These mice harbor two transgenes, Prp-PFN1C71G and Thy1.2-PFN1C71G, each expressing a C71G mutant human profilin 1 protein with N-terminal V5 tag (V5-PFN1C71G) under direction of the mouse prion protein promoter or the human Thy1.2 promoter.
The Prp-PFN1C71G transgene has V5-PFN1C71G expression predominantly in the CNS (in both neurons and non-neuronal cells), with very low expression in the periphery. Specifically, expression is highest in the spinal cord, brainstem and forebrain, lower levels in cerebellum and kidney, and at undetectable levels in other organs.
The Thy1.2-PFN1C71G transgene drives V5-PFN1C71G expression predominantly in motor neurons. Specifically, expression is highest in the spinal cord and brainstem, followed by the forebrain. Little if any is expressed in the cerebellum and the peripheral organs.
When hemizygous for both transgenes, they are referred to as Thy1.2-PFN1C71G/Prp-PFN1C71G double transgenic mice (and were previously called "pt" mice).
When homozygous for Thy1.2-PFN1C71G and hemizygous for Prp-PFN1C71G are referred to as
Thy1.2-PFN1C71G/C71G/Prp-PFN1C71G triple transgenic mice (and were previously called "pt(h)" mice).
Furthermore, mice harboring only the Thy1.2-PFN1C71G transgene are referred to as Thy1.2-PFN1C71G (previously called "t") when hemizygous, and Thy1.2-PFN1C71G/C71G (previously called "t(h)") when homozygous.
Similarly, mice harboring only the Prp-PFN1C71G transgene are referred to as Prp-PFN1C71G (previously called "p") when hemizygous, and Prp-PFN1C71G/C71G (previously called "p(h)") when homozygous.
In order of most-to-least motor neuron disease severity: "pt(h)" : "t(h)" : "pt" : "t" : "p".
The "pt(h)" and "t(h)" mice have similar disease onset age (~125d), but "pt(h)" mice develop paralysis faster than "t(h)" mice (~60d after onset compared to ~170d after onset). While "t(h)" and "pt" mice have similar overall life expectancy (~250-350d), the "pt" mice have a much later disease onset (~250d) with rapid development of paralysis (~10d after onset).
The "pt(h)" genotype is most severely affected, with mice exhibiting motor neuron degeneration and abnormalities in cytoskeleton, proteasome, autophagy and stress granules.
Specifically, beginning at 3-4 months of age, "pt(h)" exhibit progressive loss of motor capabilities, with progressive loss of motor and sensory axons. Cytoskeleton defects in motor neurons include mutant PFN1 aggregation and reduced neurofilament L expression.
Alterations in autophagy pathway are evident throughout spinal cord, particularly in motor neurons.
At the paralysis disease stage (end stage), there is significant microgliosis, astrogliosis, motor neuron loss, elevated ubiquitin levels in the spinal cord, increased stress granules in the spinal motor neurons
Both "pt" and "pt(h)" mice are viable and fertile. The donating investigator reports that "pt(h)" mice breed normally, and they maintain their double transgenic colony by breeding "t(h)" females with "pt(h)" males.
Mice singly hemizygous for the Prp-PFN1C71G transgene ("p") express V5-PFN1C71G in both neurons and glia, but the expression levels are low. The "p" genotype does not manifest motor neuron degeneration symptoms during their lifespan. The donating investigator also reports they were not able to obtain homozygous Prp-PFN1C71G animals ("p(h)").
