Osteopetrosis infantil maligna / Malignant Infantile osteopetrosis

INTRODUCCIÓN: Osteopetrosis Infantil Maligna (OIM) es un grave e inusual desorden genético debi do a una actividad osteoclástica anormal. OBJETIVO: Reportar lactante en quien se documentó una Osteopetrosis Infantil Maligna, revisando aspectos diagnósticos y terapéuticos más relevantes. CASO CLÍNICO: Reportamos un lactante de 10 meses de sexo masculino en quien se confirmó OIM tras presentar plaquetopenia y visceromegalias. En su historial destacó ser primer hijo de padres no consanguíneos, y entre sus hallazgos presentó hepatoesplenomegalia, plaquetopenia y anemia graves, compromiso sensorial visual y auditivo e infecciones a repetición. El diagnóstico fue confirmado mediante estudio genético, el cual identificó 2 mutaciones heterocigotas en el gen TCIRG1. Se rea lizó trasplante de precursores hematopoyéticos, sin haber presentado recuperación hematológica, falleciendo por enfermedad veno oclusiva. DISCUSIÓN: La OIM es una enfermedad inusual, grave y de inicio temprano, siendo necesario un elevado índice de sospecha ante hepatoesplenomegalia y falla medular. El diagnóstico temprano y el trasplante de precursores hematopoyéticos son las únicas intervenciones potencialmente curativas de esta entidad letal.

INTRODUCCIÓN: Malignant Infantile Osteopetrosis (MIOP) is a rare and severe genetic disorder due to abnormal osteoclast activity. OBJECTIVE: To report an infant who presented Malignant Infantile Osteopetrosis, reviewing the most relevant diagnostic and therapeutic aspects. CLINICAL CASE: A ten- month-old male infant with diagnosis of MIOP confirmed after presenting thrombocytopenia and visceromegaly. He was the first child of non-consanguineous parents, and among the findings, he presented severe hepatosplenomegaly, thrombocytopenia, and anemia; visual and hearing impairment, and repeated infections. The diagnosis was confirmed by genetic study, which identified two heterozygous mutations in the TCIRG1 gene. Hematopoietic stem cells were transplanted without hematological recovery. The patient died due to occlusive venous disease. DISCUSSION: MIOP is a rare, severe, and early-onset disease, with a high rate of suspicion necessary in the presence of hepatosplenomegaly and bone marrow failure. Early diagnosis and hematopoietic stem cells transplanta tion are the only potentially therapeutic interventions of this lethal entity.

Autosomal recessive osteopetrosis type I: description of pathogenic variant of TCIRG1 gene / Osteopetrosis infantil maligna: descripción de una nueva mutación patogénica de TCIRG1

Abstract Background: Autosomal malignant osteopetrosis is a rare condition arising from dysfunction of bone-resorbing osteoclasts, in which diagnosis requires a high suspicion index. Treatment of choice is allogeneic stem cell transplantation. Best outcomes occur if the procedure is carried out before damage to cranial nerves ensues; nonetheless, patients improve their clinical condition. Case report: An 8-month-old infant was referred for hematology consultation for cytopenias, hepatomegaly, and growth failure. Autosomal malignant osteopetrosis was diagnosed on the basis of physical findings, alteration in calcium and phosphorus metabolism, and hyperdensity of bone. DNA was obtained from the patient and parents; compound heterozygosity of the TCIRG1 gene with a previously non-described deletion (c.1809_1818del) was identified. Conclusions: A new pathogenic mutation of TCIRG1 was identified in a Mexican osteopetrotic patient. Hematopoietic stem cell transplantation was offered as the best available treatment but declined by the parents. An early recognition and wider access to this procedure should be implemented.

Resumen Introducción: La osteopetrosis infantil maligna es una condición rara cuyo origen es la deficiente reabsorción ósea por parte de los osteoclastos. Su diagnóstico requiere un alto índice de sospecha. El tratamiento de elección es el trasplante alogénico de células hematopoyéticas. Los mejores desenlaces ocurren si el procedimiento se lleva a cabo antes de que ocurra daño a los nervios craneales. Caso clínico: Paciente masculino de 8 meses de edad fue referido a la consulta de hematología por citopenias, hepatomegalia y falla para crecer. Se diagnosticó osteopetrosis infantil maligna basándose en los hallazgos de la exploración física, la alteración del metabolismo del calcio y el fósforo y la hiperdensidad del hueso. Se obtuvo ADN del paciente y ambos padres; se demostró un heterocigosidad compuesta del gen TCIRG1 con una deleción (c.1809_1818del) no descrita previamente. Conclusiones: Una nueva mutación patogénica de TCIRG1 se identificó en un paciente mexicano con osteopetrosis. Se ofreció trasplante de células progenitoras hematopoyéticas como el mejor tratamiento disponible, pero fue rechazado por los padres. Se necesita un reconocimiento temprano y la implementación del acceso generalizado a este procedimiento.

