Publications by authors named "Helena Pihko"

35 Publications

ZNHIT3 is defective in PEHO syndrome, a severe encephalopathy with cerebellar granule neuron loss.

Brain 2017 05;140(5):1267-1279

The Folkhälsan Institute of Genetics, Haartmaninkatu 8, 00290 Helsinki, Finland.

Progressive encephalopathy with oedema, hypsarrhythmia, and optic atrophy (PEHO) syndrome is an early childhood onset, severe autosomal recessive encephalopathy characterized by extreme cerebellar atrophy due to almost total granule neuron loss. By combining homozygosity mapping in Finnish families with Sanger sequencing of positional candidate genes and with exome sequencing a homozygous missense substitution of leucine for serine at codon 31 in ZNHIT3 was identified as the primary cause of PEHO syndrome. ZNHIT3 encodes a nuclear zinc finger protein previously implicated in transcriptional regulation and in small nucleolar ribonucleoprotein particle assembly and thus possibly to pre-ribosomal RNA processing. The identified mutation affects a highly conserved amino acid residue in the zinc finger domain of ZNHIT3. Both knockdown and genome editing of znhit3 in zebrafish embryos recapitulate the patients' cerebellar defects, microcephaly and oedema. These phenotypes are rescued by wild-type, but not mutant human ZNHIT3 mRNA, suggesting that the patient missense substitution causes disease through a loss-of-function mechanism. Transfection of cell lines with ZNHIT3 expression vectors showed that the PEHO syndrome mutant protein is unstable. Immunohistochemical analysis of mouse cerebellar tissue demonstrated ZNHIT3 to be expressed in proliferating granule cell precursors, in proliferating and post-mitotic granule cells, and in Purkinje cells. Knockdown of Znhit3 in cultured mouse granule neurons and ex vivo cerebellar slices indicate that ZNHIT3 is indispensable for granule neuron survival and migration, consistent with the zebrafish findings and patient neuropathology. These results suggest that loss-of-function of a nuclear regulator protein underlies PEHO syndrome and imply that establishment of its spatiotemporal interaction targets will be the basis for developing therapeutic approaches and for improved understanding of cerebellar development.
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http://dx.doi.org/10.1093/brain/awx040DOI Listing
May 2017

Absence of Hikeshi, a nuclear transporter for heat-shock protein HSP70, causes infantile hypomyelinating leukoencephalopathy.

Eur J Hum Genet 2017 02 21;25(3):366-370. Epub 2016 Dec 21.

Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Helsinki, Finland.

Genetic leukoencephalopathies are a heterogeneous group of central nervous system disorders with white matter involvement. In a Finnish patient, we identified a novel homozygous disease-causing variant in HIKESHI, c.11G>C, p.(Cys4Ser), leading to hypomyelinating leukoencephalopathy with periventricular cysts and vermian atrophy. A founder Ashkenazi-Jewish disease-causing variant recently linked Hikeshi and its heat-shock protective function to leukoencephalopathy. In our patient, clinical features of lower limb spasticity, optic atrophy, nystagmus, and severe developmental delay were similar to reported patients. Additional features included vermian atrophy, epileptic seizures, and an ovarian tumor. Structural modeling and protein analyses revealed that modified interactions inside Hikeshi's hydrophobic pockets induce protein instability. The patient's cells showed impaired nuclear translocation of HSP70 during heat shock, and decreased ERO1-Lα, an endoplasmic reticulum (ER) oxidoreductase. Overall, we show that: (1) the clinical spectrum associated with Hikeshi deficiency extends to leukoencephalopathy with vermian atrophy and epilepsy; (2) the cellular disease process involves both nuclear chaperone and ER functions.
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http://dx.doi.org/10.1038/ejhg.2016.189DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5315520PMC
February 2017

Dysfunctional ADAM22 implicated in progressive encephalopathy with cortical atrophy and epilepsy.

Neurol Genet 2016 Feb 21;2(1):e46. Epub 2016 Jan 21.

Institute for Molecular Medicine Finland (M.M., A.P.), Neuroscience Center (M.M., A.L., A.-E.L.), and Research Programs Unit, Molecular Neurology (M.M., A.-K.A., A.L., A.-E.L.), University of Helsinki, Finland; Folkhälsan Institute of Genetics (M.M., A.-K.A., A.L., A.-E.L.), Helsinki, Finland; Division of Membrane Physiology (Y.F., M.F.), Department of Cell Physiology, National Institute for Physiological Sciences, National Institutes of Natural Sciences, Okazaki, Japan; Department of Physiological Sciences (Y.F., M.F.), School of Life Science, SOKENDAI (The Graduate University for Advanced Studies), Okazaki, Japan; Medical and Clinical Genetics (A.-K.A.), University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Analytic and Translational Genetics Unit (A.P.), Department of Medicine, Massachusetts General Hospital and Harvard Medical School, Boston, MA; Program in Medical and Population Genetics (A.P.) and Stanley Center for Psychiatric Research (A.P.), Broad Institute of Harvard and Massachusetts Institute of Technology, Cambridge, MA; Program in Genetics and Genomics (A.P.), Biological and Biomedical Sciences, Harvard Medical School, Boston, MA; Wellcome Trust Sanger Institute (A.P.), Wellcome Trust Genome Campus, Hinxton, United Kingdom; Psychiatric & Neurodevelopmental Genetics Unit (A.P.), Department of Psychiatry, and Department of Neurology (A.P.), Massachusetts General Hospital, Boston, MA; Department of Pediatric Neurology (H.P., T.L.), Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland; Department of Radiology (L.V.), HUS Medical Imaging Center, Helsinki, Finland; and Family Federation of Finland (M.S.), Helsinki, Finland.

Objective: To identify the molecular genetic basis of a syndrome characterized by rapidly progressing cerebral atrophy, intractable seizures, and intellectual disability.

Methods: We performed exome sequencing in the proband and whole-genome single nucleotide polymorphism genotyping (copy number variant analysis) in the proband-parent trio. We used heterologous expression systems to study the functional consequences of identified mutations.

Results: The search for potentially deleterious recessive or de novo variants yielded compound heterozygous missense (c.1202G>A, p.Cys401Tyr) and frameshift deletion (c.2396delG, p.Ser799IlefsTer96) mutations in ADAM22, which encodes a postsynaptic receptor for LGI1. The deleterious effect of the mutations was observed in cell surface binding and immunoprecipitation assays, which revealed that both mutant proteins failed to bind to LGI1. Furthermore, immunoprecipitation assays showed that the frameshift mutant ADAM22 also did not bind to the postsynaptic scaffolding protein PSD-95.

