Inducible Slc7a7 Knockout Mouse Model Recapitulates Lysinuric Protein Intolerance Disease.

Lysinuric protein intolerance (LPI) is a rare autosomal disease caused by defective cationic amino acid (CAA) transport due to mutations in SLC7A7, which encodes for the y+LAT1 transporter. LPI patients suffer from a wide variety of symptoms, which range from failure to thrive, hyperammonemia, and nephropathy to pulmonar alveolar proteinosis (PAP), a potentially life-threatening complication. Hyperammonemia is currently prevented by citrulline supplementation. However, the full impact of this treatment is not completely understood. In contrast, there is no defined therapy for the multiple reported complications of LPI, including PAP, for which bronchoalveolar lavages do not prevent progression of the disease. The lack of a viable LPI model prompted us to generate a tamoxifen-inducible Slc7a7 knockout mouse (Slc7a7-/-). The Slc7a7-/- model resembles the human LPI phenotype, including malabsorption and impaired reabsorption of CAA, hypoargininemia and hyperammonemia. Interestingly, the Slc7a7-/- mice also develops PAP and neurological impairment. We observed that citrulline treatment improves the metabolic derangement and survival. On the basis of our findings, the Slc7a7-/- model emerges as a promising tool to further study the complexity of LPI, including its immune-like complications, and to design evidence-based therapies to halt its progression.

Arginase 1 deficiency presenting as complicated hereditary spastic paraplegia.

INTRODUCTION: Argininemia or arginase deficiency is a metabolic disorder caused by pathogenic variants in ARG1 and consists of a variable association of progressive spastic paraplegia, intellectual disability, and seizures. Hereditary spastic paraplegia (HSP) is a group of inherited diseases whose main feature is a progressive gait disorder characterized by lower limb spasticity. This study presents 7 patients with arginase 1 deficiency from 6 different families, all with an initial diagnosis of complicated HSP. METHODS: We evaluated the clinical data of 7 patients belonging to six independent families who were diagnosed with hyperargininemia in a neurogenetics outpatient clinic. RESULTS: All patients had lower limb spasticity and six had global developmental delay. Five individuals had intellectual disability and two had epilepsy. Psychiatric abnormalities were seen in two patients. In two participants of this study, MRI disclosed thinning of the corpus callosum. Molecular diagnosis was made by whole exome sequencing. All variants were present in homozygosis; we identified two novel missense variants, one novel frameshift variant, and one previously published missense variant. DISCUSSION: Clinical diagnosis of early onset complicated hereditary spastic paraplegia was made in all patients. Two patients were initially suspected of having SPG11 due to thinning of the corpus callosum. As argininemia may present with a highly penetrant phenotype of spastic paraplegia associated with additional symptoms, this disease may represent a specific entity amongst the complicated HSPs.