Altered energy metabolism in Fatal Familial Insomnia cerebral organoids is associated with astrogliosis and neuronal dysfunction.

Fatal familial insomnia (FFI) is a rare neurodegenerative disease caused by a dominantly inherited single amino acid substitution (D178N) within the prion protein (PrP). No in vitro human brain tissue model for this disease has previously been available. Consequently, how this mutation exerts its damaging effect on brain cells is still unknown. Using CRISPR-Cas9 engineered induced pluripotent stem cells, we made D178N cerebral organoids and compared these with isotype control organoids. We found that, in the absence of other hallmarks of FFI, the D178N organoids exhibited astrogliosis with cellular oxidative stress. Abnormal post-translational processing of PrP was evident but no tissue deposition or propagation of mis-folded PrP isoforms were observed. Neuronal electrophysiological function was compromised and levels of neurotransmitters, particularly acetylcholine and GABA, altered. Underlying these dysfunctions were changes in cellular energy homeostasis, with substantially increased glycolytic and Krebs cycle intermediates, and greater mitochondrial activity. This increased energy demand in D178N organoids was associated with increased mitophagy and depletion of lipid droplets, in turn resulting in shifts of cellular lipid composition. Using a double mutation (178NN) we could confirm that most changes were caused by the presence of the mutation rather than interaction with PrP molecules lacking the mutation. Our data strongly suggests that shifting biosynthetic intermediates and oxidative stress, caused by an imbalance of energy supply and demand, results in astrogliosis with compromised neuronal activity in FFI organoids. They further support that many of the disease associated changes are due to a corruption of PrP function and do not require propagation of PrP mis-folding.

[Fatal Familial Insomnia With Significant Correlations Between Involuntary Movements and Postural Changes:Report of One Case].

Fatal familial insomnia,an autosomal dominant prion disease,is rare.We reported the clinical symptoms,examination results,diagnosis,treatment,and prognosis of a patient who was diagnosed with fatal familial insomnia.Furthermore,we described the unique clinical manifestations that involuntary movements and laryngeal stridor were significantly correlated with postural changes,aiming to provide reference for the clinical diagnosis,treatment,and research of the disease in the future.

Met/Val129 polymorphism of the full-length human prion protein dictates distinct pathways of amyloid formation.

Methionine/valine polymorphism at position 129 of the human prion protein, huPrP, is tightly associated with the pathogenic phenotype, disease progress, and age of onset of neurodegenerative diseases such as Creutzfeldt-Jakob disease or Fatal Familial Insomnia. This raises the question of whether and how the amino acid type at position 129 influences the structural properties of huPrP, affecting its folding, stability, and amyloid formation behavior. Here, our detailed biophysical characterization of the 129M and 129V variants of recombinant full-length huPrP(23-230) by amyloid formation kinetics, CD spectroscopy, molecular dynamics simulations, and sedimentation velocity analysis reveals differences in their aggregation propensity and oligomer content, leading to deviating pathways for the conversion into amyloid at acidic pH. We determined that the 129M variant exhibits less secondary structure content before amyloid formation and higher resistance to thermal denaturation compared to the 129V variant, whereas the amyloid conformation of both variants shows similar thermal stability. Additionally, our molecular dynamics simulations and rigidity analyses at the atomistic level identify intramolecular interactions responsible for the enhanced monomer stability of the 129M variant, involving more frequent minimum distances between E196 and R156, forming a salt bridge. Removal of the N-terminal half of the 129M full-length variant diminishes its differences compared to the 129V full-length variant and highlights the relevance of the flexible N terminus in huPrP. Taken together, our findings provide insight into structural properties of huPrP and the effects of the amino acid identity at position 129 on amyloid formation behavior.

Clinical profiles and ethnic heterogeneity of sporadic fatal insomnia.

