pattern specification involved in metanephros development

Definition

Target type: biologicalprocess

Any developmental process that results in the creation of defined areas or spaces within the metanephros to which cells respond and eventually are instructed to differentiate. [GOC:mtg_kidney_jan10]

The metanephros, the adult kidney, arises from two distinct primordia: the metanephric mesenchyme and the ureteric bud. Pattern specification in metanephros development involves a complex interplay of inductive interactions, transcription factor expression, and signaling pathways, ultimately leading to the formation of the intricate structure of the nephron.

**Early Induction and Formation of the Ureteric Bud:**

* The metanephric mesenchyme, derived from the intermediate mesoderm, releases signals that induce the outgrowth of the ureteric bud from the Wolffian duct. This inductive interaction is mediated by factors like GDNF (Glial cell line-derived neurotrophic factor), a mesenchyme-derived factor that binds to its receptor RET on the ureteric bud cells.
* RET signaling activates a cascade of events, including the activation of transcription factors like Pax2 and Wnt4, leading to the branching morphogenesis of the ureteric bud.

**Metanephric Mesenchyme Induction and Differentiation:**

* The ureteric bud reciprocally induces the metanephric mesenchyme to condense and differentiate into epithelial structures. This inductive interaction involves signals like FGF2 (fibroblast growth factor 2), Wnt9b, and BMP7 (bone morphogenetic protein 7) from the ureteric bud.
* These signals trigger the expression of transcription factors, including Pax2, Pax8, and Wt1, in the metanephric mesenchyme. These factors are crucial for the specification of nephron progenitors and the development of glomeruli, tubules, and collecting ducts.

**Formation of the Nephron:**

* The condensation of metanephric mesenchyme forms nephron progenitors, which undergo a series of branching events to form the nephron.
* This process involves the formation of the renal vesicle, the S-shaped body, and ultimately the mature nephron, including the glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct.
* During this process, several signaling pathways are involved, including the Wnt, Shh (Sonic hedgehog), and Notch pathways, which regulate cell fate determination, proliferation, and differentiation.

**Formation of the Collecting Duct System:**

* The ureteric bud undergoes branching morphogenesis, forming the collecting ducts, which connect the nephrons to the renal pelvis.
* This process is regulated by factors like Wnt9b, BMP7, and Ret.

**Epithelial-Mesenchymal Interactions:**

* Throughout the development of the metanephros, there is an ongoing dialogue between the epithelial ureteric bud and the mesenchymal metanephric mesenchyme.
* These interactions, mediated by signaling pathways and transcription factors, are essential for the coordinated development of the nephron and the collecting duct system.

**Regulation of Nephrogenesis:**

* The process of metanephros development is tightly regulated by a complex network of genes and signaling pathways.
* Dysregulation of these pathways can lead to congenital kidney defects, highlighting the critical importance of pattern specification during nephrogenesis.'
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