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Eines der übergeordneten Ziele neurowissenschaftlicher Grundlagenforschung ist es, die Pathomechanismen neuropsychiatrischer Erkrankungsbilder besser zu verstehen. Als Erklärungsmodell für einige dieser Erkrankungen dient unter anderem ein gestörtes Verhältnis zwischen Exzitation und Inhibition im Gehirn. Synaptische Strukturproteine sind wichtige Modulatoren dieses Verhältnisses. Für eine unbeeinträchtigte inhibitorische synaptische Transmission spielt das postsynaptische Zelladhäsionsprotein Neuroligin 2 eine maßgebliche Rolle, um das Gleichgewicht zwischen Exzitation und Inhibition aufrechtzuerhalten. Neuroligin 2 ist an der inhibitorischen Synapse lokalisiert und beeinflusst die Entwicklung, Reifung und Funktion dieser Synapse. Die klinische Relevanz von Neuroligin 2 wurde bereits bei zahlreichen Erkrankungsbildern wie Schizophrenie, Depression oder Epilepsie im Rahmen von Studien nachgewiesen. Um das Verhältnis zwischen Exzitation und Inhibition in vivo sowie Mechanismen der synaptischen Übertragung und Plastizität zu untersuchen, hat sich die Ableitung von Feldpotentialen im Gyrus Dentatus des Hippocampus etabliert. Im Neuroligin 2 Knockout Mausmodell konnte bereits gezeigt werden, dass eine pränatale Deletion dieses Proteins eine stark erhöhte Erregbarkeit der Körnerzellen und eine verminderte GABAerge Netzwerkinhibition im Gyrus Dentatus in vivo zur Folge hat.
Unklar blieb bisher, ob diese durch den konventionellen Neuroligin 2 Knockout (pränatal) hervorgerufenen Netzwerkveränderungen alleine auf das Fehlen dieses Proteins zurückzuführen sind oder durch eine zusätzliche Beeinträchtigung der Hirnentwicklung hervorgerufen werden. Ziel dieser Dissertation ist es deshalb, die Rolle von Neuroligin 2 im Gyrus Dentatus durch einen induzierten Knockout in adulten Mäusen (postnatal) unabhängig von einem möglichen Entwicklungseffekt zu klären.
Dazu wurde im ersten methodischen Schritt dieser Dissertation durch orale Tamoxifen-Gabe eine zeitspezifische konditionale Eliminierung von Neuroligin 2 in genetisch modifizierten, adulten Mäusen erzielt. Im Anschluss an diese konditionale Eliminierung wurde die synaptische Transmission, Plastizität sowie neuronale Erregbarkeit von Körnerzellen im Gyrus Dentatus mittels elektrophysiologischer Experimente untersucht. Hierzu wurde zunächst der Tractus Perforans und die Körnerzellschicht durch stereotaktische Chirurgie in anästhesierten Mäusen lokalisiert. Anschließend wurde eine Stimulation des Tractus Perforans sowie eine Ableitung von Feldpotentialen im Gyrus Dentatus durchgeführt. Um die Erregbarkeit der Körnerzellen, die synaptische Transmission, Kurz- und Langzeitplastizität sowie Netzwerkinhibition im Gyrus Dentatus zu analysieren, wurden unterschiedliche Stimulationsprotokolle verwendet. Im Anschluss an die elektrophysiologischen Experimente wurden die Hippocampi beidseitig entnommen, konserviert und später einer Proteinquantifizierung von Neuroligin 2 mittels Western-Blotting unterzogen.
Die Ergebnisse zeigten ein signifikant verringertes Proteinlevel von Neuroligin 2 auf 41,07% im Hippocampus von konditionalen Neuroligin 2 Knockout Mäusen. Unter dieser Reduktion von Neuroligin 2 in adulten Mäusen war die in vivo Erregbarkeit der Körnerzellen des Gyrus Dentatus sowie GABAerge Netzwerkinhibition weitgehend unbeeinträchtigt und die signifikanten Beobachtungen des konventionellen Knockout Modells ließen sich nicht reproduzieren. Aufgrund der unvollständigen Proteinreduktion lässt sich jedoch nicht abschließend beurteilen, ob die Restmenge den elektrophysiologischen Effekt kompensiert oder ob die im konventionellen Neuroligin 2 Knockout Modell beobachteten Effekte auf eine ausschließliche Rolle von Neuroligin 2 in der Hirnentwicklungsperiode zurückzuführen sind. Kürzlich veröffentlichte Daten zeigten allerdings, dass die postnatale Deletion von Neuroligin 2 in anderen Hirnregionen zu einer verminderten Netzwerkinhibition führt.
