Compare SAP102 knockout mice and wild-type mice on a task designed to measure spatial learning and memory.
Synapse-associated protein 102 (SAP102) is a gene found in mice that is thought to be involved in learning. In the following experiment, you will examine how SAP102 affects learning by comparing two groups of mice – one group that lacks the gene, and a wild-type group, which has no genetic mutations.
Although mice are rather good swimmers, they do not particularly enjoy spending time in the water. If we place a mouse into a water tank, it will try to find a dry spot (a platform) as quickly as possible.
If we place the same mouse in the same water tank a number of times, the mouse should become progressively better at finding the platform – it learns where the platform is. If this does not happen, we can assume that it is having problems remembering the platform’s location.
Two reliable measures of learning in mice are 1) the speed at which they find the platform, and 2) the route which they take to the platform (i.e. do they go straight to the platform or do they get a little lost along the way?). Use these measures to assess which group is better.
SAP102: SAP102 is a gene found in mice that affects their ability to learn spatial locations. Your task is to determine whether absence of the SAP102 improves or impairs learning. The human homolog of SAP102 is a gene called DLG3. Mutations of DLG3 have been associated with mental retardation.
Platform: The platform can be either raised or lowered. If the platform is raised, it becomes visible, and therefore the mouse can see it. If the mouse can see the platform, it does not have to remember the location.
Wild-type: Wild type refers to the typical form of an organism that we expect to find it in nature. It refers to both genotype and phenotype. In laboratory experiments, wild-types are often used as controls to measure normal responses. The performance of wild-types is usually compared to that of mutants.
Water maze: The Morris water maze is an apparatus designed to assess spatial memory in mice. It consists of a water tank and a small platform, which the mouse can stand on to avoid the water. The platform is usually placed slightly below the water level, where it cannot be seen. If it is not visible, the mouse’s first attempt at finding the platform is only successful when the mouse accidentally swims into it. On subsequent trials however, the mouse should be able to remember the platform location. The efficiency with which the mouse finds the hidden platform in subsequent trials, therefore, is a measure of memory.
When the platform is visible, the SAP102 mice are as quick as the wild-type mice. Similarly, when it is visible, their routes to the platform are very direct. This suggests that the SAP102 gene does not affect the mouse’s ability to see the platform, nor does it affect their ability to swim to it. The mice that lack the SAP102 gene are only impaired.
Post-synaptic density protein 93 (PSD93), also known as channel-associated protein of synapse-110 (Chapsyn-110) or A0014, is a scaffold protein that belongs to the membrane-associated guanylate kinase (MAGUK) family (PSD93, PSD95, SAP97, SAP102).
Post-synaptic density 95 protein (PSD95), also known as synapse-associated protein 90 (SAP90) or A0013, is a scaffold protein that belongs to the membrane-associated guanylate kinase (MAGUK) family (PSD93, PSD95, SAP97, SAP102).