Conclusions: The mutations identified abolish the LGI1-ADAM22 ligand-receptor complex and are thus a likely primary cause of the proband's epilepsy syndrome, which is characterized by unusually rapidly progressing cortical atrophy starting at 3-4 months of age. These findings are in line with the implicated role of the LGI1-ADAM22 complex as a key player in nervous system development, specifically in functional maturation of postnatal synapses. Because the frameshift mutation affects an alternatively spliced exon with highest expression in postnatal brain, the combined effect of the mutations is likely to be hypomorphic rather than complete loss of function. This is compatible with the longer survival of the patient compared to Lgi1 (-/-) and Adam22 (-/-) mice, which develop lethal seizures during the first postnatal weeks.
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http://dx.doi.org/10.1212/NXG.0000000000000046DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4817901PMC
February 2016

Novel mutations in DNAJB6 gene cause a very severe early-onset limb-girdle muscular dystrophy 1D disease.

Neuromuscul Disord 2015 Nov 27;25(11):835-42. Epub 2015 Jul 27.

Department of Neurology, Neuromuscular Research Center, University of Tampere and Tampere University Hospital, Tampere, FIN-33014, Finland; Folkhälsan Institute of Genetics and the Department of Medical Genetics, Haartman Institute, University of Helsinki, Helsinki, Finland; Department of Neurology, Vaasa Central Hospital, Vaasa, Finland.

DNAJB6 is the causative gene for limb-girdle muscular dystrophy 1D (LGMD1D). Four different coding missense mutations, p.F89I, p.F93I, p.F93L, and p.P96R, have been reported in families from Europe, North America and Asia. The previously known mutations cause mainly adult-onset proximal muscle weakness with moderate progression and without respiratory involvement. A Finnish family and a British patient have been studied extensively due to a severe muscular dystrophy. The patients had childhood-onset LGMD, loss of ambulation in early adulthood and respiratory involvement; one patient died of respiratory failure aged 32. Two novel mutations, c.271T > A (p.F91I) and c.271T > C (p.F91L), in DNAJB6 were identified by whole exome sequencing as a cause of this severe form of LGMD1D. The results were confirmed by Sanger sequencing. The anti-aggregation effect of the mutant DNAJB6 was investigated in a filter-trap based system using transient transfection of mammalian cell lines and polyQ-huntingtin as a model for an aggregation-prone protein. Both novel mutant proteins show a significant loss of ability to prevent aggregation.
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http://dx.doi.org/10.1016/j.nmd.2015.07.014DOI Listing
November 2015

Selenoprotein biosynthesis defect causes progressive encephalopathy with elevated lactate.

Neurology 2015 Jul 26;85(4):306-15. Epub 2015 Jun 26.

From the Department of Medical Genetics, Haartman Institute (A.-K.A., H.T.), Folkhälsan Institute of Genetics and Neuroscience Center (A.-K.A., A.L., A.-E.L.), Research Programs Unit, Molecular Neurology, Biomedicum Helsinki (T.H., P.I., A.L., E.Y., A.-E.L.), University of Helsinki; Departments of Clinical Genetics (A.-K.A.) and Neurology (A.S.), Helsinki University Central Hospital; Department of Pediatric Neurology (T. Linnankivi, P.I., T. Lönnqvist, H.P.), Children's Hospital, University of Helsinki and Helsinki University Central Hospital, Finland; Department of Biochemistry and Molecular Genetics (R.L.F., M. Simonović), University of Illinois at Chicago; Department of Molecular Biophysics and Biochemistry (Y.L., D.S.), Yale University, New Haven, CT; Norio Centre (M. Somer), Department of Medical Genetics, Helsinki, Finland; Turku Centre for Biotechnology (D.M.-P., G.L.C.), University of Turku and Åbo Akademi University; Department of Pediatric Neurology (M.L.), South Karelia Central Hospital, Lappeenranta; Department of Radiology (L.V.), HUS Medical Imaging Center, Helsinki; and Department of Pathology (A.P.), HUSLAB and University of Helsinki, Finland. G.L.C. is currently affiliated with Van't Hoff Institute for Molecular Sciences, University of Amsterdam, the Netherlands.

Objective: We aimed to decipher the molecular genetic basis of disease in a cohort of children with a uniform clinical presentation of neonatal irritability, spastic or dystonic quadriplegia, virtually absent psychomotor development, axonal neuropathy, and elevated blood/CSF lactate.

Methods: We performed whole-exome sequencing of blood DNA from the index patients. Detected compound heterozygous mutations were confirmed by Sanger sequencing. Structural predictions and a bacterial activity assay were performed to evaluate the functional consequences of the mutations. Mass spectrometry, Western blotting, and protein oxidation detection were used to analyze the effects of selenoprotein deficiency.

Results: Neuropathology indicated laminar necrosis and severe loss of myelin, with neuron loss and astrogliosis. In 3 families, we identified a missense (p.Thr325Ser) and a nonsense (p.Tyr429*) mutation in SEPSECS, encoding the O-phosphoseryl-tRNA:selenocysteinyl-tRNA synthase, which was previously associated with progressive cerebellocerebral atrophy. We show that the mutations do not completely abolish the activity of SEPSECS, but lead to decreased selenoprotein levels, with demonstrated increase in oxidative protein damage in the patient brain.

Conclusions: These results extend the phenotypes caused by defective selenocysteine biosynthesis, and suggest SEPSECS as a candidate gene for progressive encephalopathies with lactate elevation.
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http://dx.doi.org/10.1212/WNL.0000000000001787DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4520820PMC
July 2015

[Investments of research and treatment of brain diseases will pay of time].

Duodecim 2014 ;130(17):1721-30

In 2010, a quarter of direct healthcare cost in Europe were spent on brain diseases. The importance of preventing and treating brain diseases and maintaining of functional capacity of the brain will increase in our society with ageing population and with increasing cognitive requirements of modern working life. Public funding of basic and clinical neuroscience has, however, frozen to levels achieved years ago, clinical research of brain diseases being at a particular risk. Research projects directed to prevention, treatment, and rehabilitation of brain diseases will pay off, also when assessed by economic measures.
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October 2014

Mitochondrial EFTs defects in juvenile-onset Leigh disease, ataxia, neuropathy, and optic atrophy.

Neurology 2014 Aug 18;83(8):743-51. Epub 2014 Jul 18.

