Medicine (Austin & Northern Health) - Research Publications

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Start date: 2012 × End date: 2013 × Author: DAHL, HANS-HENRIK × Author: Berkovic, Samuel ×

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    Cathepsin F mutations cause Type B Kufs disease, an adult-onset neuronal ceroid lipofuscinosis
    Smith, KR ; Dahl, H-HM ; Canafoglia, L ; Andermann, E ; Damiano, J ; Morbin, M ; Bruni, AC ; Giaccone, G ; Cossette, P ; Saftig, P ; Groetzinger, J ; Schwake, M ; Andermann, F ; Staropoli, JF ; Sims, KB ; Mole, SE ; Franceschetti, S ; Alexander, NA ; Cooper, JD ; Chapman, HA ; Carpenter, S ; Berkovic, SF ; Bahlo, M (OXFORD UNIV PRESS, 2013-04-01)
    Kufs disease, an adult-onset neuronal ceroid lipofuscinosis, is challenging to diagnose and genetically heterogeneous. Mutations in CLN6 were recently identified in recessive Kufs disease presenting as progressive myoclonus epilepsy (Type A), whereas the molecular basis of cases presenting with dementia and motor features (Type B) is unknown. We performed genome-wide linkage mapping of two families with recessive Type B Kufs disease and identified a single region on chromosome 11 to which both families showed linkage. Exome sequencing of five samples from the two families identified homozygous and compound heterozygous missense mutations in CTSF within this linkage region. We subsequently sequenced CTSF in 22 unrelated individuals with suspected recessive Kufs disease, and identified an additional patient with compound heterozygous mutations. CTSF encodes cathepsin F, a lysosomal cysteine protease, dysfunction of which is a highly plausible candidate mechanism for a storage disorder like ceroid lipofuscinosis. In silico modeling suggested the missense mutations would alter protein structure and function. Moreover, re-examination of a previously published mouse knockout of Ctsf shows that it recapitulates the light and electron-microscopic pathological features of Kufs disease. Although CTSF mutations account for a minority of cases of type B Kufs, CTSF screening should be considered in cases with early-onset dementia and may avoid the need for invasive biopsies.
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    Early onset absence epilepsy: 1 in 10 cases is caused by GLUT1 deficiency
    Arsov, T ; Mullen, SA ; Damiano, JA ; Lawrence, KM ; Huh, LL ; Nolan, M ; Young, H ; Thouin, A ; Dahl, H-HM ; Berkovic, SF ; Crompton, DE ; Sadleir, LG ; Scheffer, IE (WILEY-BLACKWELL, 2012-12)
    Glucose transporter 1 (GLUT1) deficiency caused by mutations of SLC2A1 is an increasingly recognized cause of genetic generalized epilepsy. We previously reported that >10% (4 of 34) of a cohort with early onset absence epilepsy (EOAE) had GLUT1 deficiency. This study uses a new cohort of 55 patients with EOAE to confirm that finding. Patients with typical absence seizures beginning before 4 years of age were screened for solute carrier family 2 (facilitated glucose transporter), member 1 (SLC2A1) mutations or deletions. All had generalized spike-waves on electroencephalography (EEG). Those with tonic and/or atonic seizures were excluded. Mutations were found in 7 (13%) of 55 cases, including five missense mutations, an in-frame deletion leading to loss of a single amino acid, and a deletion spanning two exons. Over both studies, 11 (12%) of 89 probands with EOAE have GLUT1 deficiency. Given the major treatment and genetic counseling implications, this study confirms that SLC2A1 mutational analysis should be strongly considered in EOAE.
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    Strikingly Different Clinicopathological Phenotypes Determined by Progranulin-Mutation Dosage
    Smith, KR ; Damiano, J ; Franceschetti, S ; Carpenter, S ; Canafoglia, L ; Morbin, M ; Rossi, G ; Pareyson, D ; Mole, SE ; Staropoli, JF ; Sims, KB ; Lewis, J ; Lin, W-L ; Dickson, DW ; Dahl, H-H ; Bahlo, M ; Berkovic, SF (CELL PRESS, 2012-06-08)
    We performed hypothesis-free linkage analysis and exome sequencing in a family with two siblings who had neuronal ceroid lipofuscinosis (NCL). Two linkage peaks with maximum LOD scores of 3.07 and 2.97 were found on chromosomes 7 and 17, respectively. Unexpectedly, we found these siblings to be homozygous for a c.813_816del (p.Thr272Serfs∗10) mutation in the progranulin gene (GRN, granulin precursor) in the latter peak. Heterozygous mutations in GRN are a major cause of frontotemporal lobar degeneration with TDP-43 inclusions (FTLD-TDP), the second most common early-onset dementia. Reexamination of progranulin-deficient mice revealed rectilinear profiles typical of NCL. The age-at-onset and neuropathology of FTLD-TDP and NCL are markedly different. Our findings reveal an unanticipated link between a rare and a common neurological disorder and illustrate pleiotropic effects of a mutation in the heterozygous or homozygous states.