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BRAIN
A JOURNAL OF NEUROLOGY
SPATACSIN mutations cause autosomal recessive
juvenile amyotrophic lateral sclerosis
Antonio Orlacchio,1,2 Carla Babalini,1 Antonella Borreca,1,2 Clarice Patrono,1 Roberto Massa,1,2
Sarenur Basaran,3 Renato P. Munhoz,4 Ekaterina A. Rogaeva,5,6
Peter H. St George-Hyslop,5,6,7 Giorgio Bernardi1,2 and Toshitaka Kawarai8
1 Laboratorio di Neurogenetica, CERC-IRCCS Santa Lucia, Rome, Italy
2 Dipartimento di Neuroscienze, Università di Roma ‘Tor Vergata’, Rome, Italy
3 Department of Medical Genetics, Istanbul University Cerrahpasa School of Medicine, Istanbul, Turkey
4 Department of Neurology, Federal University of Paraná, Curitiba, PR, Brazil
5 Centre for Research in Neurodegenerative Diseases, University of Toronto, Toronto, ON, Canada
6 Department of Medicine, University of Toronto, Toronto, ON, Canada
7 Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
8 Department of Neurology, Hyogo Brain and Heart Centre, Himeji City, Japan
Correspondence to: Prof. Antonio Orlacchio,
Laboratorio di Neurogenetica,
Centro Europeo di Ricerca sul Cervello (CERC)-Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Santa Lucia,
64 Via del Fosso di Fiorano,
Rome 00143,
Italy
E-mail: a.orlacchio@hsantalucia.it
The mutation of the spatacsin gene is the single most common cause of autosomal recessive hereditary spastic paraplegia with
thin corpus callosum. Common clinical, pathological and genetic features between amyotrophic lateral sclerosis and hereditary
spastic paraplegia motivated us to investigate 25 families with autosomal recessive juvenile amyotrophic lateral sclerosis and
long-term survival for mutations in the spatascin gene. The inclusion criterion was a diagnosis of clinically definite amyotrophic
lateral sclerosis according to the revised El Escorial criteria. The exclusion criterion was a diagnosis of hereditary spastic
paraplegia with thin corpus callosum in line with an established protocol. Additional pathological and genetic evaluations
were also performed. Surprisingly, 12 sequence alterations in the spatacsin gene (one of which is novel, IVS30 + 1 G4A)
were identified in 10 unrelated pedigrees with autosomal recessive juvenile amyotrophic lateral sclerosis and long-term survival.
The countries of origin of these families were Italy, Brazil, Canada, Japan and Turkey. The variants seemed to be pathogenic
since they co-segregated with the disease in all pedigrees, were absent in controls and were associated with amyotrophic lateral
sclerosis neuropathology in one member of one of these families for whom central nervous system tissue was available. Our
study indicates that mutations in the spatascin gene could cause a much wider spectrum of clinical features than previously
recognized, including autosomal recessive juvenile amyotrophic lateral sclerosis.
Keywords: amyotrophic lateral sclerosis; hereditary spastic paraplegia; mutations; spatacsin
Abbreviations: ALS = amyotrophic lateral sclerosis; ARJALS = autosomal recessive juvenile amyotrophic lateral sclerosis; SPG = spastic
paraplegia gene
doi:10.1093/brain/awp325 Brain 2010: 133; 591–598 | 591
Received September 24, 2009. Revised November 10, 2009. Accepted November 18, 2009
 The Author(s) 2010. Published by Oxford University Press on behalf of Brain.
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.5),
which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Introduction
Autosomal recessive hereditary spastic paraplegia with thin corpus
callosum is clinically characterized by the progressive spasticity of
the lower limbs, thin corpus callosum and cognitive impairment.
White matter alterations may be part of the clinical phenotype.
Disease onset presents itself during childhood and usually before
the second decade of life (Winner et al., 2004). Mutations of the
spatacsin gene on chromosome 15q15-21 (SPG11) represent the
most common cause of autosomal recessive hereditary spastic
paraplegia with thin corpus callosum (Stevanin et al., 2007,
2008). Autosomal recessive juvenile amyotrophic lateral sclerosis
(ARJALS) is a rare disease that occurs before the age of 25 years.
