TY - JOUR A1 - Horn, Michael A1 - Baumann, Reto A1 - Pereira, Jorge A. A1 - Sidiropoulos, Páris N. M. A1 - Somandin, Christian A1 - Welzl, Hans A1 - Stendel, Claudia A1 - Lühmann, Tessa A1 - Wessig, Carsten A1 - Toyka, Klaus V. A1 - Relvas, João B. A1 - Senderek, Jan A1 - Suter, Ueli T1 - Myelin is dependent on the Charcot–Marie–Tooth Type 4H disease culprit protein FRABIN/FGD4 in Schwann cells JF - Brain N2 - Studying the function and malfunction of genes and proteins associated with inherited forms of peripheral neuropathies has provided multiple clues to our understanding of myelinated nerves in health and disease. Here, we have generated a mouse model for the peripheral neuropathy Charcot–Marie–Tooth disease type 4H by constitutively disrupting the mouse orthologue of the suspected culprit gene FGD4 that encodes the small RhoGTPase Cdc42-guanine nucleotide exchange factor Frabin. Lack of Frabin/Fgd4 causes dysmyelination in mice in early peripheral nerve development, followed by profound myelin abnormalities and demyelination at later stages. At the age of 60 weeks, this was accompanied by electrophysiological deficits. By crossing mice carrying alleles of Frabin/Fgd4 flanked by loxP sequences with animals expressing Cre recombinase in a cell type-specific manner, we show that Schwann cell-autonomous Frabin/Fgd4 function is essential for proper myelination without detectable primary contributions from neurons. Deletion of Frabin/Fgd4 in Schwann cells of fully myelinated nerve fibres revealed that this protein is not only required for correct nerve development but also for accurate myelin maintenance. Moreover, we established that correct activation of Cdc42 is dependent on Frabin/Fgd4 function in healthy peripheral nerves. Genetic disruption of Cdc42 in Schwann cells of adult myelinated nerves resulted in myelin alterations similar to those observed in Frabin/Fgd4-deficient mice, indicating that Cdc42 and the Frabin/Fgd4–Cdc42 axis are critical for myelin homeostasis. In line with known regulatory roles of Cdc42, we found that Frabin/Fgd4 regulates Schwann cell endocytosis, a process that is increasingly recognized as a relevant mechanism in peripheral nerve pathophysiology. Taken together, our results indicate that regulation of Cdc42 by Frabin/Fgd4 in Schwann cells is critical for the structure and function of the peripheral nervous system. In particular, this regulatory link is continuously required in adult fully myelinated nerve fibres. Thus, mechanisms regulated by Frabin/Fgd4–Cdc42 are promising targets that can help to identify additional regulators of myelin development and homeostasis, which may crucially contribute also to malfunctions in different types of peripheral neuropathies. KW - Frabin/Fgd4 KW - myelination KW - hereditary motor and sensory neuropathy KW - Charcot–Marie–Tooth disease KW - Rho-GTPase Cdc42 Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-125390 VL - 135 ER - TY - JOUR A1 - Schischlevskij, Pavel A1 - Cordts, Isabell A1 - Günther, René A1 - Stolte, Benjamin A1 - Zeller, Daniel A1 - Schröter, Carsten A1 - Weyen, Ute A1 - Regensburger, Martin A1 - Wolf, Joachim A1 - Schneider, Ilka A1 - Hermann, Andreas A1 - Metelmann, Moritz A1 - Kohl, Zacharias A1 - Linker, Ralf A. A1 - Koch, Jan Christoph A1 - Stendel, Claudia A1 - Müschen, Lars H. A1 - Osmanovic, Alma A1 - Binz, Camilla A1 - Klopstock, Thomas A1 - Dorst, Johannes A1 - Ludolph, Albert C. A1 - Boentert, Matthias A1 - Hagenacker, Tim A1 - Deschauer, Marcus A1 - Lingor, Paul A1 - Petri, Susanne A1 - Schreiber-Katz, Olivia T1 - Informal caregiving in amyotrophic lateral sclerosis (ALS): a high caregiver burden and drastic consequences on caregivers' lives JF - Brain Sciences N2 - Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that causes progressive autonomy loss and need for care. This does not only affect patients themselves, but also the patients’ informal caregivers (CGs) in their health, personal and professional lives. The big efforts of this multi-center study were not only to evaluate the caregivers' burden and to identify its predictors, but it also should provide a specific understanding of the needs of ALS patients' CGs and fill the gap of knowledge on their personal and work lives. Using standardized questionnaires, primary data from patients and their main informal CGs (n = 249) were collected. Patients' functional status and disease severity were evaluated using the Barthel Index, the revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) and the King’s Stages for ALS. The caregivers' burden was recorded by the Zarit Burden Interview (ZBI). Comorbid anxiety and depression of caregivers were assessed by the Hospital Anxiety and Depression Scale. Additionally, the EuroQol Five Dimension Five Level Scale evaluated their health-related quality of life. The caregivers' burden was high (mean ZBI = 26/88, 0 = no burden, ≥24 = highly burdened) and correlated with patients' functional status (r\(_p\) = −0.555, p < 0.001, n = 242). It was influenced by the CGs' own mental health issues due to caregiving (+11.36, 95% CI [6.84; 15.87], p < 0.001), patients' wheelchair dependency (+9.30, 95% CI [5.94; 12.66], p < 0.001) and was interrelated with the CGs' depression (r\(_p\) = 0.627, p < 0.001, n = 234), anxiety (r\(_p\) = 0.550, p < 0.001, n = 234), and poorer physical condition (r\(_p\) = −0.362, p < 0.001, n = 237). Moreover, female CGs showed symptoms of anxiety more often, which also correlated with the patients' impairment in daily routine (r\(_s\) = −0.280, p < 0.001, n = 169). As increasing disease severity, along with decreasing autonomy, was the main predictor of caregiver burden and showed to create relevant (negative) implications on CGs' lives, patient care and supportive therapies should address this issue. Moreover, in order to preserve the mental and physical health of the CGs, new concepts of care have to focus on both, on not only patients but also their CGs and gender-associated specific issues. As caregiving in ALS also significantly influences the socioeconomic status by restrictions in CGs' work lives and income, and the main reported needs being lack of psychological support and a high bureaucracy, the situation of CGs needs more attention. Apart from their own multi-disciplinary medical and psychological care, more support in care and patient management issues is required. KW - amyotrophic lateral sclerosis (ALS) KW - informal caregiving KW - caregiver burden KW - functional status KW - decreasing autonomy KW - depression KW - anxiety KW - health-related quality of life KW - socioeconomic status KW - psychological support Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-240981 SN - 2076-3425 VL - 11 IS - 6 ER -