Molecular basis for heterosis for myelin basic protein content in mice

Poly(A)⁺ mRNA was isolated from the brains of C57BL/6J (B6), DBA/2J (D2), and F₁ hybrid mice (B6 x D2) of 16-17 days of age. The yield of polysomal RNA, both poly(A)⁺ and poly(A)^-, from the three strains of mice was comparable. When translated in vitro in a reticulocyte lysate system, the mRNA preparations had the same efficiency with respect to stimulation of amino acid incorporation into protein. However, a significant heterotic effect was seen for the production of myelin basic protein (MBP) by the mRNA from the F₁ mice. That is, the fraction of protein synthesized as MBP was greater for the F₁ hybrid than for either parental strain. The distribution of the form of MBPs was not different among the three strains. We therefore believe that heterosis for brain MBP content in the F₁ hybrid may be regulated at the transcriptional or post-transcriptional level.