Publications

The cellular prion protein (PrPC) plays many roles in the developing and adult brain. In addition, PrPC binds to several amyloids in oligomeric and prefibrillar forms and may act as a putative receptor of abnormal misfolded protein species. The role of PrPC in tau seeding and spreading is not known. In the present study, we have inoculated well-characterized sarkosyl-insoluble fractions of sporadic Alzheimer's disease (sAD) into the brain of adult wild-type mice (Prnp(+/+)), Prnp(0/0) (ZH3 strain) mice, and mice over-expressing the secreted form of PrPC lacking their GPI anchor (Tg44 strain). Phospho-tau (ptau) seeding and spreading involving neurons and oligodendrocytes were observed three and six months after inoculation. 3Rtau and 4Rtau deposits from the host tau, as revealed by inoculating Mapt(0/0) mice and by using specific anti-mouse and anti-human tau antibodies suggest modulation of exon 10 splicing of the host mouse Mapt gene elicited by exogenous sAD-tau. However, no tau seeding and spreading differences were observed among Prnp genotypes. Our results show that PrPC does not affect tau seeding and spreading in vivo.

JTD Keywords: Alpha-synuclein, Alzheimer's disease, Amyloid-beta oligomers, Expression, Impairmen, Mapt, Mice, Paired helical filaments, Pathological tau, Prnp, Propagation, Prpc, Seeding, Spreadin, Synaptic plasticity, Tau, Tauopathies

Heterozygous hTau mice were used for the study of tau seeding. These mice express the six human tau isoforms, with a high predominance of 3Rtau over 4Rtau. The following groups were assessed: (i) non-inoculated mice aged 9 months (n = 4); (ii) Alzheimer's Disease (AD)-inoculated mice (n = 4); (iii) Globular Glial Tauopathy (GGT)-inoculated mice (n = 4); (iv) Pick's disease (PiD)-inoculated mice (n = 4); (v) control-inoculated mice (n = 4); and (vi) inoculated with vehicle alone (n = 2). AD-inoculated mice showed AT8-immunoreactive neuronal pre-tangles, granular aggregates, and dots in the CA1 region of the hippocampus, dentate gyrus (DG), and hilus, and threads and dots in the ipsilateral corpus callosum. GGT-inoculated mice showed unique or multiple AT8-immunoreactive globular deposits in neurons, occasionally extended to the proximal dendrites. PiD-inoculated mice showed a few loose pre-tangles in the CA1 region, DG, and cerebral cortex near the injection site. Coiled bodies were formed in the corpus callosum in AD-inoculated mice, but GGT-inoculated mice lacked globular glial inclusions. Tau deposits in inoculated mice co-localized active kinases p38-P and SAPK/JNK-P, thus suggesting active phosphorylation of the host tau. Tau deposits were absent in hTau mice inoculated with control homogenates and vehicle alone. Deposits in AD-inoculated hTau mice contained 3Rtau and 4Rtau; those in GGT-inoculated mice were mainly stained with anti-4Rtau antibodies, but a small number of deposits contained 3Rtau. Deposits in PiD-inoculated mice were stained with anti-3Rtau antibodies, but rare neuronal, thread-like, and dot-like deposits showed 4Rtau immunoreactivity. These findings show that tau strains produce different patterns of active neuronal seeding, which also depend on the host tau. Unexpected 3Rtau and 4Rtau deposits after inoculation of homogenates from 4R and 3R tauopathies, respectively, suggests the regulation of exon 10 splicing of the host tau during the process of seeding, thus modulating the plasticity of the cytoskeleton.

JTD Keywords: alzheimer's disease (ad), alzheimers-disease, brain, corticobasal degeneration, globular glial tauopathy (ggt), htau, isoforms, pathological tau, pick's disease (pid), picks-disease, propagation, protein, seeding, tau splicing, tauopathy, Alzheimer’s disease (ad), Globular glial tauopathy (ggt), Htau, Paired helical filaments, Pick’s disease (pid), Seeding, Tau, Tau splicing

Alzheimer’s disease (AD) and other tauopathies are common neurodegenerative diseases in older adults; in contrast, abnormal tau deposition in neurons and glial cells occurs only exceptionally in children. Sarkosyl-insoluble fractions from sporadic AD (sAD) containing paired helical filaments (PHFs) were inoculated unilaterally into the thalamus in newborn and three-month-old wild-type C57BL/6 mice, which were killed at different intervals from 24 h to six months after inoculation. Tau-positive cells were scanty and practically disappeared at three months in mice inoculated at the age of a newborn. In contrast, large numbers of tau-positive cells, including neurons and oligodendrocytes, were found in the thalamus of mice inoculated at three months and killed at the ages of six months and nine months. Mice inoculated at the age of newborn and re-inoculated at the age of three months showed similar numbers and distribution of positive cells in the thalamus at six months and nine months. This study shows that (a) differences in tau seeding between newborn and young adults may be related to the ratios between 3Rtau and 4Rtau, and the shift to 4Rtau predominance in adults, together with the immaturity of connections in newborn mice, and (b) intracerebral inoculation of sAD PHFs in newborn mice does not protect from tau seeding following intracerebral inoculation of sAD PHFs in young/adult mice.

JTD Keywords: alzheimer's disease, alzheimer-disease, alzheimer’s disease, expression, mouse tau, neurofibrillary tangles, newborn, pathological tau, propagation, protein-tau, spread, tau seeding and spreading, thalamus, transgenic mice, Paired helical filaments, Tau seeding and spreading, Thalamus

Several studies have demonstrated the different characteristics of tau seeding and spreading following intracerebral inoculation in murine models of tau-enriched fractions of brain homogenates from AD and other tauopathies. The present study is centered on the importance of host tau in tau seeding and the molecular changes associated with the transformation of host tau into abnormal tau. The brains of three adult murine genotypes expressing different forms of tau—WT (murine 4Rtau), hTau (homozygous transgenic mice knock-out for murine tau protein and heterozygous expressing human forms of 3Rtau and 4Rtau proteins), and mtWT (homozygous transgenic mice knock-out for murine tau protein)—were analyzed following unilateral hippocampal inoculation of sarkosyl-insoluble tau fractions from the same AD and control cases. The present study reveals that (a) host tau is mandatory for tau seeding and spreading following tau inoculation from sarkosyl-insoluble fractions obtained from AD brains; (b) tau seeding does not occur following intracerebral inoculation of sarkosyl-insoluble fractions from controls; (c) tau seeding and spreading are characterized by variable genotype-dependent tau phosphorylation and tau nitration, MAP2 phosphorylation, and variable activation of kinases that co-localize with abnormal tau deposits; (d) transformation of host tau into abnormal tau is an active process associated with the activation of specific kinases; (e) tau seeding is accompanied by modifications in tau splicing, resulting in the expression of new 3Rtau and 4Rtau isoforms, thus indicating that inoculated tau seeds have the capacity to model exon 10 splicing of the host mapt or MAPT with a genotype-dependent pattern; (e) selective regional and cellular vulnerabilities, and different molecular compositions of the deposits, are dependent on the host tau of mice injected with identical AD tau inocula.

JTD Keywords: 3rtau and 4rtau, alzheimer's disease, alzheimer’s disease, brains, granulovacuolar degeneration, host tau, htau, intranuclear distribution, messenger-rna, pathological tau, propagation, protein-kinases, seeding and spreading, tauopathies, transmission, 3rtau and 4rtau, Alzheimers-disease, Alzheimer’s disease, Host tau, Htau, Seeding and spreading, Tauopathies