Across vertebrates, hematopoiesis takes place within designated tissues, wherein committed myeloid progenitors further differentiate toward cells with megakaryocyte/erythroid potential (MEP) or those with granulocyte/macrophage potential (GMP). While the liver periphery (LP) of the Xenopus laevis amphibian functions as a principal site of hematopoiesis and contains MEPs, cells with GMP potential are instead segregated to the bone marrow (BM) of this animal. Presently, using gene expression and western blot analyses of blood cell lineage-specific transcription factors, we confirmed that while the X. laevis LP hosts hematopoietic stem cells and MEPs, their BM contains GMPs. In support of our hypothesis that cells bearing GMP potential originate from the frog LP and migrate through blood circulation to the BM in response to chemical cues; we demonstrated that medium conditioned by the X. laevis BM chemoattracts LP and peripheral blood cells. Compared to LP and by examining a comprehensive panel of chemokine genes, we showed that the X. laevis BM possessed greater expression of a single chemokine, CXCL12, the recombinant form of which was chemotactic to LP and peripheral blood cells and appeared to be a major chemotactic component within BM-conditioned medium. In confirmation of the hepatic origin of the cells that give rise to these frogs' GMPs, we also demonstrated that the X. laevis BM supported the growth of their LP-derived cells.

中文翻译：

---

两栖非洲爪蟾的造血作用被隔离在骨髓中，远离造血周围肝脏。

在整个脊椎动物中，造血作用发生在指定的组织内，其中定型的骨髓祖细胞进一步分化为具有巨核细胞/红系电位（MEP）或具有粒细胞/巨噬细胞潜能（GMP）的细胞。尽管非洲爪蟾两栖动物的肝脏外围（LP）充当造血的主要位点并包含MEP，但具有GMP潜力的细胞却被隔离到了该动物的骨髓（BM）中。目前，使用基因表达和血细胞谱系特异性转录因子的蛋白质印迹分析，我们证实了X. laevis LP拥有造血干细胞和MEP，而它们的BM却含有GMP。支持我们的假设，即带有GMP潜能的细胞起源于青蛙LP，并根据化学提示通过血液循环迁移到BM。我们证明了以X. laevis BM趋化因子LP和外周血细胞为条件的培养基。与LP相比，通过检查一组全面的趋化因子基因，我们发现X.laevis BM具有更高的单个趋化因子CXCL12的表达，其重组形式对LP和外周血细胞具有趋化性，似乎是BM条件培养基中的趋化成分。为了证实引起这些青蛙的GMP的细胞的肝起源，我们还证明了X. laevis BM支持其LP衍生细胞的生长。laevis BM具有更高的单一趋化因子CXCL12的表达，其重组形式对LP和外周血细胞具有趋化作用，并且似乎是BM条件培养基中的主要趋化成分。为了证实引起这些青蛙的GMP的细胞的肝起源，我们还证明了X. laevis BM支持其LP衍生细胞的生长。laevis BM具有更高的单一趋化因子CXCL12的表达，其重组形式对LP和外周血细胞具有趋化作用，并且似乎是BM条件培养基中的主要趋化成分。为了证实引起这些青蛙的GMP的细胞的肝起源，我们还证明了X. laevis BM支持其LP衍生细胞的生长。