BACKGROUND AND PURPOSE: This study was undertaken to elucidate the clinical profile of sporadic fatal insomnia (sFI), assess the similarities and differences between sFI and fatal familial insomnia (FFI), and evaluate the influence of ethnicity on the phenotype of sFI patients. METHODS: The data of sFI and FFI patients were retrieved from our case series and through literature review. The clinical and diagnostic features of sFI and FFI were compared, as were the phenotypes of Asian and Caucasian sFI patients. RESULTS: We identified 44 sFI and 157 FFI cases. The prevalence of sleep-related, neuropsychiatric, and autonomic symptoms among the sFI patients were 65.9%, 100.0%, and 43.2%, respectively. Compared to FFI, sFI exhibited longer disease duration and a higher proportion of neuropsychiatric symptoms, whereas FFI was characterized by a higher incidence of sleep-related and autonomic symptoms in the early stages of the disease or throughout its course. In addition, a higher proportion of the sFI patients showed hyperintensity on magnetic resonance imaging (MRI) and periodic sharp wave complexes on electroencephalography compared to the FFI patients, especially those presenting with pathological changes associated with MM2-cortical type sporadic Creutzfeldt-Jakob disease. The Asian sFI patients had a higher proportion of males and positivity for cerebrospinal fluid 14-3-3 protein, and fewer sleep-related symptoms compared to Caucasian sFI patients. The age at onset and duration of sFI differed between ethnic groups, but the difference failed to reach statistical significance. CONCLUSIONS: Despite its similarities to FFI, sFI is characterized by longer disease duration, higher proportion of neuropsychiatric symptoms, and hyperintensity on MRI, along with differences in the clinical characteristics based on ethnicity.

Diagnostic accuracy of cerebrospinal fluid biomarkers in genetic prion diseases.

Genetic prion diseases are a rare and diverse group of fatal neurodegenerative disorders caused by pathogenic sequence variations in the prion protein gene, PRNP. Data on CSF biomarkers in patients with genetic prion diseases are limited and conflicting results have been reported for unclear reasons. Here, we aimed to analyse the diagnostic accuracy of CSF biomarkers currently used in prion clinical diagnosis in 302 symptomatic genetic prion disease cases from 11 prion diagnostic centres, encompassing a total of 36 different pathogenic sequence variations within the open reading frame of PRNP. CSF samples were assessed for the surrogate markers of neurodegeneration, 14-3-3 protein (14-3-3), total-tau protein (t-tau) and α-synuclein and for prion seeding activity through the real-time quaking-induced conversion assay. Biomarker results were compared with those obtained in healthy and neurological controls. For the most prevalent PRNP pathogenic sequence variations, biomarker accuracy and associations between biomarkers, demographic and genetic determinants were assessed. Additionally, the prognostic value of biomarkers for predicting total disease duration from symptom onset to death was investigated. High sensitivity of the four biomarkers was detected for genetic Creutzfeldt-Jakob disease associated with the E200K and V210I mutations, but low sensitivity was observed for mutations associated with Gerstmann-Sträussler-Scheinker syndrome and fatal familial insomnia. All biomarkers showed good to excellent specificity using the standard cut-offs often used for sporadic Creutzfeldt-Jakob disease. In genetic prion diseases related to octapeptide repeat insertions, the biomarker sensitivity correlated with the number of repeats. New genetic prion disease-specific cut-offs for 14-3-3, t-tau and α-synuclein were calculated. Disease duration in genetic Creutzfeldt-Jakob disease-E200K, Gerstmann-Sträussler-Scheinker-P102L and fatal familial insomnia was highly dependent on PRNP codon 129 MV polymorphism and was significantly associated with biomarker levels. In a large cohort of genetic prion diseases, the simultaneous analysis of CSF prion disease biomarkers allowed the determination of new mutation-specific cut-offs improving the discrimination of genetic prion disease cases and unveiled genetic prion disease-specific associations with disease duration.

Activation of Src family kinase ameliorates secretory trafficking in mutant prion protein cells.

