1
|
Ackleh AS, Elaydi S, Livadiotis G, Veprauskas A. A continuous-time mathematical model and discrete approximations for the aggregation of β-Amyloid. JOURNAL OF BIOLOGICAL DYNAMICS 2021; 15:109-136. [PMID: 33427593 DOI: 10.1080/17513758.2020.1869843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 12/11/2020] [Indexed: 06/12/2023]
Abstract
Alzheimer's disease is a degenerative disorder characterized by the loss of synapses and neurons from the brain, as well as the accumulation of amyloid-based neuritic plaques. While it remains a matter of contention whether β-amyloid causes the neurodegeneration, β-amyloid aggregation is associated with the disease progression. Therefore, gaining a clearer understanding of this aggregation may help to better understand the disease. We develop a continuous-time model for β-amyloid aggregation using concepts from chemical kinetics and population dynamics. We show the model conserves mass and establish conditions for the existence and stability of equilibria. We also develop two discrete-time approximations to the model that are dynamically consistent. We show numerically that the continuous-time model produces sigmoidal growth, while the discrete-time approximations may exhibit oscillatory dynamics. Finally, sensitivity analysis reveals that aggregate concentration is most sensitive to parameters involved in monomer production and nucleation, suggesting the need for good estimates of such parameters.
Collapse
Affiliation(s)
- Azmy S Ackleh
- Department of Mathematics, University of Louisiana at Lafayette, Lafayette, LA, USA
| | - Saber Elaydi
- Department of Mathematics, Trinity University, San Antonio, TX, USA
| | - George Livadiotis
- Department of Space Research, Southwest Research Institute, San Antonio, TX, USA
| | - Amy Veprauskas
- Department of Mathematics, University of Louisiana at Lafayette, Lafayette, LA, USA
| |
Collapse
|
2
|
Meisl G, Kurt T, Condado-Morales I, Bett C, Sorce S, Nuvolone M, Michaels TCT, Heinzer D, Avar M, Cohen SIA, Hornemann S, Aguzzi A, Dobson CM, Sigurdson CJ, Knowles TPJ. Scaling analysis reveals the mechanism and rates of prion replication in vivo. Nat Struct Mol Biol 2021; 28:365-372. [PMID: 33767451 PMCID: PMC8922999 DOI: 10.1038/s41594-021-00565-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 01/26/2021] [Indexed: 01/03/2023]
Abstract
Prions consist of pathological aggregates of cellular prion protein and have the ability to replicate, causing neurodegenerative diseases, a phenomenon mirrored in many other diseases connected to protein aggregation, including Alzheimer's and Parkinson's diseases. However, despite their key importance in disease, the individual processes governing this formation of pathogenic aggregates, as well as their rates, have remained challenging to elucidate in vivo. Here we bring together a mathematical framework with kinetics of the accumulation of prions in mice and microfluidic measurements of aggregate size to dissect the overall aggregation reaction into its constituent processes and quantify the reaction rates in mice. Taken together, the data show that multiplication of prions in vivo is slower than in in vitro experiments, but efficient when compared with other amyloid systems, and displays scaling behavior characteristic of aggregate fragmentation. These results provide a framework for the determination of the mechanisms of disease-associated aggregation processes within living organisms.
Collapse
Affiliation(s)
- Georg Meisl
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | - Timothy Kurt
- Department of Pathology, UC San Diego, San Diego, CA, USA
| | - Itzel Condado-Morales
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
| | - Cyrus Bett
- Department of Pathology, UC San Diego, San Diego, CA, USA
| | - Silvia Sorce
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
| | - Mario Nuvolone
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
- Amyloidosis Research and Treatment Center, Foundation IRCCS Policlinico San Matteo, Department of Molecular Medicine, University of Pavia, Pavia, Italy
| | - Thomas C T Michaels
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
- Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
| | - Daniel Heinzer
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
| | - Merve Avar
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
| | - Samuel I A Cohen
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
- Wren Therapeutics, Cambridge, UK
| | - Simone Hornemann
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
| | - Adriano Aguzzi
- Institute of Neuropathology, University of Zurich, Zurich, Switzerland
| | - Christopher M Dobson
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK
| | | | - Tuomas P J Knowles
- Centre for Misfolding Diseases, Yusuf Hamied Department of Chemistry, University of Cambridge, Cambridge, UK.