It is characterized by the spasticity of limb and facial muscles with
distal amyotrophy of hands and feet. It follows a slowly progressive course, with cases of prolonged survival of more than three
decades (Ben Hamida et al., 1990).
The overlap between hereditary spastic paraplegia and amyotrophic lateral sclerosis (ALS) (Fink, 2001; Meyer et al., 2005;
Strong and Gordon, 2005) prompted us to screen unrelated
families with ARJALS for mutations in SPG11.
Materials and methods
Patients
This study was performed according to a protocol reviewed and
approved by the Ethics Committee of the Istituto di Ricovero e Cura
a Carattere Scientifico Santa Lucia, Rome, Italy. Informed consent was
obtained from all individuals. Patients were recruited by contacting
neurologists in Italy, Brazil, Canada, Japan and Turkey with a special
interest in motoneuron diseases and asking them to refer suitable
affected subjects.
The study was based on 25 unrelated pedigrees with ARJALS. The
diagnosis of clinically definite ALS was made using the revised
El Escorial criteria (Brooks et al., 2000). None of the patients had
autosomal recessive hereditary spastic paraplegia with thin corpus
callosum in accordance with an established protocol (Boukhris et al.,
2008). The autopsy confirmed the diagnosis in one patient. Intellectual
quotient or Mini Mental State Examination (Folstein et al., 1975) was
available for all affected subjects. Mental retardation, as defined under
DSM-IV criteria (Diagnostic and Statistical Manual of Mental
Disorders, fourth edition), was taken into consideration when the
patient had an intellectual quotient 570 before the age of 18 years.
A brain MRI was performed in all affected individuals.
Nine hundred control chromosomes were obtained from healthy
volunteers of mixed ethnic origins, including 300 Caucasian,
200 Brazilian, 200 Japanese and 200 Turkish chromosomes.
Pathological studies
The post-mortem standard neuropathological evaluation consisted of
histological staining of paraffin-embedded material with haematoxylin
and eosin, Nı̈ssl, Klüver-Barrera and periodic acid Schiff.
Genetic analyses
Genomic DNA from peripheral blood was extracted by using
the Promega wizard genomic DNA isolation kit (http://
www.promega.com).
We carried out a linkage study of all 25 families with ARJALS using
three highly polymorphic genetic markers flanking the SPG11 gene
locus on chromosome 15q15-21 (D15S146, D15S537 and
D15S123). These are informative microsatellite markers used in previous studies (Hentati et al., 1998; Stevanin et al., 2007). The two-point
logarithm of odds scores were calculated according to a genetic
model based on clinical information as previously described
(Orlacchio et al., 2002, 2004). No phenocopies were allowed. The
primer sequences for each microsatellite marker, as well as marker
allele sizes and frequencies, were found on http://www.gdb.org
and http://www.cephb.fr.
The 40 coding exons of SPG11 and at least 50 base pairs of flanking
intronic sequence were PCR-amplified by previously described primer
pairs (Stevanin et al., 2007) and by Roche FastStart PCR Master
Mix polymerase (http://www.roche-applied-science.com). All the
PCR-amplified products were purified using a Qiagen PCR purification
kit (http://www.qiagen.com). These purified products were sequenced
with respective forward and reverse primers by a 3130 Genetic
Analyser (http://www.appliedbiosystems.com). The segregation analysis and the observation of mutations in the control population were
performed using a PCR-restriction fragment length polymorphism
method.
The mutation analysis of ALS2/ALSIN, ALS4/SETX, ALS11/FIG4 and
SPG4/SPASTIN was performed by directly sequencing all exons and
their flanking introns (full details are available on request).
Results
Clinical findings of the SPG11 families
All 10 SPG11 pedigrees showed consanguinity marriage
(first-degree cousins) in their parents. Six families were from
Italy and one each from Brazil, Canada, Japan and Turkey (Fig. 1).
