Characterization of an acrosome protein VAD1.2/AEP2 which is differentially expressed in spermatogenesis.
The release of enzymes from the acrosome of the sperm head (acrosome reaction) starts the fertilization process and enables the spermatozoa to penetrate the zona pellucida of the oocytes. Defective acrosome reaction is one of the important causes of infertility in men. To investigate the molecular regulation of spermatogenesis in vivo, we used differential display reverse transcription-polymerase chain reaction to identify stage-specific genes in a retinol-supplemented vitamin-A deficiency (VAD) rat model and identified the VAD1.2 (acrosome-expressed protein 2, AEP2) gene, which was expressed strongly in the rat testis from post-natal day 32 to adult stage. The mouse VAD1.2 mRNA shared 85% and 67% sequence homology, and 74% and 38% amino acid homology, respectively, with the rat and human counterparts. VAD1.2 transcript was abundantly expressed in the rat seminiferous tubules at stage VIII-XII, and the protein was detected in the acrosome region of the round and elongated spermatids of mouse, human, monkey and pig. VAD1.2 co-localized with lectin-PNA to the acrosome region of spermatids. Interestingly, the expression of VAD1.2 protein in human testis diminished in patients with hypospermatogenesis, maturation arrest, undescended testis and Sertoli cell-only syndrome. Co-immunoprecipitation experiments followed by western blotting and mass spectrometry (MS-MS) identified syntaxin 1, beta-actin and myosin heavy chain (MHC) proteins as putative interacting partners. Taken together, the stage-specific expression of VAD1.2 in the acrosome of spermatids and the binding of VAD1.2 protein with vesicle forming (syntaxin 1) and structural (beta-actin and MHC) proteins suggest that VAD1.2 maybe involved in acrosome formation during spermiogenesis.
Lee
Kai-Fai
KF
Department of Obstetrics and Gynaecology, LKS Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong, PR China. ckflee@hkucc.hku.hk
Tam
Yuen-Tsung
YT
Zuo
Yan
Y
Cheong
Ana W Y
AW
Pang
Ronald T K
RT
Lee
Nikki P Y
NP
Shum
Cathy K Y
CK
Tam
Po-Chor
PC
Cheung
Annie N Y
AN
Yang
Zeng-Ming
ZM
Yeung
William S B
WS
Luk
John M C
JM
D000177:Acrosome / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D020869:Gene Expression Profiling; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013091:Spermatogenesis / Q000235:genetics*; D013737:Testis / Q000378:metabolism
D011506:Proteins; C534420:Spata32 protein, rat