Uniparental disomy of chromosome 16 unmasks recessive mutations of FA2H/SPG35 in 4 families.
OBJECTIVE
Identifying an intriguing mechanism for unmasking recessive hereditary spastic paraplegias.


METHODS
Herein, we describe 4 novel homozygous FA2H mutations in 4 nonconsanguineous families detected by whole-exome sequencing or a targeted gene panel analysis providing high coverage of all known hereditary spastic paraplegia genes.


RESULTS
Segregation analysis revealed in all cases only one parent as a heterozygous mutation carrier whereas the other parent did not carry FA2H mutations. A macro deletion within FA2H, which could have caused a hemizygous genotype, was excluded by multiplex ligation-dependent probe amplification in all cases. Finally, a microsatellite array revealed uniparental disomy (UPD) in all 4 families leading to homozygous FA2H mutations. UPD was confirmed by microarray analyses and methylation profiling.


CONCLUSIONS
UPD has rarely been described as causative mechanism in neurodegenerative diseases. Of note, we identified this mode of inheritance in 4 families with the rare diagnosis of spastic paraplegia type 35 (SPG35). Since UPD seems to be a relevant factor in SPG35 and probably additional autosomal recessive diseases, we recommend segregation analysis especially in nonconsanguineous homozygous index cases to unravel UPD as mutational mechanism. This finding may bear major repercussion for genetic counseling, given the markedly reduced risk of recurrence for affected families.
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Anne S
AS
Soehn
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Tim W
TW
Rattay
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Stefanie
S
Beck-Wödl
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Karin
K
Schäferhoff
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
David
D
Monk
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Marion
M
Döbler-Neumann
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Konstanze
K
Hörtnagel
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Agatha
A
Schlüter
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Montserrat
M
Ruiz
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Aurora
A
Pujol
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Stephan
S
Züchner
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Olaf
O
Riess
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Rebecca
R
Schüle
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL. peter.bauer@med.uni-tuebingen.de.
Peter
P
Bauer
From the Institute of Medical Genetics and Applied Genomics (A.S.S., S.B.-W., K.S., O.R., P.B.) and Department of Neurology and Hertie Institute for Clinical Brain Research (T.W.R., R.S., L.S.), University of Tübingen; German Center of Neurodegenerative Diseases (DZNE) (T.W.R., R.S.), Tübingen, Germany; Imprinting and Cancer Group (D.M.), Cancer Epigenetic and Biology Program, Institut d'Investigació Biomedica de Bellvitge, Hospital Duran i Reynals, Barcelona, Spain; Department of Neuropediatrics (M.D.-N.), Tübingen University School of Medicine; CeGaT GmbH (K.H.), Tübingen, Germany; Neurometabolic Diseases Laboratory (A.S., M.R., A.P.), Institut d'Investigació Biomedica de Bellvitge IDIBELL, Hospital Duran i Reynals, Barcelona; Centre for Biomedical Research on Rare Diseases (CIBERER) (A.S., M.R., A.P.), Institute Carlos III, Madrid; Catalan Institution for Research and Advanced Studies (ICREA) (A.P.), Barcelona, Spain; and Hussman Institute for Human Genomics (S.Z., R.S.), University of Miami Miller School of Medicine, FL.
Ludger
L
Schöls
D000293:Adolescent; D002648:Child; D002885:Chromosomes, Human, Pair 16; D018389:Codon, Nonsense; D005190:Family; D005260:Female; D020271:Heredodegenerative Disorders, Nervous System / Q000235:genetics*; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats; D006899:Mixed Function Oxygenases / Q000235:genetics*; D020125:Mutation, Missense; D024182:Uniparental Disomy
D018389:Codon, Nonsense; D006899:Mixed Function Oxygenases; C019081:fatty acid alpha-hydroxylase