Fatal familial insomnia (FFI), genetic Creutzfeldt-Jakob disease (gCJD), and Gerstmann-Sträussler-Scheinker (GSS) syndrome are neurodegenerative disorders linked to prion protein (PrP) mutations. The pathogenic mechanisms are not known, but increasing evidence points to mutant PrP misfolding and retention in the secretory pathway. We previously found that the D178N/M129 mutation associated with FFI accumulates in the Golgi of neuronal cells, impairing post-Golgi trafficking. In this study we further characterized the trafficking defect induced by the FFI mutation and tested the 178N/V129 variant linked to gCJD and a nine-octapeptide repeat insertion associated with GSS. We used transfected HeLa cells, embryonic fibroblasts and primary neurons from transgenic mice, and fibroblasts from carriers of the FFI mutation. In all these cell types, the mutant PrPs showed abnormal intracellular localizations, accumulating in the endoplasmic reticulum (ER) and Golgi. To test the efficiency of the membrane trafficking system, we monitored the intracellular transport of the temperature-sensitive vesicular stomatite virus glycoprotein (VSV-G), a well-established cargo reporter, and of endogenous procollagen I (PC-I). We observed marked alterations in secretory trafficking, with VSV-G accumulating mainly in the Golgi complex and PC-I in the ER and Golgi. A redacted version of mutant PrP with reduced propensity to misfold did not impair VSV-G trafficking, nor did artificial ER or Golgi retention of wild-type PrP; this indicates that both misfolding and intracellular retention were required to induce the transport defect. Pharmacological activation of Src family kinase (SFK) improved intracellular transport, suggesting that mutant PrP impairs secretory trafficking through corruption of SFK-mediated signaling.

Neuro-Ophthalmological Findings in Early Fatal Familial Insomnia.

Fatal familial insomnia (FFI) is a rare inherited prion disease characterized by sleep, autonomic, and motor disturbances. Neuro-ophthalmological abnormalities have been reported at the onset of disease, although not further characterized. We analyzed video recordings of eye movements of 6 patients with FFI from 3 unrelated kindreds, seen within 6 months from the onset of illness. Excessive saccadic intrusions were the most prominent findings. In patients with severe insomnia, striking saccadic intrusions are an early diagnostic clue for FFI. The fact that the thalamus is the first structure affected in FFI also suggests its role in the control of steady fixation. ANN NEUROL 2021;89:823-827.

Clinical profile of fatal familial insomnia: phenotypic variation in 129 polymorphisms and geographical regions.

OBJECTIVE: Elucidate the core clinical and genetic characteristics and identify the phenotypic variation between different regions and genotypes of fatal familial insomnia (FFI). METHODS: A worldwide large sample of FFI patients from our case series and literature review diagnosed by genetic testing were collected. The prevalence of clinical symptoms and genetic profile were obtained, and then the phenotypic comparison between Asians versus non-Asians and 129Met/Met versus 129Met/Val were conducted. RESULTS: In total, 131 cases were identified. The age of onset was 47.51±12.53 (range 17-76) years, 106 patients died and disease duration was 13.20±9.04 (range 2-48) months. Insomnia (87.0%) and rapidly progressive dementia (RPD; 83.2%) occurred with the highest frequency. Hypertension (33.6%) was considered to be an objective indicator of autonomic dysfunction. Genotype frequency at codon 129 was Met/Met (84.7%) and Met/Val (15.3%), and allele frequency was Met (92.4%) and Val (7.6%).129 Met was a risk factor (OR: 3.728, 95% CI: 2.194 to 6.333, p=0.000) for FFI in the non-Asian population. Comparison of Asians and non-Asians revealed clinical symptoms and genetic background to show some differences (p<0.05). In the comparison of 129 polymorphisms, a longer disease duration was found in the 129 MV group, with alleviation of some clinical symptoms (p<0.05). After considering survival probability, significant differences in survival time between genotypes remained (p<0.0001). CONCLUSIONS: Insomnia, RPD and hypertension are representative key clinical presentations of FFI. Phenotypic variations in genotypes and geographic regions were documented. Prion protein gene 129 Met was considered to be a risk factor for FFI in the non-Asian population, and 129 polymorphisms could modify survival duration.

Plasma neurofilament light chain as a biomarker for fatal familial insomnia.