Affected subjects have a slowly progressive motor neuronopathy
with upper and lower motoneuron dysfunction. There is principally
distal muscle weakness and atrophy associated with pyramidal
signs, including hyperreflexia, extensor plantar responses and a
spastic gait. The age at onset in 23 SPG11 patients ranged from
7 to 23 with a mean of 16.3 years. The mean age at examination
was 50.6 years (range 38–61) and the mean disease duration was
34.3 years (range 27–40). A wide variation of phenotypic expression was detected. Some patients were affected by mild upper and
lower motoneuron symptoms, whilst there were others who might
be wheelchair-bound with no functional hand use by the fifth or
sixth decade of life. Pontobulbar signs, including jaw spasticity,
increased facial reflexes, poor palatal elevation, weak masseter
and/or pterygoids, tongue weakness, as well as muscle atrophy
with fasciculations, were present in the majority of the affected
individuals (Subjects 3056, Family RM306; 2792 and 2797,
TK005; 1737 and 1738, RM168; 1924 and 2001, RM190; 1806,
RM171; 2539 and 2562, RM257; 3009 and 3011, RM303; 2666
and 2699, BR002 and 623, TOR015). The site of disease onset
592 | Brain 2010: 133; 591–598 A. Orlacchio et al.
was evenly split between pontobulbar (n = 12: Subjects 3056,
Family RM306; 2792 and 2797, TK005; 1738, RM168; 1924
and 2001, RM190; 1806, RM171; 2539, RM257; 3009 and
3011, RM303 as well as 2666 and 2699, BR002) and limb,
hand or leg (n = 11: Subjects 3055, Family RM306; 1737,
RM168; 1925, RM190; 1033, 1051, and 1062, IS005; 1810,
RM171; 2561 and 2562, RM257 as well as 623 and 703,
TOR015). The Hoffmann sign was always present, unilaterally or
bilaterally. No cognitive deficits on the Mini Mental State
Examination or mental health problems (intellectual quotient
470 in all affected subjects) were observed. Brain MRI revealed
the absence of thin corpus callosum and white matter alterations
in all patients. Patient 1738, of pedigree RM 168, showed an
intracranial arachnoid cyst in the left frontal pole. Lysosomal
enzyme assay of peripheral blood leucocytes revealed that both
b-hexosaminidase A and B isoenzymes were present at a normal
level in one patient within each family (Subjects 3055, Family
RM306; 2797, TK005; 1737, RM168; 2001, RM190; 1051,
IS005; 1806, RM171; 2561, RM257; 3011, RM303; 2666,
BR002 and 703, TOR015). Also, further haematological and
biochemical profiles, including serum creatinine phosphokinase,
were unremarkable in all subjects. Sensory symptoms were
absent in all patients. No severe bladder dysfunction was found,
although minor urinary dysfunctions, such as stress and urge
incontinence, occurred in one individual (Subject 2792, Family
TK005). The examination of the ocular fundus was normal in all
affected subjects. Patients 1737 and 1738 from Family RM168
died of acute respiratory failure.
Concentric needle EMG was performed in all affected individuals and showed chronic neurogenic changes with positive sharp
waves, fibrillation and fasciculation potentials. The topography of
EMG signs of lower motoneuron dysfunction followed the revised
Figure 1 Ten ARJALS families linked to the SPG11 locus. Their origin is reported in brackets. The solid symbols refer to affected individuals
as well as carriers of the SPG11 mutations; circles = females; squares = males and slashes = deceased. The code numbers of all sampled
individuals (asterisks) are reported below the symbols. Colour barcodes designate haplotypes in each pedigree. Haplotypes created with
markers D15S146, D15S537 and D15S123 (from top to bottom) are reported under each family member investigated. The SPG11 gene is
localized between markers D15S537 and D15S123. Inferred alleles are indicated by parentheses and question marks represent alleles not
able to be inferred. Key recombination events are observed between markers D15S537 and D15S123 in Patient 1810 (Family RM171) as
well as among markers D15S537 and D15S123 in Patient 3011 (Family RM303).
