation of the brain and that the changes in INAH3 and the BSTc may belong to a complex network that may structurally and functionally be related to gender identity.

Spinal cord grey matter lesions in multiple sclerosis detected by post-mortem high field MR imaging

Background Post-mortem studies demonstrate extensive grey matter demyelination in MS, both in the brain and in the spinal cord. However the clinical significance of these plaques is unclear, largely because they are grossly underestimated by MR imaging at conventional field strengths. Indeed post-mortem MR studies suggest the great majority of lesions in the cerebral cortex go undetected, even when performed at high field. Similar studies have not been performed using post-mortem spinal cord material. Aim To assess the sensitivity of high field post-mortem MRI for detecting grey matter lesions in the spinal cord in MS. Methods Autopsy material was obtained from 11 MS cases and 2 controls. Proton Density-weighted images of this formalin-fixed material were acquired at 4.7Tesla before the tissue was sectioned and stained for Myelin Basic Protein. Both the tissue sections and the MR images were scored for grey matter and white matter plaques, with the readers of the MR images being blinded to the histopathology results. Results Our results indicate that post-mortem imaging at 4.7Tesla is highly sensitive for cord lesions, detecting 87% of white matter lesions and 73% of grey matter lesions. The MR changes were highly specific for demyelination, with all lesions scored on MRI corresponding to areas of demyelination. Conclusion Our work suggests that spinal cord grey matter lesions may be detected on MRI more readily than GM lesions in the brain, making the cord a promising site to study the functional consequences of grey matter demyelination in MS.

Hypocretin/orexin disturbances in neurological disorders

The hypothalamic hypocretin (orexin) system plays a crucial role in the regulation of sleep and wakefulness. The strongest evidence for this is the fact that the primary sleep disorder narcolepsy is caused by disrupted hypocretin signaling in humans as well as various animal models. There is a growing interest in the role of hypocretin defects not only in the pathophysiology of other sleep disorders, but also in neurological diseases with associated sleep symptomatology. In this paper we first review the current methods to measure the integrity of the hypocretin system in human patients. The most widely used technique entails the measurement of hypocretin-1 in lumbar cerebrospinal fluid. In addition, hypocretin levels can be measured in ventricular cerebrospinal fluid and brain tissue extract. Finally, in post-mortem hypothalamic material, the number of hypocretin neurons can be precisely quantified. In the second part of this paper we describe the various neurological disorders in which hypocretin defects have been reported. These include neurodegenerative, neuromuscular and immune-mediated diseases, as well as traumatic brain injury. We conclude with a discussion of the functional relevance of partial hypocretin defects, and the various pathophysiological mechanisms that can lead to such defects.

Hippocampal Estrogen Receptor-Alpha Splice Variant TADDI in the Human Brain in Aging and Alzheimer’s Disease

Background/Aims: Estrogen receptor-α (ERα) splice variants are important for understanding estrogen effects on the brain and estrogen therapy pitfalls. We addressed the question whether a novel ERα splice variant TADDI is expressed at the protein level in the human brain and whether it changes in relation to aging and Alzheimer’s disease (AD). Methods: Immunoreactivity (-ir) for TADDI was assessed on postmortem human brain material from a total of 116 cases. Results: The highest levels of this splice form were found in the hypothalamic supraoptic nucleus (SON), pontine nuclei, medulla oblongata, gray matter of the spinal cord, the hippocampus, glomeruli of the cerebellum, the nucleus basalis of Meynert (NBM), and the tuberomamillary nucleus (TMN). TADDI-ir was mainly confined to the cytoplasm but was also determined in the nuclei of hippocampal neurons from young patients. In the hippocampus, the NBM, and the TMN, TADDI-ir was higher in postmenopausal women than in women ≤50 years old. In these brain areas and in the SON, it was diminished in AD women. In the NBM of AD men, TADDI-ir was enhanced. Conclusion: Aging- and AD-related changes in TADDI-ir show that it should be considered for the sensitivity of the neural tissue to estrogen therapy.

