AZF microdeletions on the Y chromosome in infertile Chinese men: a five-year retrospective analysis / 中华男科学杂志

<p><b>OBJECTIVE</b>The past few years have seen great progress in the studies of the relationship between AZF microdeletions and male infertility. However, some molecular and clinical concerns are not supported by definitive data. The aim of this study was to investigate the prevalence and types of AZF microdeletions in infertile Chinese men, and the indications for genotype-phenotype correlation.</p><p><b>METHODS</b>We retrospectively analyzed Y chromosome AZF microdeletions among 502 patients with nonobstructive azoospermia and 306 with severe oligozoospermia received in our hospital during the past five years.</p><p><b>RESULTS</b>Microdeletions were detected in 7.80% of the patients (63/808), 9.16% in the men with nonobstructive azoospermia (46/502) and 5.56% in those with severe oligozoospermia (17/306). Complete AZFa and AZFb (P5/Proximal P1) deletions were associated with azoospermia, whereas AZFc deletion with variable spermatogenic phenotypes. A mild decline in sperm concentration was found in one male with partial AZFb deletion. The most frequent deletion was the AZFc b2/b4 subtype (60.32%, 38/63), and 39.47% of the cases (15/38) had sperm in the ejaculate. Of the 63 deletions, only one case of the AZFc b2/b4 type had a sperm concentration of over 2 million sperm/ml.</p><p><b>CONCLUSION</b>AZF microdeletions play a significant role in the diagnosis and evaluation of spermatogenic defects. Larger-scale clinical researches on Y chromosome microdeletions may give us a deeper insight into their mechanism and the genotype-phenotype relationship.</p>

Sex chromosomes and male infertility / 中华男科学杂志

Male infertility is a worldwide problem, with a variety of causes including genetic factors. Sex chromosomes are particularly interesting, as males only have a single copy of both chromosomes. The Y chromosome is obviously an area of interest in the study of male-factor infertility because it contains many of the genes that are critical for spermatogenesis and the development of male gonads. Y chromosome microdeletions are the most commonly known genetic causes of spermatogenic failure in males. The azoospermia factor (AZF) region is a particular area on the long arm of the Y chromosome, Yq, where microdeletions occur most frequently. Fourteen Y chromosome genes encoding putatively functional proteins and expressed in the human testis are found to be located in one of the three AZF intervals. The exact role of specific AZF genes in spermatogenesis is largely unknown, for each of the most classical Yq deletions removes multiple genes. The importance of the X chromosome in mammalian spermatogenesis is suggested by its enrichment of germ cell-specific genes expressed in spermatogenesis, such as AR, USP26, TAF7L, TEX11, KAL1, AKAP4, and NXF2. Genes on the X chromosome may be under unique evolutionary pressure due to their hemizygous expression in male. The mutations in the single copy X-linked genes, unlike in autosomal genes, would not be masked by a normal allele. Many researches have been conducted on the relationship between spermatogenesis and the genes on the X chromosome, but the involvement of the X chromosome in male infertility remains less understood and deserves further characterization.