SPG11 mutations cause ARJALS Brain 2010: 133; 591–598 | 593
El Escorial criteria (Brooks et al., 2000). The motor conduction
studies revealed reduced amplitudes of compound motor action
potentials, whereas the sensory conduction studies demonstrated
normal amplitudes of sensory nerve-action potentials. The motor
and sensory nerve conduction velocities were also normal
(Table 1).
In general, these clinical characteristics are comparable with
those of previously published studies (Group 1 of the juvenile
amyotrophic lateral sclerosis families described by Ben Hamida
et al., 1990; ALS5 pedigrees reported by Hentati et al., 1998).
Case reports
Patient 1737 (Family RM 168)
Subject 1737 of pedigree RM168 (Fig. 1) was a 52-year-old
Italian man, who first noticed muscle weakness in his left hand
at the age of 19. Afterwards, he developed right hand and bilateral leg weakness, which was followed by hoarseness. One year
later he started to experience dysarthria and dysphagia together
with spasticity of the lower limbs, leading to the diagnosis of ALS.
At the age of 27 he suffered from marked atrophy and flaccid
paresis of the upper limbs, as well as unsteady gait. In addition,
neurological evaluation at that time revealed a bilateral Hoffman’s
sign. At the age of 34, muscle weakness and atrophy of the
extremities progressed to the point where the patient became
unable to sit by himself and required a walking aid. At the age
of 45 he developed tongue atrophy and weakness, with visible
fasciculations in the atrophic muscles. At the age of 46 he suffered
from complete loss of upper limb motor function, became
wheelchair-bound and his dysarthria worsened. At the age of 51
he developed breathing difficulties and the difficulty in swallowing
worsened. At the age of 52 he died of sudden respiratory arrest
caused by suffocation.
The total duration of the disease was 33 years. No bladder
dysfunction, sensory disturbance, cognitive decline, mental impairment, ocular fundus defects, abnormal levels of b-hexosaminidase
A and B isoenzymes or serum creatinine phosphokinase alterations
were detected throughout the clinical course. Brain MRI
performed at the age of 48 disclosed no abnormal findings. The
electrodiagnostic studies showed the occurrence of a motoneuron
disorder by high-amplitude polyphasic motor unit potentials, fibrillation and fasciculation potentials, incomplete interference pattern,
in addition to reduced amplitudes of compound motor action
potentials and normal amplitudes of sensory nerve-action potentials. The motor and sensory nerve conduction velocities were also
normal. The patient fulfilled the El Escorial criteria for definite ALS
(Brooks et al., 2000). The CNS at post-mortem showed
neuropathological changes consistent with a diagnosis of ALS.
A family history of ALS was detected with another family
member (1738) suffering from the same illness. Consanguinity
of the parents was reported (Fig. 1).
Table 1 Clinical characteristics of 23 patients with mutations in the SPG11 gene
Patient (sex) Age at
onset
(years)
Age at
examination
(years)
Disease
duration
(years)
El Escorial
category
Amyotrophy/
weakness
Pyramidal
signs/
disability
Pontobulbar
signs/
fasciculations
Denervation on
EMG
TCC/
WMA
CD/MI Other
clinical
features
RM306-3055 (F) 15 54 39 Definite Severe/moderate Yes/3 No/no Yes No/no No/no None
RM306-3056 (F) 9 47 38 Definite Severe/severe Yes/4 Yes/yes Yes No/no No/no None
TK005-2792 (M) 21 58 37 Definite Moderate/mild Yes/1 Yes/yes Yes No/no No/no UI
TK005-2797 (M) 16 50 34 Definite Severe/moderate Yes/3 Yes/yes Yes No/no No/no None
RM168-1737 (M) 19 52 33 Definite Severe/severe Yes/5 Yes/yes Yes No/no No/no ARF
RM168-1738 (F) 7 38 31 Definite Severe/severe Yes/5 Yes/yes Yes No/no No/no ARF, IAC