Neben der hier verwendeten in vivo Methodik ist eine Ergänzung von Untersuchungen in nicht-anästhesierten Tieren sowie Messungen einzelner Zellen durch whole-cell patch-clamp Untersuchungen in vitro oder in vivo zu erwägen. Es sollte dabei auf eine konditionale Proteineliminierung geachtet werden, damit mögliche Kompensationsmechanismen weitgehend ausgeschlossen werden können. Eine weiterführende immunhistochemische Bildgebung der Hippocampuspräparate, wie sie im konventionellen Knockout durchgeführt wurde, könnte sich hierbei ebenso als aufschlussreich für die Funktion von Neuroligin 2 im Hippocampus des adulten Tieres erweisen.
HLA-DRB1 and HLA-DQB1 genetic diversity modulates response to lithium in bipolar affective disorders
(2021)
Bipolar affective disorder (BD) is a severe psychiatric illness, for which lithium (Li) is the gold standard for acute and maintenance therapies. The therapeutic response to Li in BD is heterogeneous and reliable biomarkers allowing patients stratification are still needed. A GWAS performed by the International Consortium on Lithium Genetics (ConLiGen) has recently identified genetic markers associated with treatment responses to Li in the human leukocyte antigens (HLA) region. To better understand the molecular mechanisms underlying this association, we have genetically imputed the classical alleles of the HLA region in the European patients of the ConLiGen cohort. We found our best signal for amino-acid variants belonging to the HLA-DRB1*11:01 classical allele, associated with a better response to Li (p < 1 × 10−3; FDR < 0.09 in the recessive model). Alanine or Leucine at position 74 of the HLA-DRB1 heavy chain was associated with a good response while Arginine or Glutamic acid with a poor response. As these variants have been implicated in common inflammatory/autoimmune processes, our findings strongly suggest that HLA-mediated low inflammatory background may contribute to the efficient response to Li in BD patients, while an inflammatory status overriding Li anti-inflammatory properties would favor a weak response.
Bipolar disorder (BD) is a genetically complex mental illness characterized by severe oscillations of mood and behavior. Genome-wide association studies (GWAS) have identified several risk loci that together account for a small portion of the heritability. To identify additional risk loci, we performed a two-stage meta-analysis of >9 million genetic variants in 9,784 bipolar disorder patients and 30,471 controls, the largest GWAS of BD to date. In this study, to increase power we used ~2,000 lithium-treated cases with a long-term diagnosis of BD from the Consortium on Lithium Genetics, excess controls, and analytic methods optimized for markers on the Xchromosome. In addition to four known loci, results revealed genome-wide significant associations at two novel loci: an intergenic region on 9p21.3 (rs12553324, p = 5.87×10-9; odds ratio = 1.12) and markers within ERBB2 (rs2517959, p = 4.53×10-9; odds ratio = 1.13). No significant X-chromosome associations were detected and X-linked markers explained very little BD heritability. The results add to a growing list of common autosomal variants involved in BD and illustrate the power of comparing well-characterized cases to an excess of controls in GWAS.
Treatment‐related complications contribute substantially to morbidity and mortality in acute myeloid leukemia (AML) patients undergoing induction chemotherapy. Although AML patients are susceptible to fluid overload (FO) (e.g., in the context of chemotherapy protocols, during sepsis treatment or to prevent tumor lysis syndrome), little attention has been paid to its role in AML patients undergoing induction chemotherapy. AML patients receiving induction chemotherapy between 2014 and 2019 were included in this study. FO was defined as ≥5% weight gain on day 7 of induction chemotherapy compared to baseline weight determined on the day of admission. We found FO in 23 (12%) of 187 AML patients undergoing induction chemotherapy. Application of >100 ml crystalloid fluids/kg body weight until day 7 of induction chemotherapy was identified as an independent risk factor for FO. AML patients with FO suffered from a significantly increased 90-day mortality rate and FO was demonstrated as an independent risk factor for 90-day mortality. Our data suggests an individualized, weight-adjusted calculation of crystalloid fluids in order to prevent FO-related morbidity and mortality in AML patients during induction chemotherapy. Prospective trials are required to determine the adequate fluid management in this patient population.
