Casper Jansen

Quantifying prion disease penetrance using large population control cohorts

Large genomic reference data sets reveal a spectrum of pathogenicity in the prion protein gene and provide genetic validation for a therapeutic strategy in prion disease. Share trumps rare No longer just buzz words, “patient empowerment” and “data sharing” are enabling breakthrough research on rare genetic diseases. Although more than 100,000 genetic variants are believed to drive disease in humans, little is known about penetrance—the probability that a mutation will actually cause disease in the carrier. This conundrum persists because small sample sizes breed imperfect alliance estimates between mutations and disease risk. Now, a patient-turned-scientist joined with a large bioinformatics team to analyze vast amounts of shared data—from the Exome Aggregation Consortium and the 23andMe database—to provide insights into genetic-variant penetrance and possible treatment approaches for a rare, fatal genetic prion disease. More than 100,000 genetic variants are reported to cause Mendelian disease in humans, but the penetrance—the probability that a carrier of the purported disease-causing genotype will indeed develop the disease—is generally unknown. We assess the impact of variants in the prion protein gene (PRNP) on the risk of prion disease by analyzing 16,025 prion disease cases, 60,706 population control exomes, and 531,575 individuals genotyped by 23andMe Inc. We show that missense variants in PRNP previously reported to be pathogenic are at least 30 times more common in the population than expected on the basis of genetic prion disease prevalence. Although some of this excess can be attributed to benign variants falsely assigned as pathogenic, other variants have genuine effects on disease susceptibility but confer lifetime risks ranging from <0.1 to ~100%. We also show that truncating variants in PRNP have position-dependent effects, with true loss-of-function alleles found in healthy older individuals, a finding that supports the safety of therapeutic suppression of prion protein expression.

Middle east respiratory syndrome coronavirus (MERS-CoV) infections in two returning travellers in the Netherlands, May 2014

Two patients, returning to the Netherlands from pilgrimage in Medina and Mecca, Kingdom of Saudi Arabia, were diagnosed with Middle East respiratory syndrome coronavirus (MERS-CoV) infection in May 2014. The source and mode of transmission have not yet been determined. Hospital-acquired infection and community-acquired infection are both possible.

The first case of protease-sensitive prionopathy (PSPr) in The Netherlands: a patient with an unusual GSS-like clinical phenotype

An atypical case of prion disease is described in a 54-year-old Dutch man, homozygous for valine at codon 129 of the prion protein gene (PRNP). The clinical phenotype was characterised by progressive dementia, spastic paraplegia and sensorimotor polyneuropathy. The disease duration was 20 months. Genetic analysis of PRNP did not reveal any abnormalities. Neuropathologically, only mild spongiform change and a coarse granular immunohistochemical staining for the abnormal prion protein, PrPSc, was observed, with poorly formed plaques in the molecular layer of the cerebellar cortex. However, Western blotting showed low but detectable levels of proteinase K(PK)-resistant PrPSc occurring in an unusual ladder-like profile. These features define a phenotype that corresponds to the recently described protease-sensitive prionopathy (PSPr). Our report on the first Dutch patient with PSPr further expands the spectrum of prionopathies and exemplifies the need to re-evaluate cases of atypical prion disease.

Panencephalopathic Creutzfeldt–Jakob disease in the Netherlands and the UK: clinical and pathological characteristics of nine patients

Aims: The panencephalopathic type of Creutzfeldt–Jakob disease (PECJD) has extensive abnormalities in cerebral white matter as well as the cortex. PECJD has rarely been described in Caucasians and debate continues on its classification and pathogenesis. We describe our experience of PECJD over a 14‐year period of surveillance for CJD in the Netherlands and the UK. Methods: Between 1993 and 2006, nine cases of PECJD were identified. Clinical, histological and biochemical characteristics of all patients were analysed and compared; all cases were classified clinically as sporadic CJD. Results: The median age at onset was 57.8 years and median disease duration was 22 months. The average brain weight was 887 g. Most patients showed a two‐stage clinical course with initial rapid deterioration to a state of akinetic mutism, which then persisted over a longer time scale. Neuropathological findings were characterized by severe global atrophy with status spongiosus. Cerebral white matter involvement tended to be associated with either disease duration or severity of cerebral cortical lesions. Five patients could be classified into the MM1 subtype of sporadic CJD, one patient into the MM2 subgroup and another into the MV2 subgroup. Two patients were heterozygous at codon 129 in the prion protein gene and contained both type 1 and type 2 PrPres isoforms in the brain. Conclusions: We believe that white matter pathology in PECJD represents an end‐stage pattern that reflects secondary degeneration due to widespread cortical neuronal loss that occurs in the early part of the disease, rather than representing a primary lesion.

