European Journal of Paediatric Neurology, May 1, 2015
Objective Respiratory chain complex (RCC) I is the second most common biochemical abnormality cau... more Objective Respiratory chain complex (RCC) I is the second most common biochemical abnormality causing Leigh syndrome (LS), an early-onset neurodegenerative disorder. NDUFS4 gene presents a hotspot of mutations leading to an inappropriate assembly of complex I. Our aim was to describe a 67-days-old female presenting with severe hypotonia, abnormal eye movements, lethargy, seizures and respiratory failure leading to death on day 5 of evolution. Plasma lactate was 5.83 mmol/L and amino acids and organic acids were normal. MRI showed swelling lesions in the basal ganglia and brainstem with restricted diffusion and a lactate peak on MRS. Methods Pyruvate dehydrogenase (PDH) and oxidation-reduction activity assays were performed in fibroblasts and muscle. Spectrophotometric assays of RCC were performed in muscle. Genetic analysis of nuclear genes involved in mitochondrial disorders was assessed by targeted exome sequencing using the TruSight One Sequencing Panel (Illumina). Results The patient showed a significative reduction in PDH activity in fibroblasts and muscle, with values of 0.22 mmol/min*mg prot (normal values 0.34–2.6) and 0.5 mmol/min*mg prot, (normal values 0.8–3.4) respectively, and reduced oxidation of pyruvate in fibroblasts. Muscle analysis of RCC showed a 50% reduction in the residual activity of CI and CIII compared to control. Muscle Q10 was low when related to cytrate synthase (2.18 nmol/U CS, reference values 2.7–8.4). Massive sequencing revealed a previously described homozygous mutation c.291delG (p. Trp97Ter) in NDUFS4 gene, which was further confirmed by Sanger sequencing. No disease-causing mutations were detected in the PDHc genes. Conclusion NDUFS4 defect in our patient led to a rapidly progressive and fatal Leigh encephalopathy in the second month of life. A combined defect in pyruvate metabolism and respiratory chain complexes was misleading; probably, mild Q10 deficiency was secondary to inappropriate assembly of complex I. Finally, NGS techniques allowed genetic diagnosis in our patient.
CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a pub... more CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on Rare Diseases currently consists of 75 research groups belonging to universities, research centers and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical and cellular research of rare diseases. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this paper, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions towards the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to rare disease research. This article is protected by copyright. All rights reserved.
There are few causes of treatable neurodevelopmental diseases described to date. Branched-chain k... more There are few causes of treatable neurodevelopmental diseases described to date. Branched-chain ketoacid dehydrogenase kinase (BCKDK) deficiency causes branched-chain amino acid (BCAA) depletion and is linked to a neurodevelopmental disorder characterized by autism, intellectual disability and microcephaly. We report the largest cohort of patients studied, broadening the phenotypic and genotypic spectrum. Moreover, this is the first study to present newborn screening findings and mid-term clinical outcome. In this cross-sectional study, patients with a diagnosis of BCKDK deficiency were recruited via investigators’ practices through a MetabERN initiative. Clinical, biochemical and genetic data were collected. Dried blood spot (DBS) newborn screening (NBS) amino acid profiles were retrieved from collaborating centres and compared to a healthy newborn reference population. Twenty-one patients with BCKDK mutations were included from 13 families. Patients were diagnosed between 8 months...
Maintaining protein lipoylation is vital for cell metabolism. The H-protein encoded by GCSH has a... more Maintaining protein lipoylation is vital for cell metabolism. The H-protein encoded by GCSH has a dual role in protein lipoylation required for bioenergetic enzymes including pyruvate dehydrogenase and 2-ketoglutarate dehydrogenase, and in the one-carbon metabolism through its involvement in glycine cleavage enzyme system, intersecting two vital roles for cell survival. Here, we report six patients with biallelic pathogenic variants in GCSH and a broad clinical spectrum ranging from neonatal fatal glycine encephalopathy to an attenuated phenotype of developmental delay, behavioral problems, limited epilepsy and variable movement problems. The mutational spectrum includes one insertion c.293-2_293–1insT, one deletion c.122_(228 + 1_229–1) del, one duplication of exons 4 and 5, one nonsense variant p.Gln76*and four missense p.His57Arg, p.Pro115Leu and p.Thr148Pro and the previously described p.Met1?. Via functional studies in patient’s fibroblasts, molecular modeling, expression analy...