BACKGROUND AND PURPOSE: Fatal familial insomnia is a rare hereditary prion disease associated with the D178N-129M PRNP mutation. Early diagnosis is difficult, because the clinical syndrome may overlap with affective disorders. In addition, most known cerebrospinal fluid biomarkers for prion diseases and magnetic resonance imaging do not show a good diagnostic accuracy for fatal familial insomnia. In this context, data on plasma biomarkers are scarce. METHODS: We analyzed levels of neurofilament light chain, glial fibrillary acidic protein, chitinase-3-like protein 1, calcium-binding protein B, and total tau protein in six serial plasma samples from a patient with fatal familial insomnia. Subsequently, plasma neurofilament light chain was analyzed in n = 25 patients and n = 19 controls. The diagnostic accuracy and associations with disease stage and duration were explored. RESULTS: Among all biomarker candidates in the case study, only neurofilament light chain levels showed a constant evolution and increased over time. They discriminated fatal familial insomnia from controls with an area under the curve of 0.992 (95% confidence interval [CI] = 0.974-1) in the case-control study. Higher concentrations were associated with methionine homozygosity at codon 129 PRNP (p = 0.006), shorter total disease duration (rho = -0.467, p = 0.019, 95% CI = -0.790 to -0.015), and shorter time from sampling to death (rho = -0.467, p = 0.019, 95% CI = -0.773 to -0.019). CONCLUSIONS: Plasma neurofilament light chain may be a valuable minimally invasive diagnostic biomarker for fatal familial insomnia after clinical onset. Most important, stage-related increase and association with disease duration indicate potential as a prognostic marker and as a surrogate marker in clinical trials.

A case of fatal familial insomnia: diagnostic and therapeutic approaches.

Fatal Familial Insomnia (FFI) is an uncommon but fatal genetic condition that is characterized by severe progressive insomnia, dysautonomia, neuropsychiatric changes, and gait instability. Diagnostic workup includes genetic testing, EEG, MRI imaging of the brain, polysomnography, and CSF analysis. MRI brain imaging may be notable for areas of restricted diffusion in the thalamus. Therapeutic approaches are centered on symptom management, predominantly for insomnia. It is important for clinicians to consider FFI in patients presenting with progressive insomnia, cognitive deficits, and gait instability, and to direct patients and families toward genetic counseling and palliative care services.

Can insomnia be fatal? An Australian case of fatal familial insomnia.

Fatal familial insomnia (FFI) is a rare prion disease with autosomal dominant inheritance. Currently, there is only one published case study of FFI in Australia. FFI is universally fatal, with the disease duration ranging from 8 to 72 months. Clinically, it manifests with disordered sleep-wake cycle, dysautonomia, motor disturbances and neuropsychiatric disorders. We describe a case of FFI detailing the investigative process, including the importance of sleep assessment and polysomnography in obtaining a diagnosis.

Doxycycline rescues recognition memory and circadian motor rhythmicity but does not prevent terminal disease in fatal familial insomnia mice.

Fatal familial insomnia (FFI) is a dominantly inherited prion disease linked to the D178N mutation in the gene encoding the prion protein (PrP). Symptoms, including insomnia, memory loss and motor abnormalities, appear around 50 years of age, leading to death within two years. No treatment is available. A ten-year clinical trial of doxycycline (doxy) is under way in healthy individuals at risk of FFI to test whether presymptomatic doxy prevents or delays the onset of disease. To assess the drug's effect in a tractable disease model, we used Tg(FFI-26) mice, which accumulate aggregated and protease-resistant PrP in their brains and develop a fatal neurological illness highly reminiscent of FFI. Mice were treated daily with 10 mg/kg doxy starting from a presymptomatic stage for twenty weeks. Doxy rescued memory deficits and restored circadian motor rhythmicity in Tg(FFI-26) mice. However, it did not prevent the onset and progression of motor dysfunction, clinical signs and progression to terminal disease. Doxy did not change the amount of aggregated and protease-resistant PrP, but reduced microglial activation in the hippocampus. Presymptomatic doxy treatment rescues cognitive impairment and the motor correlates of sleep dysfunction in Tg(FFI-26) mice but does not prevent fatal disease.

Phenotypic diversity of genetic Creutzfeldt-Jakob disease: a histo-molecular-based classification.

