Han Dong, Haunerland Norbert H, Williams Tony D
Department of Biological Sciences, Simon Fraser University, Burnaby, Canada, V5A 1S6.
J Exp Biol. 2009 May;212(Pt 9):1277-83. doi: 10.1242/jeb.026906.
The vitellogenin/very low density lipoprotein receptor (VTG/VLDL-R), a 95 kDa protein that belongs to the low density lipoprotein receptor gene family, mediates the uptake of yolk precursors by developing follicles during oocyte growth. However, the extent to which variation in VTG/VLDL-R expression plays a role in determining inter-individual variation in reproductive phenotype (e.g. follicle or egg size) is not known. Here we show that the mRNA sequence of the zebra finch (Taeniopygia guttata) VTG/VLDL-R shows a high degree of sequence identity (92%) with chicken VTG/VLDL-R mRNA. Using quantitative real-time PCR we measured transcriptional expression of VTG/VLDL-R mRNA in various tissues, and for different stages of oocyte growth, in individual female zebra finches. VTG/VLDL-R mRNA was expressed at high levels in vitellogenic oocytes and in skeletal muscle, and was also detectable in liver, but these tissues expressed different splice variants: the short-form LR8-in oocytes and liver, and the LR8+ form in skeletal muscle. There was significant temporal variation in VTG/VLDL-R expression during follicle growth, with highest levels in ovary and a gradual decrease from pre-F3 to F1 vitellogenic follicles. Variation in ovary mRNA expression was correlated with inter-individual variation in clutch size and laying interval. Furthermore, variation in F3 follicle VTG/VLDL-R mRNA expression was correlated with inter-individual variation in egg mass and F1 follicle mass, suggesting that VTG/VLDL receptor mRNA expression is a key determinant of inter-individual variation in reproductive phenotype.
卵黄蛋白原/极低密度脂蛋白受体（VTG/VLDL-R）是一种95 kDa的蛋白质，属于低密度脂蛋白受体基因家族，在卵母细胞生长过程中介导发育中的卵泡摄取卵黄前体。然而，VTG/VLDL-R表达的变化在决定生殖表型的个体间差异（如卵泡或卵的大小）中所起的作用程度尚不清楚。在此我们表明，斑胸草雀（Taeniopygia guttata）VTG/VLDL-R的mRNA序列与鸡VTG/VLDL-R mRNA具有高度的序列同一性（92%）。我们使用定量实时PCR测量了单个雌性斑胸草雀不同组织以及卵母细胞生长不同阶段VTG/VLDL-R mRNA的转录表达。VTG/VLDL-R mRNA在卵黄生成期的卵母细胞和骨骼肌中高水平表达，在肝脏中也可检测到，但这些组织表达不同的剪接变体：卵母细胞和肝脏中为短形式LR8-，骨骼肌中为LR8+形式。在卵泡生长过程中，VTG/VLDL-R表达存在显著的时间变化，在卵巢中水平最高，从F3前期到F1卵黄生成期卵泡逐渐下降。卵巢mRNA表达的变化与窝卵数和产卵间隔的个体间差异相关。此外，F3卵泡VTG/VLDL-R mRNA表达的变化与卵重和F1卵泡重量的个体间差异相关，表明VTG/VLDL受体mRNA表达是生殖表型个体间差异的关键决定因素。