Variably Protease-Sensitive Prionopathy, a Unique Prion Variant with Inefficient Transmission Properties

Transmission properties of this prion disease are biologically distinct, and the disease has limited potential for human-to-human transmission.

A second case of Gerstmann-Sträussler-Scheinker disease linked to the G131V mutation in the prion protein gene in a Dutch patient.

A rare case of Gerstmann-Sträussler-Scheinker disease in a 36-year-old Dutch man is reported. The clinical phenotype was characterized by slowly progressive cognitive decline, later followed byataxia and parkinsonism. Neuropathologic findings consisted of numerous amyloid plaques in the cerebellum, which showed positive staining for the abnormal prion protein (PrPSc). In addition, there were tau accumulations around numerous amyloid deposits in the cerebral cortex, striatum, hippocampal formation, and midbrain. There was nospongiform degeneration. Western blot analysis showed the co-occurrence of 2 distinct abnormal prion protein species comprising anunglycosylated, protease-resistant fragment of approximately 8 kd, which was found to be truncated at both N- and C-terminal ends by epitope mapping, and a detergent-insoluble but protease-sensitive formof full-length PrPSc. Sequence analysis disclosed a mutation at codon 131 of the prion protein gene (PRNP), resulting in a valine-for-glycine substitution (G131V). The patient was heterozygous at the polymorphic codon 129 and carried the mutation on the methionine allele. To our knowledge, this is the second family worldwide in which this mutation has been identified. Gerstmann-Sträussler-Scheinker disease should be considered in patients with a clinical diagnosis of familial frontotemporal dementia.

Neuroinflammation and Common Mechanism in Alzheimer’s Disease and Prion Amyloidosis: Amyloid-Associated Proteins, Neuroinflammation and Neurofibrillary Degeneration

Background: In cases with a long (>1 year) clinical duration of prion disease, the prion protein can form amyloid deposits. These cases do not show accumulation of 4-kDa β-amyloid, which is observed in amyloid deposits in Alzheimer’s disease (AD). In AD, amyloid is associated with inflammation and neurofibrillary degeneration, and it is elusive whether prion amyloid is associated with these changes as well. Objectives: The presence of inflammation and neurofibrillary degeneration was evaluated in prion amyloidosis. Material and Methods: Cortical areas of variant Creutzfeldt-Jakob disease (CJD; n = 3), young sporadic CJD (n = 4), different Gerstmann-Sträussler-Scheinker’s disease patients (n = 5) and AD cases (n = 5) were examined using immunohistochemistry and specific stainings for amyloid. Results: In both AD and prion disease cases, which were negative for 4-kDa β-amyloid, parenchymal and vascular amyloid deposits were positive for amyloid-associated proteins such as complement protein and were associated with microglia clusters. Tau and ubiquitin were found near prion plaques in some of the Gerstmann-Sträussler-Scheinker’s disease and sporadic CJD cases and also near vascular prion amyloid deposits. In variant CJD cases, occasionally, microglia clustering was found in plaques but no ubiquitin or complement proteins and hardly tau protein. Conclusions: In both AD and prion disease amyloid formation, irrespective of the protein involved, there seems to be a neuroinflammatory response with secondary neurofibrillary degeneration.

Inherited Creutzfeldt–Jakob disease in a Dutch patient with a novel five octapeptide repeat insertion and unusual cerebellar morphology

An atypical case of inherited Creutzfeldt–Jakob disease (CJD) is described in a 35-year-old Dutch woman, homozygous for methionine at codon 129 of the prion protein gene (PRNP). The clinical phenotype was characterised by slowly progressive cognitive decline and parkinsonism. Neuropathological findings consisted of scanty spongiosis and only faint to absent immunohistochemical staining for the abnormal prion protein, PrPSc, with patchy deposits in the cerebellar cortex. Purkinje cells were abnormally located in the molecular layer of the cerebellum. Western blot analysis showed the co-occurrence of PrPSc types 1 and 2 with an unusual distribution. Sequence analysis disclosed a novel 120 bp insertion in the octapeptide repeat region of the PRNP, encoding five additional R2 octapeptide repeats. These features define an unusual neuropathological phenotype and novel genotype, further expanding the spectrum of genotype–phenotype correlations in inherited prion diseases and emphasising the need to carry out pre-mortem PRNP sequencing in all young patients with atypical dementias.

