{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nHuman sperm acrosome‐associated protein 1 (SPACA1), originally identified as SAMP32, is a testis‐specific membrane protein of approximately 32 kDa that localizes to the inner acrosomal membrane and key regions of the sperm head, including the equatorial segment. Biochemical analyses demonstrated that it contains a potential carboxyl terminal transmembrane domain and is phosphorylated in vivo, suggesting an active role in acrosome biogenesis and the sperm–egg binding/fusion process. This protein also shows homology to surface proteins from other species, indicating conserved functions in gamete interaction."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "Different immunocytochemical studies of SPACA1 have revealed that, while it is consistently found in the acrosomal equatorial segment, its presence in the acrosomal principal segment exhibits marked variability among spermatozoa. These inter-individual differences, quantified as SPACA1 indexes, are significantly correlated with subsequent blastocyst development rates in conventional in vitro fertilization (IVF) procedures, suggesting that SPACA1 distribution within the acrosome may serve as a predictive biomarker for embryo quality and developmental potential."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "2"}]}, {"type": "t", "text": "In the context of immunocontraception, SPACA1 has emerged as a desirable target antigen for vaccine development. Epitope mapping using phage-display techniques allowed the isolation of several SPACA1-derived peptides that, when conjugated to carrier proteins, elicited a sperm-specific antibody response in both male and female models. These antibodies disrupted normal sperm function, ultimately inducing a reversible contraceptive state without apparent side effects, and thus highlight the potential utility of SPACA1 epitopes in the design of immunocontraceptive vaccines."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": "Further in vivo investigations using a prokaryotic expression vector of human SPACA1 (hSAMP32) have reinforced its pivotal role during the acrosome reaction and subsequent sperm–egg fusion. Immunization studies in mice not only generated significant IgG responses against hSAMP32 but also resulted in a marked reduction in litter sizes, thereby confirming its antifertility effects. These results provide a theoretical and experimental basis for further mechanistic studies of SPACA1 in the fertilization process and support its potential as a molecular target for both contraception and the diagnosis of fertility impairments."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Zhonglin Hao, Michael J Wolkowicz, Jagathpala Shetty, et al. "}, {"type": "b", "children": [{"type": "t", "text": "SAMP32, a testis-specific, isoantigenic sperm acrosomal membrane-associated protein."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Biol Reprod (2002)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1095/biolreprod66.3.735"}], "href": "https://doi.org/10.1095/biolreprod66.3.735"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "11870081"}], "href": "https://pubmed.ncbi.nlm.nih.gov/11870081"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "K Kishida, H Harayama, F Kimura, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Individual differences in the distribution of sperm acrosome-associated 1 proteins among male patients of infertile couples; their possible impact on outcomes of conventional in vitro fertilization."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Zygote (2016)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1017/S0967199415000623"}], "href": "https://doi.org/10.1017/S0967199415000623"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "27185107"}], "href": "https://pubmed.ncbi.nlm.nih.gov/27185107"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Xuemei Chen, Xiaodong Liu, Xiuhua Ren, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Discovery of human posterior head 20 (hPH20) and homo sapiens sperm acrosome associated 1 (hSPACA1) immunocontraceptive epitopes and their effects on fertility in male and female mice."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Reprod Fertil Dev (2016)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1071/RD14134"}], "href": "https://doi.org/10.1071/RD14134"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "25209425"}], "href": "https://pubmed.ncbi.nlm.nih.gov/25209425"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Tianwu Zhang, Junmin Wang, Wenbin Niu, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Bioinformatic prediction of the structure and characteristics of human sperm acrosome membrane-associated protein 1 (hSAMP32) and evaluation of its antifertility function in vivo."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Reprod Fertil Dev (2020)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1071/RD20198"}], "href": "https://doi.org/10.1071/RD20198"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "33220718"}], "href": "https://pubmed.ncbi.nlm.nih.gov/33220718"}]}]}]}