Arterial Vascularization in the Giraffe Brain

The aim of this study was to analyze the system of arteries in the brain of the giraffe, including the arterial circle of the brain, its branches and junctions, as well as individual variation of the vessels. Analyses were performed on postmortem material of 12 heads of giraffes obtained from Polish zoological gardens. The age of the examined animals ranged from 1.5 to 12 years. Moreover, arteries of one fetus aged approximately 10 months were also analyzed. Arteries of the heads were injected with latex and vinyl superchloride dissolved in acetone. In the giraffe, similarly as in other ruminant species, obliteration of the intracranial segment of the internal carotid artery was observed, together with the presence in the cranial cavity of the rostral epidural rete mirabile, from which the preserved intracranial segment of the internal carotid artery exteriorizes. The rostral cerebral artery of the brain and the caudal communicating artery, participating in the formation of the arterial circle of the brain, are formed by segments of the terminal intracranial part of the internal carotid artery. In the giraffe branches of the arterial circle of the brain included: the internal ethmoidal artery, the middle cerebral artery, the rostral choroid artery, the caudal cerebral artery, the rostral cerebellar artery and the caudal cerebellar artery. It was shown that the basilar artery was thin and could not participate in the blood supply for the brain. On the basis of the conducted analysis it was found that in the giraffe the arterial circle of the brain is supplied with blood mainly by the maxillary artery.

Cerebellar αsynuclein levels are decreased in Parkinson's disease and do not correlate with SNCA polymorphisms associated with disease in a Swedish material

Alterations of brain and plasma alpha-synuclein levels and SNCA gene variability have been implicated in the pathogenesis of Parkinson's disease (PD). We therefore measured alpha-synuclein protein levels in postmortem PD and control cerebellum tissue using Western blot and investigated whether the levels correlated to SNCA genotype. We found markedly decreased alpha-synuclein levels in PD patients (n=16) compared to gender- and age-matched controls (n=14; P=0.004) normalized to alpha-tubulin. We also performed an association study of the noncoding polymorphisms rs2737029 (A/G) and rs356204 (A/G) (intron 4), and of rs356219 (T/C) (3'-region) of SNCA in a Swedish PD case-control material. Using a two-sided chi(2) test, we found significant association of rs2737029 (P=0.003; chi(2)=9.07) and rs356204 (P=0.048; chi(2)=3.91) with disease, strengthening the involvement of SNCA polymorphisms in sporadic PD. Stratification of the human postmortem brain material by genotype of the three investigated polymorphisms, did not indicate any influence of genotype on alpha-synuclein protein levels when comparing PD with controls. Taken together, our findings demonstrate that the investigated Parkinson patients have markedly reduced levels of alpha-synuclein in cerebellum, and that this reduction is general, rather then correlated to the investigated polymorphisms, although two of the polymorphisms also associated with disease in a Swedish material.

Evaluation of post mortem stability of porcine skeletal muscle RNA

The objective of this study was to evaluate the effect of postmortem times on the quality of porcine skeletal muscle total RNA in order to consider the possibility to use postmortem material for gene expression analysis. Samples of Musculus semimembranosus were collected at 20 min, 2 h, 6 h, 24 h and 48 h postmortem from the left legs of four commercial heavy pigs. Total RNA was analysed by agarose gel electrophoresis stained with ethidium bromide and by microfluidic capillary electrophoresis on an Agilent 2100 Bioanalyzer instrument obtaining 28S:18S rRNA peak ratios and RIN values. The average RIN values of the analysed samples were 7.45 ± 0.13, 7.43 ± 0.15, 7.45 ± 0.10, 7.33 ± 0.15 and 3.95 ± 0.58 for the same postmortem times, respectively, indicating that RNA degradation was present at 48 h postmortem. In a similar experiment, carried out by other authors on beef cattle muscle total RNA extracted at different postmortem times, RNA was stable up to 8 days after death as indicated by intact 28S and 18S rRNA bands. Thus, differences among species or other environmental factors might affect the level of RNA degradation. In the porcine postmortem samples, qualitative assessment of GAPDH transcripts by PCR amplification of different cDNA fragments indicated that postmortem stages did not affect the possibility of analysing this housekeeping gene. Thus, postmortem porcine skeletal muscle can be an useful tissue to obtain gene expression based information.

