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Y chromosome microdeletion (YCM) is a family of genetic disorders caused by missing genes in the Y chromosome. Many men with YCM exhibit no symptoms and lead normal lives. It is present in a significant number of men with reduced fertility.Carlo Foresta, et al.: Y chromosome microdeletions and alterations of spermatogenesis. Endocrine Reviews 22 (2): 226-239. Reduced sperm production varies from oligozoospermia, significant lack of sperm, or azoospermia, complete lack of sperm.

Cause

The mechanism of mutation is not different for Y-chromosome microdeletion. However, the ability to repair it differs from other chromosomes. The human Y chromosome is passed directly from father to son, and is not protected against accumulating copying errors, whereas other chromosomes are error corrected by recombining genetic information from mother and father. This may leave natural selection as the primary repair mechanism for the Y chromosome.{{cn|date=September 2021}}

Diagnosis

Y chromosome microdeletion is currently diagnosed by extracting DNA from leukocytes in a man's blood sample, mixing it with some of the about 300 known genetic markers for sequence-tagged sites (STS) on the Y chromosome, and then using polymerase chain reaction amplification and gel electrophoresis in order to test whether the DNA sequence corresponding to the selected markers is present in the DNA.{{cn|date=September 2021}} Such procedures can test only the integrity of a tiny part of the overall 23 million base pair long Y chromosome. Therefore, the sensitivity of such tests depends on the choice and number of markers used. Present diagnostic techniques can only discover certain types of deletions and mutations on a chromosome and give therefore no complete picture of genetic causes of infertility. They can only demonstrate the presence of some defects, but not the absence of any possible genetic defect on the chromosome.{{cn|date=September 2021}}The preferred test for genetic mutation, namely complete DNA sequencing of a patient's Y chromosome, is too expensive for use in epidemiological research or clinical diagnostics.{{cn|date=September 2021}}In up to 20% of men with reduced sperm count, some form of YCM has been detected.JOURNAL,weblink Human Reproduction, 15, 7, 1431–1434, July 2000, Prognostic value of Y deletion analysis, Csilla, Krausz, Lluis Quintana-Murci, Ken McElreavey, 10.1093/humrep/15.7.1431, 10875846, free,

Infertility

Microdeletions in the Y chromosome have been found at a much higher rate in infertile men than in fertile controlsJOURNAL, Song NH, Wu HF, Zhang W, etal, Screening for Y chromosome microdeletions in idiopathic and nonidiopathic infertile men with varicocele and cryptorchidism, Chin. Med. J., 118, 17, 1462–7, September 2005, 16157049,weblink and the correlation found may still go up as improved genetic testing techniques for the Y chromosome are developed.{{cn|date=September 2021}} Much study has been focused upon the "azoospermia factor locus" (AZF), at Yq11.JOURNAL, Poongothai J, Gopenath TS, Manonayaki S, Genetics of human male infertility, Singapore Med J, 50, 4, 336–47, April 2009, 19421675,weblink A specific partial deletion of AZFc called gr/gr deletion is significantly associated with male infertility among Caucasians in Europe and the Western Pacific region.JOURNAL, 10.1093/humupd/dmq046, What about gr/gr deletions and male infertility? Systematic review and meta-analysis, 2010, Stouffs, K., Lissens, W., Tournaye, H., Haentjens, P., Human Reproduction Update, 17, 2, 197–209, 20959348, free, Additional genes associated with spermatogenesis in men and reduced fertility upon Y chromosome deletions include RBM, DAZ, SPGY, and TSPY.JOURNAL, Acta Med Port, April 1998, 11, 4, 365–72, Y chromosome and male infertility, pt, Goncalves, J, Lavinha J., 9644848,

See also

• Infertility
• AZF1

References

{{reflist|30em}}

Further reading

• GeneReviews/NCBI/NIH/UW entry on Y Chromosome Infertility

{{chromosomal abnormalities}}