Inborn errors of metabolism (IEM) constitute a huge group of rare diseases affecting 1 in every 1... more Inborn errors of metabolism (IEM) constitute a huge group of rare diseases affecting 1 in every 1000 newborns. Next-generation sequencing has transformed the diagnosis of IEM, leading to its proposed use as a second-tier technology for confirming cases detected by clinical/biochemical studies or newborn screening. The diagnosis rate is, however, still not 100%. This paper reports the use of a personalized multi-omics (metabolomic, genomic and transcriptomic) pipeline plus functional genomics to aid in the genetic diagnosis of six unsolved cases, with a clinical and/or biochemical diagnosis of galactosemia, mucopolysaccharidosis type I (MPS I), maple syrup urine disease (MSUD), hyperphenylalaninemia (HPA), citrullinemia, or urea cycle deficiency. Eight novel variants in six genes were identified: six (four of them deep intronic) located in GALE, IDUA, PTS, ASS1 and OTC, all affecting the splicing process, and two located in the promoters of IDUA and PTS, thus affecting these genes’ e...
Background: MSUD is caused by the defective activity of branched-chain alpha-ketoacid dehydrogena... more Background: MSUD is caused by the defective activity of branched-chain alpha-ketoacid dehydrogenase complex, a mitochondrial enzyme complex. Defects in mitochondrial enzymes can lead to oxidative stress. Aim: To analyze oxidative stress markers in fibroblasts from MSUD patients with classic phenotype and an enzymatic activity below 2.5% in comparison to controls: E1β[p.R216G+R216G], E1β[p.R285X+p.R285X] and E1α[p.R40fs+p.R40fs]. Results: We measured mitochondrial superoxide levels with MitoSOX and we observed an up to 2.1-fold increase in fibroblasts from patients. Higher superoxide levels can lead to protein oxidative damage that was measured by protein carbonylation. We detected protein carbonylation by ELISA of DNPH-derivatized proteins. Fibroblasts from patients showed up to 1.5-fold higher carbonylation levels To evaluate possible effects on the antioxidant defense system we measured protein levels of manganese superoxide dismutase (SOD2), which catalyzes the conversion of mito...
The biochemical characteristics of a patient with most of the clinical symptoms of nonketotic-hyp... more The biochemical characteristics of a patient with most of the clinical symptoms of nonketotic-hyperglycinemia have been studied. Despite the extremely low plasma/cerebrospinal fluid glycine ratio of the patient, typical of the nonketotic syndrome, at autopsy we found no enhancement of glycine levels in brain and glycine cleavage enzyme activities in the brain and liver that were similar to those of a control newborn. In order to ascertain the basic defect responsible for glycine accumulation in the cerebrospinal fluid and for the neurological damage, we examined the possible existence of altered glycine transport systems in nervous cells. Our findings indicate that (1) low and high affinity, Na+-dependent transport systems for glycine can be detected in both rat and control human postmortem tissue and (2) the low affinity glycine transport system is absent in the brain of the patient, whereas an alteration of transport systems occurs in the patient's spinal cord, probably involv...
Creatine transporter deficiency is a recently identified X-linked inborn error of metabolism. The... more Creatine transporter deficiency is a recently identified X-linked inborn error of metabolism. The natural course of the disease is not well delineated since clinical data from adult patients have scarcely been reported. A progressive course of the disease has been noted in a few described cases. We report the first two Spanish adult patients with creatine transporter deficiency and compare their clinical phenotype and the evolution of the disease with those of other published cases. The two brothers were identified in a study of a cohort of 610 mentally handicapped male patients. The disease was detected by biochemical studies and confirmed by DNA studies. The most significant clinical features were mental retardation, epilepsy and autistic behaviour, and these symptoms did not worsen, in contrast to other reports. They did not present gastrointestinal problems or movement disorders. Creatine transporter deficiency could be an underdiagnosed metabolic disorder and should be considered in adult patients with mental retardation. Clinical presentation of this disorder showed marked differences among adult patients and the course of the disease was static in our cases. Detection of additional adult patients might allow better understanding of the phenotypic outcome at a later age.
We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families wi... more We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families with neurological disease due to mutations in ADAR1. The clinicoradiological phenotype encompassed a spectrum of Aicardi-Goutières syndrome, isolated bilateral striatal necrosis, spastic paraparesis with normal neuroimaging, a progressive spastic dystonic motor disorder, and adult-onset psychological difficulties with intracranial calcification. Homozygous missense mutations were recorded in five families. We observed a p.Pro193Ala variant in the heterozygous state in 22 of 23 families with compound heterozygous mutations. We also ascertained 11 cases from nine families with a p.Gly1007Arg dominant-negative mutation, which occurred de novo in four patients, and was inherited in three families in association with marked phenotypic variability. In 50 of 52 samples from 34 patients, we identified a marked upregulation of type I interferon-stimulated gene transcripts in peripheral blood, with ...