- Cavendish Laboratory, University of Cambridge, Cambridge, UK.
| |
Collapse
|
3
|
Cavalli B. A probabilistic view on the long-time behaviour of growth-fragmentation semigroups with bounded fragmentation rates. ESAIM-PROBAB STAT 2021. [DOI: 10.1051/ps/2021008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The growth-fragmentation equation models systems of particles that grow and reproduce as time passes. An important question concerns the asymptotic behaviour of its solutions. Bertoin and Watson (2018) developed a probabilistic approach relying on the Feynman-Kac formula, that enabled them to answer to this question for sublinear growth rates. This assumption on the growth ensures that microscopic particles remain microscopic. In this work, we go further in the analysis, assuming bounded fragmentations and allowing arbitrarily small particles to reach macroscopic mass in finite time. We establish necessary and sufficient conditions on the coefficients of the equation that ensure Malthusian behaviour with exponential speed of convergence to the asymptotic profile. Furthermore, we provide an explicit expression of the latter.
Collapse
|
4
|
|
5
|
Helal M, Igel-Egalon A, Lakmeche A, Mazzocco P, Perrillat-Mercerot A, Pujo-Menjouet L, Rezaei H, Tine LM. Stability analysis of a steady state of a model describing Alzheimer's disease and interactions with prion proteins. J Math Biol 2018; 78:57-81. [PMID: 30099569 DOI: 10.1007/s00285-018-1267-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2017] [Revised: 04/09/2018] [Indexed: 01/20/2023]
Abstract
Alzheimer's disease (AD) is a neuro-degenerative disease affecting more than 46 million people worldwide in 2015. AD is in part caused by the accumulation of A[Formula: see text] peptides inside the brain. These can aggregate to form insoluble oligomers or fibrils. Oligomers have the capacity to interact with neurons via membrane receptors such as prion proteins ([Formula: see text]). This interaction leads [Formula: see text] to be misfolded in oligomeric prion proteins ([Formula: see text]), transmitting a death signal to neurons. In the present work, we aim to describe the dynamics of A[Formula: see text] assemblies and the accumulation of toxic oligomeric species in the brain, by bringing together the fibrillation pathway of A[Formula: see text] peptides in one hand, and in the other hand A[Formula: see text] oligomerization process and their interaction with cellular prions, which has been reported to be involved in a cell-death signal transduction. The model is based on Becker-Döring equations for the polymerization process, with delayed differential equations accounting for structural rearrangement of the different reactants. We analyse the well-posedness of the model and show existence, uniqueness and non-negativity of solutions. Moreover, we demonstrate that this model admits a non-trivial steady state, which is found to be globally stable thanks to a Lyapunov function. We finally present numerical simulations and discuss the impact of model parameters on the whole dynamics, which could constitute the main targets for pharmaceutical industry.
Collapse
Affiliation(s)
- Mohammed Helal
- Laboratory of Biomathematics, University Sidi Bel Abbes, Sidi Bel Abbès, Algeria
| | | | - Abdelkader Lakmeche
- Laboratory of Biomathematics, University Sidi Bel Abbes, Sidi Bel Abbès, Algeria
| | - Pauline Mazzocco
- CNRS UMR 5558, Laboratoire de Biométrie et Biologie Evolutive, Université Claude Bernard Lyon 1, Université de Lyon, 69100, Villeurbanne, France
| | - Angélique Perrillat-Mercerot
- Laboratoire de Mathématiques et Applications, UMR CNRS 7348, SP2MI Equipe DACTIM-MIS, Université de Poitiers, 86962, Chasseneuil Futuroscope Cedex, France
| | - Laurent Pujo-Menjouet
- CNRS UMR 5208 Institut Camille Jordan, Université Claude Bernard Lyon 1, Université de Lyon, 69622, Villeurbanne Cedex, France. .,Inria Team Dracula, Inria Grenoble Rhône-Alpes Center, 69100, Villeurbanne, France.