The current classification of sporadic Creutzfeldt-Jakob disease (sCJD) includes six major clinicopathological subtypes defined by the physicochemical properties of the protease-resistant core of the pathologic prion protein (PrPSc), defining two major PrPSc types (i.e., 1 and 2), and the methionine (M)/valine (V) polymorphic codon 129 of the prion protein gene (PRNP). How these sCJD subtypes relate to the well-documented phenotypic heterogeneity of genetic CJD (gCJD) is not fully understood. We analyzed molecular and phenotypic features in 208 individuals affected by gCJD, carrying 17 different mutations, and compared them with those of a large series of sCJD cases. We identified six major groups of gCJD based on the combination PrPSc type and codon 129 genotype on PRNP mutated allele, each showing distinctive histopathological characteristics, irrespectively of the PRNP associated mutation. Five gCJD groups, named M1, M2C, M2T, V1, and V2, largely reproduced those previously described in sCJD subtypes. The sixth group shared phenotypic traits with the V2 group and was only detected in patients carrying the E200K-129M haplotype in association with a PrPSc type of intermediate size ("i") between type 1 and type 2. Additional mutation-specific effects involved the pattern of PrP deposition (e.g., a "thickened" synaptic pattern in E200K carriers, cerebellar "stripe-like linear granular deposits" in those with insertion mutations, and intraneuronal globular dots in E200K-V2 or -M"i"). A few isolated cases linked to rare PRNP haplotypes (e.g., T183A-129M), showed atypical phenotypic features, which prevented their classification into the six major groups. The phenotypic variability of gCJD is mostly consistent with that previously found in sCJD. As in sCJD, the codon 129 genotype and physicochemical properties of PrPSc significantly correlated with the phenotypic variability of gCJD. The most common mutations linked to CJD appear to have a variable and overall less significant effect on the disease phenotype, but they significantly influence disease susceptibility often in a strain-specific manner. The criteria currently used for sCJD subtypes can be expanded and adapted to gCJD to provide an updated classification of the disease with a molecular basis.

Clinical manifestations and polysomnography-based analysis in nine cases of probable sporadic Creutzfeldt-Jakob disease.

PURPOSE: To summarize the clinical characteristics of patients with sporadic Creutzfeldt-Jakob disease (sCJD), analyze its sleep disorder characteristics using polysomnography (PSG), and compare sleep disturbances with those of fatal familial insomnia (FFI). PATIENTS AND METHODS: We retrospectively reviewed the sleep disturbances; cerebrospinal fluid (CSF) protein 14-3-3 (CSF-14-3-3 protein); prion protein gene, PRNP; magnetic resonance imaging; and electroencephalogram (EEG) of nine sCJD patients RESULTS: Of the nine sCJD patients, six were positive for CSF-14-3-3 protein. In the eight patients who completed diffusion-weighted imaging, seven showed cortical "ribbons sign" and two showed high signal in the basal ganglia. All nine patients had an EEG, which showed an increase in background slow waves; moreover, four showed typical periodic sharp wave complexes. The codon diversity at position 129, 219 of nine patients were MM, EE. Almost all nine patients had sleep disturbances such as insomnia, hypersomnia, and periodic limb movement disorder (PLMD). Five patients completed PSG, which demonstrated severe sleep structure disorder, prolonged total waking time, significantly reduced sleep efficiency, and absent rapid eye movement in some severe patients. CONCLUSION: Sleep disturbances are common in sCJD patients, manifested as insomnia, lethargy, and PLMD. The sCJD patients often demonstrate severe sleep structure disorder through PSG, which is similar to patients with FFI.

Virus Infection, Genetic Mutations, and Prion Infection in Prion Protein Conversion.

Conformational conversion of the cellular isoform of prion protein, PrPC, into the abnormally folded, amyloidogenic isoform, PrPSc, is an underlying pathogenic mechanism in prion diseases. The diseases manifest as sporadic, hereditary, and acquired disorders. Etiological mechanisms driving the conversion of PrPC into PrPSc are unknown in sporadic prion diseases, while prion infection and specific mutations in the PrP gene are known to cause the conversion of PrPC into PrPSc in acquired and hereditary prion diseases, respectively. We recently reported that a neurotropic strain of influenza A virus (IAV) induced the conversion of PrPC into PrPSc as well as formation of infectious prions in mouse neuroblastoma cells after infection, suggesting the causative role of the neuronal infection of IAV in sporadic prion diseases. Here, we discuss the conversion mechanism of PrPC into PrPSc in different types of prion diseases, by presenting our findings of the IAV infection-induced conversion of PrPC into PrPSc and by reviewing the so far reported transgenic animal models of hereditary prion diseases and the reverse genetic studies, which have revealed the structure-function relationship for PrPC to convert into PrPSc after prion infection.

