Molecular approaches to understanding variation in reproductive phenotype of female zebra finches (Taeniopygia guttata)

I investigated inter-individual variation at the cell and molecular level in relation to reproductive phenotype (egg and clutch size, timing of laying) in female zebra finches (Taeniopygia guttata). First, I developed an antibody against zebra finch apoVLDL-II. I then developed a dot-blot assay to quantify plasma apoVLDL-II levels. This revealed marked inter-individual variation in apoVLDL-II levels but this was not correlated with differences in reproductive phenotype. Second, I described variation in VTG/VLDL receptor mRNA expression in relation to variation in reproductive phenotype. VTG/VLDL-R mRNA was expressed at high levels in growing oocytes and skeletal muscle and was also detectable in liver, but these tissues contain different splice variants. VTG/VLDL-R mRNA expression decreased during follicle growth. Ovary mRNA expression was correlated with clutch size and laying interval. F3 follicle mRNA expression was correlated with egg size. Thus, VTG/VLDL receptor mRNA expression is a key determinant of inter-individual variation in reproductive phenotype.