Abstract
The World Health Organization (WHO) defines infertility as the inability of a sexually active, non-contracepting couple to achieve spontaneous pregnancy within one year. Statistics show that the two sexes are equally at risk. Several causes may be responsible for male infertility; however, in 30–40% of cases a diagnosis of idiopathic male infertility is made in men with normal urogenital anatomy, no history of familial fertility-related diseases and a normal panel of values as for endocrine, genetic and biochemical markers. Idiopathic male infertility may be the result of gene/environment interactions, genetic and epigenetic abnormalities. Numerical and structural anomalies of the Y chromosome represent a minor yet significant proportion and are the topic discussed in this review. We searched the PubMed database and major search engines for reports about Y-linked male infertility. We present cases of Y-linked male infertility in terms of (i) anomalies of the Y chromosome structure/number; (ii) Y chromosome misbehavior in a normal genetic background; (iii) Y chromosome copy number variations (CNVs). We discuss possible explanations of male infertility caused by mutations, lower or higher number of copies of otherwise wild type, Y-linked sequences. Despite Y chromosome structural anomalies are not a major cause of male infertility, in case of negative results and of normal DNA sequencing of the ascertained genes causing infertility and mapping on this chromosome, we recommend an analysis of the karyotype integrity in all cases of idiopathic fertility impairment, with an emphasis on the structure and number of this chromosome.
Highlights
The World Health Organization (WHO) defines infertility as the inability of a sexually active, non-contracepting couple to achieve spontaneous pregnancy within one year [1]
Y#idiogram (note: The region q12 is shortened, due to its large extension compared to the rest of the chromosome); (4) localization of the Sex-determining Region Y (SRY) gene, of the pseudoautosomal regions (PARs) regions (PAR2 is indicated by an asterisk, due to its small size) and of the Azoospermia Factor (AZF) regions; (5) extension of the euchromatic (MSYe) and heterochromatic (MSYh) portions of the male-specific Y (MSY) region; (6) approximate length in megabases of the short arm, euchromatic portion of the long arm and heterocromatic portion of the long arm
This study demonstrates that, in some cases, the mis-segregating Y chromosome, in the time frame of three consecutive cell cycles, is first included in a micronucleus, fragmented, and its fragments are re-joined through the error-prone Non-Homologous End Joining (NHEJ) mechanism
Summary
The World Health Organization (WHO) defines infertility as the inability of a sexually active, non-contracepting couple to achieve spontaneous pregnancy within one year [1]. Focusing on the clinical characteristics of the patient and on the anatomical/temporal characteristics of infertility might be a better approach in the diagnosis and treatment of this condition, since male infertility can be caused by several, different factors that may affect semen quality in very different ways, so that this quality can be seen as the final output of different pathophysiological mechanisms Obstructive azoospermia can be further divided into (a) intratesticular (post-inflammatory or post-traumatic), (b) epidydimal (secondary to epididymitis or chronic infections), (c) vas deferens (post-vasectomy), (d) ejaculatory duct (cystic or post-inflammatory), and (e) distal seminal ducts (local neuropathy) obstruction [7] Environmental factors, such as tobacco smoking and assumption of steroids, seemingly play a role in altering male fertility [8]. We discuss the male sterility caused by alterations in the shape, overall content or behavior of the Y chromosome, and describe how the size variation of specific regions of this chromosome or Y chromosome aneuploidies, irrespectively of point mutations in coding gene sequences, affects the male fertility
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