Prion dimer is heterogenous and is modulated by multiple negative and positive motifs.

The conversion of the normal prion protein (PrP) into a scrapie prion (PrPSc) is incompletely understood. Theoretically, the smallest PrP aggregate is a dimer. Human PrP contains two cysteines at positions 179 (C179) and 214 (C214) enabling disulfide bonding. Here, we report that our recombinant human PrP (r-hPrP) preparations contain 0.2-0.8% dimer, which is linked by either one or two disulfide bonds, connected by C179-C179, C214-C214, or C179-C214. Furthermore, dimerization is regulated by multiple motifs. While residues 36-42 inhibit, residues 90-125, and 195-212 promote dimerization. Mutating individual residue between 36 and 42 enhances dimerization whereas mutating the positively charged residues within 95-115, or the negatively charged residues within 195-212 prevent dimerization. Although deletion of the entire octapeptide-repeat (5OR) region prevents dimerization, mutating the histidines within the 5OR enhances dimerization. In addition, we found that two out of three brain lysates from patients with inherited prion disease had more PrP dimers than controls. Thus, PrP dimerization may contribute to prion diseases.

Identification of new molecular alterations in fatal familial insomnia.

Fatal familial insomnia is a rare disease caused by a D178N mutation in combination with methionine (Met) at codon 129 in the mutated allele of PRNP (D178N-129M haplotype). FFI is manifested by sleep disturbances with insomnia, autonomic disorders and spontaneous and evoked myoclonus, among other symptoms. This study describes new neuropathological and biochemical observations in a series of eight patients with FFI. The mediodorsal and anterior nuclei of the thalamus have severe neuronal loss and marked astrocytic gliosis in every case, whereas the entorhinal cortex is variably affected. Spongiform degeneration only occurs in the entorhinal cortex. Synaptic and fine granular proteinase K digestion (PrPres) immunoreactivity is found in the entorhinal cortex but not in the thalamus. Interleukin 6, interleukin 10 receptor alpha subunit, colony stimulating factor 3 receptor and toll-like receptor 7 mRNA expression increases in the thalamus in FFI. PrPc levels are significantly decreased in the thalamus, entorhinal cortex and cerebellum in FFI. This is accompanied by a particular PrPc and PrPres band profile. Altered PrP solubility consistent with significantly reduced PrP levels in the cytoplasmic fraction and increased PrP levels in the insoluble fraction are identified in FFI cases. Amyloid-like deposits are only seen in the entorhinal cortex. The RT-QuIC assay reveals that all the FFI samples of the entorhinal cortex are positive, whereas the thalamus is positive only in three cases and the cerebellum in two cases. The present findings unveil particular neuropathological and neuroinflammatory profiles in FFI and novel characteristics of natural prion protein in FFI, altered PrPres and Scrapie PrP (abnormal and pathogenic PrP) patterns and region-dependent putative capacity of PrP seeding.

The clinical features in Chinese patients with PRNP D178N mutation.

