Mutation at codon 210 (V210I) of the prion protein gene in a North African patient with Creutzfeldt-Jakob disease

Mutation at codon 210 (V210I) of the prion protein gene in a North African patient with Creutzfeldt-Jakob disease

Journal of the Neurological Sciences 168 (1999) 141–144 www.elsevier.com / locate / jns Mutation at codon 210 (V210I) of the prion protein gene in a ...

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Journal of the Neurological Sciences 168 (1999) 141–144 www.elsevier.com / locate / jns

Mutation at codon 210 (V210I) of the prion protein gene in a North African patient with Creutzfeldt-Jakob disease ´ Sophie Mouillet-Richard a,b , Christine Teil c , Martine Lenne a , Stephanie Hugon a , Oussama Taleb c , a, Jean-Louis Laplanche * a

ˆ ` , 2 rue A. Pare´ , 75475 Paris, Cedex 10, Centre de Recherche C. Bernard, IFR 6, Service de Biochimie ( Pr. J.-M. Launay), Hopital Lariboisiere France b ´ Groupe de Diff erenciation Cellulaire, Institut Pasteur, Paris, France c ´ Service de Neurologie, Centre Hospitalier, Beziers , France Received 19 February 1999; received in revised form 15 July 1999; accepted 16 July 1999

Abstract A point mutation at codon 210 of the prion protein gene (PRNP), resulting in the substitution of isoleucine for valine (V210I) has been found in a 54-year-old Moroccan patient affected with Creutzfeldt-Jakob disease (CJD). This patient is the first carrier of the PRNP V210I mutation reported from North Africa. The clinical presentation of the patient was rather similar to that seen in classical CJD, except that unusual early sensory symptoms were observed. The mother of the proband, aged 72, is a further example of an asymptomatic elderly carrier of the PRNP V210I mutation, suggesting an incomplete penetrance of the disease.  1999 Elsevier Science B.V. All rights reserved. Keywords: Creutzfeldt-Jakob disease; Prion protein; PRNP gene; Mutation

1. Introduction Creutzfeldt-Jakob disease (CJD) is a rare neurodegenerative transmissible disorder belonging to the family of human prion diseases, defined by an accumulation in the brain of an abnormally folded isoform of the cellular prion protein (PrP c). PrP c is a ubiquitous glycoprotein attached to the cell membrane by a glycosylphosphatidylinositol anchor. Its exact function remains elusive; knock-out mice for the PrP gene are viable and fertile. The PrP Sc *Corresponding author. Tel.: 133-1-49-95-64-34; fax: 133-1-49-9584-77. E-mail address: [email protected] (J.-L. Laplanche)

pathogenic isoform, accumulating in the brain, results from post-translational modifications of PrP c . It is a component of the infectious particle called ‘prion’, responsible for the disease transmissibility [1,2]. CJD has three known origins: genetic, sporadic and acquired. In genetic CJD, point mutations or insertions in the prion protein gene, located on chromosome 20 (PRNP), are linked or associated with different clinical and / or neuropathologic features of the disease and are thought to be causative. Among the known point mutations, the mutation at codon 210, changing the code for valine into isoleucine, abbreviated as V210I, has been described in one French patient, one Italian family and two Asians, one Japanese and the other Chinese [3–6]. One of the striking features of this CJD form is its incomplete

0022-510X / 99 / $ – see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0022-510X( 99 )00179-3

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penetrance, confirmed by the observation of asymptomatic elderly carriers of the mutation. Here we report a new patient and family, with a different ethnic background, originating from North Africa, carrying a V210I mutation in PRNP.

2. Material and methods

2.1. Case report The proband was a 54-year-old Muslim Moroccan of Berber ancestry without a notable medical history who lived in France for 30 years and initially complained of severe pain in the lower limbs with asthenia and mood alteration. Sleep disorders also appeared, characterized by insomnia and involuntary movements during sleep. One month later, weakness in the legs and asthenia became conspicuous, with vertigo, visual disturbances and unsteady gait. A neurologic examination was then normal. The patient complained of back pain and paresthesia in his left side just before being hospitalized, two and half months after the first signs and symptoms. A cerebellar syndrome with ataxia, dysmetria and dysarthria, a cortical blindness and confusion were noted. The patient scored 20 out of 30 on the Mini Mental-State Examination (MMSE). CT scans were normal. At that time, EEGs performed regularly showed a general slowing without periodic synchronous discharge. CJD markers in the cerebrospinal fluid (CSF) were positive; 14-3-3 protein was detected by Western blotting; neuron-specific enolase concentration was increased to 110 ng ml 21 (cut-off: 25 ng ml 21 [7]). The deterioration then progressed rapidly; the patient became bedridden with more and more myoclonic jerks, hypertonia and primitive reflexes. Communication was impossible. One month before death, the EEGs showed characteristic one per second periodic discharges. The patient developed hyperthermia and died 7.5 months after the onset of the disease. An autopsy was not authorized by his family. The patient’s father and mother, aged 80 and 72, respectively, his wife and his four offspring were normal on physical examination and without mental or cognitive troubles. Among the patient’s eight brothers and sisters, five were healthy and three had died from diseases or in circumstances not suggestive of CJD. Information on the grandparents was limited; his paternal grandfather had developed rapid ‘dementia’ and died six months after the onset, as reported by the family.

