Leticia Miravalle

Expression of a mutant form of the ferritin light chain gene induces neurodegeneration and iron overload in transgenic mice

Increased iron levels and iron-mediated oxidative stress play an important role in the pathogenesis of many neurodegenerative diseases. The finding that mutations in the ferritin light polypeptide (FTL) gene cause a neurodegenerative disease known as neuroferritinopathy or hereditary ferritinopathy (HF) provided a direct connection between abnormal brain iron storage and neurodegeneration. HF is characterized by a severe movement disorder and by the presence of nuclear and cytoplasmic ferritin inclusion bodies in glia and neurons throughout the CNS and in tissues of multiple organ systems. Here we report that the expression in transgenic mice of a human FTL cDNA carrying a thymidine and cytidine insertion at position 498 (FTL498–499InsTC) leads to the formation of nuclear and cytoplasmic ferritin inclusion bodies. As in HF, ferritin inclusions are seen in glia and neurons throughout the CNS as well as in cells of other organ systems. Our studies show histological, immunohistochemical, and biochemical similarities between ferritin inclusion bodies found in transgenic mice and in individuals with HF. Expression of the transgene in mice leads to a significant decrease in motor performance and a shorter life span, formation of ferritin inclusion bodies, misregulation of iron metabolism, accumulation of ubiquitinated proteins, and incorporation of elements of the proteasome into inclusions. This new transgenic mouse represents a relevant model of HF in which to study the pathways that lead to neurodegeneration in HF, to evaluate the role of iron mismanagement in neurodegenerative disorders, and to evaluate potential therapies for HF and related neurodegenerative diseases.

Cerebral amyloid angiopathy and parenchymal amyloid deposition in transgenic mice expressing the Danish mutant form of human BRI2.

Familial Danish dementia (FDD) is an autosomal dominant neurodegenerative disease clinically characterized by the presence of cataracts, hearing impairment, cerebellar ataxia and dementia. Neuropathologically, FDD is characterized by the presence of widespread cerebral amyloid angiopathy (CAA), parenchymal amyloid deposition and neurofibrillary tangles. FDD is caused by a 10‐nucleotide duplication‐insertion in the BRI2 gene that generates a larger‐than‐normal precursor protein, of which the Danish amyloid subunit (ADan) comprises the last 34 amino acids. Here, we describe a transgenic mouse model for FDD (Tg‐FDD) in which the mouse Prnp (prion protein) promoter drives the expression of the Danish mutant form of human BRI2 . The main neuropathological findings in Tg‐FDD mice are the presence of widespread CAA and parenchymal deposition of ADan. In addition, we observe the presence of amyloid‐associated gliosis, an inflammatory response and deposition of oligomeric ADan. As the animals aged, they showed abnormal grooming behavior, an arched back, and walked with a wide‐based gait and shorter steps. This mouse model may give insights on the pathogenesis of FDD and will prove useful for the development of therapeutics. Moreover, the study of Tg‐FDD mice may offer new insights into the role of amyloid in neurodegeneration in other disorders, including Alzheimer disease.

Genetic disruption of both Fancc and Fancg in mice recapitulates the hematopoietic manifestations of Fanconi anemia.

Fanconi anemia (FA) is an inherited chromosomal instability syndrome characterized by bone marrow failure, myelodysplasia (MDS), and acute myeloid leukemia (AML). Eight FA proteins associate in a nuclear core complex to monoubiquitinate FANCD2/FANCI in response to DNA damage. Additional functions have been described for some of the core complex proteins; however, in vivo genetic proof has been lacking. Here we show that double-mutant Fancc(-/-);Fancg(-/-) mice develop spontaneous hematologic sequelae including bone marrow failure, AML, MDS and complex random chromosomal abnormalities that the single-mutant mice do not. This genetic model provides evidence for unique core complex protein function independent of their ability to monoubiquitinate FANCD2/FANCI. Importantly, this model closely recapitulates the phenotypes found in FA patients and may be useful as a preclinical platform to evaluate the molecular pathogenesis of spontaneous bone marrow failure, MDS and AML in FA.