From the Research Programs Unit, Molecular Neurology, Biomedicum Helsinki (S.A., P.I., L.E., V.B., H.T., A.S.), Institute for Molecular Medicine Finland (A.P.), Department of Medical Genetics, Haartman Institute (H.T.), and Neuroscience Center (A.S.), University of Helsinki; Department of Child Neurology, Children's Hospital (P.I., H.P., T. Lönnqvist), and Department of Neurology (A.S.), Helsinki University Central Hospital, Finland; Analytic and Translational Genetics Unit, Department of Medicine (A.P.), and Psychiatric & Neurodevelopmental Genetics Unit, Department of Psychiatry (A.P.), Massachusetts General Hospital, Boston; Program in Medical and Population Genetics (A.P.), Broad Institute of MIT and Harvard, Cambridge, MA; and Department of Pathology (T. Lehtonen, J.L.), University of Turku, Finland.

Objective: We report novel defects of mitochondrial translation elongation factor Ts (EFTs), with high carrier frequency in Finland and expand the manifestations of this disease group from infantile cardiomyopathy to juvenile neuropathy/encephalopathy disorders.

Methods: DNA analysis, whole-exome analysis, protein biochemistry, and protein modeling.

Results: We used whole-exome sequencing to find the genetic cause of infantile-onset mitochondrial cardiomyopathy, progressing to juvenile-onset Leigh syndrome, neuropathy, and optic atrophy in 2 siblings. We found novel compound heterozygous mutations, c.944G>A [p.C315Y] and c.856C>T [p.Q286X], in the TSFM gene encoding mitochondrial EFTs. The same p.Q286X variant was found as compound heterozygous with a splice site change in a patient from a second family, with juvenile-onset optic atrophy, peripheral neuropathy, and ataxia. Our molecular modeling predicted the coding-region mutations to cause protein instability, which was experimentally confirmed in cultured patient cells, with mitochondrial translation defect and lacking EFTs. Only a single TSFM mutation has been previously described in different populations, leading to an infantile fatal multisystem disorder with cardiomyopathy. Sequence data from 35,000 Finnish population controls indicated that the heterozygous carrier frequency of p.Q286X change was exceptionally high in Finland, 1:80, but no homozygotes were found in the population, in our mitochondrial disease patient collection, or in an intrauterine fetal death material, suggesting early developmental lethality of the homozygotes.

Conclusions: We show that in addition to early-onset cardiomyopathy, TSFM mutations should be considered in childhood and juvenile encephalopathies with optic and/or peripheral neuropathy, ataxia, or Leigh disease.
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http://dx.doi.org/10.1212/WNL.0000000000000716DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4150129PMC
August 2014

Mitochondrial encephalomyopathy and retinoblastoma explained by compound heterozygosity of SUCLA2 point mutation and 13q14 deletion.

Eur J Hum Genet 2015 Mar 2;23(3):325-30. Epub 2014 Jul 2.

1] Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Helsinki, Finland [2] Department of Neurology, Helsinki University Central Hospital, Helsinki, Finland [3] Neuroscience center, University of Helsinki, Helsinki, Finland.

Mutations in SUCLA2, encoding the ß-subunit of succinyl-CoA synthetase of Krebs cycle, are one cause of mitochondrial DNA depletion syndrome. Patients have been reported to have severe progressive childhood-onset encephalomyopathy, and methylmalonic aciduria, often leading to death in childhood. We studied two families, with children manifesting with slowly progressive mitochondrial encephalomyopathy, hearing impairment and transient methylmalonic aciduria, without mtDNA depletion. The other family also showed dominant inheritance of bilateral retinoblastoma, which coexisted with mitochondrial encephalomyopathy in one patient. We found a variant in SUCLA2 leading to Asp333Gly change, homozygous in one patient and compound heterozygous in one. The latter patient also carried a deletion of 13q14 of the other allele, discovered with molecular karyotyping. The deletion spanned both SUCLA2 and RB1 gene regions, leading to manifestation of both mitochondrial disease and retinoblastoma. We made a homology model for human succinyl-CoA synthetase and used it for structure-function analysis of all reported pathogenic mutations in SUCLA2. On the basis of our model, all previously described mutations were predicted to result in decreased amounts of incorrectly assembled protein or disruption of ADP phosphorylation, explaining the severe early lethal manifestations. However, the Asp333Gly change was predicted to reduce the activity of the otherwise functional enzyme. On the basis of our findings, SUCLA2 mutations should be analyzed in patients with slowly progressive encephalomyopathy, even in the absence of methylmalonic aciduria or mitochondrial DNA depletion. In addition, an encephalomyopathy in a patient with retinoblastoma suggests mutations affecting SUCLA2.
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http://dx.doi.org/10.1038/ejhg.2014.128DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4326715PMC
March 2015

A multicenter study on Leigh syndrome: disease course and predictors of survival.

Orphanet J Rare Dis 2014 Apr 15;9:52. Epub 2014 Apr 15.

Department of Paediatrics, University of Gothenburg, The Queen Silvia's Children Hospital, SE-416 85 Gothenburg, Sweden.

Background: Leigh syndrome is a progressive neurodegenerative disorder, associated with primary or secondary dysfunction of the mitochondrial oxidative phosphorylation. Despite the fact that Leigh syndrome is the most common phenotype of mitochondrial disorders in children, longitudinal natural history data is missing. This study was undertaken to assess the phenotypic and genotypic spectrum of patients with Leigh syndrome, characterise the clinical course and identify predictors of survival in a large cohort of patients.

Methods: This is a retrospective study of patients with Leigh syndrome that have been followed at eight centers specialising in mitochondrial diseases in Europe; Gothenburg, Rotterdam, Helsinki, Copenhagen, Stockholm, Brussels, Bergen and Oulu.

Results: A total of 130 patients were included (78 males; 52 females), of whom 77 patients had identified pathogenic mutations. The median age of disease onset was 7 months, with 80.8% of patients presenting by the age of 2 years. The most common clinical features were abnormal motor findings, followed by abnormal ocular findings. Epileptic seizures were reported in 40% of patients. Approximately 44% of patients experienced acute exacerbations requiring hospitalisation during the previous year, mainly due to infections. The presence of pathological signs at birth and a history of epileptic seizures were associated with higher occurrence of acute exacerbations and/or relapses. Increased lactate in the cerebrospinal fluid was significantly correlated to a more severe disease course, characterised by early onset before 6 months of age, acute exacerbations and/or relapses, as well as brainstem involvement. 39% of patients had died by the age of 21 years, at a median age of 2.4 years. Disease onset before 6 months of age, failure to thrive, brainstem lesions on neuroimaging and intensive care treatment were significantly associated with poorer survival.

