Normal Fertility Requires the Expression of Carbonic Anhydrases II and IV in Sperm.
HCO3 (-) is a key factor in the regulation of sperm motility. High concentrations of HCO3 (-) in the female genital tract induce an increase in sperm beat frequency, which speeds progress of the sperm through the female reproductive tract. Carbonic anhydrases (CA), which catalyze the reversible hydration of CO2 to HCO3 (-), represent potential candidates in the regulation of the HCO3 (-) homeostasis in sperm and the composition of the male and female genital tract fluids. We show that two CA isoforms, CAII and CAIV, are distributed along the epididymal epithelium and appear with the onset of puberty. Expression analyses reveal an up-regulation of CAII and CAIV in the different epididymal sections of the knockout lines. In sperm, we find that CAII is located in the principal piece, whereas CAIV is present in the plasma membrane of the entire sperm tail. CAII and CAIV single knockout animals display an imbalanced HCO3 (-) homeostasis, resulting in substantially reduced sperm motility, swimming speed, and HCO3 (-)-enhanced beat frequency. The CA activity remaining in the sperm of CAII- and CAIV-null mutants is 35% and 68% of that found in WT mice. Sperm of the double knockout mutant mice show responses to stimulus by HCO3 (-) or CO2 that were delayed in onset and reduced in magnitude. In comparison with sperm from CAII and CAIV double knockout animals, pharmacological loss of CAIV in sperm from CAII knockout animals, show an even lower response to HCO3 (-). These results suggest that CAII and CAIV are required for optimal fertilization.
From the Institute of Anatomy, University Hospital, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany.
Petra M
PM
Wandernoth
From the Institute of Anatomy, University Hospital, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany.
Nadja
N
Mannowetz
From the Institute of Anatomy, University Hospital, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany.
Jaroslaw
J
Szczyrba
From the Institute of Anatomy, University Hospital, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany.
Laura
L
Grannemann
the Department of Internal Medicine I, Saarland University Medical Center, Kirrberger Straße, 66421 Homburg/Saar, Germany.
Anne
A
Wolf
the Division of Zoology/Membrane Transport, Department of Biology, University of Kaiserslautern, Erwin-Schrödinger-Straße 13, 67663 Kaiserslautern, Germany, and.
Holger M
HM
Becker
the Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, St. Louis, Missouri 63104.
William S
WS
Sly
From the Institute of Anatomy, University Hospital, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany, gunther.wennemuth@uk-essen.de.
Gunther
G
Wennemuth
D000818:Animals; D024402:Carbonic Anhydrase II / Q000378:metabolism*; D030741:Carbonic Anhydrase IV / Q000378:metabolism*; D002384:Catalysis; D002462:Cell Membrane / Q000201:enzymology; D005260:Female; D005298:Fertility; D005306:Fertilization; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D006706:Homeostasis; D006863:Hydrogen-Ion Concentration; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010641:Phenotype; D013081:Sperm Motility; D013094:Spermatozoa / Q000201:enzymology*
D024402:Carbonic Anhydrase II; D030741:Carbonic Anhydrase IV; C548248:Car4 protein, mouse
bicarbonate; carbon dioxide; carbonic anhydrase; fertilization; mutant; sperm; subfertility