Early detection of lysosomal diseases by screening of cases of idiopathic splenomegaly and/or thrombocytopenia with a next-generation sequencing gene panel.

Lysosomal diseases (LD) are a group of about 70 rare hereditary disorders (combined incidence 1:5000) in which diverse lysosomal functions are impaired, impacting multiple organs and systems. The first clinical signs and symptoms are usually unspecific and shared by hundreds of other disorders. Diagnosis of LD traditionally relies on performing specific enzymatic assays, if available, upon clinical suspicion of the disorder. However, the combination of the insidious onset of LD and the lack of awareness on these rare diseases among medical personnel results in undesirable diagnostic delays, with unchecked disease progression, appearance of complications and a worsened prognosis. We tested the usefulness of a next-generation sequencing-based gene panel for quick, early detection of LD among cases of idiopathic splenomegaly and/or thrombocytopenia, two of the earliest clinical signs observed in most LD. Our 73-gene panel interrogated 28 genes for LD, 1 biomarker and 44 genes underlying non-LD differential diagnoses. Among 38 unrelated patients, we elucidated eight cases (21%), five with LD (GM1 gangliosidosis, Sanfilippo disease A and B, Niemann-Pick disease B, Gaucher disease) and three with non-LD conditions. Interestingly, we identified three LD patients harboring pathogenic mutations in two LD genes each, which may result in unusual disease presentations and impact treatment. Turnaround time for panel screening and genetic validation was 1 month. Our results underline the usefulness of resequencing gene panels for quick and cost-effective screening of LDs and disorders sharing with them early clinical signs.

Secuenciación de genoma completo: un salto cualitativo en los estudios genéticos / Whole genome sequencing: a qualitative leap forward in genetic studies

Resumen. En estos momentos se encuentra en plena expansión la llamada secuenciación paralela o de siguiente generación -next generation sequencing (NGS)-, que establece un salto de varios órdenes de magnitud en la longitud de los fragmentos secuenciados y la rapidez de su secuenciación. La NGS permite la secuenciación de un genoma humano completo en el tiempo y el coste económico de secuenciar dos o tres genes grandes con la técnica de Sanger. Mediante la NGS se pasa de examinar genes específicos seleccionados mediante estudio del fenotipo a explorar genomas enteros de grupos humanos o de otras especies. Esto está permitiendo conocer no sólo cómo es un genoma individual, sino cómo cambia el genoma humano de persona a persona, cómo difieren los genomas entre diferentes grupos humanos, e incluso cómo difiere el genoma de un tumor respecto del genoma sano del huésped (AU)

Summary. At the present time the so-called parallel or next generation sequencing (NGS) technique is rapidly expanding and developing; this process establishes a jump by several orders of magnitude in the length of the fragments sequenced and the speed with which this sequencing is carried out. NGS allows a whole human genome to be sequenced in the same amount of time and with the same economic cost required to sequence two or three large genes using the Sanger technique. Use of NGS allows us to go from examining specific genes selected by studying the phenotype to exploring whole genomes of groups of humans or other species. This is making it possible to know not only what an individual genome is like but also how the human genome changes from one person to another, how genomes differ from one group of humans to another, and even how the genome differs in a tumour with respect to the healthy genome of the host (AU)

[Whole genome sequencing: a qualitative leap forward in genetic studies]. / Secuenciación de genoma completo: un salto cualitativo en los estudios genéticos.

At the present time the so-called parallel or next generation sequencing (NGS) technique is rapidly expanding and developing; this process establishes a jump by several orders of magnitude in the length of the fragments sequenced and the speed with which this sequencing is carried out. NGS allows a whole human genome to be sequenced in the same amount of time and with the same economic cost required to sequence two or three large genes using the Sanger technique. Use of NGS allows us to go from examining specific genes selected by studying the phenotype to exploring whole genomes of groups of humans or other species. This is making it possible to know not only what an individual genome is like but also how the human genome changes from one person to another, how genomes differ from one group of humans to another, and even how the genome differs in a tumour with respect to the healthy genome of the host.

Autosomal recessive Emery-Dreifuss muscular dystrophy caused by a novel mutation (R225Q) in the lamin A/C gene identified by exome sequencing.