Conclusions: This is a multicenter study performed in a large cohort of patients with Leigh syndrome. Our data help define the natural history of Leigh syndrome and identify novel predictors of disease severity and long-term prognosis.
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http://dx.doi.org/10.1186/1750-1172-9-52DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4021638PMC
April 2014

Mutation update and genotype-phenotype correlations of novel and previously described mutations in TPM2 and TPM3 causing congenital myopathies.

Hum Mutat 2014 Jul 1;35(7):779-90. Epub 2014 May 1.

The Folkhälsan Institute of Genetics and the Department of Medical Genetics, University of Helsinki, Haartman Institute, Biomedicum Helsinki, Finland.

Mutations affecting skeletal muscle isoforms of the tropomyosin genes may cause nemaline myopathy, cap myopathy, core-rod myopathy, congenital fiber-type disproportion, distal arthrogryposes, and Escobar syndrome. We correlate the clinical picture of these diseases with novel (19) and previously reported (31) mutations of the TPM2 and TPM3 genes. Included are altogether 93 families: 53 with TPM2 mutations and 40 with TPM3 mutations. Thirty distinct pathogenic variants of TPM2 and 20 of TPM3 have been published or listed in the Leiden Open Variant Database (http://www.dmd.nl/). Most are heterozygous changes associated with autosomal-dominant disease. Patients with TPM2 mutations tended to present with milder symptoms than those with TPM3 mutations, DA being present only in the TPM2 group. Previous studies have shown that five of the mutations in TPM2 and one in TPM3 cause increased Ca(2+) sensitivity resulting in a hypercontractile molecular phenotype. Patients with hypercontractile phenotype more often had contractures of the limb joints (18/19) and jaw (6/19) than those with nonhypercontractile ones (2/22 and 1/22), whereas patients with the non-hypercontractile molecular phenotype more often (19/22) had axial contractures than the hypercontractile group (7/19). Our in silico predictions show that most mutations affect tropomyosin-actin association or tropomyosin head-to-tail binding.
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http://dx.doi.org/10.1002/humu.22554DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4200603PMC
July 2014

Whole-exome sequencing identifies a mutation in the mitochondrial ribosome protein MRPL44 to underlie mitochondrial infantile cardiomyopathy.

J Med Genet 2013 Mar 12;50(3):151-9. Epub 2013 Jan 12.

Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, r.C523B, Haartmaninkatu 8, Helsinki 00290, Finland.

Background: The genetic complexity of infantile cardiomyopathies is remarkable, and the importance of mitochondrial translation defects as a causative factor is only starting to be recognised. We investigated the genetic basis for infantile onset recessive hypertrophic cardiomyopathy in two siblings.

Methods And Results: Analysis of respiratory chain enzymes revealed a combined deficiency of complexes I and IV in the heart and skeletal muscle. Exome sequencing uncovered a homozygous mutation (L156R) in MRPL44 of both siblings. MRPL44 encodes a protein in the large subunit of the mitochondrial ribosome and is suggested to locate in close proximity to the tunnel exit of the yeast mitochondrial ribosome. We found severely reduced MRPL44 levels in the patient's heart, skeletal muscle and fibroblasts suggesting that the missense mutation affected the protein stability. In patient fibroblasts, decreased MRPL44 affected assembly of the large ribosomal subunit and stability of 16S rRNA leading to complex IV deficiency. Despite this assembly defect, de novo mitochondrial translation was only mildly affected in fibroblasts suggesting that MRPL44 may have a function in the assembly/stability of nascent mitochondrial polypeptides exiting the ribosome. Retroviral expression of wild-type MRPL44 in patient fibroblasts rescued the large ribosome assembly defect and COX deficiency.

Conclusions: These findings indicate that mitochondrial ribosomal subunit defects can generate tissue-specific manifestations, such as cardiomyopathy.
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http://dx.doi.org/10.1136/jmedgenet-2012-101375DOI Listing
March 2013

Mitochondrial phenylalanyl-tRNA synthetase mutations underlie fatal infantile Alpers encephalopathy.

Hum Mol Genet 2012 Oct 23;21(20):4521-9. Epub 2012 Jul 23.

Research Programs Unit, Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, 00290 Helsinki, Finland.

Next-generation sequencing has turned out to be a powerful tool to uncover genetic basis of childhood mitochondrial disorders. We utilized whole-exome analysis and discovered novel compound heterozygous mutations in FARS2 (mitochondrial phenylalanyl transfer RNA synthetase), encoding the mitochondrial phenylalanyl transfer RNA (tRNA) synthetase (mtPheRS) in two patients with fatal epileptic mitochondrial encephalopathy. The mutations affected highly conserved amino acids, p.I329T and p.D391V. Recently, a homozygous FARS2 variant p.Y144C was reported in a Saudi girl with mitochondrial encephalopathy, but the pathogenic role of the variant remained open. Clinical features, including postnatal onset, catastrophic epilepsy, lactic acidemia, early lethality and neuroimaging findings of the patients with FARS2 variants, resembled each other closely, and neuropathology was consistent with Alpers syndrome. Our structural analysis of mtPheRS predicted that p.I329T weakened ATP binding in the aminoacylation domain, and in vitro studies with recombinant mutant protein showed decreased affinity of this variant to ATP. Furthermore, p.D391V and p.Y144C were predicted to disrupt synthetase function by interrupting the rotation of the tRNA anticodon stem-binding domain from a closed to an open form. In vitro characterization indicated reduced affinity of p.D391V mutant protein to phenylalanine, whereas p.Y144C disrupted tRNA binding. The stability of p.I329T and p.D391V mutants in a refolding assay was impaired. Our results imply that the three FARS2 mutations directly impair aminoacylation function and stability of mtPheRS, leading to a decrease in overall tRNA charging capacity. This study establishes a new genetic cause of infantile mitochondrial Alpers encephalopathy and reports a new mitochondrial aminoacyl-tRNA synthetase as a cause of mitochondrial disease.
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http://dx.doi.org/10.1093/hmg/dds294DOI Listing
October 2012

Mutations in CTC1, encoding the CTS telomere maintenance complex component 1, cause cerebroretinal microangiopathy with calcifications and cysts.

Am J Hum Genet 2012 Mar 1;90(3):540-9. Epub 2012 Mar 1.

Folkhälsan Institute of Genetics, Helsinki, Finland.

