Diseases of the Synaptic Vesicle: A Potential New Group of Neurometabolic Disorders Affecting Neurotransmission.

The general concept of inborn error of metabolism is currently evolving into the interface between classical biochemistry and cellular biology. Basic neuroscience is providing increasing knowledge about the mechanisms of neurotransmission and novel related disorders are being described. There is a necessity of updating the classic concept of "inborn error of neurotransmitters (NT)" that considers mainly defects of synthesis and catabolism and transport of low weight NT molecules. Monogenic defects of the synaptic vesicle (SV), and especially those affecting the SV cycle are a potential new group of NT disorders since they end up in abnormal NT turnover and release. The most common clinical manifestations include epilepsy, intellectual disability, autism and movement disorders, and are in the continuum symptoms of synaptopathies. Interestingly, brain malformations and neurodegenerative conditions are also present within SV diseases. Metabolomics, proteomics, and other -omic techniques probably will provide biomarkers and contribute to therapeutic targets in the future.

Comunicación neuronal y metabolismo sináptico en epilepsia infantil / Neuronal communication and synaptic metabolism in childhood epilepsy

Introducción. Los conocimientos que la neurociencia básica y el neurometabolismo están aportando en epilepsia pediátrica, y en concreto en mecanismos de comunicación sináptica, crecen rápidamente. Existe, no obstante, una desconexión entre estos avances y una visión que los integre de manera global y en la práctica clínica y terapéutica. Objetivos. Ofrecer una visión integradora de los diferentes mecanismos moleculares y metabólicos que se conocen y postulan en epilepsia pediátrica, y sugerir conceptos como el de ‘metabolismo sináptico’ y ‘fenotipos sinápticos’ como herramientas útiles para desarrollar este enfoque. Desarrollo. Se revisan los estudios más destacados que intentan explicar las características esenciales de la comunicación sináptica en el cerebro en desarrollo, a través de diferentes moléculas, básicamente proteínas sinápticas, canales iónicos (cotransportadores de cloro, sodio y potasio), la compartimentalización pre y postsináptica, y los principales actores metabólicos (neurotransmisores, metabolismo energético, factores de crecimiento y lípidos). A partir de esta combinación de mecanismos biológicos se sugieren ejemplos de ‘fenotipos sinápticos’ en dos casos concretos de epilepsia genética (SCN1A) y metabólica (epilepsia con respuesta a la piridoxina). Conclusiones. Una perspectiva holística, entendiendo la diversidad de elementos relacionados y que suceden en determinados momentos del neurodesarrollo, puede ayudar a delinear fenotipos, vías de metabolismo sináptico y conectividad cerebral, que faciliten no sólo la comprensión de la fisiopatología, sino nuevas aproximaciones terapéuticas en epilepsia pediátrica (AU)

Introduction. Basic neuroscience and neurometabolism are providing a rapidly increasing amount of knowledge on paediatric epilepsy and, more specifically, on the mechanisms involved in synaptic communication. There is, however, a mismatch between these advances and a vision that integrates them in a global way, in clinical and therapeutic practice. Aims. To offer an integrative view of the different molecular and metabolic mechanisms that are known and postulated in paediatric epilepsy, and to suggest concepts such as ‘synaptic metabolism’ and ‘synaptic phenotypes’ as useful tools for developing this approach. Development. We also review the most notable studies that attempt to explain the essential characteristics of synaptic communication in the developing brain by means of different molecules, essentially synaptic proteins, ion channels (chlorine, sodium and potassium co-transporters), and pre- and post-synaptic compartmentalisation, as well as the main players in metabolism (neurotransmitters, energy metabolism, growth factors and lipids). This combination of biological mechanisms has led to examples of ‘synaptic phenotypes’ being suggested in two specific cases of genetic (SCN1A) and metabolic epilepsy (epilepsy with response to pyridoxine). Conclusions. A holistic perspective, which takes into account the diversity of elements that are related and which take place at certain times in neurodevelopment, can help to define phenotypes, channels for synaptic metabolism and brain connectivity, which facilitate not only the understanding of the pathophysiology, but also new therapeutic approaches in paediatric epilepsy (AU)

Infantile parkinsonism and GABAergic hypotransmission in a patient with pyruvate carboxylase deficiency.