2.2. Genetic study Genomic DNA was extracted from peripheral blood leukocytes by standard methods after the informed consent of family members. The coding sequence of PRNP was amplified using polymerase chain reaction (PCR) and screened for size and nucleotide variations, according to

our previously published strategy with slight modifications [3]. Samples were analyzed using double gradient denaturing gradient gel electrophoresis (DG-DGGE [8]) in a 6.5–12% polyacrylamide gradient gel in the presence of 40–80% denaturant (100% denaturant57 M urea, 40% formamide) in TEA 1X buffer at 160 V for 6 h. The sequence of the PRNP coding region was obtained after direct cycle sequencing on both strands by the dideoxy chain-termination method (Epicentre Technologies) using an ALFexpress automated sequencer (Amersham-Pharmacia).

3. Results A nucleotide variation in the coding region of PRNP was first shown by DG-DGGE in the DNA of the proband (II-1) and in three members of the family who were analyzed, the proband’s mother (I-2) and two out of his four offspring (III-1 and III-2); see Fig. 1. Direct sequencing of the PCR products identified a G-to-A change at the first position of codon 210, leading to a predicted amino acid change from valine to isoleucine in PrP (Fig. 2). In addition, a rare polymorphism, i.e. a 24-base pair deletion in the octapeptide coding region of PRNP, was found in the patient’s wife (II-2) and two offspring (III-2 and III-4). This deletion, already found in Moroccan controls, was of the R3–R4 type which is the most common of this rare polymorphism [9,10]. All subjects were methionine homozygous at the polymorphic codon 129.

4. Discussion Although no neuropathologic examination could be done, the rapid progressive dementia with periodic EEG activity and positive 14-3-3 in the CSF indicated that the proband of this new family died of probable CJD. By itself, the V210I mutation in PRNP was a strong argument in favor of the diagnosis, as this mutation has previously been found in other CJD patients but not in controls. This mutation was initially described in two families, one French and the other Italian [3,4], and later in two Asian patients, one Japanese [5] and the other Chinese [6]. Our patient is the first carrier of the PRNP V210I mutation reported from North Africa, where the most commonly observed mutation modifies codon 200 (E200K), mainly in Jewish populations originating from Tunisia and Libya [11]. The clinical and neuropathologic features of the European cases with the PRNP V210I mutation were nearly identical to those seen in sporadic CJD patients, with no PRNP mutation, including the age at onset and the course of the disease. By contrast, the Chinese patient developed a panencephalitic CJD at age 48 with a long duration of the

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Fig. 1. Pedigree of the family and DG-DGGE of the PRNP gene amplified products from each member analyzed. Square, male; circle, female; diamond, gender not defined for confidentiality. Black square, proband. The two upper bands are heteroduplexes, and the presence of two homoduplexes in the two lower bands was indicative of a mutation in the fragment analyzed. In subject III-2, heteroduplexes were destabilized and did not appear owing to the presence of a 24-bp deletion on the normal allele that did not influence the migration of the homoduplexes.

disease, up to 24 months. This phenotypic variability may be due to different genetic backgrounds. In this respect, the clinical presentation of the Moroccan patient appeared closer to that of European patients and not very different from the typical CJD picture. The early unusual sensory

Fig. 2. Direct sequencing of the PRNP coding sequence of the proband. The arrow indicates the heterozygous G-to-A change at codon 210.

symptoms observed here, such as leg pain and paresthesia, are prominent signs of the new-variant CJD, as compared to sporadic or genetic CJD [12]. Interestingly, almost all patients carrying the PRNP V210I mutation reported to date lacked a known family history of CJD and were considered as sporadic cases. The presence of the mutation in the DNA of the patient’s mother excluded a de novo mutation. The 72-year-old mother of the proband (I-2), presently healthy, is living in Morocco. A similar observation of elderly asymptomatic carriers of the PRNP V210I mutation was reported in an Italian family in which two women, aged 81 and 82, respectively, were unaffected, while their two sisters died of CJD at 68 and 50 years of age [4]. The genotype at the polymorphic codon 129 has been shown to influence the survival time of patients carrying different mutations of PRNP. Notably, a delaying effect was observed in methionine / valine heterozygotes with a six extra repeat insert [13]. This influence, however, did not seem predominant in this new family with a PRNP V210I mutation, as both the patient and his mother were methionine homozygotes at codon 129. A large variance in the age of manifestation of the disease has also been described in familial CJD linked to the PRNP E200K mutation in Libyan Jews [14]. Undoubtedly, other unknown factors, genetic or environmental, may explain the variable pathogenicity of the PRNP V210I mutation. Reports of cases and families from different ethnic backgrounds carrying

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this relatively unfrequent mutation, will help solve this issue. [7]

Acknowledgements We thank Dr K.H. El Hachimi for his help during the interviews of the patient’s family.

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