RM190-1924 (M) 23 61 38 Definite Moderate/moderate Yes/2 Yes/yes Yes No/no No/no None
RM190-1925 (M) 20 59 39 Definite Moderate/moderate Yes/2 No/no Yes No/no No/no None
RM190-2001 (F) 23 50 27 Definite Severe/moderate Yes/3 Yes/yes Yes No/no No/no None
IS005-1033 (F) 20 55 35 Definite Moderate/moderate Yes/2 No/no Yes No/no No/no None
IS005-1051 (F) 16 44 28 Definite Severe/mild Yes/2 No/no Yes No/no No/no None
IS005-1062 (F) 10 42 32 Definite Severe/mild Yes/3 No/no Yes No/no No/no None
RM171-1806 (F) 21 48 27 Definite Severe/severe Yes/4 Yes/yes Yes No/no No/no None
RM171-1810 (F) 15 53 38 Definite Severe/severe Yes/5 No/no Yes No/no No/no None
RM257-2539 (M) 20 55 35 Definite Severe/moderate Yes/3 Yes/yes Yes No/no No/no None
RM257-2561 (F) 22 53 31 Definite Severe/moderate Yes/3 No/no Yes No/no No/no None
RM257-2562 (M) 18 49 31 Definite Severe/severe Yes/5 Yes/yes Yes No/no No/no None
RM303-3009 (M) 18 53 35 Definite Moderate/moderate Yes/2 Yes/yes Yes No/no No/no None
RM303-3011 (M) 14 45 31 Definite Moderate/mild Yes/1 Yes/yes Yes No/no No/no None
BR002-2666 (M) 12 52 40 Definite Moderate/mild Yes/2 Yes/yes Yes No/no No/no None
BR002-2699 (F) 8 44 36 Definite Severe/severe Yes/4 Yes/yes Yes No/no No/no None
TOR015-623 (M) 15 54 39 Definite Moderate/moderate Yes/2 Yes/yes Yes No/no No/no None
TOR015-703 (F) 12 47 35 Definite Moderate/moderate Yes/3 No/no Yes No/no No/no None
ARF = acute respiratory failure; CD = cognitive decline; F = female; IAC = intracranial arachnoid cyst; M = male; MI = mental impairment; TCC = thin corpus callosum;
UI = urinary incontinence; WMA = white matter alterations. Age at onset was calculated approximately as the time when the first symptoms appeared. Disease duration was
calculated by subtracting age at onset of symptoms from age at examination. Disability stages are the following: 1, no mobility problems or slight stiffness of the legs; 2,
moderate gait stiffness; 3, problems in running, but ability to walk alone; 4, problems in walking; 5, wheelchair-bound.
594 | Brain 2010: 133; 591–598 A. Orlacchio et al.
Patient 2562 (Family RM 257)
Subject 2562 of pedigree RM 257 (Figs 1 and 2) was a 49-yearold Italian man; at the age of 18, he developed a slowly
progressive lower and upper motoneuron syndrome. The disease
commenced with wasting and weakness of upper limbs, followed
by wasting and weakness of the lower extremities. The patient
had also suffered from a spastic gait since the age of 33. He
became wheelchair-bound and, on neurological examination,
revealed severe bilateral wasting of triceps, biceps, intrinsic hand,
tibialis anterior and posterior, soleus and extensor digitorum
longus muscles. Fasciculations were observed in the atrophic
muscles and poor palatal elevation was also reported. Hoffman’s
sign was present bilaterally. No bladder dysfunction or sensory
disturbances were found. Higher mental functions, cranial nerves
and ocular fundus examination were normal. Brain MRI showed
normal brain images. Haematological and biochemical profiles,
including serum creatinine phosphokinase, were unremarkable.
The electrophysiological studies revealed normal motor and
sensory nerve conduction velocities along with reduced amplitudes
of compound motor action potentials and normal amplitudes
of sensory nerve-action potentials. They also disclosed highamplitude polyphasic motor unit potentials, fibrillation and
fasciculation potentials, as well as incomplete interference pattern,
suggesting an active muscle denervation–reinnervation process.
The patient satisfied the El Escorial criteria for definite ALS
(Brooks et al., 2000).
Two other family members (2539 and 2561) suffered from the
same illness and the consanguinity of the parents was reported
(Figs 1 and 2).