Background: Rare diseases are, by definition, very serious and chronic diseases with a high negative impact on quality of life. Approximately 350 million people worldwide live with rare diseases. The resulting high disease burden triggers health information search, but helpful, high-quality, and up-to-date information is often hard to find. Therefore, the improvement of health information provision has been integrated in many national plans for rare diseases, discussing the telephone as one access option. In this context, this study examines the need for a telephone service offering information for people affected by rare diseases, their relatives, and physicians.
Methods: In total, 107 individuals participated in a qualitative interview study conducted in Germany. Sixty-eight individuals suffering from a rare disease or related to somebody with rare diseases and 39 health care professionals took part. Individual interviews were conducted using a standardized semi-structured questionnaire. Interviews were analysed using the qualitative content analysis, triangulating patients, relatives, and health care professionals. The fulfilment of qualitative data processing standards has been controlled for.
Results: Out of 68 patients and relatives and 39 physicians, 52 and 18, respectively, advocated for the establishment of a rare diseases telephone service. Interviewees expected a helpline to include expert staffing, personal contact, good availability, low technical barriers, medical and psychosocial topics of counselling, guidance in reducing information chaos, and referrals. Health care professionals highlighted the importance of medical topics of counselling—in particular, differential diagnostics—and referrals.
Conclusions: Therefore, the need for a national rare diseases helpline was confirmed in this study. Due to limited financial resources, existing offers should be adapted in a stepwise procedure in accordance with the identified attributes.
Background: Recently, public and political interest has focused on people living with rare diseases and their health concerns. Due to the large number of different types of rare diseases and the sizable number of patients, taking action to improve the life of those affected is gaining importance. In 2013, the federal government of Germany adopted a national action plan for rare diseases, including the call to establish a central information portal on rare diseases (Zentrales Informationsportal über seltene Erkrankungen, ZIPSE).
Objective: The objective of this study, therefore, was to conduct scientific research on how such a portal must be designed to meet the needs of patients, their families, and medical professionals, and to provide high-quality information for information seekers.
Methods: We chose a 3-step procedure to develop a needs-based prototype of a central information portal. In the first step, we determined the information needs of patients with rare diseases, their relatives, and health care professionals by means of qualitative interviews and their content-analytical evaluation. On the basis of this, we developed the basic structure of the portal. In the second step, we identified quality criteria for websites on rare diseases to ensure that the information linked with ZIPSE meets the quality demands. Therefore, we gathered existing criteria catalogs and discussed them in an expert workshop. In the third step, we implemented and tested the developed prototypical information portal.
Results: A portal page was configured and made accessible on the Web. The structure of ZIPSE was based on the findings from 108 qualitative interviews with patients, their relatives, and health care professionals, through which numerous information needs were identified. We placed particularly important areas of information, such as symptoms, therapy, research, and advisory services, on the start page. Moreover, we defined 13 quality criteria, referring to factors such as author information, creation date, and privacy, enabling links with high-quality information. Moreover, 19 users tested all the developed routines based on usability and comprehensibility. Subsequently, we improved the visual presentation of search results and other important search functions.
Conclusions: The implemented information portal, ZIPSE, provides high-quality information on rare diseases from a central point of access. By integrating the targeted groups as well as different experts on medical information during the construction, the website can assure an improved search for information for users. ZIPSE can also serve as a model for other Web-based information systems in the field of rare diseases.
Registered Report Identifier: RR1-10.2196/7425.
