Nusinersen rescues taurine deficiency in patients with type 1 Spinal Muscular Atrophy

Background: Spinal Muscular Atrophy (SMA) is a genetic disorder resulting from deficiency of the survival motor neuron (SMN) protein. Emerging evidence indicates that SMA is associated with disruptions in neuroactive amino acid metabolism, contributing to altered neurotransmission. Taurine, the predominant inhibitory neuromodulator in the developing central nervous system (CNS), is critical for synaptic function, osmoregulation, and neuroprotection. Despite its physiological significance, the effects of SMN deficiency on taurine homeostasis and its potential role in SMA pathophysiology remain unexplored. Methods: We used high-performance liquid chromatography (HPLC) to quantify taurine in the spinal cord, brainstem, cortex, and cerebellum in SMN∆7 mice, during postnatal development. We then translate our observation into the clinic by measuring taurine concentrations in the cerebrospinal fluid (CSF) from control individuals (n = 7) and SMA patients of varying disease severity (n = 37) before and after therapy with the SMN-inducing drug Nusinersen. Results: Our data show a downregulation of taurine levels in the brainstem of SMN∆7 mice at late symptomatic stage relative to control littermates. Furthermore, we highlight a taurine reduction in the CSF of naïve SMA1 patients compared to controls. Importantly, Nusinersen treatment restored the taurine deficit in these SMA patients. Conclusions: These findings demonstrate that SMN deficiency dysregulates taurine homeostasis in the CNS of overt symptomatic mouse models and SMA1 patients. They also reveal the therapeutic efficacy of Nusinersen treatment in correcting this amino acid deficit. However, further research is needed to determine the mechanisms by which SMN deficiency causes taurine dysregulation and its potential contribution to SMA pathology.