GFRalpha1 is an essential receptor component for GDNF in the developing nervous system and kidney

Abstract

Glial cell line-derived neurotrophic factor (GDNF) is a distant member of the TGFbeta protein family that is essential for neuronal survival and renal morphogenesis. We show that mice who are deficient in the glycosyl-phosphatidyl inositol (GPI) -linked protein GFRalpha1 (GDNFRalpha) display deficits in the kidneys, the enteric nervous system, and spinal motor and sensory neurons that are strikingly similar to those of the GDNF- and Ret-deficient mice. GFRalpha1-deficient dopaminergic and nodose sensory ganglia neurons no longer respond to GDNF or to the structurally related protein neurturin (NTN) but can be rescued when exposed to GDNF or neurturin in the presence of soluble GFRalpha1. In contrast, GFRalpha1-deficient submandibular parasympathetic neurons retain normal response to these two factors. Taken together with the available genetic and biochemical data, these findings support the idea that GFRalpha1 and the transmembrane tyrosine kinase Ret are both necessary receptor components for GDNF in the developing kidney and nervous system, and that GDNF and neurturin can mediate some of their activities through a second receptor.

Figure 1. Disruption of the GFRα1 Gene

(A) Targeting vector, wild-type GFRα1 allele and the disrupted allele. Amino acids 14–66 are missing from the disrupted gene. The location of the probe used in Southern blot is indicated (Probe). The directions of gene transcription are marked by horizontal arrows. (B) Detection of homologous recombination event in an ES clone by a Southern blot. (C) Genotype analysis of wild-type (+/+), heterozygous mutant (+/−), and homozygous mutant (−/−) animals by polymerase chain reaction. The band in the upper panel (GFRα1) is specific for the wild-type GFRα1 gene. The upper band in the lower panel (IL8R) represents a control fragment from the IL8 receptor gene. The lower band in this panel (neo) is specific for the neo gene. (D and E) In situ hybridization of wild-type (D) and GFRα1^−/− (E) E15 mouse embryos with exon 2 GFRα1 probe. Abbreviations: drg, dorsal root ganglia; gut, gut; kid, kidney; sc, spinal cord; st, stomach; tg, trigeminal gangilon; vib, vibrissa; and vm, ventral midbrain. Scale bar, 1 mm.

Figure 2. Neuronal Populations in P0 wild-type (+/+) and GFRα1^−/− (−/−) Mice

Tyrosine hydroxylase staining of substantia nigra (A and B), striatum (C and D), and locus coeruleus (E and F). Tyrosine hydroxylase is the rate-limiting enzyme in dopamine and noradrenaline synthesis. Cresyl violet staining of superior cervical ganglia (G and H) and petrosal nodose ganglia (I and J) neurons from 129 × CD-1, F2 mice. No deficits or abnormalities in neuronal number, morphology, or innervation pattern are detected in the GFRα1^−/− mice. Scale bar: ~100 μm in (A), (B), (E), and (F), 30 μm in (C), (D), (I), and (J), and 50 μm in (G) and (H).

Figure 3. Enteric Nervous System in Wild-Type (+/+) and GFRα1^−/− (−/−) Mice

(A and B) Whole mounts of small intestine from E18 mice stained with the general neuronal antibody PGP 9.5. Inset in (A) depicts the expression of GFRα1 mRNA in E18 wild-type mouse gut as detected by in situ hybridization. (C–I) Section through the small intestine (C and D), colon (E and F), and rectum (G–I) of E17 embryos stained with neurofilament (C and D) or peripherin (E–I). Enteric neurons (ENS) were not found in the intestine and are very rarely found in the stomach and colon of the GFRα1^−/− 129 × CD-1, F2 mice. No ENS neurons were detected in the colon of the GDNF^−/− mice. (I) Sym represents afferent fibers probably derived from sympathetic innervation to the gut. Scale bar: ~100 μm in (A) and (B), 30 μm in (C) and (D), 50 μm in (E) and (F), and 300 μm in (G) through (J).

Figure 4. Kidneys in Wild-Type and GFRα1^−/− Mice

(A and B) Photographs of the abdomen in E17 wild type (A) and GDNF^−/− (B) 129 × CD-1, F2 mice. Note the position of the kidneys (Ki) subadjacent to the adrenals (Ad) in (A) and their absence in the mutant (B). (C–H) Sagittal sections through the kidney region of E12.5 wild-type (+/+) and GFRα1^−/− (−/−) embryos stained with hematoxylin and eosin (C and D), Pax2 antibodies (E and F), or WT1 antibodies (G and H). Inset in (C) represents in situ hybridization of GFRα1 cDNA probe to developing nephrons and ureteric bud in wild-type kidney. Abbreviations: UB, uretric bud; MM, metanephric (condensing) mesenchyme; and NR, nephrogenic region (the region that undergoes mesenchymal-to-epithelial conversion and differentiated nephrons). Scale bar: ~500 μm in (A) and (B), 100 μm in (C) and (D), and 20 μm in (E) through (H).

Figure 5. Survival of Primary Embryonic Neurons from Wild-Type and GFRα1^−/− Mice in the Presence of GDNF

The response of primary embryonic wild-type (+/+) and GFRα1^−/− (−/−) nodose (A), dopaminergic (B), and submandibular (C) neurons from 129 × CD-1, F2 mice to GDNF. Neuronal survival is presented as percent or absolute number over control.

Figure 6. Survival of Primary Embryonic Neurons from Wild-Type and GFRα1^−/− Mice in the Presence of NTN

The response of primary embryonic wild-type (+/+) and GFRα1^−/− (−/−) nodose (A), dopaminergic (B), and submandibular (C) neurons from 129 × CD-1, F2 mice to NTN. Neuronal survival is presented as percent or absolute number over control.