Multiplex families with a high prevalence of a psychiatric disorder are often examined to identify rare genetic variants with large effect sizes. In the present study, we analysed whether the risk for bipolar disorder (BD) in BD multiplex families is influenced by common genetic variants. Furthermore, we investigated whether this risk is conferred mainly by BD-specific risk variants or by variants also associated with the susceptibility to schizophrenia or major depression. In total, 395 individuals from 33 Andalusian BD multiplex families as well as 438 subjects from an independent, sporadic BD case-control cohort were analysed. Polygenic risk scores (PRS) for BD, schizophrenia, and major depression were calculated and compared between the cohorts. Both the familial BD cases and unaffected family members had significantly higher PRS for all three psychiatric disorders than the independent controls, suggesting a high baseline risk for several psychiatric disorders in the families. Moreover, familial BD cases showed significantly higher BD PRS than unaffected family members and sporadic BD cases. A plausible hypothesis is that, in multiplex families with a general increase in risk for psychiatric disease, BD development is attributable to a high burden of common variants that confer a specific risk for BD. The present analyses, therefore, demonstrated that common genetic risk variants for psychiatric disorders are likely to contribute to the high incidence of affective psychiatric disorders in the multiplex families. The PRS explained only part of the observed phenotypic variance and rare variants might have also contributed to disease development.
Multiplex families with a high prevalence of a psychiatric disorder are often examined to identify rare genetic variants with large effect sizes. In the present study, we analysed whether the risk for bipolar disorder (BD) in BD multiplex families is influenced by common genetic variants. Furthermore, we investigated whether this risk is conferred mainly by BD-specific risk variants or by variants also associated with the susceptibility to schizophrenia or major depression. In total, 395 individuals from 33 Andalusian BD multiplex families (166 BD, 78 major depressive disorder, 151 unaffected) as well as 438 subjects from an independent, BD case/control cohort (161 unrelated BD, 277 unrelated controls) were analysed. Polygenic risk scores (PRS) for BD, schizophrenia (SCZ), and major depression were calculated and compared between the cohorts. Both the familial BD cases and unaffected family members had higher PRS for all three psychiatric disorders than the independent controls, with BD and SCZ being significant after correction for multiple testing, suggesting a high baseline risk for several psychiatric disorders in the families. Moreover, familial BD cases showed significantly higher BD PRS than unaffected family members and unrelated BD cases. A plausible hypothesis is that, in multiplex families with a general increase in risk for psychiatric disease, BD development is attributable to a high burden of common variants that confer a specific risk for BD. The present analyses demonstrated that common genetic risk variants for psychiatric disorders are likely to contribute to the high incidence of affective psychiatric disorders in the multiplex families. However, the PRS explained only part of the observed phenotypic variance, and rare variants might have also contributed to disease development.
No association between Parkinson disease and autoantibodies against NMDA-type glutamate receptors
(2019)
Background: IgG-class autoantibodies to N-Methyl-D-Aspartate (NMDA)-type glutamate receptors define a novel entity of autoimmune encephalitis. Studies examining the prevalence of NMDA IgA/IgM antibodies in patients with Parkinson disease with/without dementia produced conflicting results. We measured NMDA antibodies in a large, well phenotyped sample of Parkinson patients without and with cognitive impairment (n = 296) and controls (n = 295) free of neuropsychiatric disease. Detailed phenotyping and large numbers allowed statistically meaningful correlation of antibody status with diagnostic subgroups as well as quantitative indicators of disease severity and cognitive impairment.
Methods: NMDA antibodies were analysed in the serum of patients and controls using well established validated assays. We used anti-NMDA antibody positivity as the main independent variable and correlated it with disease status and phenotypic characteristics.
Results: The frequency of NMDA IgA/IgM antibodies was lower in Parkinson patients (13%) than in controls (22%) and higher than in previous studies in both groups. NMDA IgA/IgM antibodies were neither significantly associated with diagnostic subclasses of Parkinson disease according to cognitive impairment, nor with quantitative indicators of disease severity and cognitive impairment. A positive NMDA antibody status was positively correlated with age in controls but not in Parkinson patients.
Conclusion: It is unlikely albeit not impossible that NMDA antibodies play a significant role in the pathogenesis or progression of Parkinson disease e.g. to Parkinson disease with dementia, while NMDA IgG antibodies define a separate disease of its own.