INTRODUCTION: The aim of this study is to describe a new mutation in the LMNA gene diagnosed by whole exome sequencing. METHODS: A two-generation kindred with recessive limb-girdle muscular dystrophy was evaluated by exome sequencing of the proband's DNA. RESULTS: Exome sequencing disclosed 194,618 variants (170,196 SNPs, 8482 MNPs, 7466 insertions, 8307 deletions, and 167 mixed combinations); 71,328 were homozygotic and 123,290 were heterozygotic, with 11,753 non-synonymous, stop-gain, stop-loss, or frameshift mutations occurring in the coding region or nearby intronic region. The cross-referencing of these mutations in candidate genes for muscular dystrophy showed a homozygote mutation c.G674A in exon 4 of LMNA causing a protein change R225Q in an arginine conserved from human to Xenopus tropicalis and in lamin B1. CONCLUSIONS: This technique will be preferred for studying patients with muscular dystrophy in the coming years.

[Involvement of vesicular monoamine transporter in attention deficit hyperactivity disorder]. / Implicacion del transportador vesicular de monoaminas en el trastorno por deficit de atencion/hiperactividad.

INTRODUCTION: A number of genetic and neuroimagen proofs support the idea that attention-deficit/hyperactivity disorder (ADHD) present a neurobiological alteration. Vesicular monoamine transporters (VMATs) are important proteins that regulate the intraneuronal monoamine concentration and disposition as this protein sequesters cytoplasmic dopamine within synaptic vesicles thus contributing to subsequent excitotoxic release. DEVELOPMENT: Two pharmacologically distinct VMAT isoforms VMAT1 and VMAT2 have been cloned and described. The VMAT2, in the CNS, is responsible for the translocation of dopamine from the cytoplasm into synaptic vesicles. In addition, it has been described a neuroprotector role for these transporters. The platelet vesicular monoamine transporter VMAT2 is used as a peripheral model of neuronal VMAT2. Its quantification has been used to perform studies of ADHD and other neuropsychiatry diseases related with the monoamines metabolism. CONCLUSION: Since dopamine and other monoamines (epinephrine and serotonine) play a role in ADHD, and methylphenidate, an usual treatment for this type of patients, modifies the VMAT2 activity, we may argue that VMAT2 is involved in ADHD pathogeny.

Implicación del transportador vesicular de monoaminas en el trastorno por déficit de atención/hiperactividad / Involvement of vesicular monoamine transporter in attention deficit hyperactivity disorder

Introducción. Existen numerosas evidencias genéticas y de neuroimagen que apoyan la presencia de una alteración neurobiológica en el trastorno por déficit de atención/hiperactividad (TDAH). Los transportadores vesiculares de monoaminas (VMAT) son proteínas localizadas en las vesículas sinápticas, que se encargan de introducir las aminas biógenas desde el citoplasma celular al interior de dichas vesículas, para posteriormente poder ser liberadas. Desarrollo. Se han identificado y clonado dos isoformas de este transportador, el tipo 1 (VMAT1) y el tipo 2 (VMAT2). El VMAT2, en el sistema nervioso central, se encarga de secuestrar la dopamina citosólica y llevarla al interior de las vesículas sinápticas. Además, se le ha atribuido un papel neuroprotector. La cuantificación del VMAT2 plaquetario se utiliza como un modelo periférico de la actividad del VMAT2 cerebral para el estudio del TDAH y de otras enfermedades neuropsiquiátricas relacionadas con el metabolismo de las bioaminas. Conclusión. Considerando el papel que desempeñan la dopamina y otras monoaminas (noradrenalina, serotonina) en el TDAH, y que el metilfenidato, un tratamiento habitual de estos pacientes, puede modificar la actividad del VMAT2, sería lógico pensar que este transportador esté involucrado en la patogenia del TDAH (AU)

Introduction. A number of genetic and neuroimagen proofs support the idea that attention-deficit/hyperactivity disorder (ADHD) present a neurobiological alteration. Vesicular monoamine transporters (VMATs) are important proteins that regulate the intraneuronal monoamine concentration and disposition as this protein sequesters cytoplasmic dopamine within synaptic vesicles thus contributing to subsequent excitotoxic release. Development. Two pharmacologically distinct VMAT isoforms VMAT1 and VMAT2 have been cloned and described. The VMAT2, in the CNS, is responsible for the translocation of dopamine from the cytoplasm into synaptic vesicles. In addition it has been described a neuroprotector role for these transporters. The platelet vesicular monoamine transporter VMAT2 is used as a peripheral model of neuronal VMAT2. Its quantification has been used to perform studies of ADHD and other neuropsychiatry diseases related with the monoamines metabolism.Conclusion. Since dopamine and other monoamines (epinephrine and serotonine) play a role in ADHD, and methylphenidate, an usual treatment for this type of patients, modifies the VMAT2 activity, we may argue that VMAT2 is involved in ADHD pathogen (AU)