Molecular Genetics

Y microdeletion test

In some couples with Y chromosome microdeletion test, male factor is observed and some of these patients are recommended to do the test. Specifically, chromosome analysis and Y chromosome microdeletion analysis is desirable in those individuals with azoospermia or severe oligoasthenoteratospermia. The human Y chromosome accounts for about 2–3 % of the entire genome. The short arm is called Yp and the long arm is called Yq. Y chromosome consists of pseudootosomal, heterochromatin and euchromatin regions. Pseudootosomal regions (PARs) are located at the end portions of Yp (PAR1) and Yq (PAR2). These regions recombinate with pseudootosomal regions of the X chromosome during meiosis. Genes in the pseudootosomal region are inherited just like autosomal genes. Genes in the short arm (Yp) (SRY) of the Y chromosome are involved in testicular development, and the genes in the long arm (Yq) are involved in spermatogenesis. There are links between microdeletions of these genes on Y chromosome and infertility. The AZF genes are located in the AZFa, AZFb, AZFc and AZFd regions on the long arm of the Y chromosome. Among the AZF regions, deletions are most commonly seen in the AZFc region, resulting in hypospermatogenesis. AZFc region deletions are approximately 12 % in men with nonobstructive azoospermia, while approximately 6 % in men with severe oligospermia (sperm count less than 5 million). Although microdeletions in Y chromosome that cause male infertility can be easily detected by polymerase chain reaction (PCR), there is no treatment to correct these microdeletions. Detection of Y chromosome microdeletions allows the understanding of the cause of oligosospermia and the prognosis of the patients. Especially in patients with AZFa and AZFb microdeletion, it is very important to know that it is not possible to obtain sperm by TESA for ICSI. In addition, it is stated that the number of recurrent miscarriages increases in spouses of Y chromosome microdeletions and that children may have learning disabilities. For these reasons, Y chromosome microdeletion analysis should be performed before ICSI, especially in patients with severe oligospermia or azoospermia. It should be advised that the boys that their families will have can be subfertile and follow up the sexual maturation periods of these children.