Abstract
In the vertebrate embryo, the kidney is derived from the intermediate mesoderm. The LIM-class homeobox transcription factor lhx1 is expressed early in the intermediate mesoderm and is one of the first genes to be expressed in the nephric mesenchyme. In this study, we investigated the role of Lhx1 in specification of the kidney field by either overexpressing or depleting lhx1 in Xenopus embryos or depleting lhx1 in an explant culture system. By overexpressing a constitutively-active form of Lhx1, we established its capacity to expand the kidney field during the specification stage of kidney organogenesis. In addition, the ability of Lhx1 to expand the kidney field diminishes as kidney organogenesis transitions to the morphogenesis stage. In a complimentary set of experiments, we determined that embryos depleted of lhx1, show an almost complete loss of the kidney field. Using an explant culture system to induce kidney tissue, we confirmed that expression of genes from both proximal and distal kidney structures is affected by the absence of lhx1. Taken together our results demonstrate an essential role for Lhx1 in driving specification of the entire kidney field from the intermediate mesoderm.
Highlights
The vertebrate kidney performs an essential function of removing waste products from the blood and osmoregulation
Expression of scl was not affected in embryos at either stage 20 (Fig. 3M, 3N) or stage 26 (Fig. 3O, 3P) injected with Lhx1-VP16 construct (LL-VP16) RNA. These results suggest that Lim domain binding protein 1 (Ldb1)-Lhx1 transcriptional complex is able to induce fate transformation of cells from the paraxial mesoderm to contribute to the intermediate mesoderm and adopt a pronephric kidney fate
By manipulating lhx1 expression in Xenopus embryos we have established that Lhx1 function is required during the specification stage of pronephric kidney organogenesis
Summary
The vertebrate kidney performs an essential function of removing waste products from the blood and osmoregulation. Three types of kidneys have evolved in vertebrates, the pronephros, mesonephros and metanephros, with specification of each kidney induced by the preceding nephric tissue. This inductive event results in a progressively more complex organization ending with the metanephric kidney, which exists in mammals and birds [1,2,3]. Each nephron consists of the renal corpuscle and the renal tubule [4]. In Xenopus laevis, it consists of a bilaterally paired organ, comprising a single non-integrated nephron on each side of the embryo [5]
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