Pathological assessments
A post-mortem examination of the brain and spinal cord was performed in Patient 1737 (aged 52 years at death) from Family
RM168. The brain showed no cerebral or cerebellar atrophy,
and a normal corpus callosum as well as the absence of white
matter alterations were found. The bilateral pyramids were small
Figure 2 (A) Family RM 257. Black symbols designate affected individuals and carriers of SPG11 mutation. White symbols symbolize
unaffected subjects. Circles indicate females and squares represent males. The proband is designated with an arrow. The numbers are an
internal reference for each subject. Asterisks indicate sampled individuals. (B) Electropherogram of exon/intron 30 of the SPG11 gene.
The new homozygous substitution (G4A) is clearly defined in the affected individuals (Subjects 2539, 2561 and 2562) as well as the
heterozygous status in the parents (Subjects 2532 and 2534) and in a sibling (Subject 2537). (C) Restriction digestion assay in the family
members. Heterozygous individuals showed two bands at 600 and 500 base pairs, wild-type samples showed one band at 500 base pairs
and the homozygous affected individuals remain uncleaved after digestion with EcoP15I.
SPG11 mutations cause ARJALS Brain 2010: 133; 591–598 | 595
in size. The microscopic examination documented Betz cell
loss in the primary cortex, whereas the cerebellum did not
exhibit abnormalities. The hippocampus, parahippocampal gyrus,
amygdala, nucleus basalis of Meynert, caudate nucleus, putamen,
pallidum, thalamus, subthalamic nucleus appeared intact. Neuronal
loss with astrocytosis was found in the glossopharyngeal and
hypoglossal nuclei. The reticular formation, red nucleus, substantia
nigra, locus ceruleus, oculomotor, trochlear and abducens nuclei,
motor nucleus of the facial, dorsal motor nucleus of the vagus,
inferior olive, in addition to other nuclei of the brainstem appeared
preserved. Atrophy of the anterior roots and shrinkage of the
anterior horns of spinal cord prominently in the cervical cord, as
well as myelin pallor in the antero-lateral columns, were also
observed. Moreover, microscopic analysis showed marked loss of
anterior horn large motoneurons at all spinal cord levels,
associated with loss of large myelinated fibres in the anterolateral
columns (Fig. 3A). Most of the remaining spinal motoneurons
displayed pathological features, such as central chromatolysis
(Fig. 3B), pigmentary degeneration and round hyaline inclusions
(Fig. 3C). Bunina bodies and skein-like inclusions were not
observed. The posterior columns, dorsal-root ganglia, as well as
sensory roots, did not show pathological changes. The main
autoptic findings outside the CNS were neurogenic atrophy of
the skeletal muscles and bilateral bronchopneumonia.
Genetic appraisals
Eight families with ARJALS (RM168, RM190, IS005, RM171,
RM257, RM303, BR002 and TOR015) showed homozygous
haplotypes and produced positive logarithm of odds scores with
microsatellite markers D15S146, D15S537 and D15S123 in all
affected subjects, showing a cumulative two-point logarithm of
odds score of 11.51 at the recombination fraction  = 0.0 for
marker D15S537 (Fig. 1). The other ARJALS families (RM306
and TK005) showed heterozygous haplotypes and produced
negative or slightly significant cumulative logarithm of odds
scores by the genetic program HOMOG (data not shown)
(Ott, 1983).
Detailed mutations in SPG11 of 10 unrelated families with
ARJALS are described in Table 2. Eight of these nucleotide
changes were homozygous and two others were heterozygous
compounds. The majority of mutations were truncating mutations,
including five non-sense mutations, two frameshift insertions,
two frameshift small deletions and two splice site mutations;
furthermore, one was identified as a missense mutation. Variants
segregated with the disease in all pedigrees and were absent in a
panel of control chromosomes (see Materials and methods
section). Eleven mutations had already been reported while
IVS30 + 1 G4A, affecting the consensus splice site junction, was
novel (Table 2 and Fig. 2). The sequence analysis of the ALS2,
ALS4, ALS11 and SPG4 genes did not reveal any coding mutations
in any of the unrelated 25 families with ARJALS.
