Smith W C, Harland R M
Department of Molecular and Cell Biology, University of California, Berkeley 94720.
Cell. 1992 Sep 4;70(5):829-40. doi: 10.1016/0092-8674(92)90316-5.
We have cloned a cDNA encoding a novel polypeptide capable of inducing dorsal development in Xenopus embryos. RNA transcripts from this clone rescue normal development when injected into ventralized embryos and result in excessive head development at high doses. Therefore, we have named the cDNA noggin, noggin cDNA contains a single reading frame encoding a 26 kd protein with a hydrophobic amino-terminal sequence, suggesting that it is secreted. In Northern blot analysis this cDNA hybridizes to two mRNAs that are expressed both maternally and zygotically. Although noggin transcript is not localized in the oocyte and cleavage stage embryo, zygotic transcripts are initially restricted to the presumptive dorsal mesoderm and reach their highest levels at the gastrula stage in the dorsal lip of the blastopore (Spemann organizer). In the neurula, noggin is transcribed in the notochord and prechordal mesoderm. The activity of exogenous noggin RNA in embryonic axis induction and the localized expression of endogenous noggin transcripts suggest that noggin plays a role in normal dorsal development.
我们克隆了一个编码新型多肽的cDNA，该多肽能够诱导非洲爪蟾胚胎的背部发育。将此克隆的RNA转录本注射到腹侧化胚胎中可挽救正常发育，高剂量时会导致头部过度发育。因此，我们将该cDNA命名为头蛋白，头蛋白cDNA包含一个单一的阅读框，编码一个26kd的蛋白质，其氨基末端序列具有疏水性，表明它是分泌型的。在Northern印迹分析中，该cDNA与两种母源和合子都表达的mRNA杂交。虽然头蛋白转录本在卵母细胞和卵裂期胚胎中没有定位，但合子转录本最初局限于预定的背侧中胚层，并在原肠胚期在胚孔背唇（施佩曼组织者）达到最高水平。在神经胚中，头蛋白在脊索和脊索前中胚层中转录。外源性头蛋白RNA在胚胎轴诱导中的活性以及内源性头蛋白转录本的局部表达表明，头蛋白在正常的背部发育中起作用。