Interferon-γ-dependent cytotoxic activation of human astrocytes and astrocytoma cells

Astrocytes and microglia become activated in a broad spectrum of inflammatory neurodegenerative diseases. Activated microglia are widely believed to be the principal source of inflammation-induced neuronal degeneration in these disorders. To investigate the neurotoxic potential of human astrocytes, we exposed them and human astrocytic U-373 MG cells to a variety of inflammatory stimulants. We then assessed the effects of their supernatants on human SH-SY5 cells. When astrocytes and U-373 MG cells were stimulated with interferon (IFN)-γ (150U/ml), their supernatants significantly reduced SH-SY5Y cell viability. Other powerful inflammatory stimulants such as lipopolysaccharide (0.5μg/ml), tumor necrosis factor-α (10ng/ml) and interleukin-1β (10ng/ml), alone or in combination, were without effect. These combinations were also unable to enhance the IFN-γ effect. The induced cytotoxicities were reversed by JAK inhibitor I, a potent and specific inhibitor of JAKs. This result indicates that the neurotoxic effect was proceeding through the IFN-γ receptor (IFNGR)-JAK-STAT intracellular pathway. To establish that the IFNGR is expressed on both cultured astrocytes and U-373 MG cells, we performed RT-PCR on total RNA extracts to identify a specific IFNGR product. We showed the protein product on these cultured cells by immunocytochemistry using an antibody to IFNGR. Finally, using human postmortem material, we showed sharp upregulation of the IFNGR on activated astrocytes in affected areas in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis. These findings suggest that activated astrocytes may become neurotoxic when stimulated by IFN-γ and may therefore exacerbate the pathology in a spectrum of neurodegenerative diseases.

Erythromycin Precipitation in Vena Femoralis: Investigation of Crystals Found in Postmortem Material of an Intensive Care Unit Patient

A case of intravenous precipitation of erythromycin is reported along with the patient history, pathologic findings, and a description of the analytical methods and results. The patient was a 75-year-old woman with a history of myocardial infarction, deep venous thrombosis, and diabetes mellitus who underwent aortic valve replacement. She developed endocarditis and recurrent episodes of urosepsis, with multiple organ failure including severe gastric retention, for which she was treated with erythromycin intravenously. She died because of refractory septic shock. Autopsy revealed aortic valve endocarditis, thrombi in the right femoral vein, arterial (nonfungal) thromboemboli in the celiac trunk, and coarse material in the right femoral vein where the tip of the central venous catheter had been located. Microscopical examination of the coarse material showed that it was birefringent crystalline material. Part of the postmortem material was analyzed in the laboratory of the department of clinical pharmacy and revealed the presence of erythromycin. Erythromycin was detected using Fourier transform infrared spectroscopy. An additional specific color test and thin-layer chromatography confirmed this finding. On the basis of the postmortem findings, patient history, and analytical-toxicologic results, we conclude that erythromycin precipitation can occur in vivo after intravenous administration in patients with impaired blood flow.

THE COMBINATION OF SILVER TECHNIQUES FOR STUDYING THE PATHOLOGY OF ALZHEIMER'S DISEASE

Alzheimer's diseaseis a progressive neurodegenerative disorder, which implicates the whole central nervous system. The hallmarks of the disease are the development of neuritic plaques and neurofibrillary tangles, the accumulation of β-amyloid in the cytoplasm of the neurons (soluble β-amyloid oligomers) and the neuropile space (insoluble amyloidal fibrils), the neuronal loss, and the devastating synaptic alterations. Despite the fact that for the identification of the plaques and tangles and for the detection of the amyloid deposits and the neuronal loss, there are specific techniques even in light microscopy, synaptic pathology can be studied only with electron microscopy or indirectly with immunohistochemistry, because several alterations in the density of proteins located in synaptic junction (drebrin, synapsin, synaptophisin) may be occurring. Thus, this article presents original Nauta method impregnating degenerating axons as well as axonic terminals in post-mortem material derived from patients suffering from Alzheimer's disease. Furthermore, the article proposes its application in combination with Golgi method and Gallyas technique for a spheroid view of the neuronal degeneration and synaptic pathology in the study of any brain region in Alzheimer's disease.