Cerebroretinal microangiopathy with calcifications and cysts (CRMCC) is a rare multisystem disorder characterized by extensive intracranial calcifications and cysts, leukoencephalopathy, and retinal vascular abnormalities. Additional features include poor growth, skeletal and hematological abnormalities, and recurrent gastrointestinal bleedings. Autosomal-recessive inheritance has been postulated. The pathogenesis of CRMCC is unknown, but its phenotype has key similarities with Revesz syndrome, which is caused by mutations in TINF2, a gene encoding a member of the telomere protecting shelterin complex. After a whole-exome sequencing approach in four unrelated individuals with CRMCC, we observed four recessively inherited compound heterozygous mutations in CTC1, which encodes the CTS telomere maintenance complex component 1. Sanger sequencing revealed seven more compound heterozygous mutations in eight more unrelated affected individuals. Two individuals who displayed late-onset cerebral findings, a normal fundus appearance, and no systemic findings did not have CTC1 mutations, implying that systemic findings are an important indication for CTC1 sequencing. Of the 11 mutations identified, four were missense, one was nonsense, two resulted in in-frame amino acid deletions, and four were short frameshift-creating deletions. All but two affected individuals were compound heterozygous for a missense mutation and a frameshift or nonsense mutation. No individuals with two frameshift or nonsense mutations were identified, which implies that severe disturbance of CTC1 function from both alleles might not be compatible with survival. Our preliminary functional experiments did not show evidence of severely affected telomere integrity in the affected individuals. Therefore, determining the underlying pathomechanisms associated with deficient CTC1 function will require further studies.
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http://dx.doi.org/10.1016/j.ajhg.2012.02.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3309194PMC
March 2012

FGF-21 as a biomarker for muscle-manifesting mitochondrial respiratory chain deficiencies: a diagnostic study.

Lancet Neurol 2011 Sep 3;10(9):806-18. Epub 2011 Aug 3.

Research Programmes Unit, Molecular Neurology, University of Helsinki, Helsinki, Finland.

Background: Muscle biopsy is the gold standard for diagnosis of mitochondrial disorders because of the lack of sensitive biomarkers in serum. Fibroblast growth factor 21 (FGF-21) is a growth factor with regulatory roles in lipid metabolism and the starvation response, and concentrations are raised in skeletal muscle and serum in mice with mitochondrial respiratory chain deficiencies. We investigated in a retrospective diagnostic study whether FGF-21 could be a biomarker for human mitochondrial disorders.

Methods: We assessed samples from adults and children with mitochondrial disorders or non-mitochondrial neurological disorders (disease controls) from seven study centres in Europe and the USA, and recruited healthy volunteers (healthy controls), matched for age where possible, from the same centres. We used ELISA to measure FGF-21 concentrations in serum or plasma samples (abnormal values were defined as >200 pg/mL). We compared these concentrations with values for lactate, pyruvate, lactate-to-pyruvate ratio, and creatine kinase in serum or plasma and calculated sensitivity, specificity, and positive and negative predictive values for all biomarkers.

Findings: We analysed serum or plasma from 67 patients (41 adults and 26 children) with mitochondrial disorders, 34 disease controls (22 adults and 12 children), and 74 healthy controls. Mean FGF-21 concentrations in serum were 820 (SD 1151) pg/mL in adult and 1983 (1550) pg/mL in child patients with respiratory chain deficiencies and 76 (58) pg/mL in healthy controls. FGF-21 concentrations were high in patients with mitochondrial disorders affecting skeletal muscle but not in disease controls, including those with dystrophies. In patients with abnormal FGF-21 concentrations in serum, the odds ratio of having a muscle-manifesting mitochondrial disease was 132·0 (95% CI 38·7-450·3). For the identification of muscle-manifesting mitochondrial disease, the sensitivity was 92·3% (95% CI 81·5-97·9%) and specificity was 91·7% (84·8-96·1%). The positive and negative predictive values for FGF-21 were 84·2% (95% CI 72·1-92·5%) and 96·1 (90·4-98·9%). The accuracy of FGF-21 to correctly identify muscle-manifesting respiratory chain disorders was better than that for all conventional biomarkers. The area under the receiver-operating-characteristic curve for FGF-21 was 0·95; by comparison, the values for other biomarkers were 0·83 lactate (p=0·037, 0·83 for pyruvate (p=0·015), 0·72 for the lactate-to-pyruvate ratio (p=0·0002), and 0·77 for creatine kinase (p=0·013).

Interpretation: Measurement of FGF-21 concentrations in serum identified primary muscle-manifesting respiratory chain deficiencies in adults and children and might be feasible as a first-line diagnostic test for these disorders to reduce the need for muscle biopsy.

Funding: Sigrid Jusélius Foundation, Jane and Aatos Erkko Foundation, Molecular Medicine Institute of Finland, University of Helsinki, Helsinki University Central Hospital, Academy of Finland, Novo Nordisk, Arvo and Lea Ylppö Foundation.
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http://dx.doi.org/10.1016/S1474-4422(11)70155-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7568343PMC
September 2011

[Mitochondrial recessive ataxia syndrome (MIRAS) and valproate toxicity].

Duodecim 2010 ;126(13):1552-9

Helsingin yliopisto, Biomedicum, molekyylineurologian tutkimusohjelma.

The clinical phenotypes vary considerably and can be divided into three groups: 1) childhood-onset encephalopathy and hepatopathy, 2) juvenile onset refractory epilepsy and migraine-like headaches, and 3) adult-onset ataxia and neuropathy with additional symptoms such as psychiatric symptoms and cognitive impairment. The life-threatening MIRAS epilepsy should be actively treated, as it is associated with poor prognosis. The form of MIRAS, starting as acute, treatment resistant epilepsy, is important to diagnose, since valproate therapy almost always leads to acute liver failure requiring liver transplantation.
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September 2010

Long-term follow-up in patients with congenital myasthenic syndrome due to CHAT mutations.

Eur J Paediatr Neurol 2010 Jul 8;14(4):326-33. Epub 2009 Nov 8.

Dept. of Paediatric Neurology, University of Essen, Hufelandstr. 55, D-45122 Essen, Germany.

Background: Congenital myasthenic syndromes (CMSs) are a group of clinically and genetically heterogeneous inherited disorders of the neuromuscular junction. Mutations in the acetylcholine transferase (CHAT) gene cause a pre-synaptic CMS, typically associated with episodic apnoea and worsening of myasthenic symptoms during crises caused by infections, fever or stress. Between crises symptoms may be mild and variable. Acetylcholinesterase - inhibitor therapy is reported to improve clinical symptoms and reduce crises.

