Mice

All procedures involving animals were approved by and performed in accordance with the guidelines of the Kantonales Veterinäramt Basel-Stadt. Accordingly, measures were taken to minimize pain and discomfort of the animals. Sam68^KO mice were previously described (Richard et al., 2005) and kept in a C57BL/6JRj background (backcrossed for >10 generations). To reduce the increased perinatal lethality described for Sam68^KO mice (Richard et al., 2005), littermate (WT and Sam68^KO) male offspring (F2) of RjOrl:SWISS X B6 hybrid heterozygous (Sam68^+/-) females (F1) and heterozygous (Sam68^+/-) C57BL/6JRj males was used for the analysis of spine morphology.

Sample sizes were determined based on previous experience with the manipulations, advice from colleagues, and literature surveys. A formal sample size calculation was not performed as the effect sizes were unknown during the time of study design. Animals that differed by 20% in weight from the mean of the group or that exhibit visible behavioural abnormalities were excluded from the analysis (preestablished criterion). Investigators performing anatomical analysis were blinded to the genotype of the sample.