Association between the PRNP 1368 polymorphism and the occurrence of sporadic Creutzfeldt-Jakob disease

Creutzfeldt-Jakob disease (CJD) is a rare transmissible neurodegenerative disorder. The etiology of sporadic form of CJD remains unsolved. In addition to the codon 129 polymorphism, polymorphisms in the non-coding region of PRNP are considered as important factors in sCJD development. To assess a possible association between PRNP 1368 SNP and sCJD, we compared the genotype, allele and haplotype frequencies of the 1368 SNP among 46 sCJD patients of Dutch origin with the respective frequencies in healthy controls. We detected a significant association between sCJD and 1368T/T genotype. A significant difference was also observed in 1368 alleles’ distribution. In the haplotype analysis, haplotype 1368C-129G was associated with decreased risk of sCJD in Dutch population. Our findings support the hypothesis that genetic variations in the regulatory region of the PRNP gene may influence the pathogenesis of sCJD.

The first case of fatal familial insomnia (ffi) in the netherlands: A patient from egyptian descent with concurrent four repeat tau deposits

Transmissible spongiform encephalopathies or prion diseases are a unique group of neurodegenerative disorders, occurring as sporadic, inherited or acquired forms [1]. These diseases are caused by accumulation in the brain of protease resistant PrP, an abnormal structural conformer of the cellular protein PrP [2,3]. In humans, inherited prion diseases are associated with three major phenotypes: Creutzfeldt-Jakob disease (CJD), GerstmannSträussler-Scheinker disease and fatal familial insomnia (FFI). The c.532G>A, p.Asp178Asn mutation, also known as the D178N mutation, in the prion protein gene (PRNP) is the only known mutation associated with FFI [4]. The same mutation is also associated with a CJD phenotype depending on the genotype at the polymorphic codon 129 on the mutated allele; the methionine allele is linked to FFI, whereas the valine allele is associated with a CJD phenotype [5]. The onset of FFI is in middle to late adulthood, although age at onset under 30 years has been reported in eight patients worldwide [6]. Clinical signs involve disturbances of the wake and sleep cycle, autonomic disorders, motor abnormalities, myoclonus and cognitive decline [7]. In its classical form, neuropathological features consist of thalamic and olivary degeneration with mild degrees of spongiform change in the cerebral cortex, absence of amyloid and low levels of PrP deposition throughout affected brain regions [8]. Tauopathy, which is sometimes seen in prion diseases with amyloidosis, has thus far not been reported in patients with FFI. In this report, we describe an unusual neuropathological phenotype in the first patient with FFI in the Netherlands, consisting of tau accumulations in several brain regions. A 57-year-old man presented with double vision and progressive memory loss. He was of Egyptian descent, but had lived in the Netherlands for 19 years. His family noted that he had become disoriented, confused and increasingly paranoid. For most of the day, he showed a tendency to fall asleep even during routine daily activities. However, while in this state, he experienced vivid dreaming and displayed frequent muscular jerks rather than resting as in normal slow-wave sleep. Later, he also suffered from a painful and itching sensation in both arms. In addition, he lost a significant amount of weight, despite an increased food intake. At neurological examination, 4 months after the onset of symptoms, the patient was disoriented in space and time, exhibited perseveration, mental confusion and an attention deficit. Spontaneous and evoked myoclonic jerks were observed in the hands, trunk and lower limbs. There was persistent hypertension, with loss of physiological nocturnal drop in blood pressure. The 14-3-3 test in cerebrospinal fluid was negative. Electroencephalography showed slowing of the global background rhythm, but no periodic sharp wave complexes were recorded. Polysomnography was abolished after 1.5 h due to confused behaviour. During this short recording there was excessive Rapid Eye Movement-sleep without atonia, sudden onset of slow-wave sleep with lack of K-complexes and sleep spindles and deep-sleep stages. Magnetic resonance imaging was hampered by movement artefacts. Over the next 2 months, his condition declined rapidly. He died at the age of 58 years, 7 months after the clinical onset of the disease. The family history indicated that his two sisters and possibly his father had been affected by a similar disorder (Figure 1). Permission was obtained for post mortem examination and tissues were retained for diagnosis and research. In the Netherlands, all autopsies are performed after informed consent has been obtained and ethical approval for research is automatically included for hospital autopsies. Samples of tissue from several brain regions were frozen at -80°C. Histopathological examination was performed on 5-mm-thick sections of formalin-fixed and paraffin-embedded brain tissue blocks, after decontamination for 1 h in 98% formic acid. Sections were taken from all areas of the cerebral cortex, the caudate nucleus, putamen, pallidum, hippocampal formation, including the transentorhinal and entorhinal regions, amygdala, Competing interests: none.