Expression and distribution of OCTN2 in mouse epididymis and its association with obstructive azoospermia in juvenile visceral steatosis mice.
OBJECTIVE
L-carnitine, an essential cofactor for mitochondrial, beta-oxidation of long-chain fatty acids, is known to play important roles in sperm maturation and metabolism when spermatozoa pass and acquire motility in the epididymis. We reported that obstructive azoospermia occurred in the epididymis in the juvenile visceral steatosis (JVS) mice, which are OCTN2 dysfunction mice caused by mutations in the gene encoding OCTN2, have been used for animal models of primary systemic carnitine deficiency. The aim of present study is to investigate the expression of OCTN2 protein in the mouse epididymis and its relation between the localization of OCTN2 and obstructive azoospermia in JVS mice as animal models for human male infertility.


METHODS
Animals used in this study were wild-type (C57BL/6 J) mice (n = 4) and JVS mice (n = 4). We made a specific polyclonal antibody against OCTN2 and examined immunohistochemically the localization of OCTN2 in the mouse epididymis.


RESULTS
OCTN2 was localized on the apical membrane of the principal cells of distal corpus and cauda epididymides. Immunocytochemistry demonstrated that OCTN2 was localized on the surface of microvillus upon the principal cells. In JVS mice, immunoreactivity started in a region immediately distal to where the sperm obstruction occurred.


CONCLUSIONS
Our results suggest that OCTN2 functions as a carnitine transporter between the epithelium and the lumen in distal corpus and cauda epididymides and provides a clue as to why obstructive azoospermia is induced in distal parts of epididymis.
Yakushiji
Kazumichi
K
Department of Urology, Miyazaki Medical College, University of Miyazaki, Miyazaki, Japan. k-yaku@fc.miyazaki-u.ac.jp
Kai
Saori
S
Yamauchi
Masamichi
M
Kuwajima
Masamichi
M
Osada
Yukio
Y
Toshimori
Kiyotaka
K
D000818:Animals; D003251:Constriction, Pathologic / Q000150:complications / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D004822:Epididymis / Q000378:metabolism* / Q000473:pathology; D015870:Gene Expression; D015151:Immunoblotting; D007150:Immunohistochemistry; D050152:Intra-Abdominal Fat / Q000473:pathology; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D009845:Oligospermia / Q000209:etiology / Q000378:metabolism*; D027701:Organic Cation Transport Proteins / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000074058:Solute Carrier Family 22 Member 5
D027701:Organic Cation Transport Proteins; D012333:RNA, Messenger; C492019:Slc22a5 protein, mouse; D000074058:Solute Carrier Family 22 Member 5