Thiamine transporter-2 deficiency is caused by mutations in the SLC19A3 gene. As opposed to other... more Thiamine transporter-2 deficiency is caused by mutations in the SLC19A3 gene. As opposed to other causes of Leigh syndrome, early administration of thiamine and biotin has a dramatic and immediate clinical effect. New biochemical markers are needed to aid in early diagnosis and timely therapeutic intervention. Thiamine derivatives were analysed by high performance liquid chromatography in 106 whole blood and 38 cerebrospinal fluid samples from paediatric controls, 16 cerebrospinal fluid samples from patients with Leigh syndrome, six of whom harboured mutations in the SLC19A3 gene, and 49 patients with other neurological disorders. Free-thiamine was remarkably reduced in the cerebrospinal fluid of five SLC19A3 patients before treatment. In contrast, free-thiamine was slightly decreased in 15.2% of patients with other neurological conditions, and above the reference range in one SLC19A3 patient on thiamine supplementation. We also observed a severe deficiency of free-thiamine and low ...
Background Monocarboxylate transporter 1 (MCT1) deficiency has recently been described as a rare ... more Background Monocarboxylate transporter 1 (MCT1) deficiency has recently been described as a rare cause of recurrent ketosis, the result of impaired ketone utilization in extrahepatic tissues. To date, only six patients with this condition have been identified, and clinical and biochemical details remain incomplete. Results The present work reports a patient suffering from severe, recurrent episodes of metabolic acidosis and psychomotor delay, showing a pathogenic loss-of-function variation c.747_750del in homozygosity in SLC16A1 (which codes for MCT1). Persistent ketotic and lactic acidosis was accompanied by an abnormal excretion of organic acids related to redox balance disturbances. Together with an altered bioenergetic profile detected in patient-derived fibroblasts, this suggests possible mitochondrial dysfunction. Brain MRI revealed extensive, diffuse bilateral, symmetric signal alterations for the subcortical white matter and basal ganglia, together with corpus callosum agene...
Propionyl-CoA carboxylase (PCC) is a biotin-dependent enzyme located in the mitochondrial matrix.... more Propionyl-CoA carboxylase (PCC) is a biotin-dependent enzyme located in the mitochondrial matrix. Mutations in the PCCA and PCCB genes, which encode the a and b subunits of this heteropolymer, result in propionic acidemia (PA). We report the molecular analysis of b-deficient patients from Spain and Austria. Subjects were screened for defects affecting the PCCB gene by direct sequencing from genomic PCR products, restriction digests and mRNA analysis by RT-PCR. Study by western blot of the presence of immunoreactive b-PCC protein was also performed. A total of four novel sequence variations were found including the point mutations V205D, and M442T, and the frameshift mutation 790-791insG. Additionally, a new point change, L17M, was identified on the same allele as 790-791insG. The missense changes described above were not found in at least 40 control chromosomes analyzed. The Austrian patients were homozygous for V205D. One of the Spanish subjects was heterozygous for M442T and the known mutation c1170insT. The other Spanish patient carried L17M+790-791insG on one allele, and the described mutation E168K on the other mutant chromosome. The mutations V205D and M442T were confirmed at RNA level and also we have detected the presence of immunoreactive b-PCC protein translated from these mutant alleles. The patient having L17M+790-791insG and E168K also presented immunoreactive b-PCC protein. However, no cDNA product was obtained from the chromosome carrying L17M+790-791insG. We propose that 790-791insG, which causes a frameshift and a premature stop codon, is responsible for this finding. In any case, the translation from this mutant cDNA would produce a severity truncated peptide and, in consequence, a non-functional protein. Expression analysis of all these changes will help us to clarify their structural/functional consequences.
