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A gonad,sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sperm in the form of spermatozoa. The female gonad, the ovary, produces egg cells. Both of these gametes are haploid cells. Some hermaphroditic animals have a type of gonad called an ovotestis.
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms. Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining because it is the presence or absence of Y chromosome that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the SRY gene, which triggers development of male gonads. The Y chromosome is passed only from male parents to male offspring.
Azoospermia is the medical condition of a man whose semen contains no sperm. It is associated with male infertility, but many forms are amenable to medical treatment. In humans, azoospermia affects about 1% of the male population and may be seen in up to 20% of male infertility situations in Canada.
Terms oligospermia, oligozoospermia, and low sperm count refer to semen with a low concentration of sperm and is a common finding in male infertility. Often semen with a decreased sperm concentration may also show significant abnormalities in sperm morphology and motility. There has been interest in replacing the descriptive terms used in semen analysis with more quantitative information.
Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen, and semen quality is used as a surrogate measure of male fecundity. More recently, advance sperm analyses that examine intracellular sperm components are being developed.
A chromosomal abnormality, chromosomal anomaly, chromosomal aberration, chromosomal mutation, or chromosomal disorder, is a missing, extra, or irregular portion of chromosomal DNA. These can occur in the form of numerical abnormalities, where there is an atypical number of chromosomes, or as structural abnormalities, where one or more individual chromosomes are altered. Chromosome mutation was formerly used in a strict sense to mean a change in a chromosomal segment, involving more than one gene. Chromosome anomalies usually occur when there is an error in cell division following meiosis or mitosis. Chromosome abnormalities may be detected or confirmed by comparing an individual's karyotype, or full set of chromosomes, to a typical karyotype for the species via genetic testing.
Azoospermia factor (AZF) is one of several proteins or their genes, which are coded from the AZF region on the human male Y chromosome. Deletions in this region are associated with inability to produce sperm. Subregions within the AZF region are AZFa, AZFb and AZFc. AZF microdeletions are one of the major causes of male infertility for azoospermia and severe oligozoospermia males. AZF is the term used by the HUGO Gene Nomenclature Committee.
Sertoli cell-only syndrome (SCOS), also known as germ cell aplasia, is defined by azoospermia where the testicular seminiferous tubules are lined solely with sertoli cells. Sertoli cells contribute to the formation of the blood-testis barrier and aid in sperm generation. These cells respond to follicle-stimulating hormone, which is secreted by the hypothalamus and aids in spermatogenesis.
Deleted in azoospermia 1, also known as DAZ1, is a protein which in humans is encoded by the DAZ1 gene.
Ubiquitin specific peptidase 9, Y-linked , also known as USP9Y, is an enzyme which in humans is encoded by the USP9Y gene. It is required for sperm production. This enzyme is a member of the peptidase C19 family and is similar to ubiquitin-specific proteases, which cleave the ubiquitin moiety from ubiquitin-fused precursors and ubiquitinylated proteins.
Deleted in azoospermia protein 3 is a protein that in humans is encoded by the DAZ3 gene.
Deleted in azoospermia protein 2 is a protein that in humans is encoded by the DAZ2 gene.
DAZ-associated protein 1 is a protein that in humans is encoded by the DAZAP1 gene.
Synaptonemal complex protein 3 is a protein that in humans is encoded by the SYCP3 gene. It is a component of the synaptonemal complex formed between homologous chromosomes during the prophase of meiosis.
Testis-specific basic protein Y 2 also known as basic charge, Y-linked 2 is a protein that in humans is encoded by the BPY2 gene which resides on the Y chromosome.
Mild androgen insensitivity syndrome (MAIS) is a condition that results in a mild impairment of the cell's ability to respond to androgens. The degree of impairment is sufficient to impair spermatogenesis and / or the development of secondary sexual characteristics at puberty in males, but does not affect genital differentiation or development. Female genital and sexual development is not significantly affected by the insensitivity to androgens; as such, MAIS is only diagnosed in males. The clinical phenotype associated with MAIS is a normal male habitus with mild spermatogenic defect and / or reduced secondary terminal hair.
Stromal antigen 3 is a protein that in humans is encoded by the STAG3 gene. STAG3 protein is a component of a cohesin complex that regulates the separation of sister chromatids specifically during meiosis. STAG3 appears to be paramount in sister-chromatid cohesion throughout the meiotic process in human oocytes and spermatocytes.
About 10–15% of human couples are infertile, unable to conceive. In approximately in half of these cases, the underlying cause is related to the male. The underlying causative factors in the male infertility can be attributed to environmental toxins, systemic disorders such as, hypothalamic–pituitary disease, testicular cancers and germ-cell aplasia. Genetic factors including aneuploidies and single-gene mutations are also contributed to the male infertility. Patients with nonobstructive azoospermia or oligozoospermia show microdeletions in the long arm of the Y chromosome and/or chromosomal abnormalities, each with the respective frequency of 9.7% and 13%. A large percentage of human male infertility is estimated to be caused by mutations in genes involved in primary or secondary spermatogenesis and sperm quality and function. Single-gene defects are the focus of most research carried out in this field.
The DAZprotein family is a group of three highly conserved RNA-binding proteins that are important in gametogenesis and meiosis. Therefore, mutations in the genes that encode for the DAZ proteins can have detrimental consequences for fertility.
Spermatogenesis-associated protein 16 is a mammalian protein encoded by the SPATA16 gene. SPATA16, also known as NYD-SP12, is a developmental protein that aids in differentiation of germ cells for spermatogenesis and participates in acrosome formation for appropriate sperm-egg fusion. SPATA16 is located on chromosome 3 at position 26.31 and is a member of the tetratricopeptide repeat-like superfamily, which facilitate interactions and assemblies between proteins and protein complexes.
References
- ↑ Carlo Foresta, et al.: Y chromosome microdeletions and alterations of spermatogenesis. Endocrine Reviews 22 (2): 226-239.
- ↑ Krausz, Csilla; Lluis Quintana-Murci; Ken McElreavey (July 2000). "Prognostic value of Y deletion analysis". Human Reproduction. 15 (7): 1431–1434. doi: 10.1093/humrep/15.7.1431 . PMID 10875846.
- ↑ Song NH, Wu HF, Zhang W, et al. (September 2005). "Screening for Y chromosome microdeletions in idiopathic and nonidiopathic infertile men with varicocele and cryptorchidism". Chin. Med. J. 118 (17): 1462–7. PMID 16157049.
- ↑ Poongothai J, Gopenath TS, Manonayaki S (April 2009). "Genetics of human male infertility" (PDF). Singapore Med J. 50 (4): 336–47. PMID 19421675.
- ↑ Stouffs, K.; Lissens, W.; Tournaye, H.; Haentjens, P. (2010). "What about gr/gr deletions and male infertility? Systematic review and meta-analysis". Human Reproduction Update. 17 (2): 197–209. doi: 10.1093/humupd/dmq046 . PMID 20959348.
- ↑ Goncalves, J; Lavinha J. (April 1998). "Y chromosome and male infertility". Acta Med Port (in Portuguese). 11 (4): 365–72. PMID 9644848.