| | - Human Rezaei
- UR892 Virologie Immunologie Moléculaires, INRA, 78352, Jouy-en-Josas, France
| | - Léon M Tine
- CNRS UMR 5208 Institut Camille Jordan, Université Claude Bernard Lyon 1, Université de Lyon, 69622, Villeurbanne Cedex, France.,Inria Team Dracula, Inria Grenoble Rhône-Alpes Center, 69100, Villeurbanne, France
| |
Collapse
|
6
|
Carbonell F, Iturria-Medina Y, Evans AC. Mathematical Modeling of Protein Misfolding Mechanisms in Neurological Diseases: A Historical Overview. Front Neurol 2018; 9:37. [PMID: 29456521 PMCID: PMC5801313 DOI: 10.3389/fneur.2018.00037] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 01/16/2018] [Indexed: 12/12/2022] Open
Abstract
Protein misfolding refers to a process where proteins become structurally abnormal and lose their specific 3-dimensional spatial configuration. The histopathological presence of misfolded protein (MP) aggregates has been associated as the primary evidence of multiple neurological diseases, including Prion diseases, Alzheimer's disease, Parkinson's disease, and Creutzfeldt-Jacob disease. However, the exact mechanisms of MP aggregation and propagation, as well as their impact in the long-term patient's clinical condition are still not well understood. With this aim, a variety of mathematical models has been proposed for a better insight into the kinetic rate laws that govern the microscopic processes of protein aggregation. Complementary, another class of large-scale models rely on modern molecular imaging techniques for describing the phenomenological effects of MP propagation over the whole brain. Unfortunately, those neuroimaging-based studies do not take full advantage of the tremendous capabilities offered by the chemical kinetics modeling approach. Actually, it has been barely acknowledged that the vast majority of large-scale models have foundations on previous mathematical approaches that describe the chemical kinetics of protein replication and propagation. The purpose of the current manuscript is to present a historical review about the development of mathematical models for describing both microscopic processes that occur during the MP aggregation and large-scale events that characterize the progression of neurodegenerative MP-mediated diseases.
Collapse
Affiliation(s)
| | - Yasser Iturria-Medina
- Department of Neurology & Neurosurgery, McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, QC, Canada
- Ludmer Centre for NeuroInformatics and Mental Health, Montreal, QC, Canada
| | - Alan C. Evans
- Department of Neurology & Neurosurgery, McConnell Brain Imaging Centre, Montreal Neurological Institute, Montreal, QC, Canada
- Ludmer Centre for NeuroInformatics and Mental Health, Montreal, QC, Canada
| |
Collapse
|
7
|
Gabriel P. Global stability for the prion equation with general incidence. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2015; 12:789-801. [PMID: 25974345 DOI: 10.3934/mbe.2015.12.789] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We consider the so-called prion equation with the general incidence term introduced in [14], and we investigate the stability of the steady states. The method is based on the reduction technique introduced in [11]. The argument combines a recent spectral gap result for the growth-fragmentation equation in weighted L1 spaces and the analysis of a nonlinear system of three ordinary differential equations.
Collapse
Affiliation(s)
- Pierre Gabriel
- Laboratoire de Mathematiques de Versailles, CNRS UMR 8100, Universite de Versailles Saint-Quentin-en-Yvelines, 45 Avenue de Etats-Unis, 78035 Versailles cedex, France.
| |
Collapse
|
8
|
Coron JM, Gabriel P, Shang P. Optimization of an amplification protocol for misfolded proteins by using relaxed control. J Math Biol 2014; 70:289-327. [PMID: 24567169 DOI: 10.1007/s00285-014-0768-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2013] [Revised: 01/27/2014] [Indexed: 11/29/2022]
Abstract
We investigate an optimal control problem which arises in the optimization of an amplification technique for misfolded proteins. The improvement of this technique may play a role in the detection of prion diseases. The model consists in a linear system of differential equations with a nonlinear control. The appearance of oscillations in the numerical simulations is understood by using the Perron and Floquet eigenvalue theory for nonnegative irreducible matrices. Then to overcome the unsolvability of the optimal control, we relax the problem. In the two dimensional case, we solve explicitly the optimal relaxed control problem when the final time is large enough.