European Journal of Paediatric Neurology, May 1, 2015
Objective Respiratory chain complex (RCC) I is the second most common biochemical abnormality cau... more Objective Respiratory chain complex (RCC) I is the second most common biochemical abnormality causing Leigh syndrome (LS), an early-onset neurodegenerative disorder. NDUFS4 gene presents a hotspot of mutations leading to an inappropriate assembly of complex I. Our aim was to describe a 67-days-old female presenting with severe hypotonia, abnormal eye movements, lethargy, seizures and respiratory failure leading to death on day 5 of evolution. Plasma lactate was 5.83 mmol/L and amino acids and organic acids were normal. MRI showed swelling lesions in the basal ganglia and brainstem with restricted diffusion and a lactate peak on MRS. Methods Pyruvate dehydrogenase (PDH) and oxidation-reduction activity assays were performed in fibroblasts and muscle. Spectrophotometric assays of RCC were performed in muscle. Genetic analysis of nuclear genes involved in mitochondrial disorders was assessed by targeted exome sequencing using the TruSight One Sequencing Panel (Illumina). Results The patient showed a significative reduction in PDH activity in fibroblasts and muscle, with values of 0.22 mmol/min*mg prot (normal values 0.34–2.6) and 0.5 mmol/min*mg prot, (normal values 0.8–3.4) respectively, and reduced oxidation of pyruvate in fibroblasts. Muscle analysis of RCC showed a 50% reduction in the residual activity of CI and CIII compared to control. Muscle Q10 was low when related to cytrate synthase (2.18 nmol/U CS, reference values 2.7–8.4). Massive sequencing revealed a previously described homozygous mutation c.291delG (p. Trp97Ter) in NDUFS4 gene, which was further confirmed by Sanger sequencing. No disease-causing mutations were detected in the PDHc genes. Conclusion NDUFS4 defect in our patient led to a rapidly progressive and fatal Leigh encephalopathy in the second month of life. A combined defect in pyruvate metabolism and respiratory chain complexes was misleading; probably, mild Q10 deficiency was secondary to inappropriate assembly of complex I. Finally, NGS techniques allowed genetic diagnosis in our patient.
CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a pub... more CIBER (Center for Biomedical Network Research; Centro de Investigación Biomédica En Red) is a public national consortium created in 2006 under the umbrella of the Spanish National Institute of Health Carlos III (ISCIII). This innovative research structure comprises 11 different specific areas dedicated to the main public health priorities in the National Health System. CIBERER, the thematic area of CIBER focused on Rare Diseases currently consists of 75 research groups belonging to universities, research centers and hospitals of the entire country. CIBERER's mission is to be a center prioritizing and favoring collaboration and cooperation between biomedical and clinical research groups, with special emphasis on the aspects of genetic, molecular, biochemical and cellular research of rare diseases. This research is the basis for providing new tools for the diagnosis and therapy of low-prevalence diseases, in line with the International Rare Diseases Research Consortium (IRDiRC) objectives, thus favoring translational research between the scientific environment of the laboratory and the clinical setting of health centers. In this paper, we intend to review CIBERER's 15-year journey and summarize the main results obtained in terms of internationalization, scientific production, contributions towards the discovery of new therapies and novel genes associated to diseases, cooperation with patients' associations and many other topics related to rare disease research. This article is protected by copyright. All rights reserved.
There are few causes of treatable neurodevelopmental diseases described to date. Branched-chain k... more There are few causes of treatable neurodevelopmental diseases described to date. Branched-chain ketoacid dehydrogenase kinase (BCKDK) deficiency causes branched-chain amino acid (BCAA) depletion and is linked to a neurodevelopmental disorder characterized by autism, intellectual disability and microcephaly. We report the largest cohort of patients studied, broadening the phenotypic and genotypic spectrum. Moreover, this is the first study to present newborn screening findings and mid-term clinical outcome. In this cross-sectional study, patients with a diagnosis of BCKDK deficiency were recruited via investigators’ practices through a MetabERN initiative. Clinical, biochemical and genetic data were collected. Dried blood spot (DBS) newborn screening (NBS) amino acid profiles were retrieved from collaborating centres and compared to a healthy newborn reference population. Twenty-one patients with BCKDK mutations were included from 13 families. Patients were diagnosed between 8 months...
Maintaining protein lipoylation is vital for cell metabolism. The H-protein encoded by GCSH has a... more Maintaining protein lipoylation is vital for cell metabolism. The H-protein encoded by GCSH has a dual role in protein lipoylation required for bioenergetic enzymes including pyruvate dehydrogenase and 2-ketoglutarate dehydrogenase, and in the one-carbon metabolism through its involvement in glycine cleavage enzyme system, intersecting two vital roles for cell survival. Here, we report six patients with biallelic pathogenic variants in GCSH and a broad clinical spectrum ranging from neonatal fatal glycine encephalopathy to an attenuated phenotype of developmental delay, behavioral problems, limited epilepsy and variable movement problems. The mutational spectrum includes one insertion c.293-2_293–1insT, one deletion c.122_(228 + 1_229–1) del, one duplication of exons 4 and 5, one nonsense variant p.Gln76*and four missense p.His57Arg, p.Pro115Leu and p.Thr148Pro and the previously described p.Met1?. Via functional studies in patient’s fibroblasts, molecular modeling, expression analy...
