De novo TRPV4 Leu619Pro variant causes a new channelopathy characterised by giant cell lesions of the jaws and skull, skeletal abnormalities and polyneuropathy.

BACKGROUND: Pathogenic germline variants in Transient Receptor Potential Vanilloid 4 Cation Channel (TRPV4) lead to channelopathies, which are phenotypically diverse and heterogeneous disorders grossly divided in neuromuscular disorders and skeletal dysplasia. We recently reported in sporadic giant cell lesions of the jaws (GCLJs) novel, somatic, heterozygous, gain-of-function mutations in TRPV4, at Met713. METHODS: Here we report two unrelated women with a de novo germline p.Leu619Pro TRPV4 variant and an overlapping systemic disorder affecting all organs individually described in TRPV4 channelopathies. RESULTS: From an early age, both patients had several lesions of the nervous system including progressive polyneuropathy, and multiple aggressive giant cell-rich lesions of the jaws and craniofacial/skull bones, and other skeletal lesions. One patient had a relatively milder disease phenotype possibly due to postzygotic somatic mosaicism. Indeed, the TRPV4 p.Leu619Pro variant was present at a lower frequency (variant allele frequency (VAF)=21.6%) than expected for a heterozygous variant as seen in the other proband, and showed variable regional frequency in the GCLJ (VAF ranging from 42% to 10%). In silico structural analysis suggests that the gain-of-function p.Leu619Pro alters the ion channel activity leading to constitutive ion leakage. CONCLUSION: Our findings define a novel polysystemic syndrome due to germline TRPV4 p.Leu619Pro and further extend the spectrum of TRPV4 channelopathies. They further highlight the convergence of TRPV4 mutations on different organ systems leading to complex phenotypes which are further mitigated by possible post-zygotic mosaicism. Treatment of this disorder is challenging, and surgical intervention of the GCLJ worsens the lesions, suggesting the future use of MEK inhibitors and TRPV4 antagonists as therapeutic modalities for unmet clinical needs.

Two decades of research towards a potential first anti-epileptic drug.

The basic mechanisms by which brain insults, such as trauma, stroke or status epilepticus produce epilepsy are not completely understood, and effective preventive measures and treatment are still not available in the clinical setting. Over the last 2 decades we have conducted several studies with animal models of epilepsy (rodents and non-human primates) and demonstrated that drugs that modify neuronal plastic processes, such as anticholinergic agents (e.g., antimuscarinic compounds), if administered soon after brain injury and over a period of 10-20 days, have the potential to modify the natural course of post-traumatic epilepsy. To that end treatment with scopolamine showed promising results as a candidate agent in both the pilocarpine and kainate models. We then showed that biperiden, yet another cholinergic antagonist acting in the muscarinic receptor, that is widely used to treat Parkinson's disease, also decreased the incidence and intensity of spontaneous epileptic seizures, delaying their appearance in the pilocarpine model of epilepsy. In other words, biperiden showed to be a potential candidate to be further investigated as an antiepileptogenic agent. Accordingly, we tested the safety of biperiden in a small group of patients (as a small phase II safety assessment) and confirmed its safety in the context of traumatic brain injury (TBI). Now, we provide information on our ongoing project to evaluate the efficacy of biperiden in preventing the development of epilepsy in patients that suffered TBI, in a double blind, randomized, placebo-controlled trial.