BACKGROUND AND PURPOSE: Fatal familial insomnia (FFI) is an autosomal dominant disease due to the D178N mutation of PRNP gene coupling with homozygous methionine (Met) at codon 129. It is generally considered that D178N mutation cases with 129 M/M homozygotes present as FFI, and 129 V/V as genetic CJD. However, the frequency of 129 Met alleles in Chinese population is much higher than that in Caucasians. This study aims to investigate the clinical features and genetic characteristics of Chinese D178N mutants in this genetic context. METHODS: We reviewed the clinical and genetic features of seven D178N patients. The clinical data, genetic data, electroencephalogram (EEG), brain magnetic resonance imaging (MRI), polysomnography (PSG), CSF 14-3-3 protein examinations of the seven patients were analyzed. RESULTS: The genotypes at codon 129 were all M/M. Four of the seven cases reported positive family history. Four patients were more likely the CJD phenotype and three were FFI phenotype according to the core clinical features. No major differences were found on the EEG, CSF 14-3-3 protein, and PSG presentations between this study and western studies. Novel neuroimaging findings were two patients had typical neuroimaging abnormalities of CJD and frontotemporal dementia, respectively. CONCLUSIONS: Unlike the western populations, the diverse phenotypical presentations of D178N mutants were not simply determined by the 129 genotypes in Chinese. The underlying modifying factors for phenotypical variations warrant further investigations. For those with atypical clinical and imaging features, genetic testing was important for final diagnosis.

[Clinical, neuroimaging and genetic features of two Chinese families with fatal familial insomnia].

Objective: To examine clinical, neuroimaging and genetic features of two Chinese families with fatal familial insomnia (FFI). Methods: The clinical data, including case history, physical examination, biochemical analysis of blood and neuroimaging of two pedigrees with FFI who admitted to the Navy General Hospital in 2014 and 2017 were collected. The D178N prion protein (PRNP) mutation were determined by DNA sequencing among the proband and family members. Results: There were 6 patients in 2 families, 5 male and 1 female. The onset age of disease in family 1 was 47 and 60 years old respectively, and 46, 58, 58, 60 years old respectively in family 2. In terms of disease course, patients in family 1 had a rapid disease course and died half year after onset while patients in family 2 had a relatively slow disease course and survived more than 1 year after onset.The induced factors of the patients in the family 1 were fright, followed by abnormal behaviors and sleep disorders accompanied by autonomic nervous dysfunction; the clinical features of the pedigree 2 were memory loss, decreased sleep and motor disorder without obvious inducement, and the autonomic nervous dysfunction was not significant. The neuroimaging examination of 2 probands showed a mild atrophy of the whole brain and no ribbon sign. The electroencephalography (EEG) did not show typical triphasic waves. Both cases had a positive cerebrospinal fluid (CSF) 14-3-3 protein and PrP D178N /Met-129 mutation.All patients were given traditional sedatives or anti-anxiety and depression drugs which were with poor efficacy. Conclusions: The major clinical manifestations of FFI are sleep disorders accompanied by mental disorders. The clinical manifestations are similar among different individuals within one family, however, there is obvious clinical variability among different families. The neuroimaging examination shows a mild atrophy of the whole brain and no ribbon sign. There are no typical triphasic waves in EEG. Positive CSF 14-3-3 protein and PrP D178N /Met-129 mutation are common in FFI. Traditional sedatives or anti-anxiety and depression drugs may have poor efficacy.

Transgenic fatal familial insomnia mice indicate prion infectivity-independent mechanisms of pathogenesis and phenotypic expression of disease.

Fatal familial insomnia (FFI) and a genetic form of Creutzfeldt-Jakob disease (CJD178) are clinically different prion disorders linked to the D178N prion protein (PrP) mutation. The disease phenotype is determined by the 129 M/V polymorphism on the mutant allele, which is thought to influence D178N PrP misfolding, leading to the formation of distinctive prion strains with specific neurotoxic properties. However, the mechanism by which misfolded variants of mutant PrP cause different diseases is not known. We generated transgenic (Tg) mice expressing the mouse PrP homolog of the FFI mutation. These mice synthesize a misfolded form of mutant PrP in their brains and develop a neurological illness with severe sleep disruption, highly reminiscent of FFI and different from that of analogously generated Tg(CJD) mice modeling CJD178. No prion infectivity was detectable in Tg(FFI) and Tg(CJD) brains by bioassay or protein misfolding cyclic amplification, indicating that mutant PrP has disease-encoding properties that do not depend on its ability to propagate its misfolded conformation. Tg(FFI) and Tg(CJD) neurons have different patterns of intracellular PrP accumulation associated with distinct morphological abnormalities of the endoplasmic reticulum and Golgi, suggesting that mutation-specific alterations of secretory transport may contribute to the disease phenotype.