Discussion
SPG11 gene was analysed in patients of 25 unrelated pedigrees
with ARJALS along with long-term survival. Interestingly, a high
frequency of SPG11 mutations, one of which is novel, was found
in 10 families (10/25 mutated pedigrees, 40%). Most of the
ARJALS pedigrees carrying mutations in SPG11 originated in
Italy, but mutations were also detected in families from Brazil,
Figure 3 Histopathological findings on spinal cord postmortem samples in Patient 1737 from Family RM168. (A) Low
magnification photomicrograph of the anterior horn at L1 shows
a striking decrease of large motoneurons. (B) At higher
magnification, several large motoneurons display central
chromatolysis. (C) Most of the remaining neurons are laden
with dark lipofuscin granules (pigmentary degeneration) and
contain round hyaline inclusions (arrows). Klüver-Barrera
staining. Bar = 800 mm (A); 100 mm (B, C).
596 | Brain 2010: 133; 591–598 A. Orlacchio et al.
Canada, Japan and Turkey, showing a worldwide distribution of
this clinico-genetic entity.
Clinical heterogeneity, including the presence of amyotrophy
or lack of thin corpus callosum, is well-known in SPG11 (Hehr
et al., 2007; Paisan-Ruiz et al., 2008; Crimella et al., 2009).
Nevertheless, the phenotype of these families is different from
the phenotype of hereditary spastic paraplegia with amyotrophy.
This is due to the occurrence of bulbar symptoms in most patients,
the presence of the typical pathological features of ALS, and the
non-appearance of symptoms or signs of sensory involvement
documented by nerve conduction studies. The absence of thin
corpus callosum and white matter alterations, shown by the
brain MRI, as well as the lack of cognitive deficits or mental
health problems in any of the pedigrees, excluded the diagnosis
of autosomal recessive hereditary spastic paraplegia with thin
corpus callosum. Moreover, an additional distinctive trait of
these families is the non-appearance of ocular abnormalities,
such as macular degeneration, ptosis, skew deviation, poor
upgaze, saccadic pursuit and nystagmus, which are prominent
clinical features in many other SPG11 families (Paisan-Ruiz
et al., 2008; Stevanin et al., 2008). Finally, the existence of symptoms of upper motoneuron involvement in all of our pedigrees
rejected the diagnosis of spinal muscular atrophy.
To our knowledge, this is the first report of ARJALS occurrence
in subjects with SPG11 mutations. All of our families can be classified as ALS5, since ALS5 locus for ARJALS with slow progression
of symptoms maps to a 6 cM segment flanked by D15S123 and
D15S146, which is the same chromosomal segment to which the
SPG11 gene was mapped. This is also because the clinical
phenotype of our patients is comparable to that of ALS5
(Hentati et al., 1998; Stevanin et al., 2008).
A previous study reported one patient with a non-fatal course of
juvenile ALS and a long-term progression for 49 years, who presented a missense mutation in spastin (SPG4), the major gene for
dominantly inherited hereditary spastic paraplegia (Meyer et al.,
2005). Another study described a further missense mutation of
SPG4 in a patient with a rapidly progressive spinal and bulbar
upper motoneuron syndrome that progressed to ALS (Brugman
et al., 2005). Similar to the SPG4 gene, the SPG11 gene is
known to be involved in axonal transport (Salinas et al., 2008).
Given the common finding of axonal involvement in both ALS and
hereditary spastic paraplegia, SPG11 genetic variants may contribute to a common pathway in hereditary spastic paraplegia and
ARJALS.
Several causative genes for juvenile ALS or ARJALS have been
reported (Hadano et al., 2001; Chen et al., 2004; Meyer et al.,
2005; Chow et al., 2009; Wijesekera and Leigh, 2009), although
mutations are successfully identified in only a fraction of the
patients. The absence of pathological mutations in ALS2, ALS4,
ALS11 and SPG4 in ARJALS subjects suggests that these genes are
rare causes of this clinico-genetic entity.