Amyloidogenesis in Familial British Dementia Is Associated with a Genetic Defect on Chromosome 13

Abstract: Familial British dementia (FBD) is a disorder characterized by the presence of amyloid deposits in cerebral blood vessels and brain parenchyma coexisting with neurofibrillary tangles in limbic areas. The amyloid subunit (ABri) is a 4 kDa fragment of a 266 amino acid type II single‐spanning transmembrane precursor protein encoded by the BRI gene located on chromosome 13. In FBD patients, a single base substitution at the stop codon of this gene generates a larger 277‐residue precursor (ABriPP‐277). Proteolytic processing by a furin‐like enzyme at the C‐terminus of the elongated precursor generates the 34 amino acid ABri that undergoes rapid aggregation and fibrillization. ABri is structually unrelated to all known amyloids including Aβ, the main component of the amyloid lesions in Alzheimers disease (AD), indicating that cerebral deposition of amyloid molecules other than Aβ can trigger similar neuropathological changes leading to neuronal loss and dementia. These data support the concept that amyloid deposition in the vascular wall and brain parenchyma is of primary importance in the initiation of neurogeneration.

Failure to Detect the Presence of Prions in the Uterine and Gestational Tissues from a Gravida with Creutzfeldt-Jakob Disease

The vertical transmission of a prion disease from infected mothers to their offspring is believed to be one of the routes for the natural spread of animal prion diseases. Supporting this notion is the observation that prion infectivity occurs in the placenta of infected ewes. Furthermore, the prion protein (PrP), both in its cellular form (PrP(C)) and its pathological isoform (PrP(Sc)), has been observed at the fetal-maternal interface of scrapie-infected sheep. However, whether these features of prion infectivity also hold true for human prion diseases is currently unknown. To begin to address such an important question, we examined PrP in the uterus as well as gestational tissues, including the placenta and amniotic fluid, in a pregnant woman with sporadic Creutzfeldt-Jakob disease (CJD). Although the proteinase K (PK)-resistant prion protein, PrP27-30, was present in the brain tissues of the mother, the PrP detected in the uterus, placenta, and amniotic fluid was sensitive to PK digestion. Unlike PrP(C) in the brain and adjacent cerebrospinal fluid, the predominant PrP species in the reproductive and gestational tissues were N-terminally truncated, similar to urine PrP. Our study did not detect abnormal PrP in the reproductive and gestational tissues in this case of CJD. Nevertheless, examination by a highly sensitive bioassay is ongoing to ascertain possible prion infectivity from CJD in the amniotic fluid.

The Psen1-L166P-knock-in mutation leads to amyloid deposition in human wild-type amyloid precursor protein YAC transgenic mice

Genetically engineered mice have been generated to model cerebral β‐amyloidosis, one of the hallmarks of Alzheimer disease (AD) pathology, based on the overexpression of a mutated cDNA of the amyloid‐β precursor protein (AβPP) or by knock‐in of the murine Aβpp gene alone or with presenilin1 mutations. Here we describe the generation and initial characterization of a new mouse line based on the presence of 2 copies of the human genomic region encoding the wild‐type AβPP and the L166P presenilin 1 mutation. At ∼6 mo of age, double‐mutant mice develop amyloid pathology, with signs of neuritic dystrophy, intracellular Aβ accumulation, and glial inflammation, an increase in AβPP C‐terminal fragments, and an 8 times increase in Aβ42 levels with a 40% decrease in Aβ40 levels, leading to a significant increase (14 times) of Aβ42/Aβ40 ratios, with minimal effects on presenilin or the Notch1 pathway in the brain. We conclude that in mice, neither mutations in AβPP nor overexpression of an AβPP isoform are a prerequisite for Aβ pathology. This model will allow the study of AD pathogenesis and testing of therapeutic strategies in a more relevant environment without experimental artifacts due to the overexpression of a single‐mutant AβPP isoform using exogenous promoters.—Vidal, R., Sammeta, N., Garringer, H. J., Sambamurti, K., Miravalle, L., Lamb B. T., Ghetti, B. The Psen1‐L166P‐knock‐in mutation leads to amyloid deposition in human wild‐type amyloid precursor protein YAC transgenic mice. FASEB J. 26, 2899–2910 (2012). www.fasebj.org

