Fig. 1.

Myelin content is reduced in forebrain of fyn^−/− mice but not insrc^−/−,yes^−/−, orlyn^−/− mice. A, Myelin content is reduced in fyn^−/−mouse forebrain. Myelin from C57BL/6J,129Svfyn^−/− or C57BL/6Jfyn^+/+ control mouse forebrain was isolated by sucrose density centrifugation and quantified at P14, P26, P55, P95, P283, or P385. Each point represents at least six mice. Data are expressed as milligrams of myelin (dry weight) per gram of brain (wet weight). fyn^−/−values are significantly different from control at days P26, P55, P95, and P385 (p < 0.05). B, Western blot analysis of MBP content infyn^−/− forebrain and spinal cord. Samples of lysate containing 30 μg of protein from P28fyn^−/− and control mouse forebrain or spinal cord were separated on a 12% polyacrylamide gel and transferred to a PVDF membrane, and the blot was probed with antibodies against NF-L, GAPDH, and MBP, followed by ¹²⁵I-protein A. Bands were visualized by autoradiography. C, The amount of radioactivity in individual bands of the blot shown inB was quantified by PhosphorImager analysis, and the amount of MBP or NF-L was normalized to the amount of GAPDH in the same lane. Each bar represents the mean ± SEM normalized MBP or NF-L from four different animals, expressed as percent of that infyn^+/+ controls. The amount of MBP and NF-L is significantly different from controls in forebrain offyn^−/− mice (p < 0.01 and p < 0.05, respectively) but not in spinal cord (p > 0.5). D, Src is expressed in oligodendrocytes. Samples of lysate containing 80 μg of protein from B6 mouse forebrain (WT brain),src^−/− mouse forebrain, highly purified B6 oligodendrocytes (WT oligos), and highly purified fyn^−/− oligodendrocytes were separated on a 12% polyacrylamide gel and transferred to a PVDF membrane, and the blot was probed with monoclonal antibody against Src. Bands were visualized by autoradiography. Src immunoreactivity is evident in all samples except lysate fromsrc^−/− mouse forebrain.E, Myelin is reduced in forebrain offyn^−/− mice but not in forebrain ofsrc^−/−,yes^−/−, orlyn^−/− mice. Myelin was isolated from forebrain of fyn^−/−,src^−/−,yes^−/−,lyn^−/−, and control mice by sucrose density gradient centrifugation and quantified. Data, calculated as milligrams of myelin (dry weight) per gram of brain (wet weight), are shown as percent of control. Each bar represents the mean of at least five mice; error bars represent SEM. The myelin content of B6,129 fyn^−/− mouse forebrain at P26 is shown relative to age-matched B6 control mice. In addition, myelin content of strain 129Svfyn^−/− mouse forebrain at P26 is shown compared with age-matched 129Sv control mice. In both genetic backgrounds, myelin content was significantly less infyn^−/− mice than in controls (p < 0.05). Myelin content ofsrc^−/−,yes^−/−, andlyn^−/− mice at day P28 is shown compared with that of age-matched control mice. There is no significant difference in myelin content when comparing mice lacking Src, Yes, or Lyn and control mice (p > 0.05).