A multicenter cross-sectional French study of the impact of COVID-19 on neuromuscular diseases.

BACKGROUND: Due to their health condition, patients with neuromuscular diseases (NMD) are at greater risk of developing serious complications with COVID-19. The objective of this study was to analyze the prevalence of COVID-19 among NMD patients and the risk factors for its impact and severity during the first wave of the pandemic. Clinical data were collected from NMD-COVID-19 patients, between March 25, 2020 and May 11, 2020 in an anonymous survey carried out by expert physicians from the French Health Care Network Filnemus. RESULTS: Physicians reported 84 patients, including: 34 with myasthenia gravis, 27 with myopathy and 23 with neuropathy. COVID-19 had no effect on NMD for 48 (58%) patients and 48 (58%) patients developed low COVID-19 severity. COVID-19 caused the death of 9 (11%) NMD patients. Diabetic patients were at greater risk of dying. Patients with diabetes, hypertension or severe forms of NMD had a higher risk of developing a moderate or severe form of COVID-19. In our cohort, corticosteroids and other immunosuppressants were not significantly associated with higher COVID-19 severity for acquired NMD. CONCLUSION: During this period, a small percentage of French NMD patients was affected by COVID-19 compared to the general French population and COVID-19 had a limited short-term effect on them. Diabetes, hypertension and a severe degree of NMD were identified as risk factors of unfavorable outcome following COVID-19. Conversely, in our cohort of patients with acquired NMD, corticosteroids or other immunosuppressants did not appear to be risk factors for more severe COVID-19.

Impaired regulation of KCC2 phosphorylation leads to neuronal network dysfunction and neurodevelopmental pathology.

KCC2 is a vital neuronal K+/Cl- cotransporter that is implicated in the etiology of numerous neurological diseases. In normal cells, KCC2 undergoes developmental dephosphorylation at Thr906 and Thr1007 We engineered mice with heterozygous phosphomimetic mutations T906E and T1007E (KCC2E/+ ) to prevent the normal developmental dephosphorylation of these sites. Immature (postnatal day 15) but not juvenile (postnatal day 30) KCC2E/+ mice exhibited altered GABAergic inhibition, an increased glutamate/GABA synaptic ratio, and greater susceptibility to seizure. KCC2E/+ mice also had abnormal ultrasonic vocalizations at postnatal days 10 to 12 and impaired social behavior at postnatal day 60. Postnatal bumetanide treatment restored network activity by postnatal day 15 but failed to restore social behavior by postnatal day 60. Our data indicate that posttranslational KCC2 regulation controls the GABAergic developmental sequence in vivo, indicating that deregulation of KCC2 could be a risk factor for the emergence of neurological pathology.

Developmental Switch of Leptin Action on Network Driven Activity in the Neonatal Rat Hippocampus.

The adipose-derived circulating hormone leptin plays a pivotal role in the control of energy balance and body weight. Sound data indicate that this hormone also acts as an important developmental signal impacting a number of brain regions during fetal and postnatal stages. Leptin levels surge during the two first postnatal weeks of life in rodents. This period is characterized by the presence of early network driven activity in the immature hippocampus, the so-called Giant Depolarizing Potentials (GDPs). GDPs are thought to contribute to the wiring of the hippocampal network. We therefore tested the effect of leptin on GDPs. Leptin increased GDPs frequency between the postnatal days (P) 1 and 3 via a calcium/Calmodulin-dependent kinase (CaMK) and extracellular signal-related kinase (ERK) dependent pathways. Between P6 and P7, leptin inhibited the frequency of GDPs through the activation of large conductance Ca2+ activated K+ (BK) channels driven by a phosphoinositol-3 kinase (PI3K) dependent pathway. These results show that leptin exerts a bi-directional and age-dependent control of GDPs and extends the scope of leptin's action in the developing brain.

Molecular cloning and biochemical characterization of two cation chloride cotransporter subfamily members of Hydra vulgaris.

Cation Chloride Cotransporters (CCCs) comprise secondary active membrane proteins mainly mediating the symport of cations (Na+, K+) coupled with chloride (Cl-). They are divided into K+-Cl- outward transporters (KCCs), the Na+-K+-Cl- (NKCCs) and Na+-Cl- (NCCs) inward transporters, the cation chloride cotransporter interacting protein CIP1, and the polyamine transporter CCC9. KCCs and N(K)CCs are established in the genome since eukaryotes and metazoans, respectively. Most of the physiological and functional data were obtained from vertebrate species. To get insights into the basal functional properties of KCCs and N(K)CCs in the metazoan lineage, we cloned and characterized KCC and N(K)CC from the cnidarian Hydra vulgaris. HvKCC is composed of 1,032 amino-acid residues. Functional analyses revealed that hvKCC mediates a Na+-independent, Cl- and K+ (Tl+)-dependent cotransport. The classification of hvKCC as a functional K-Cl cotransporter is furthermore supported by phylogenetic analyses and a similar structural organization. Interestingly, recently obtained physiological analyses indicate a role of cnidarian KCCs in hyposmotic volume regulation of nematocytes. HvN(K)CC is composed of 965 amino-acid residues. Phylogenetic analyses and structural organization suggest that hvN(K)CC is a member of the N(K)CC subfamily. However, no inorganic ion cotransport function could be detected using different buffer conditions. Thus, hvN(K)CC is a N(K)CC subfamily member without a detectable inorganic ion cotransporter function. Taken together, the data identify two non-bilaterian solute carrier 12 (SLC12) gene family members, thereby paving the way for a better understanding of the evolutionary paths of this important cotransporter family.

WNK1-regulated inhibitory phosphorylation of the KCC2 cotransporter maintains the depolarizing action of GABA in immature neurons.

Activation of Cl(-)-permeable γ-aminobutyric acid type A (GABAA) receptors elicits synaptic inhibition in mature neurons but excitation in immature neurons. This developmental "switch" in the GABA function depends on a postnatal decrease in intraneuronal Cl(-) concentration mediated by KCC2, a Cl(-)-extruding K(+)-Cl(-) cotransporter. We showed that the serine-threonine kinase WNK1 [with no lysine (K)] forms a physical complex with KCC2 in the developing mouse brain. Dominant-negative mutation, genetic depletion, or chemical inhibition of WNK1 in immature neurons triggered a hyperpolarizing shift in GABA activity by enhancing KCC2-mediated Cl(-) extrusion. This increase in KCC2 activity resulted from reduced inhibitory phosphorylation of KCC2 at two C-terminal threonines, Thr(906) and Thr(1007). Phosphorylation of both Thr(906) and Thr(1007) was increased in immature versus mature neurons. Together, these data provide insight into the mechanism regulating Cl(-) homeostasis in immature neurons, and suggest that WNK1-regulated changes in KCC2 phosphorylation contribute to the developmental excitatory-to-inhibitory GABA sequence.