Patients And Methods: We present data on the long-term follow-up of 11 patients with a congenital myasthenic syndrome due to nine different CHAT mutations; ten of the patients have not been previously reported.

Results And Conclusions: Manifestation varied from the neonatal period to the age of two years, follow-up time from nine months to 12 years. This cohort of CHAT patients studied here enabled us to describe two distinct phenotypes: The neonatal-onset group suffers from apnoeic crises, respirator dependency and bulbar weakness. Apnoea should be carefully distinguished from seizures; a CMS should be taken into account early to start appropriate therapy. Infantile-onset patients show mild permanent weakness, but experience apnoeic crises and worsening which resolve with Acetylcholinesterase - inhibitor treatment. However, after several years of treatment proximal muscle strength may decrease and lead to wheelchair dependency despite the continuation of Acetylcholinesterase - inhibitor therapy.
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http://dx.doi.org/10.1016/j.ejpn.2009.09.009DOI Listing
July 2010

Low bone mass in patients with motor disability: prevalence and risk factors in 59 Finnish children.

Dev Med Child Neurol 2010 Mar 26;52(3):276-82. Epub 2010 Aug 26.

Department of Paediatric Neurology, Päijät-Häme Central Hospital, Lahti, Finland.

Aim: Children with motor disabilities are at increased risk of compromised bone health. This study evaluated prevalence and risk factors of low bone mass and fractures in these children.

Method: This cross-sectional cohort study evaluated bone health in 59 children (38 males, 21 females; median age 10 y 11 mo) with motor disability (Gross Motor Function Classification System levels II-V). Bone mineral density (BMD) in the lumbar spine was measured with dual-energy X-ray absorptiometry; BMD values were corrected for bone size (bone mineral apparent density [BMAD]) and skeletal maturity, and compared with normative data. Spinal radiographs were obtained to assess vertebral morphology. Blood biochemistry included vitamin D concentration and other parameters of calcium homeostasis.

Results: Ten children (17%) had sustained in total 14 peripheral fractures; lower-limb fractures predominated. Compression fractures were present in 25%. The median spinal BMAD z-score was -1.0 (range -5.0 to 2.0); it was -0.6 in those without fractures and -1.7 in those with fractures (p=0.004). Vitamin D insufficiency was present in 59% of participants (serum 25-hydroxyvitamin D <50 nmol/l) and hypercalciuria in 27%. Low BMAD z-score and hypercalciuria were independent predictors for fractures.

Interpretation: Children with motor disability are at high risk of peripheral and vertebral fractures and low BMD. Evaluation of bone health and prevention of osteoporosis should be included in the follow-up.
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http://dx.doi.org/10.1111/j.1469-8749.2009.03464.xDOI Listing
March 2010

Recessive twinkle mutations cause severe epileptic encephalopathy.

Brain 2009 Jun 20;132(Pt 6):1553-62. Epub 2009 Mar 20.

Division of Child Neurology, Helsinki University Central Hospital, Helsinki, Finland.

The C10orf2 gene encodes the mitochondrial DNA helicase Twinkle, which is one of the proteins important for mitochondrial DNA maintenance. Dominant mutations cause multiple mitochondrial DNA deletions and progressive external ophthalmoplegia, but recent findings associate recessive mutations with mitochondrial DNA depletion and encephalopathy or hepatoencephalopathy. The latter clinical phenotypes resemble those associated with recessive POLG1 mutations. We have previously described patients with infantile onset spinocerebellar ataxia (MIM271245) caused either by homozygous (Y508C) or compound heterozygous (Y508C and A318T) Twinkle mutations. Our earlier reports focused on the spinocerebellar degeneration, but the 20-year follow-up of 23 patients has shown that refractory status epilepticus, migraine-like headaches and severe psychiatric symptoms are also pathognomonic for the disease. All adolescent patients have experienced phases of severe migraine, and seven patients had antipsychotic medication. Epilepsia partialis continua occurred in 15 patients leading to generalized epileptic statuses in 13 of them. Eight of these patients have died. Valproate treatment was initiated on two patients, but had to be discontinued because of a severe elevation of liver enzymes. The patients recovered, and we have not used valproate in infantile onset spinocerebellar ataxia since. The first status epilepticus manifested between 15 and 34 years of age in the homozygotes, and at 2 and 4 years in the compound heterozygotes. The epileptic statuses lasted from several days to weeks. Focal, stroke-like lesions were seen in magnetic resonance imaging, but in infantile onset spinocerebellar ataxia these lesions showed no predilection. They varied from resolving small cortical to large hemispheric oedematous lesions, which reached from cerebral cortex to basal ganglia and thalamus and caused permanent necrotic damage and brain atrophy. Brain atrophy with focal laminar cortical necrosis and hippocampal damage was confirmed on neuropathological examination. The objective of our study was to describe the development and progression of encephalopathy in infantile onset spinocerebellar ataxia syndrome, and compare the pathognomonic features with those in other mitochondrial encephalopathies.
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http://dx.doi.org/10.1093/brain/awp045DOI Listing
June 2009

Thymidine kinase 2 defects can cause multi-tissue mtDNA depletion syndrome.

Brain 2008 Nov 26;131(Pt 11):2841-50. Epub 2008 Sep 26.

Research Programme of Molecular Neurology, Biomedicum-Helsinki, University of Helsinki, Helsinki, Finland.

Mitochondrial DNA depletion syndrome (MDS) is a severe recessively inherited disease of childhood. It manifests most often in infancy, is rapidly progressive and leads to early death. MDS is caused by an increasing number of nuclear genes leading to multisystemic or tissue-specific decrease in mitochondrial DNA (mtDNA) copy number. Thymidine kinase 2 (TK2) has been reported to cause a myopathic form of MDS. We report here the clinical, autopsy and molecular genetic findings of rapidly progressive fatal infantile mitochondrial syndrome. All of our seven patients had rapidly progressive myopathy/encephalomyopathy, leading to respiratory failure within the first 3 years of life, with high creatine kinase values and dystrophic changes in the muscle with cytochrome c oxidase-negative fibres. In addition, two patients also had terminal-phase seizures, one had epilepsia partialis continua and one had cortical laminar necrosis. We identified two different homozygous or compound heterozygous mutations in the TK2 gene in all the patients: c.739 C s -> T and c.898 C -> T, leading to p.R172W and p.R225W changes at conserved protein sites. R172W mutation led to myopathy or encephalomyopathy with the onset during the first months of life, and was associated with severe mtDNA depletion in the muscle, brain and liver. Homozygosity for R225W mutation manifested during the second year of life as a myopathy, and showed muscle-specific mtDNA depletion. Both mutations originated from single ancient founders, with Finnish origin and enrichment for the new R172W mutation, and possibly Scandinavian ancestral origin for the R225W. We conclude that TK2 mutations may manifest as infantile-onset fatal myopathy with dystrophic features, but should be considered also in infantile progressive encephalomyopathy with wide-spread mtDNA depletion.
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http://dx.doi.org/10.1093/brain/awn236DOI Listing
November 2008

Headache in children and adolescents after organ transplantation.

