title: Missense mutations in SLC26A8, encoding a sperm-specific activator of CFTR, are associated with human asthenozoospermia.
abstract: The cystic fibrosis transmembrane conductance regulator (CFTR) is present in mature sperm and is required for sperm motility and capacitation. Both these processes are controlled by ions fluxes and are essential for fertilization. We have shown that SLC26A8, a sperm-specific member of the SLC26 family of anion exchangers, associates with the CFTR channel and strongly stimulates its activity. This suggests that the two proteins cooperate to regulate the anion fluxes required for correct sperm motility and capacitation. Here, we report on three heterozygous SLC26A8 missense mutations identified in a cohort of 146 men presenting with asthenozoospermia: c.260G>A (p.Arg87Gln), c.2434G>A (p.Glu812Lys), and c.2860C>T (p.Arg954Cys). These mutations were not present in 121 controls matched for ethnicity, and statistical analysis on a control population of 8,600 individuals (from dbSNP and 1000 Genomes) showed them to be associated with asthenozoospermia with a power > 95%. By cotransfecting Chinese hamster ovary (CHO)-K1 cells with SLC26A8 variants and CFTR, we showed that the physical interaction between the two proteins was partly conserved but that the capacity to activate CFTR-dependent anion transport was completely abolished for all mutants. Biochemical studies revealed the presence of much smaller amounts of protein for all variants, but these amounts were restored to wild-type levels upon treatment with the proteasome inhibitor MG132. Immunocytochemistry also showed the amounts of SLC26A8 in sperm to be abnormally small in individuals carrying the mutations. These mutations might therefore impair formation of the SLC26A8-CFTR complex, principally by affecting SLC26A8 stability, consistent with an impairment of CFTR-dependent sperm-activation events in affected individuals.
authors.affiliation: Institut National de la Santé et de la Recherche Médicale U1016, Institut Cochin, 75014 Paris, France.
authors.forename: Thassadite
authors.initials: T
authors.lastname: Dirami
authors.forename: Baptiste
authors.initials: B
authors.lastname: Rode
authors.forename: Mathilde
authors.initials: M
authors.lastname: Jollivet
authors.forename: Nathalie
authors.initials: N
authors.lastname: Da Silva
authors.forename: Denise
authors.initials: D
authors.lastname: Escalier
authors.forename: Natacha
authors.initials: N
authors.lastname: Gaitch
authors.forename: Caroline
authors.initials: C
authors.lastname: Norez
authors.forename: Pierre
authors.initials: P
authors.lastname: Tuffery
authors.forename: Jean-Philippe
authors.initials: JP
authors.lastname: Wolf
authors.forename: Frédéric
authors.initials: F
authors.lastname: Becq
authors.forename: Pierre F
authors.initials: PF
authors.lastname: Ray
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Dulioust
authors.forename: Gérard
authors.initials: G
authors.lastname: Gacon
authors.forename: Thierry
authors.initials: T
authors.lastname: Bienvenu
authors.forename: Aminata
authors.initials: A
authors.lastname: Touré
mesh_terms: D000818:Animals; D027321:Anion Transport Proteins / Q000235:genetics* / Q000378:metabolism; D017920:Antiporters / Q000235:genetics* / Q000378:metabolism; D053627:Asthenozoospermia / Q000235:genetics*; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000378:metabolism; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D008297:Male; D020125:Mutation, Missense / Q000235:genetics*; D013075:Sperm Capacitation / Q000235:genetics; D013081:Sperm Motility / Q000235:genetics; D013094:Spermatozoa / Q000378:metabolism; D000076988:Sulfate Transporters
chemical_list: D027321:Anion Transport Proteins; D017920:Antiporters; C455627:SLC26A8 protein, human; D000076988:Sulfate Transporters; D019005:Cystic Fibrosis Transmembrane Conductance Regulator