Collapse
Affiliation(s)
- Jean-Michel Coron
- Laboratoire Jacques-Louis Lions, UPMC Univ Paris 06, UMR 7598, Sorbonne Universités, 75005 , Paris, France,
| | | | | |
Collapse
|
9
|
Helal M, Hingant E, Pujo-Menjouet L, Webb GF. Alzheimer's disease: analysis of a mathematical model incorporating the role of prions. J Math Biol 2013; 69:1207-35. [PMID: 24146290 DOI: 10.1007/s00285-013-0732-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2013] [Revised: 08/01/2013] [Indexed: 11/28/2022]
Abstract
We introduce a mathematical model of the in vivo progression of Alzheimer's disease with focus on the role of prions in memory impairment. Our model consists of differential equations that describe the dynamic formation of β-amyloid plaques based on the concentrations of Aβ oligomers, PrP(C) proteins, and the Aβ-x-Aβ-PrP(C)complex, which are hypothesized to be responsible for synaptic toxicity. We prove the well-posedness of the model and provided stability results for its unique equilibrium, when the polymerization rate of Aβ-amyloid is constant and also when it is described by a power law.
Collapse
Affiliation(s)
- Mohamed Helal
- Département de Mathématique, Faculté des Sciences, Université Djillali Liabes, 22000 , Sidi Bel Abbès, Algeria,
| | | | | | | |
Collapse
|
10
|
Sindi SS, Olofsson P. A Discrete-Time Branching Process Model of Yeast Prion Curing Curves. MATHEMATICAL POPULATION STUDIES 2013; 20:1-13. [PMID: 30287982 PMCID: PMC6168217 DOI: 10.1080/08898480.2013.748566] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The infectious agent of many neurodegenerative disorders is thought to be aggregates of prion protein, which are transmitted between cells. Recent work in yeast supports this hypothesis, but suggests that only aggregates below a critical size are transmitted efficiently. The total number of transmissible aggregates in a typical cell is a key determinant of strain infectivity. In a discrete-time branching process model of a yeast colony with prions, prion aggregates increase in size according to a Poisson process and only aggregates below a threshold size are transmitted during cell division. The total number of cells with aggregates in a growing population of yeast is expressed.
Collapse
|
11
|
Prigent S, Ballesta A, Charles F, Lenuzza N, Gabriel P, Tine LM, Rezaei H, Doumic M. An efficient kinetic model for assemblies of amyloid fibrils and its application to polyglutamine aggregation. PLoS One 2012; 7:e43273. [PMID: 23152746 PMCID: PMC3496744 DOI: 10.1371/journal.pone.0043273] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2012] [Accepted: 07/18/2012] [Indexed: 11/23/2022] Open
Abstract
Protein polymerization consists in the aggregation of single monomers into polymers that may fragment. Fibrils assembly is a key process in amyloid diseases. Up to now, protein aggregation was commonly mathematically simulated by a polymer size-structured ordinary differential equations (ODE) system, which is infinite by definition and therefore leads to high computational costs. Moreover, this Ordinary Differential Equation-based modeling approach implies biological assumptions that may be difficult to justify in the general case. For example, whereas several ordinary differential equation models use the assumption that polymerization would occur at a constant rate independently of polymer size, it cannot be applied to certain protein aggregation mechanisms. Here, we propose a novel and efficient analytical method, capable of modelling and simulating amyloid aggregation processes. This alternative approach consists of an integro-Partial Differential Equation (PDE) model of coalescence-fragmentation type that was mathematically derived from the infinite differential system by asymptotic analysis. To illustrate the efficiency of our approach, we applied it to aggregation experiments on polyglutamine polymers that are involved in Huntington’s disease. Our model demonstrates the existence of a monomeric structural intermediate acting as a nucleus and deriving from a non polymerizing monomer (). Furthermore, we compared our model to previously published works carried out in different contexts and proved its accuracy to describe other amyloid aggregation processes.
