title: Excision of Trpv6 gene leads to severe defects in epididymal Ca2+ absorption and male fertility much like single D541A pore mutation.
abstract: Replacement of aspartate residue 541 by alanine (D541A) in the pore of TRPV6 channels in mice disrupts Ca(2+) absorption by the epididymal epithelium, resulting in abnormally high Ca(2+) concentrations in epididymal luminal fluid and in a dramatic but incomplete loss of sperm motility and fertilization capacity, raising the possibility of residual activity of channels formed by TRPV6(D541A) proteins (Weissgerber, P., Kriebs, U., Tsvilovskyy, V., Olausson, J., Kretz, O., Stoerger, C., Vennekens, R., Wissenbach, U., Middendorff, R., Flockerzi, V., and Freichel, M. (2011) Sci. Signal. 4, ra27). It is known from other cation channels that introducing pore mutations even if they largely affect their conductivity and permeability can evoke considerably different phenotypes compared with the deletion of the corresponding protein. Therefore, we generated TRPV6-deficient mice (Trpv6(-/-)) by deleting exons encoding transmembrane domains with the pore-forming region and the complete cytosolic C terminus harboring binding sites for TRPV6-associated proteins that regulate its activity and plasma membrane anchoring. Using this strategy, we aimed to determine whether the TRPV6(D541A) pore mutant still contributes to residual channel activity and/or channel-independent functions in vivo. Trpv6(-/-) males reveal severe defects in fertility and motility and viability of sperm and a significant increase in epididymal luminal Ca(2+) concentration that is mirrored by a lack of Ca(2+) uptake by the epididymal epithelium. Therewith, Trpv6 excision affects epididymal Ca(2+) handling and male fertility to the same extent as the introduction of the D541A pore mutation, arguing against residual functions of the TRPV6(D541A) pore mutant in epididymal epithelial cells.
authors.affiliation: Experimentelle und Klinische Pharmakologie und Toxikologie, Universitaet des Saarlandes, Homburg, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Weissgerber
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kriebs
authors.forename: Volodymyr
authors.initials: V
authors.lastname: Tsvilovskyy
authors.forename: Jenny
authors.initials: J
authors.lastname: Olausson
authors.forename: Oliver
authors.initials: O
authors.lastname: Kretz
authors.forename: Christof
authors.initials: C
authors.lastname: Stoerger
authors.forename: Stefanie
authors.initials: S
authors.lastname: Mannebach
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wissenbach
authors.forename: Rudi
authors.initials: R
authors.lastname: Vennekens
authors.forename: Ralf
authors.initials: R
authors.lastname: Middendorff
authors.forename: Veit
authors.initials: V
authors.lastname: Flockerzi
authors.forename: Marc
authors.initials: M
authors.lastname: Freichel
mesh_terms: D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000235:genetics*; D017931:DNA Primers; D004822:Epididymis / Q000378:metabolism*; D005260:Female; D005298:Fertility / Q000235:genetics*; D017353:Gene Deletion; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D013081:Sperm Motility / Q000235:genetics; D050916:TRPV Cation Channels / Q000235:genetics*
chemical_list: D015220:Calcium Channels; D017931:DNA Primers; D050916:TRPV Cation Channels; C446923:Trpv6 protein, mouse; D002118:Calcium