Neuropathology-for the Living and the Future

Postmortem examinations and brain-cutting sessions are the core of the training and the bases for the practice of neuropathology. Essentially all studies of human neurological diseases are based on concepts derived from the gross and microscopic examination of CNS tissues. When I began my term as Editor-in-Chief of the JNEN , outgoing Editor-in-Chief Michael N. Hart presented me with a first issue of the Journal from January 1942. In it, six of the seven original papers (on infections, trauma, multiple sclerosis, and tumors) were based on detailed gross and microscopic descriptions of CNS autopsy material. In 1981, the year I started my post-training career in neuropathology, a Letter to the Editor in these pages from Drs. Alvord and Shaw of the University of Washington addressed their concerns regarding the decline in autopsy rates and in the disappearance of the glamour and prestige formerly associated with pathologists who had the traditional last word in the classical CPC… (1). Much of what Drs. Alvord and Shaw wrote is remarkably relevant today. In that particular issue of the JNEN , six of the seven original papers also were studies based on human postmortem material. Since 1981, a great deal has been written about falling rates of autopsies in general and neuropathologic examinations in the US; the numbers continue to decline. Lack of financial incentive for …

Radial Glia Cells in the Developing Human Brain

Human radial glia (RG) share many of the features described in rodents, but also have a number of characteristics unique to the human brain. Results obtained from different mammalian species including human and non-human primates reveal differences in the involvement of RG in neurogenesis and oligodendrogenesis and in the timing of the initial expression of typical RG immunomarkers. A common problem in studying the human brain is that experimental procedures using modern molecular and genetic methods, such as in vivo transduction with retroviruses or creation of knockout or transgenic mutants, are not possible. Nevertheless, abundant and valuable information about the development of the human brain has been revealed using postmortem human material. Additionally, a combination and spectrum of in vitro techniques are used to gain knowledge about normal developmental processes in the human brain, including better understanding of RG as progenitor cells. Molecular and functional characterization of multipotent progenitors, such as RG, is important for future cell replacement therapies in neurological and psychiatric disorders, which are often resistant to conventional treatments. The protracted time of development and larger size of the human brain could provide insight into processes that may go unnoticed in the much smaller rodent cortex, which develops over a much shorter period. With that in mind, we summarize results on the role of RG in the human fetal brain. NEUROSCIENTIST 14(5):459—473, 2008. DOI: 10.1177/1073858407313512

Exploring the functional role of the CHRM2 gene in human cognition: results from a dense genotyping and brain expression study

BackgroundThe CHRM2 gene, located on the long arm of chromosome 7 (7q31-35), is involved in neuronal excitability, synaptic plasticity and feedback regulation of acetylcholine release, and has been implicated in higher cognitive processing. The aim of this study is the identification of functional (non)coding variants underlying cognitive phenotypic variation.MethodsWe previously reported an association between polymorphisms in the 5'UTR regions of the CHRM2 gene and intelligence.. However, no functional variants within this area have currently been identified. In order to identify the relevant functional variant(s), we conducted a denser coverage of SNPs, using two independent Dutch cohorts, consisting of a children's sample (N = 371 ss; mean age 12.4) and an adult sample (N= 391 ss; mean age 37.6). For all individuals standardized intelligence measures were available. Subsequently, we investigated genotype-dependent CHRM2 gene expression levels in the brain, to explore putative enhancer/inhibition activity exerted by variants within the muscarinic acetylcholinergic receptor.ResultsUsing a test of within-family association two of the previously reported variants – rs2061174, and rs324650 – were again strongly associated with intelligence (P < 0.01). A new SNP (rs2350780) showed a trend towards significance. SNP rs324650, is located within a short interspersed repeat (SINE). Although the function of short interspersed repeats remains contentious, recent research revealed potential functionality of SINE repeats in a gene-regulatory context. Gene-expression levels in post-mortem brain material, however were not dependent on rs324650 genotype.ConclusionUsing a denser coverage of SNPs in the CHRM2 gene, we confirmed the 5'UTR regions to be most interesting in the context of intelligence, and ruled out other regions of this gene. Although no correlation between genomic variants and gene expression was found, it would be interesting to examine allele-specific effects on CHRM2 transcripts expression in much more detail, for example in relation to transcripts specific halve-life and their relation to LTP and memory.