Inborn errors of metabolism (IEM) constitute a huge group of rare diseases affecting 1 in every 1... more Inborn errors of metabolism (IEM) constitute a huge group of rare diseases affecting 1 in every 1000 newborns. Next-generation sequencing has transformed the diagnosis of IEM, leading to its proposed use as a second-tier technology for confirming cases detected by clinical/biochemical studies or newborn screening. The diagnosis rate is, however, still not 100%. This paper reports the use of a personalized multi-omics (metabolomic, genomic and transcriptomic) pipeline plus functional genomics to aid in the genetic diagnosis of six unsolved cases, with a clinical and/or biochemical diagnosis of galactosemia, mucopolysaccharidosis type I (MPS I), maple syrup urine disease (MSUD), hyperphenylalaninemia (HPA), citrullinemia, or urea cycle deficiency. Eight novel variants in six genes were identified: six (four of them deep intronic) located in GALE, IDUA, PTS, ASS1 and OTC, all affecting the splicing process, and two located in the promoters of IDUA and PTS, thus affecting these genes’ e...
Background: MSUD is caused by the defective activity of branched-chain alpha-ketoacid dehydrogena... more Background: MSUD is caused by the defective activity of branched-chain alpha-ketoacid dehydrogenase complex, a mitochondrial enzyme complex. Defects in mitochondrial enzymes can lead to oxidative stress. Aim: To analyze oxidative stress markers in fibroblasts from MSUD patients with classic phenotype and an enzymatic activity below 2.5% in comparison to controls: E1β[p.R216G+R216G], E1β[p.R285X+p.R285X] and E1α[p.R40fs+p.R40fs]. Results: We measured mitochondrial superoxide levels with MitoSOX and we observed an up to 2.1-fold increase in fibroblasts from patients. Higher superoxide levels can lead to protein oxidative damage that was measured by protein carbonylation. We detected protein carbonylation by ELISA of DNPH-derivatized proteins. Fibroblasts from patients showed up to 1.5-fold higher carbonylation levels To evaluate possible effects on the antioxidant defense system we measured protein levels of manganese superoxide dismutase (SOD2), which catalyzes the conversion of mito...
The biochemical characteristics of a patient with most of the clinical symptoms of nonketotic-hyp... more The biochemical characteristics of a patient with most of the clinical symptoms of nonketotic-hyperglycinemia have been studied. Despite the extremely low plasma/cerebrospinal fluid glycine ratio of the patient, typical of the nonketotic syndrome, at autopsy we found no enhancement of glycine levels in brain and glycine cleavage enzyme activities in the brain and liver that were similar to those of a control newborn. In order to ascertain the basic defect responsible for glycine accumulation in the cerebrospinal fluid and for the neurological damage, we examined the possible existence of altered glycine transport systems in nervous cells. Our findings indicate that (1) low and high affinity, Na+-dependent transport systems for glycine can be detected in both rat and control human postmortem tissue and (2) the low affinity glycine transport system is absent in the brain of the patient, whereas an alteration of transport systems occurs in the patient's spinal cord, probably involv...
Creatine transporter deficiency is a recently identified X-linked inborn error of metabolism. The... more Creatine transporter deficiency is a recently identified X-linked inborn error of metabolism. The natural course of the disease is not well delineated since clinical data from adult patients have scarcely been reported. A progressive course of the disease has been noted in a few described cases. We report the first two Spanish adult patients with creatine transporter deficiency and compare their clinical phenotype and the evolution of the disease with those of other published cases. The two brothers were identified in a study of a cohort of 610 mentally handicapped male patients. The disease was detected by biochemical studies and confirmed by DNA studies. The most significant clinical features were mental retardation, epilepsy and autistic behaviour, and these symptoms did not worsen, in contrast to other reports. They did not present gastrointestinal problems or movement disorders. Creatine transporter deficiency could be an underdiagnosed metabolic disorder and should be considered in adult patients with mental retardation. Clinical presentation of this disorder showed marked differences among adult patients and the course of the disease was static in our cases. Detection of additional adult patients might allow better understanding of the phenotypic outcome at a later age.