KRAS mutation is present in a small subset of primary urinary bladder adenocarcinomas

Alexander R E, Lopez‐Beltran A, Montironi R, MacLennan G T, Post K M, Bilbo S A, Jones T D, Huang W, Rao Q, Sen J D, Meehan K, Cornwell A, Miravalle L & Cheng L 
(2012) Histopathology
KRAS mutation is present in a small subset of primary urinary bladder adenocarcinomas

Follow-up of the first American report of familial Alzheimer's disease

Background: Familial Alzheimer’s disease associated with PSEN1 mutations has a wide spectrum of clinical presentations. Cognitive deficits are the dominant features; however, other signs and symptoms can be seen including some associated with movement disorders. Methods: Affected individuals from a family were studied clinically (2), genetically (3), and neuropathologically (1). Results: The proband, a female, reportedly began to have seizures, headaches and psychiatric problems at age 14. She attempted suicide and was considered to have conversion disorder at age 15. Her seizure disorder was treated with phenytoin and carbamazepine at age 19. Also, she was diagnosed by a psychiatrist as having adolescent adjustment reaction and reactive depression. Her family noted episodes of confusion and memory difficulty at age 27. Her memory worsened, speech became dysarthric and spasticity developed in the lower extremities at age 29. A diagnosis of spinocerebellar degeneration was considered at that time. Her condition progressed until she died at age 36. The proband’s mother was reported to have had ataxia and spasticity at age 18, dementia by 30 and died at 55. The proband’s sister developed a gait disorder at age 21, dementia at 25 and died at 47 after having been in a vegetative state for 9 years. The proband’s brother was known to have a gait disorder at age 28, but was lost to follow-up. Genetic analysis of the proband and two siblings identified a single nucleotide substitution (C for T) in exon 6 in the PSEN1 gene leading to a proline for leucine substitution at codon 166 (L166P). Autopsy of the proband showed corticospinal tract degeneration with atrophy of the cerebral hemispheres, pons, cerebellum, and rostral spinal cord. Histopathology revealed advanced stage neurofibrillary tangle and neuritic plaque pathology accompanied by prominent amyloid-b (Ab) deposition as well as “cotton wool” plaques and severe amyloid angiopathy. Conclusions: This mutation in PSEN1 results in one of the earliest onsets of symptoms and most “malignant” clinical courses reported to date. This report underscores the importance of close clinical, genetic, and neuropathologic studies to diagnose atypical presentations of a neurodegenerative disease.

O3-01-04: Vascular amyloid deposition and related pathology in a transgenic mouse model of familial Danish dementia

(p 0, 01) and grip hanging task (p 0,05), compared to age-matched untrained APP/PS1KI mice. No difference in the swimming distance could be detected and the swimming pattern was as impaired as the one displayed by the untrained APP/PS1KI mice. Interestingly, the enriched environment failed to restore the neurogenesis and didn’t result in any improvement of the working memory. Reduced neurogenesis measured by doublecortin staining in the dentate gyrus of APP/PS1KI mice was already visible at 2 months of age (62%, p 0.05), resulting in a complete loss of the of doublecortin signal at the age of 6 months. Conclusions: Enriched environment has a beneficial effect on some motor abilities of APP/PS1KI mice however hippocampal dysfunction could not be restored. We speculate that the fast and severe neuron loss in hippocampus can not be modulated by increasing neurogenesis in the dentate gyrus. Enriched environment has however significant beneficial effects on motor performance and may be translated to some symptoms reported in AD patients.