Conditional Acvr1 Allele for FOP Rodent Model
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Solution Overview
Problem
Current methods for creating genetically modified rodents to model fibrodysplasia ossificans progressiva (FOP) face challenges in expressing perinatal lethal mutations and maintaining the desired genetic lesion, as existing approaches often result in premature expression or instability of the modified Acvr1 gene, limiting their utility for research and therapeutic development.
Innovation Solution
The development of a genetically modified rodent model using a conditional Acvr1 allele with a FlEx design, where a functioning exon is conditionally deleted and replaced with an altered exon encoding a R258G variation, utilizing site-specific recombinase recognition sites and an inducible Cre-ERT2 recombinase to control expression, allowing for controlled induction of the pathological phenotype in adulthood.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a perinatal lethal mutation is introduced into the Acvr1 gene to model FOP, then the rodent model accurately represents the human disease, but the rodent dies during perinatal period and cannot be used for long-term research
Solution Approach 1:
The patent introduces a conditional allele design where the mutated Acvr1 gene is prepared in advance but kept inactive during critical developmental periods. The mutation is embedded in the genome with flanking recombinase recognition sites, allowing it to be activated only when needed for research purposes, thus preventing perinatal lethality while preserving disease modeling capability
Solution Approach 2:
The patent creates a dynamic system where the Acvr1 mutation can be conditionally activated or deactivated based on research needs. By using inducible recombinase systems, the mutation status can be changed over time, allowing rodents to survive perinatal period with wild-type gene expression and later express the mutated allele for studying FOP pathology
2Reliability
If the Acvr1 mutation is expressed from embryonic development, then the full disease phenotype is established, but the rodent cannot be maintained for therapeutic screening studies
Solution Approach 1:
The patent segments the gene expression timeline into distinct phases: a perinatal phase where the wild-type Acvr1 gene is expressed to ensure normal development, and a postnatal research phase where the mutated allele can be activated. This temporal segmentation allows the rodent to fulfill both developmental requirements and research utility
Solution Approach 2:
The patent introduces recombinase recognition sites as intermediary elements that mediate between the embedded mutation and its expression. These sites serve as control points that allow researchers to selectively activate the mutated allele using inducible recombinases, thus controlling when the disease phenotype is expressed
3Adaptability or versatility
If a conditional allele design with flanking recombinase recognition sites is used, then the mutation can be controlled, but the genetic construct becomes more complex
Solution Approach 1:
The patent employs universal recombinase recognition sites (such as LoxP sites) that can be recognized by specific recombinases. These universal sites serve multiple functions: they mark the boundaries of the conditional allele, enable precise excision or inversion of the mutation, and work with various inducible recombinase systems, thus providing versatile control without proportionally increasing complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables the controlled expression of the R258G Acvr1 allele in rodents, mimicking FOP, allowing for the study of the disease and testing of therapeutic compounds while avoiding perinatal lethality and maintaining the genetic lesion indefinitely, thus providing a reliable model for research and therapeutic screening.
Implementation Method 1
utilizing site-specific recombinase recognition sites and an inducible Cre-ERT2 recombinase to control expression
Data Source
AI summary
A genetically modified rodent is provided that comprises a modified Acvr1 gene that comprises a conditional altered exon 7 encoding R258G in antisense orientation, flanked by site-specific recombinase recognition sites, wherein the altered exon is inverted to sense orientation upon action of a recombinase, resulting in ectopic bone formation.