This study revealed pathological evidence of neurodegeneration
in lower motoneurons. The absence of Bunina bodies and
skein-like inclusions in the autopsied patient suggests that the
pathological makeup in SPG11 might be different from that in
classic ALS, similar to other variants of ALS with long survival
(Honma et al., 1999). Most of the currently-known proteins
involved in hereditary spastic paraplegia have a biological function
in axonal transport, membrane trafficking, or biogenesis in
mitochondria, and spatacsin is ubiquitously expressed in the
nervous system (Salinas et al., 2008). Therefore lower motoneuron
involvement in SPG11 is not a surprise. However, it is still
unknown why some SPG11 mutations lead to clinical outcomes
similar to ALS. Further analysis on the biological role of spatacsin is
an essential requisite for the better understanding of motoneuron
diseases.
In conclusion, taking into account the low frequency of ARJALS
(Orlacchio et al., 2007; Wijesekera and Leigh, 2009), the
pathological confirmation of the clinical diagnosis in one family,
the presence of SPG11 mutations in a large number of families
worldwide as well as their exclusion in control individuals, our
findings indicate that the clinical spectrum caused by SPG11 mutations is much wider than previously observed, from autosomal
recessive hereditary spastic paraplegia with thin corpus callosum
to ARJALS with long-term survival. It will be crucial to analyse
SPG11 mutations in other families suffering from motoneuron
Table 2 Mutations identified in the SPG11 gene
Family Location Mutation (cDNA) Effect on protein RFLP Reference study
RM306 Exon 1 C118T Gln40X TseI (loss) Hehr et al., 2007
Exon 2 G267A Trp89X — Hehr et al., 2007
TK005 Exon 4 733_734 delAT Met245Valfs NlaIII (loss) Stevanin et al., 2007
Exon 31 C5974T Arg1992X TaqI (loss) Stevanin et al., 2007
RM168 Exon 11 T2198G Leu733X MseI (loss) Stevanin et al., 2007
RM190 Exon 14 A2608G Ile870Valfs — Pippucci et al., 2009
IS005 Exon 17 3076_3077 insA Arg1026fs — Hehr et al., 2007
RM171 Exon 26 4461_4462 delGT Val1468Leufs — Lee et al., 2008
RM257 Intron 30 IVS30 + 1 G4A Predicted exon 31 skipping EcoP15I (loss) This study
RM303 Exon 31 C5970G Tyr1990X BfaI (gain) Denora et al., 2009
BR002 Exon 32 G6157A Val2053Met NlaIII (gain) Del Bo et al., 2007
TOR015 Exon 39 7029_7030 insT Val2344Cysfs — Stevanin et al., 2007
del = deletion; fs = frameshift; ins = insertion; IVS = intervening sequence; X = STOP codon; RFLP = restriction fragment length polymorphism.
SPG11 mutations cause ARJALS Brain 2010: 133; 591–598 | 597
disorders with similar clinical features. The remaining question is
whether genetic variants of SPG11 play any role in the common
adult-onset ALS followed by long-term progression or in other
forms of ALS.
Funding
The Comitato Telethon Fondazione Onlus, the Amministrazione
Autonoma dei Monopoli di Stato (AAMS) and the city of
Gubbio, Italy (Grant No. GGP06209 to A.O.); the Italian
Ministero della Salute (Grants Nos EBRI1.O, PS05.11, PS05.21
and REG.17O to A.O.); the Italian Consiglio Nazionale delle
Ricerche (CNR), International Exchange Program Year 2009
(to A.O.).
Acknowledgements
We thank the patients and their family members for taking part in
this study. We also thank Michela Renna for language advice and
assistance, and members of our laboratories for stimulating
discussions and helpful comments on this manuscript. We are
extremely grateful to the Genetic Bank of the Laboratorio di
Neurogenetica, Centro Europeo del Cervello-Istituto di Ricovero
e Cura a Carattere Scientifico (CERC-IRCCS) Santa Lucia, Rome,
Italy (http://www.hsantalucia.it/neurogen/index_en.htm) for the
service provided.
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