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First published online 13 December 2005
doi: 10.1242/jcs.02704

Journal of Cell Science 119, 75-84 (2006)
Published by The Company of Biologists 2006
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FGFR-1 signaling is involved in spermiogenesis and sperm capacitation

Leanne Cotton1, Gerard M. Gibbs1, L. Gabriel Sanchez-Partida1, John R. Morrison1, David M. de Kretser1,2 and Moira K. O'Bryan1,2,*

1 Monash Institute of Medical Research, Monash University, Melbourne, Australia
2 The ARC Centre of Excellence in Biotechnology and Development, Monash University, Melbourne, Australia


Figure 1
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  		Fig. 1. FGFR-1 mRNA expression in wild-type and transgenic testes. (A) A representative northern blot from transgenic mouse line 4. Testis RNA from five transgenic and wild-type mice was probed with a cDNA probe designed to detect both the native (n) FGFR-1 mRNA and the transgenic (t) FGFR-1 mRNA at 3.8 kb and 1.4 kb, respectively. A band was also observed at 6.0 kb, which may be representative of another FGFR-1 splice variant. (B) The relative FGFR-1 mRNA expression levels in wild-type and transgenic mice. Ratios indicate the fold over-expression of tFGFR-1 mRNA compared with nFGFR-1.

 

Figure 2
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  		Fig. 2. Fertility analysis of wild-type and transgenic FGFR-1 mice. (A) Average litter sizes produced by wild-type and transgenic male mice. (B) Average testis weights produced by wild-type and transgenic mice. (C) The daily sperm production (DSP) per testis for wild-type and transgenic mice. (#) Number of mice assessed; **P<0.01.

 

Figure 3
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  		Fig. 3. Capacitation induced changes in tyrosine phosphorylation in wild-type and tFGFR-1 mice. (A) A comparison of tyrosine phosphorylation patterns of wild-type and transgenic, line 4, mouse sperm under capacitating conditions for the times indicated. The relative absorbance of tyrosine phosphorylation for each assay was determined and all data was normalized to ß-tubulin. The relative change in tyrosine phosphorylation was determined and plotted, n=3. (B) A comparison of ERK 1/2 activation in wild-type and transgenic mouse sperm under capacitating conditions for the times indicated. The relative absorbance of ERK phosphorylation for each assay was determined and normalized to the expression of ß-tubulin. The relative changes are plotted, n=3. (C) A comparison of p85 activation in wild-type and transgenic mouse sperm under capacitating conditions for the times indicated. The relative absorbance of p85 phosphorylation for each assay was determined and normalized to ß-tubulin expression. The relative changes in p85 activation are plotted, n=3. *P<0.05; **P<0.01; ***P<0.001.

 

Figure 4
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  		Fig. 4. The effect of FGFR-1 activation on wild-type and tFGFR-1 sperm capacitation induced tyrosine phosphorylation. (A) A comparison of tyrosine phosphorylation patterns of wild-type sperm +/- 10 ng/ml bFGF under capacitating conditions for the times indicated. The relative absorbance of tyrosine phosphorylation was determined and all data was normalized to ß-tubulin, n=3. (B) A comparison of ERK 1/2 activation in wild-type mouse sperm +/- 10 ng/ml bFGF under capacitating conditions. The relative absorbance of ERK phosphorylation for each sample was determined and all data was normalized to the expression of ß-tubulin, n=3. (C) A comparison of PI3K activation in wild-type mouse sperm +/- 10 ng/ml bFGF under capacitating conditions. The relative absorbance of p85 phosphorylation for each sample was determined and all data normalized to the expression ß-tubulin. *P<0.05, **P<0.01, ***P<0.001.

 

Figure 5
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  		Fig. 5. A proposed mechanism for the regulation of events leading to sperm capacitation. Ejaculated sperm entering the female reproductive tract are exposed to a FGFR-1 ligand. The ligand induces a FGFR-1 signaling cascade. Activation of the PI3K pathway results in the phosphorylation of a `master controller of capacitation' (MCC), which suppresses downstream tyrosine phosphorylation of signal transduction pathways including protein kinase A (Konopka et al., 1984Go) activation. Following the disengagement of FGFR-1 from its ligand, or the suppression of the PI3K pathway, PTPs dephosphorylate the MCC, allowing the tyrosine phosphorylation and activation of target proteins leading to the correlates of sperm capacitation. Furthermore, activation of the PI3K pathway results in the suppression of the MAPK pathway. The level at which this suppression occurs is not known, however, it is upstream of ERK 1/2.

 




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