The growing research toolbox for SLC13A5 citrate transporter disorder: a rare disease with animal models, cell lines, an ongoing Natural History Study and an engaged patient advocacy organization.

ABSTRACT

TESS Research Foundation (TESS) is a patient-led nonprofit organization seeking to understand the basic biology and clinical impact of pathogenic variants in the SLC13A5 gene. TESS aims to improve the fundamental understanding of citrate's role in the brain, and ultimately identify treatments and cures for the associated disease. TESS identifies, organizes, and develops collaboration between researchers, patients, clinicians, and the pharmaceutical industry to improve the lives of those suffering from SLC13A5 citrate transport disorder. TESS and its partners have developed multiple molecular tools, cellular and animal models, and taken the first steps toward drug discovery and development for this disease. However, much remains to be done to improve our understanding of the disorder associated with SLC13A5 variants and identify effective treatments for this devastating disease. Here, we describe the available SLC13A5 resources from the community of experts, to foundational tools, to in vivo and in vitro tools, and discuss unanswered research questions needed to move closer to a cure.

Overview of research in SLC13A5 citrate transporter disorder SLC13A5 citrate transporter disorder is an ultra-rare, neurodevelopmental disorder that severely impacts cognition and motor control. It is characterized by frequent, intractable seizures that develop hours or days after birth, low tone, global developmental delay, a unique, varied, and difficult to categorize movement disorder, limited expressive verbal capabilities, tooth abnormalities, and increased citrate in both the CNS and serum. Seizures are frequently medically intractable, patients are often on multiple antiseizure medications and have frequent emergency room visits and hospitalizations for status epilepticus. SLC13A5 citrate transporter disorder is caused by mutations in the SLC13A5 gene which encodes a sodium-dependent citrate transporter, NaCT. NaCT is responsible for transporting citrate, a key molecule in cellular metabolism, from the extracellular space into cells, especially in the central nervous system and the liver. NaCT has been extensively studied in multiple animal models and affects lifespan and loss of some transporter activity actually improves metabolic syndrome in all animal species tested so far while causing mild neurological dysfunction in rodents. Although not definitively proven, it is presumed that loss of neuronal cell citrate transporter activity in the brain is the cause of seizures. Since the discovery of the disorder in 2014, there has been a rapid expansion in characterization of the disease. This has been aided by development of multiple models and molecular tools for studying wild type and mutant SLC13A5 making it a tractable candidate for therapeutic development. TESS Research Foundation is dedicated to driving SLC13A5 research and supporting children and families living with the disorder. Here, we describe the available SLC13A5 resources from the community of experts, to foundational tools, to in vivo and in vitro tools, and discuss unanswered research questions needed to move closer to a cure.