ArticlePRM1 variant rs35576928 (Arg>Ser) is associated with defective spermatogenesis in the Chinese Han population
Introduction
Infertility affects about 10% of couples worldwide, approximately half of which are due to male factors (In Vayena E, 2002). Non-obstructive azoospermia (NOA) and severe oligozoospermia are the two representative phenotypes of severely defective spermatogenesis. Intracytoplasmic sperm injection has been used as an effective alternative therapy in cases of severe male infertility. Although some of the causes such as genital tract infection, cryptorchidism orchitis and Y chromosome microdeletions are known (De Kretser and Baker, 1999, Huynh et al., 2002, Sadeghi-Nejad and Oates, 2008), the effect of genetic predisposition on male infertility remains to be clarified.
Protamines, which were isolated from the spermatozoa one century ago, play vital roles in the sperm chromatin condensation. Two types of protamines were identified in mammals: protamines 1 (PRM1) and protamines 2 (PRM2). The PRM1 presents in all species of vertebrates. PRM2 only exists in some of mammalian species including human and mouse (Balhorn et al., 1987, Oliva and Dixon, 1991, Yoshii et al., 2005). It has been proposed that biological and physiological functions of protamines were involved in: (i) paternal genome packing; (ii) competition and removal of transcription factors and other proteins from the spermatid; and (iii) imprinting of the paternal genome during spermatogenesis (Oliva and Dixon, 1991). In addition, increasing evidence indicates that abnormal protamine expression might be associated with defective spermatogenesis (Carrell et al., 2007, Matzuk and Lamb, 2008).
Mutations or polymorphisms harbour in the protamine or transition protein genes might induce conformational changes of the proteins, alter their incorporation into sperm chromatin and lead to sperm defects. Deficiency of Prm1 and Prm2 in mice results in sperm morphology defects, motility reduction and infertility due to haploinsufficiency (Cho et al., 2003, Cho et al., 2001). Clinical studies in humans have demonstrated that PRM1 (NC_000016.9, GI: 224589807) and PRM2 (NC_000016.9, GI: 224589807) variants could be related to male infertility (Aoki et al., 2006, Aston et al., 2010, de Yebra et al., 1993, Gazquez et al., 2008, Iguchi et al., 2006, Ravel et al., 2007, Tanaka et al., 2003, Tuttelmann et al., 2010). A number of case–control genetic studies have been carried out, but most of the patients involved had the clinical phenotype of slightly defective spermatogenesis (Gazquez et al., 2008, Iguchi et al., 2006, Ravel et al., 2007, Tuttelmann et al., 2010). Ravel et al. (2007) screened PRM1 variants in a large cohort of French infertile population and found that the SNP rs35576928 (p.A34R) was detectable only in two patients, one with idiopathic infertility and the other with oligozoospermia with increased sperm DNA fragmentation. Tuttelmann et al. (2010) showed that five SNP (rs35262993, rs35576928, rs737008, rs1646022 and rs2070923) of PRM1 and PRM2 were associated with teratozoospermia (n = 88) or mild oligozoospermia (n = 77) in a Caucasian population. The haplotype ACC (rs7377008, rs1646022 and rs2070923) of the genes seemed to be a protective haplotype and was associated with higher sperm concentration (Tuttelmann et al., 2010). Gazquez et al. (2008) screened PRM1 mutations in a cohort of teratozoospermia (Kruger strict criteria) and found that rs2301365 (c.−190C > A) was associated with altered sperm head morphology and an abnormal P1/P2 ratio. A few studies have investigated the cases with severely defective spermatogenesis and the results are quite ambiguous. Tanaka et al. (2003) performed a direct sequencing analysis for PRM1 and PRM2 in a cohort study of 153 NOA and 73 severe oligozoospermia patients. The study found eight novel SNP (rs187174862, c.160C > A, rs145663132, rs737008, c.431A > G, c.248C > T, rs1646022 and rs2070923), but none caused amino acid change. Also a stop codon (c.248C > T) was identified in PRM2, which led to a premature termination of the protamine 2 mRNA and would result in azoospermia (Tanaka et al., 2003). However, a recent pilot genome-wide analysis study of 172 NOA and severe oligozoospermia patients has demonstrated that none of the three tag SNP, rs2301365, rs35576928 and rs3177008, of PRM1 and PRM2 was associated with severely defective spermatogenesis (Aston et al., 2010).
To address the effect of the gene variants described above on spermatogenesis, a genetic analysis was performed as a case–control study of the Chinese Han population with NOA or severe oligozoospermia. Such an association study would provide a better understanding of genetic susceptibility of PRM1 and PRM2 to spermatogenesis.
Section snippets
Ethics statement
All patients provided written informed consent for the collection of samples and subsequent analysis. This study was conducted in accordance with the tenets of the Declaration of Helsinki and its amendments and approved by the ethics committee of Anhui Medical University (reference no. 2008035, 10 January 2008).
Subjects and sample collection
This study recruited 338 infertile men for a genetic questionnaire. All the patients attended the Reproductive Medicine Centre, the First Affiliated Hospital of Anhui Medical University
Clinical data
The clinical characteristics of the cases and controls are shown in Table 1. Testis volume in the cases was significantly smaller than that in the controls (P < 0.0125). Sperm concentration, progressive motility rate and normal morphology rate were significantly lower in severe oligozoospermia cases than those in the controls (P < 0.0125).
Genetic analysis of PRM1 and PRM2
Four SNP (rs737008, rs35576928, rs35262993 and rs2301365) in PRM1 and three SNP (rs424908, rs2070923 and rs3177008) in PRM2 were selected in this study (Table 2).
Discussion
So far, only a few studies have analysed the correlation of PRM1 and PRM2 variants to particular phenotypes of NOA and severe oligozoospermia (Aoki et al., 2006, Aston et al., 2010, Grassetti et al., 2011, Tanaka et al., 2003). This study detected the allele frequencies of PRM1 and PRM2 variants in NOA and severe oligozoospermia, respectively, to investigate the effect of the gene variants on the different phenotypes of severely defect spermatogenesis. The PRM1 variant rs35576928 (p.R34S) was
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2020, Revista Internacional de AndrologiaCitation Excerpt :Similarly, this SNP was found in Chinese population which is associated with teratozoospermia.23 Another study on Chinese population revealed that the PRM1 variant rs35576928 (p.R34S) (Arg > Ser) is correlated to severe oligozoospermia, however the dominant model of rs 35576928 has a protective effect on spermatogenesis.13 In general, histone H1-like plays a key role in sperm-specific chromatin compaction and comprises of higher quantities of both arginine and lysine in comparison to the somatic cells.
Xiao-Jin He has worked as a urologist in the Reproductive Medicine Centre of the First Affiliated Hospital of Anhui Medical University for 7 years. Now he is pursuing for his PhD on reproductive medicine in Anhui Medical University for the second year. He has published more than 10 manuscripts in the past 4 years. His current interests include cytogenetics of meiosis in male and microsurgery in male infertility.
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The authors contributed equally to this manuscript.