Pediatr Transplant 2009 Aug 5;13(5):565-70. Epub 2008 May 5.

Department of Pediatric Nephrology, Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland.

The prevalence and characteristics of headache were studied in a national cohort of 177 pediatric patients with kidney, liver, and heart transplants. All patients received triple drug immunosuppression with CsA, Aza, and MP. Data on headaches were collected by sending two questionnaires and reviewing the medical records. Statements on headache were found in the medical records of 46% of the patients. According to a questionnaire, two thirds had experienced headaches sometime after transplantation, and 40% had present headaches. The episodes had significantly affected the quality of life in a third of the patients, and resulted in neurological examination in 15%. Most of the subjects (61%) described typical episode as mild or moderate, and 39% as severe or very severe. The usual episodes lasted <4 h in 73% of the patients and >4 h in 27%. The headache could be classified as migraine, probable migraine or headache without specific features in 33%, 31%, and 36%, respectively. Most patients (82%) had used pain-killers, mainly acetaminophen and ibuprofen. Headache episodes may significantly impair the quality of life in children and adolescents after organ transplantation.
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http://dx.doi.org/10.1111/j.1399-3046.2008.00973.xDOI Listing
August 2009

Screening of BCS1L mutations in severe neonatal disorders suspicious for mitochondrial cause.

J Hum Genet 2008 2;53(6):554-558. Epub 2008 Apr 2.

Department of Medical Genetics, University of Helsinki, Helsinki, Finland.

The BCS1L gene encodes a chaperone responsible for assembly of respiratory chain complex III (CIII). A homozygous point mutation (232A-->G) has been found as the genetic etiology for fetal growth retardation, amino aciduria, cholestasis, iron overload, lactic acidosis, and early death (GRACILE) syndrome (MIM 603358). Variable phenotypes have been found with other mutations. Our aim was to assess whether 232A-->G or other BCS1L mutations were present in infants (n = 21) of Finnish origin with severe, lethal disease compatible with mitochondrial disorder. A further aim was to confirm the GRACILE genotype-phenotype constancy (n = 8). Three new cases with homozygous 232A-->G mutation were identified; all had the primary GRACILE characteristics. No other mutations were found in the gene in other cases. All infants with GRACILE syndrome had the typical mutation. In conclusion, the rather homogenous population of Finns seems to have a specific BCS1L mutation that, as homozygous state, causes GRACILE syndrome, whereas other mutations are rare or not occurring. Thus, the novel clinical implication of this study is to screen for BCS1L mutations only if CIII is dysfunctioning or lacking Rieske protein, and to assess 232A-->G mutation in cases with GRACILE syndrome.
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http://dx.doi.org/10.1007/s10038-008-0284-0DOI Listing
August 2008

Skeletal dysplasia presenting as a neuromuscular disorder - report of three children.

Neuromuscul Disord 2007 Mar 22;17(3):231-4. Epub 2007 Jan 22.

Hospital for Children and Adolescents, Department of Pediatrics, P.O. Box 281, FIN-00029, Helsinki, Finland.

Three pediatric patients were investigated because of suspected muscle disorder. They were clumsy with an awkward looking waddling gait and had increasing muscle weakness and pain in the legs. Serum CK-values, electroneuromyography (ENMG) and muscle biopsy were all normal. A post-traumatic X-ray of the ankle of one of them showed epiphyseal changes and his condition was diagnosed as Camurati-Engelmann disease. Because of similarities in the clinical presentation of these boys, bone changes were looked for in the two other patients and a diagnosis of multiple epiphyseal dysplasia was made. Skeletal dysplasia should be considered as a diagnostic alternative when a child presents with an unexplained muscle weakness accompanied with pain in the limbs. Specific treatment for bone dysplasias can alleviate symptoms and prevent fractures.
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http://dx.doi.org/10.1016/j.nmd.2006.11.005DOI Listing
March 2007

18q deletions: clinical, molecular, and brain MRI findings of 14 individuals.

Am J Med Genet A 2006 Feb;140(4):331-9

Department of Pediatric Neurology, Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland.

We studied 14 individuals with partial deletions of the long arm of chromosome 18, including terminal and interstitial de novo and inherited deletions. Study participants were examined clinically and by brain MRI. The size of the deletion was determined by segregation analysis using microsatellite markers. We observed that the phenotype was highly variable, even in two families with three 1st degree relatives. Among the 14 individuals, general intelligence varied from normal to severe mental retardation. The more common features of 18q-deletions (e.g., foot deformities, aural atresia, palatal abnormalities, dysmyelination, and nystagmus) were present in individuals lacking only the distal portion 18q22.3-qtel. Interstitial deletions exerted very heterogeneous effects on phenotype. In individuals with distal 18q22.3-q23 deletions, brain MRI was very distinctive with poor differentiation of gray and white matter on T2-weighted images.
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http://dx.doi.org/10.1002/ajmg.a.31072DOI Listing
February 2006

A juvenile case of MELAS with T3271C mitochondrial DNA mutation.

Pediatr Res 2005 Aug 8;58(2):258-62. Epub 2005 Jul 8.

Department of Neurology, Biomedicum Helsinki, Helsinki University, FIN-00290 Helsinki, Finland.

We present here a patient with muscle fatigue and poor growth since the age of 6 y. The diagnosis of a mitochondrial disease was based on the presence of ragged red fibers in the muscle biopsy and on a combined defect of mitochondrial DNA-encoded respiratory enzymes. Epilepsia partialis continua with stroke-like episodes appeared 2 mo before death at the age of 18 and prompted a search for mitochondrial DNA mutations associated with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes. Minisequencing of the patient's DNA samples revealed a heteroplasmic T3271C mutation with a 78-94% mutation load in her fibroblasts or autopsy-derived tissue samples. This is the ninth reported non-Japanese patient with T3271C mutation. Our patient shows that despite very high proportion of mutant mtDNA, the T3271C mutation can give rise to mild symptoms in childhood and to a rapid terminal phase that simulates encephalitis.
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http://dx.doi.org/10.1203/01.PDR.0000169966.82325.1ADOI Listing
August 2005

[Updating recommendation for respiratory care of patients with neuromuscular disorders].