Sequenciamento total do exoma como ferramenta de diagnóstico de acidose tubular renal distal / Whole-exome sequencing as a diagnostic tool for distal renal tubular acidosis

Resumo Objetivo A acidose tubular renal distal (ATRd) é caracterizada por acidose metabólica devido à excreção renal de ácido prejudicada. O objetivo deste artigo é apresentar o diagnóstico genético de quatro crianças com ATRd com uso do sequenciamento total do exoma. Métodos Selecionamos duas famílias não relacionadas, quatro crianças com ATRd e seus pais, para fazer o sequenciamento total do exoma. A audição foi preservada em ambas as crianças da família um, porém em nenhuma criança da família dois, na qual um par de gêmeas teve perda auditiva severa. Fizemos o sequenciamento total do exoma em dois conjuntos de amostras e confirmamos os achados com o método de sequenciamento de Sanger. Resultados Duas mutações foram identificadas nos genes ATP6V0A4 e ATP6V1B1. Na família um, detectamos uma nova mutação no éxon 13 do gene ATP6V0A4 com uma alteração em um nucleotídeo único GAC → TAC (c.1232G>T) que causou substituição de ácido aspártico por tirosina na posição 411. Na família dois, detectamos uma mutação recorrente do homozigoto com inserção de um par de bases (c.1149_1155insC) no éxon 12 do gene ATP6V1B1. Conclusão Nossos resultados confirmam o valor do sequenciamento total do exoma para o estudo de nefropatias genéticas complexas e permitem a identificação de mutações novas e recorrentes. Adicionalmente, demonstramos claramente pela primeira vez a aplicação desse método molecular em doenças tubulares renais.

Abstract Objective Distal renal tubular acidosis (dRTA) is characterized by metabolic acidosis due to impaired renal acid excretion. The aim of this study was to demonstrate the genetic diagnosis of four children with dRTA through use of whole-exome sequencing. Methods Two unrelated families were selected; a total of four children with dRTA and their parents, in order to perform whole-exome sequencing. Hearing was preserved in both children from the first family, but not in the second, wherein a twin pair had severe deafness. Whole-exome sequencing was performed in two pooled samples and findings were confirmed with Sanger sequencing method. Results Two mutations were identified in the ATP6V0A4 and ATP6V1B1 genes. In the first family, a novel mutation in the exon 13 of the ATP6V0A4 gene with a single nucleotide change GAC → TAC (c.1232G>T) was found, which caused a substitution of aspartic acid to tyrosine in position 411. In the second family, a homozygous recurrent mutation with one base-pair insertion (c.1149_1155insC) in exon 12 of the ATP6V1B1 gene was detected. Conclusion These results confirm the value of whole-exome sequencing for the study of rare and complex genetic nephropathies, allowing the identification of novel and recurrent mutations. Furthermore, for the first time the application of this molecular method in renal tubular diseases has been clearly demonstrated.

Physiological implications of the regulation of vacuolar H+-ATPase by chloride ions

Vacuolar H+-ATPase is a large multi-subunit protein that mediates ATP-driven vectorial H+ transport across the membranes. It is widely distributed and present in virtually all eukaryotic cells in intracellular membranes or in the plasma membrane of specialized cells. In subcellular organelles, ATPase is responsible for the acidification of the vesicular interior, which requires an intraorganellar acidic pH to maintain optimal enzyme activity. Control of vacuolar H+-ATPase depends on the potential difference across the membrane in which the proton ATPase is inserted. Since the transport performed by H+-ATPase is electrogenic, translocation of H+-ions across the membranes by the pump creates a lumen-positive voltage in the absence of a neutralizing current, generating an electrochemical potential gradient that limits the activity of H+-ATPase. In many intracellular organelles and cell plasma membranes, this potential difference established by the ATPase gradient is normally dissipated by a parallel and passive Cl- movement, which provides an electric shunt compensating for the positive charge transferred by the pump. The underlying mechanisms for the differences in the requirement for chloride by different tissues have not yet been adequately identified, and there is still some controversy as to the molecular identity of the associated Cl--conducting proteins. Several candidates have been identified: the ClC family members, which may or may not mediate nCl-/H+ exchange, and the cystic fibrosis transmembrane conductance regulator. In this review, we discuss some tissues where the association between H+-ATPase and chloride channels has been demonstrated and plays a relevant physiologic role.

Cloning and characterization of a V-ATPase subunit C from the American visceral leishmaniasis vector Lutzomyia longipalpis modulated during development and blood ingestion

Visceral leishmaniasis (VL) is a serious tropical disease that affects approximately 500 thousand people worldwide every year. In the Americas, VL is caused by the parasite Leishmania (Leishmania) infantum chagasi mainly transmitted by the bite of the sand fly vector Lutzomyia longipalpis. Despite recent advances in the study of interaction between Leishmania and sand flies, very little is known about sand fly protein expression profiles. Understanding how the expression of proteins may be affected by blood feeding and/or presence of parasite in the vector's midgut might allow us to devise new strategies for controlling the spread of leishmaniasis. In this work, we report the characterization of a vacuolar ATPase subunit C from L. longipalpis by screening of a midgut cDNA library with a 220 bp fragment identified by means of differential display reverse transcriptase-polymerase chain reaction analysis. The expression of the gene varies along insect development and is upregulated in males and bloodfed L. longipalpis, compared to unfed flies.

H+_Atpasa Vacuolar Renal. Fisiología y Regulación / Vacuolar H (+)_ATPase renal. Physiologi and Regulation

Las H+ _ATPasas vacuolares son complejos proteicos ubicuos con múltiples subunidades que incluyen un dominio catalítico V1 compuesto por proteínas periféricas que hidrolizan adenosina trisfosfato (ATP) y proveen energía a la bomba de H+ a través de un segundo dominio transmembrana Vº en contra de importantes gradientes. Estas H+_ATPasas vacuolares, que intervienen en la translocación de protones, son responsables en células eucariotas de la acidificación de las organelas intracelulares y de la acidificación de los espacios luminales e intersticiales adyacentes a las membranas plasmáticas celulares. Mutaciones en los genes que codifican las subunidades de H+ATPasa vacuolar específicas de células intercalares de ríñón; Vºa4 y V1B1, causan el síndrome de acidosis tubular distal renal. Esta revisión se focalizará en función, regulación y en el rol de H+ATPasa vacuolar en fisiología renal. La localización de H+ _ATPasa en el rión y su rol en la regulación de pHintracelular, transporte de protones y la homostsis del ácido base, será discutida.