Pyruvate carboxylase deficiency is a rare metabolic disorder, with three different phenotypes. We aim to report the case of a newborn presenting the severe neonatal form of this deficiency (the B or "French" phenotype, hypokinesia and rigidity being the main features) and the results of the study of classic neurotransmitters involved in movement control. Hyperdopaminergic transmission (both in the cerebrospinal fluid and in the substantia nigra) and hypoGABAergic transmission (in the substantia nigra) were found. Both gamma-aminobutyric acid and dopamine markers were found coexisting in individual neurons of the substantia nigra. This is the first time this phenomenon has been reported in the literature. We discuss the possible role of GABAergic deficiency, its interaction with other neurotransmitters and its implication in neurotransmitter homeostasis. A better comprehension of that field would increase understanding of the pathophysiology of neurological symptoms and neurotransmitter plasticity.

Síndrome de Sotos: nueva mutación «sin sentido» del gen NSD1 que presenta cutis laxa neonatal / Sotos syndrome: a novel nonsense mutation in nsd1 gene, presenting with neonatal cutis laxa

El síndrome de Sotos se caracteriza por sobrecrecimiento con facies peculiar, macrocefalia, talla alta y alteraciones del desarrollo psicomotor. Presentamos a un paciente de 20 meses de edad con diagnóstico confirmado por genética molecular con detección de mutación nonsense en el gen NSD1 no descrita previamente, exhibiendo cutis laxa como la característica fenotípica más llamativa en el periodo neonatal. Esta asociación se había descrito previamente en 3 pacientes con diagnóstico clínico de síndrome de Sotos sin diagnóstico molecular confirmatorio. En nuestro paciente, la presencia de cutis laxa llevó al diagnóstico diferencial con los defectos congénitos de glucosilación. En el seguimiento posnatal presentó una somatometría con perímetro cefálico y talla mayores de p97 (cercano a p50 al nacimiento), junto con el desarrollo de rasgos fenotípicos característicos del síndrome de Sotos durante los primeros meses de vida, los que proporcionaron la clave para el diagnóstico clínico y la investigación molecular (AU)

Sotos syndrome is an overgrowth condition characterized by facial gestalt, macrocephaly, excessive height, and different degrees of developmental delay. We report the case of a 20-month-old boy with a confirmatory molecular study, showing a novel nonsense mutation in NSD1 gene, presenting cutis laxa as the main phenotypic trait in the neonatal period. This association has been previously described in 3 patients with a clinical diagnosis of Sotos syndrome, without confirmatory molecular analysis. Our patient was tested for congenital disorders of glycosilation as part of the cutis laxa differential diagnosis. During the postnatal follow-up period the head circumference and height became greater than 97th percentile (having been close to the 50th in the newborn period). These facts and the progressive development of characteristic phenotypic features of Sotos syndrome during the first months of life gave us the clue for the clinical diagnosis and the molecular investigation (AU)

[Sotos syndrome: a novel nonsense mutation in NSD1 gene, presenting with neonatal cutis laxa]. / Síndrome de Sotos: nueva mutación «sin sentido¼ del gen NSD1 que presenta cutis laxa neonatal.

Sotos syndrome is an overgrowth condition characterized by facial gestalt, macrocephaly, excessive height, and different degrees of developmental delay. We report the case of a 20-month-old boy with a confirmatory molecular study, showing a novel nonsense mutation in NSD1 gene, presenting cutis laxa as the main phenotypic trait in the neonatal period. This association has been previously described in 3 patients with a clinical diagnosis of Sotos syndrome, without confirmatory molecular analysis. Our patient was tested for congenital disorders of glycosilation as part of the cutis laxa differential diagnosis. During the postnatal follow-up period the head circumference and height became greater than 97(th) percentile (having been close to the 50(th) in the newborn period). These facts and the progressive development of characteristic phenotypic features of Sotos syndrome during the first months of life gave us the clue for the clinical diagnosis and the molecular investigation.