Spermatogenesis is a complex process of proliferation and differentiation during male germ cell development involving mitosis, meiosis and spermiogenesis. Endogenous and exogenous physical, chemical and biological sources modify the genome of spermatozoa. The genomic integrity and stability of the sperm is protected by DNA repair mechanisms. In the male germline cells, DNA repair mechanisms include nucleotide excision repair, base excision repair, DNA mismatch repair, double strand break repair and post-replication repair. Defects in repair mechanisms cause arrest of spermatogenesis and abnormal recombination, ultimately resulting in male infertility. This review focuses on molecular mechanisms of the DNA repair pathways, DNA repair defects and male infertility.

Many studies have reported that the contents of cigarette smoke negatively affect sperm parameters, seminal plasma, and various other fertility factors. Nevertheless, the actual effect of smoking on male fertility is not clear. The effect of smoking on semen parameters is based on the well-established biological finding that smoking increases the presence of reactive oxygen species, thereby resulting in oxidative stress (OS). OS has devastating effects on sperm parameters, such as viability and morphology, and impairs sperm function, hence reducing male fertility. However, not all studies have come to the same conclusions. This review sheds light upon the arguable association between smoking and male fertility and also assesses the impact of non-smoking routes of tobacco consumption on male infertility. It also highlights the evidence that links smoking with male infertility, including newly emerging genetic and epigenetic data, and discusses the clinical implications thereof.

The study aims to discuss the effects of aging on the male reproductive system. A systematic review was performed using PubMed from 1980 to 2014. Aging is a natural process comprising of irreversible changes due to a myriad of endogenous and environmental factors at the level of all organs and systems. In modern life, as more couples choose to postpone having a child due to various socioeconomic reasons, research for understanding the effects of aging on the reproductive system has gained an increased importance. Paternal aging also causes genetic and epigenetic changes in spermatozoa, which impair male reproductive functions through their adverse effects on sperm quality and count as, well as, on sexual organs and the hypothalamic-pituitarygonadal axis. Hormone production, spermatogenesis, and testes undergo changes as a man ages. These small changes lead to decrease in both the quality and quantity of spermatozoa. The offspring of older fathers show high prevalence of genetic abnormalities, childhood cancers, and several neuropsychiatric disorders. In addition, the latest advances in assisted reproductive techniques give older men a chance to have a child even with poor semen parameters. Further studies should investigate the onset of gonadal senesce and its effects on aging men.

Male infertility is a heterogeneous and common condition that might be a result of genetic or epigenetic variations or both. The frequency of genetic aberrations in azoospermic or severely oligozoospermic men is at least 15%, and the major genetic causes are karyotype abnormalities, microdeletions on Y chromosome, and mutations of cystic fibrosis transmembrane conductance regulator (CFTR) (Hamada, Esteves, & Agarwal, 2013; Hotaling & Carrell, 2014). Beyond these widely accepted genetic causes, a number of both autosomal and particularly X-chromosomal genes are associated with male infertility (Ropke & Tuttelmann, 2017). Furthermore, epigenetic control of gene expression plays a crucial role in both sperm function and fertilising ability (Gunes, Arslan, Hekim, & Asci, 2016a). Epigenetic regulation might be changed by external and internal factors or both, including environmental factors, nutrition and stress (Gunes, 2018b). This review summarises the latest evidence concerning the role of genetics and epigenetics on male infertility. 1.1 | Overview of human genome and genetics The haploid human genome consists of about 3 billion letters (3.3 billion nucleotides) distributed in 24 chromosomes. However, only 1.5% of the human genome encodes a protein (Gregory & Gilbert, 2005; Maher, 2012). The human genome project (HGP) has shown that genomes of nonrelated people exhibit a single base variation in every 1,200-1,500 DNA bases. These variations are

Infertility is a complex disorder with multiple genetic and environmental causes. Although some specific mutations have been identified, other factors responsible for sperm defects remain largely unknown. Despite considerable efforts to identify the pathophysiology of the disease, we cannot explain the underlying mechanisms of approximately half of infertility cases. This study reviews current data on epigenetic regulation and idiopathic male infertility. Recent data have shown an association between epigenetic modifications and idiopathic infertility. In this regard, epigenetics has emerged as one of the promising research areas in understanding male infertility. Many studies have indicated that epigenetic modifications, including DNA methylation in imprinted and developmental genes, histone tail modifications and short non-coding RNAs in spermatozoa may have a role in idiopathic male infertility.

Urolithiasis is a multifactorial disease, the onset and severity of which is influenced by both genetic and environmental factors. This study represents an investigation of the role of vitamin D receptor (VDR) gene polymorphisms (ApaI, BsmI, and TaqI) and combined genotypes in urolithiasis in a Turkish population. We studied 110 patients with urinary stones and 150 control subjects. The polymorphic regions were amplified using polymerase chain reaction, followed by digestion with restriction enzymes BsmI, ApaI, and TaqI, and analyzed electrophoretically. Genotype and allele frequencies were calculated, and the association with urolithiasis, family history, and recurrence of stone was investigated. Our data provide no evidence for an association between urolithiasis and VDR ApaI, BsmI, and TaqI genotypes. We also analyzed the effects of VDR ApaI, BsmI, and TaqI genotypes in combination; the "GTT" VDR haplotype, constructed from three adjacent restriction fragment length polymorphisms was overrepresented among the urolithiasis patients. However, no significant differences between heterozygous carriers (OR 1.302; 95% CI 0.527-3.215) and homozygous carriers (OR 3.39; 95% CI 0.719-15.985) were observed in our study population. A significant association was found only between the ApaI polymorphism and family history (P=0.017; chi (2)=5.657). Our data indicate that the VDR ApaI, BsmI, and TaqI polymorphisms do not confer a significant risk for urolithiasis.

Genetic and environmental factors are thought to play roles in the etiopathology of fibromyalgia syndrome (FMS). The objective of this study was to determine the potential effects of single nucleotide polymorphisms (SNPs) in catechol-O-methyltransferase (COMT) (rs4680) and 5-hydroxytryptamine (serotonin) 2A (5-HT2A) receptor (rs6313 and rs6311) genes on susceptibility to FMS. One hundred seventy-one women (80 FMS, 91 control) were enrolled in the study. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used for the genotyping analyses. Genotype and allele frequencies were calculated by the chi-square test. Beck depression inventory, state and trait anxiety inventory and symptom checklist-90 revised (SCL-90-R) tests were applied to both patients and controls. There were no observed differences in the frequencies of alleles and genotypes between patients and controls for the COMT, and the two 5-HT2A receptor gene polymorphisms (P>0.05). Our results suggest that the investigated polymorphisms seem not to be the susceptibility factors in etiology of FMS.

Within the limitations of sample selection and number, the IL-10 gene polymorphism at position -597 seems to be associated with severe generalized CP.