We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families wi... more We investigated the genetic, phenotypic, and interferon status of 46 patients from 37 families with neurological disease due to mutations in ADAR1. The clinicoradiological phenotype encompassed a spectrum of Aicardi-Goutières syndrome, isolated bilateral striatal necrosis, spastic paraparesis with normal neuroimaging, a progressive spastic dystonic motor disorder, and adult-onset psychological difficulties with intracranial calcification. Homozygous missense mutations were recorded in five families. We observed a p.Pro193Ala variant in the heterozygous state in 22 of 23 families with compound heterozygous mutations. We also ascertained 11 cases from nine families with a p.Gly1007Arg dominant-negative mutation, which occurred de novo in four patients, and was inherited in three families in association with marked phenotypic variability. In 50 of 52 samples from 34 patients, we identified a marked upregulation of type I interferon-stimulated gene transcripts in peripheral blood, with ...
Thiamine transporter-2 deficiency is caused by mutations in the SLC19A3 gene. As opposed to other... more Thiamine transporter-2 deficiency is caused by mutations in the SLC19A3 gene. As opposed to other causes of Leigh syndrome, early administration of thiamine and biotin has a dramatic and immediate clinical effect. New biochemical markers are needed to aid in early diagnosis and timely therapeutic intervention. Thiamine derivatives were analysed by high performance liquid chromatography in 106 whole blood and 38 cerebrospinal fluid samples from paediatric controls, 16 cerebrospinal fluid samples from patients with Leigh syndrome, six of whom harboured mutations in the SLC19A3 gene, and 49 patients with other neurological disorders. Free-thiamine was remarkably reduced in the cerebrospinal fluid of five SLC19A3 patients before treatment. In contrast, free-thiamine was slightly decreased in 15.2% of patients with other neurological conditions, and above the reference range in one SLC19A3 patient on thiamine supplementation. We also observed a severe deficiency of free-thiamine and low ...
Background Monocarboxylate transporter 1 (MCT1) deficiency has recently been described as a rare ... more Background Monocarboxylate transporter 1 (MCT1) deficiency has recently been described as a rare cause of recurrent ketosis, the result of impaired ketone utilization in extrahepatic tissues. To date, only six patients with this condition have been identified, and clinical and biochemical details remain incomplete. Results The present work reports a patient suffering from severe, recurrent episodes of metabolic acidosis and psychomotor delay, showing a pathogenic loss-of-function variation c.747_750del in homozygosity in SLC16A1 (which codes for MCT1). Persistent ketotic and lactic acidosis was accompanied by an abnormal excretion of organic acids related to redox balance disturbances. Together with an altered bioenergetic profile detected in patient-derived fibroblasts, this suggests possible mitochondrial dysfunction. Brain MRI revealed extensive, diffuse bilateral, symmetric signal alterations for the subcortical white matter and basal ganglia, together with corpus callosum agene...
Propionyl-CoA carboxylase (PCC) is a biotin-dependent enzyme located in the mitochondrial matrix.... more Propionyl-CoA carboxylase (PCC) is a biotin-dependent enzyme located in the mitochondrial matrix. Mutations in the PCCA and PCCB genes, which encode the a and b subunits of this heteropolymer, result in propionic acidemia (PA). We report the molecular analysis of b-deficient patients from Spain and Austria. Subjects were screened for defects affecting the PCCB gene by direct sequencing from genomic PCR products, restriction digests and mRNA analysis by RT-PCR. Study by western blot of the presence of immunoreactive b-PCC protein was also performed. A total of four novel sequence variations were found including the point mutations V205D, and M442T, and the frameshift mutation 790-791insG. Additionally, a new point change, L17M, was identified on the same allele as 790-791insG. The missense changes described above were not found in at least 40 control chromosomes analyzed. The Austrian patients were homozygous for V205D. One of the Spanish subjects was heterozygous for M442T and the known mutation c1170insT. The other Spanish patient carried L17M+790-791insG on one allele, and the described mutation E168K on the other mutant chromosome. The mutations V205D and M442T were confirmed at RNA level and also we have detected the presence of immunoreactive b-PCC protein translated from these mutant alleles. The patient having L17M+790-791insG and E168K also presented immunoreactive b-PCC protein. However, no cDNA product was obtained from the chromosome carrying L17M+790-791insG. We propose that 790-791insG, which causes a frameshift and a premature stop codon, is responsible for this finding. In any case, the translation from this mutant cDNA would produce a severity truncated peptide and, in consequence, a non-functional protein. Expression analysis of all these changes will help us to clarify their structural/functional consequences.
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Papers by Pilar Rodríguez-Pombo