The presynaptic protein α-synuclein is involved in a range of neurodegenerative diseases. Here we analyze potential compensatory mechanisms in α-synuclein null mutant mice. Furthermore, the findings reveal problems that may be associated with inbred mouse strains.

Expression profiling by cDNA array technology in a transgenic mouse model revealed striking differences only in the expression level of α-synuclein. This was caused by a chromosomal deletion of the α-synuclein locus in the C57BL/6J inbred strain used for backcrossing. However, the deletion is only present in a subpopulation of C57BL/6J mice, namely animals from Harlan. No other genes are known to be affected by the deletion, which is estimated to be smaller than 2 cM. We propose to name this strain C57BL/6S. C57BL/6S animals appear phenotypically normal. They show no upregulation of β-synuclein or γ-synuclein, excluding a compensatory mechanism. Also, the expression of synphilin-1 was unaffected.

The C57BL/6S strain should help in the understanding of the physiological function of α-synuclein and its involvement in synucleinopathies. Also, the findings exemplify unexpected complications that may arise during the study of transgenic models or inbred strains, in particular when combined with genome wide screening techniques.