Dysregulation of the hippocampal neuronal network by LGI1 auto-antibodies.

LGI1 is a neuronal secreted protein highly expressed in the hippocampus. Epileptic seizures and LGI1 hypo-functions have been found in both ADLTE, a genetic epileptogenic syndrome and LGI1 limbic encephalitis (LE), an autoimmune disease. Studies, based mainly on transgenic mouse models, investigated the function of LGI1 in the CNS and strangely showed that LGI1 loss of function, led to a decreased AMPA-receptors (AMPA-R) expression. Our project intends at better understanding how an altered function of LGI1 leads to epileptic seizures. To reach our goal, we infused mice with LGI1 IgG purified from the serum of patients diagnozed with LGI1 LE. Super resolution imaging revealed that LGI1 IgG reduced AMPA-R expression at the surface of inhibitory and excitatory neurons only in the dentate gyrus of the hippocampus. Complementary electrophysiological approaches indicated that despite reduced AMPA-R expression, LGI1 IgG increased the global hyperexcitability in the hippocampal neuronal network. Decreased AMPA-R expression at inhibitory neurons and the lack of LGI1 IgG effect in presence of GABA antagonist on excitability, led us to conclude that LGI1 function might be essential for the proper functioning of the overall network and orchestrate the imbalance between inhibition and excitation. Our work suggests that LGI1 IgG reduced the inhibitory network activity more significantly than the excitatory network shedding lights on the essential role of the inhibitory network to trigger epileptic seizures in patients with LGI1 LE.

Role of LGI1 protein in synaptic transmission: From physiology to pathology.

Leucine-Rich Glioma Inactivated protein 1 (LGI1) is a secreted neuronal protein highly expressed in the central nervous system and high amount are found in the hippocampus. An alteration of its function has been described in few families of patients with autosomal dominant temporal lobe epilepsy (ADLTE) or with autoimmune limbic encephalitis (LE), both characterized by epileptic seizures. Studies have shown that LGI1 plays an essential role during development, but also in neuronal excitability through an action on voltage-gated potassium Kv1.1 channels, and in synaptic transmission by regulating the surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPA-R). Over the last decade, a growing number of studies investigating LGI1 functions have been published. They aimed to improve the understanding of LGI1 function in the regulation of neuronal networks using different animal and cellular models. LGI1 appears to be a major actor of synaptic regulation by modulating trans-synaptically pre- and post-synaptic proteins. In this review, we will focus on LGI1 binding partners, "A Disintegrin And Metalloprotease (ADAM) 22 and 23", the complex they form at the synapse, and will discuss the effects of LGI1 on neuronal excitability and synaptic transmission in physiological and pathological conditions. Finally, we will highlight new insights regarding N-terminal Leucine-Rich Repeat (LRR) domain and C-terminal Epitempin repeat (EPTP) domain and their potentially distinct role in LGI1 function.

And if we had to do it all over again, would we send medical students to the emergency departments during a pandemic? Lessons learned from the COVID-19 outbreak.

The COVID-19 pandemic has led to increased staffing needs in emergency departments. The question quickly arose as to whether it was appropriate to offer medical students the opportunity to assist this staff. The dilemma stems in part from the potential impact on their psychological well-being as well as their academic and clinical performances. We sought to determine the level of anxiety of medical students during the COVID-19 outbreak, and whether it was higher among the students who chose to return to the clinical setting, especially in first-line units (i.e., emergency departments and resuscitation units). In May 2020, 1180/1502 (78.5%) undergraduate medical students at Strasbourg Medical School (France) completed a questionnaire assessing their anxiety and clinical experience. A 2018 cohort of undergraduate medical students served as the baseline. The 2020 COVID cohort had higher rates of anxiety than the 2018 cohort. This difference was specifically observed in the students who chose not to return to the clinical setting during the crisis (N = 684, 59%). At linear regression, the main factors associated with anxiety were gender (p < 0.005) and perceived clinical activity personal conditions (p < 0.001). Employment site, including COVID first-line units, was not correlated with anxiety. Working in the clinical setting during the COVID-19 outbreak is not a risk factor for anxiety in medical students. Instead, it is an active coping strategy, suggesting that there are no barriers to allowing students to return to clinical settings during a pandemic, including first-line units, in terms of their psychological well-being.