The IMPC aims to systematically discover and ascribe biological function for every gene by generating a knockout mouse line for each protein-coding gene and identifying phenotypic changes between the knockout and control animals. Essential to this effort is to establish collaborative networks that work together to standardise protocols and data analysis.
The IMPC Consortium collates data from its international member institutes, which collect phenotyping data guided by their own ethical review panels, licenses, and accrediting bodies that are in line with national and/or geo-political constructs.
Housing and Husbandry
To capture housing and husbandry information, the international community came together and based on the requirements of the ARRIVE guidelines, the Gold Standard publication Checklist reporting Guidelines and the Genetically Altered (GA) Passport, compiled a series of questions used in the construction of a housing and husbandry survey at the start of the project. Since then a Housing and Husbandry procedure has been implemented on IMPReSS allowing the capture of this data through the regular data submission process.
The phenotyping pipelines have been designed to ensure that there are no welfare related issues for a normal mouse, however incidental welfare issues may arise. These will be driven by both the environment and the genetic background of the mice, and commonly include runting, malocclusion and hydrocephalus. Animals presenting with these incidental welfare issues will be assessed on a case by case basis to determine if the issue can be managed through remedial care, such as wet mash on the cage floor for runting or clipping teeth in the case of malocclusions, or whether our ethical obligation to the animals and the scientific endpoints are better served by euthanising the affected animal and providing a replacement.
In addition to these incidental welfare concerns, a welfare issue could occur with genetically altered mice. Two standard complementary approaches are used within the community to identify and manage the potential systematic welfare issues that could arise.
During the generation of the first homozygous progeny, a series of basic dysmorphology assessments are carried out to identify any welfare concerns.
If significant welfare concerns are raised then the breeding strategy is modified to avoid the generation of homozygous mice and heterozygous mice are phenotyped instead.
In addition to this early assessment, ongoing monitoring is carried out throughout the lifetime of the colony. Should the animals present a welfare concern, either an intervention is made in the form of the Alternative Pipeline or, when applicable, remedial action is taken within husbandry (e.g. long water spouts or food on cage base) or within experimental procedures (e.g. an alternate anaesthetic is used or tests are dropped). The Alternative Pipeline has been implemented on IMPReSS and allows the capture of data at a time point that deviates from the standard pipeline. A Welfare procedure has also been implemented which allows the recording of welfare issues identified for the animals.
These two complementary approaches allow us to maximise the value of information extracted from the lines while minimising welfare issues. If the mice or cryopreserved sperm are requested by the community, the welfare concerns are documented in a report (e.g. to the Genetically Altered (GA) passport) when ordered from the mouse repositories.
As a high throughput project, the sample size is relatively low with a target number of knockout animals being processed of 14 (7 per sex) for the Early Adult pipeline. This target was agreed upon after a community-wide debate involving statisticians, biologists and project managers to find a number that would consume the fewest possible resources while still achieving the goal of detecting phenotype abnormalities in a strain. At times, practical factors such as viability issues or difficulty administering a test might limit the number of animals it is possible to test. As such, each time data are shown, the number of animals phenotyped per sex per genotype is listed with the graphical visualisation of the data.
In a high throughput environment, replication of individual lines is not cost effective. Instead, multiple IMPC centres generated and characterised the same six reference knockout lines (Nxn, Rnf10, Ap4e1, Prkab1, Dnase1l2, Dbn1) which were known to present a wide range of phenotypes based on previously published research.
For our full list of ARRIVE Guidelines, please click here