Collapse
Affiliation(s)
| | - Annabelle Ballesta
- Institut National de Recherche en Informatique et Automatique, Rocquencourt, France
| | | | | | - Pierre Gabriel
- Institut National de Recherche en Informatique et Automatique Rhônes-Alpes, Lyon, France
| | | | - Human Rezaei
- Institut National de Recherche Agronomique, Jouy-en-Josas, France
| | - Marie Doumic
- Institut National de Recherche en Informatique et Automatique, Rocquencourt, France
- * E-mail:
| |
Collapse
|
12
|
DiSalvo S, Serio TR. Insights into prion biology: integrating a protein misfolding pathway with its cellular environment. Prion 2011; 5:76-83. [PMID: 21654204 DOI: 10.4161/pri.5.2.16413] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Protein misfolding and assembly into ordered, self-templating aggregates (amyloid) has emerged as a novel mechanism for regulating protein function. For a subclass of amyloidogenic proteins known as prions, this process induces transmissible changes in normal cellular physiology, ranging from neurodegenerative disease in animals and humans to new traits in fungi. The severity and stability of these altered phenotypic states can be attenuated by the conformation or amino-acid sequence of the prion, but in most of these cases, the protein retains the ability to form amyloid in vitro. Thus, our ability to link amyloid formation in vitro with its biological consequences in vivo remains a challenge. In two recent studies, we have begun to address this disconnect by assessing the effects of the cellular environment on traits associated with the misfolding of the yeast prion Sup35. Remarkably, the effects of quality control pathways and of limitations on protein transfer in vivo amplify the effects of even slight differences in the efficiency of Sup35 misfolding, leading to dramatic changes in the associated phenotype. Together, our studies suggest that the interplay between protein misfolding pathways and their cellular context is a crucial contributor to prion biology.
Collapse
Affiliation(s)
- Susanne DiSalvo
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, RI, USA
| | | |
Collapse
|
13
|
Doumic-Jauffret M, Kim PS, Perthame B. Stability Analysis of a Simplified Yet Complete Model for Chronic Myelogenous Leukemia. Bull Math Biol 2010; 72:1732-59. [DOI: 10.1007/s11538-009-9500-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 12/10/2009] [Indexed: 01/09/2023]
|
14
|
Calvez V, Lenuzza N, Doumic M, Deslys JP, Mouthon F, Perthame B. Prion dynamics with size dependency-strain phenomena. JOURNAL OF BIOLOGICAL DYNAMICS 2010; 4:28-42. [PMID: 22881069 DOI: 10.1080/17513750902935208] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Models for the polymerization process involved in prion self-replication are well-established and studied [H. Engler, J. Pruss, and G.F. Webb, Analysis of a model for the dynamics of prions II, J. Math. Anal. Appl. 324 (2006), pp. 98-117; M.L. Greer, L. Pujo-Menjouet, and G.F. Webb, A mathematical analysis of the dynamics of prion proliferation, J. Theoret. Biol. 242 (2006), pp. 598-606; J. Pruss, L. Pujo-Menjouet, G.F. Webb, and R. Zacher, Analysis of a model for the dynamics of prions, Discrete Cont. Dyn. Sys. Ser. B 6(1) (2006), pp. 215-225] in the case where the dynamics coefficients do not depend on the size of polymers. However, several experimental studies indicate that the structure and size of the prion aggregates are determinant for their pathological effect. This motivated the analysis in Calvez et al. [Size distribution dependence of prion aggregates infectivity, Math Biosci. 217 (2009), pp. 88-99] where the authors take into account size-dependent replicative properties of prion aggregates. We first improve a result concerning the dynamics of prion aggregates when a pathological state exists (high production of the normal protein). Then we study the strain phenomena and more specifically we wonder what specific replicative properties are determinant in strain propagation. We propose to interpret it also as a dynamical property of size repartitions.
Collapse
Affiliation(s)
- V Calvez
- UMPA, ENS-Lyon, 46, allée d'Italie, 69000, Lyon, France
| | | | | | | | | | | |
Collapse
|
15
|
Sindi SS, Serio TR. Prion dynamics and the quest for the genetic determinant in protein-only inheritance. Curr Opin Microbiol 2009; 12:623-30. [PMID: 19864176 DOI: 10.1016/j.mib.2009.09.003] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Revised: 09/12/2009] [Accepted: 09/14/2009] [Indexed: 01/24/2023]
Abstract
According to the prion hypothesis, proteins may act in atypical roles as genetic elements of infectivity and inheritance by undergoing self-replicating changes in physical state. While the preponderance of evidence strongly supports this concept particularly in fungi, the detailed mechanisms by which distinct protein forms specify unique phenotypes are emerging concepts. A particularly active area of investigation is the molecular nature of the heritable species, which has been probed through genetic, biochemical, and cell biological experimentation as well as by mathematical modeling. Here, we suggest that these studies are converging to implicate small aggregates composed of prion-state conformers as the transmissible genetic determinants of protein-based phenotypes.
Collapse
Affiliation(s)
- Suzanne S Sindi
- Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, 185 Meeting St., Box G-L2, Providence, RI 02912, USA
| | | |
Collapse
|