Journal
DEVELOPMENT
Volume 134, Issue 13, Pages 2501-2509Publisher
COMPANY BIOLOGISTS LTD
DOI: 10.1242/dev.005033
Keywords
kidney; integrin; extracellular matrix; GDNF; mouse; ureteric bud
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Funding
- NICHD NIH HHS [R37 HD025331, R37 HD25331] Funding Source: Medline
- NIDDK NIH HHS [R01 DK064338-04, 5 R01 DK64338, R01 DK064338] Funding Source: Medline
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Development of the metanephric kidney crucially depends on proper interactions between cells and the surrounding extracellular matrix. For example, we showed previously that in the absence of alpha 8 beta 1 integrin, invasion by the ureteric bud into the metanephric mesenchyme is inhibited, resulting in renal agenesis. Here we present genetic evidence that the extracellular matrix protein nephronectin is an essential ligand that engages alpha 8 beta 1 integrin during early kidney development. We show that embryos lacking a functional nephronectin gene frequently display kidney agenesis or hypoplasia, which can be traced to a delay in the invasion of the metanephric mesenchyme by the ureteric bud at an early stage of kidney development. Significantly, we detected no defects in extracellular matrix organization in the nascent kidneys of the nephronectin mutants. Instead, we found that Gdnf expression was dramatically reduced in both nephronectin- and alpha 8 integrin-null mutants specifically in the metanephric mesenchyme at the time of ureteric bud invasion. We show that this reduction is sufficient to explain the agenesis and hypoplasia observed in both mutants. Interestingly, the reduction in Gdnf expression is transient, and its resumption presumably enables the nephronectin-deficient ureteric buds to invade the metanephric mesenchyme and begin branching. Our results thus place nephronectin and alpha 8 beta 1 integrin in a pathway that regulates Gdnf expression and is essential for kidney development.
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