Duodecim 2004 ;120(13):1547-8

Folkhälsanin perinöllisyystieteen laitos ja Lääketieteellisen genetiikan osasto, Helsinki.

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February 2005

Neuroradiologic findings in children with renal transplantation under 5 years of age.

Pediatr Transplant 2004 Feb;8(1):44-51

Department of Radiology, Helsinki University, Haartmaninkatu 4, Box 340, 00029 Helsinki, Finland.

Chronic renal failure (CRF) is known to have adverse effects on the neurodevelopmental outcome of affected children. Some of these effects can be ameliorated by transplantation (TX). The cause and nature of the underlying brain injury is not known. We performed a brain magnetic resonance imaging (MRI) study on a group of children after TX to look for brain abnormalities and, if possible, to draw conclusions about their origin. Thirty-three children who received a renal allograft before 5 yr of age were studied. The most common diagnosis was the congenital nephrotic syndrome of Finnish type (29 patients). The male/female ratio was 22/11, the age range 6-11 yr. Pre-TX CT studies of 26 patients were available for comparison. The patient files were studied for relevant clinical history, including pre- and perinatal events, infections, hypertension, hypertensive crises, hypovolemic states and medical emergencies. These risk factors were correlated with the MRI findings. Eighteen patients (54%) had ischemic lesions in the vascular border zones. Mild lesions were seen in 10 patients, moderate in six and severe in two patients. Other findings were rare, including infarcts in the main vascular territories and basal ganglia, and central and cortical atrophy. The pre-TX CT's revealed border zone infarcts in six patients. Hemodynamic crises were reported in 14 patients and correlated well with border zone infarcts. The age at TX was greater and the duration of dialysis longer in those with border zone infarcts than in those without. Low gestational age, perinatal complications, and septic infections were not statistically significant risk factors. Because of the lack on serial imaging studies we do not know the exact timing of these brain infarcts. The good correlation to pre-TX hemodynamic crises seems, however, to indicate that most of these lesions could be prevented by careful clinical monitoring and early TX.
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http://dx.doi.org/10.1046/j.1397-3142.2003.00125.xDOI Listing
February 2004

Cerebral palsy is characterized by protein mediators in cord serum.

Ann Neurol 2004 Feb;55(2):186-94

Department of Pediatrics and Biocenter Oulu, University of Oulu, Oulu, Finland.

Cerebral palsy (CP) is a major neurodevelopmental disability in childhood. An association between intrauterine infection and CP has been reported. We examined the relationship between inflammatory mediators in cord serum and CP in term and preterm children. Regional multicenter study was conducted on 19 CP children and 19 gestation-matched paired controls. CP children (n = 27) were further compared with controls of similar gestation at birth (n = 25). Serum levels of 78 protein mediators were analyzed. Eleven analytes correlated with the length of gestation both in cases and controls. In paired analysis, B-lymphocyte chemoattractant, ciliary neurotrophic factor, epidermal growth factor, interleukin (IL)-5, IL-12, IL-13, IL-15, macrophage migration inhibitory factor, monocyte chemoattractant protein-3, monokine induced by interferon gamma, and tumor necrosis factor-related apoptosis-inducing ligand were higher in children with CP (p < or = 0.05). Preterm infants with CP showed higher epidermal growth factor and lower levels of granulocyte-macrophage colony-stimulating factor, IL-2, macrophage-derived chemokine, and pulmonary and activation-regulated chemokine than their paired controls. Inflammatory mediators and growth factors serve as a footprint of the fetal response to an insult manifesting after birth as a permanent brain damage. The cytokine patterns at birth differ between premature and term infants who develop CP.
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http://dx.doi.org/10.1002/ana.10809DOI Listing
February 2004

Hereditary neuropathy with liability to pressure palsies (HNPP) in a toddler presenting with toe-walking, pain and stiffness.

Neuromuscul Disord 2003 Dec;13(10):827-9

Department of Child Neurology, Hospital for Children and Adolescents, University of Helsinki, Helsinki University Central Hospital (HUCH), 00029 Helsinki, Finland.

The typical clinical presentation of hereditary neuropathy with liability to pressure palsies is an adult-onset recurrent, painless monoparesis. Electrophysiological abnormalities--decreased nerve conduction velocities and delayed distal latencies--can be detected even in asymptomatic patients. We describe a toddler, who presented with asymmetric toe walking, painful cramps and stiffness in the legs. He had calf hypertrophy, brisk tendon reflexes and bilateral Babinski signs and the electrophysiological examination was normal. The unlikely diagnosis of hereditary neuropathy with liability to pressure palsies was reached 5 years later, when the boy started to complain of episodic numbness and weakness in the upper extremities. His father, paternal aunt and grandmother had similar symptoms, but they had never been investigated. The typical 1.5 Mb deletion on chromosome 17p11.2-12 was found in our patient and his affected relatives.
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http://dx.doi.org/10.1016/s0960-8966(03)00134-2DOI Listing
December 2003

18q-syndrome: brain MRI shows poor differentiation of gray and white matter on T2-weighted images.

J Magn Reson Imaging 2003 Oct;18(4):414-9

Department of Pediatric Neurology, Hospital for Children and Adolescents, University of Helsinki, Helsinki, Finland.

Purpose: To study brain MRI findings in patients with 18q- syndrome and to correlate these findings with the results of the molecular breakpoint analysis.

Materials And Methods: Brain MR images of 17 patients with 18q- syndrome were evaluated. Segregation analysis was performed with 15 microsatellite markers to determine the deletion breakpoints and whether the deletion included the myelin basic protein (MBP) gene.

Results: One patient had an interstitial deletion of 18q which spared the MBP gene. He was the only one with normal brain MRI. All 16 patients with deletions including the MBP gene had abnormal white matter in MRI. The main finding was poor differentiation of gray and white matter on T2-weighted images due to increased white matter signal intensity. In addition, measured signal intensity of the white matter was significantly increased in patients compared with controls.

Conclusions: Poor differentiation of gray and white matter on T2-weighted images is the most typical MRI finding of the 18q- syndrome. These results support the postulation that abnormal myelination in 18q- syndrome is due to haploinsufficiency at or near the MBP locus.
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http://dx.doi.org/10.1002/jmri.10383DOI Listing
October 2003
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