Y Chromosome Microdeletion Test

Infertility is a major health concern around the world, infertility is contributed by both the partners. In the evaluation of male contribution to infertility, semen analysis is the initial diagnosis. A sperm concentration of <15 million sperms per mL is considered to oligospermia and is further classified into mild, moderate and severe. Absence of sperm in the ejaculate is considered to be Azoospermic condition and is classified into obstructive and non obstructive azoospermia. Azoospermia, the absence of sperm in semen is associated with male infertility. Azoospermic condition is caused by many external and intrinsic factors. Many genetic factors like chromosomal abnormalities, CFTR gene variants, and Y chromosome microdeletions (YCM) can cause azoospermia in men. 

YCM is a type of genetic disorder caused by small deletions on the male specific region of Y chromosome(MSY),eliminating very important genes responsible for normal spermatogenesis. Compared to oligospermic men azoospermic men have higher incidence of microdeletions. The male specific region of Y chromosome contain three important regions on the long arm of the Y chromosome namely azoospermic factor (AZFa-proximal segment, AZFb-middle, and AZFC-distal region) regions are studied for the presence of deletions. These deletions are caused by homologous recombination within the chromosome. There is large heterogeneity in the prevalence of these microdeletions among infertile men, some committees report it to be 2% and some report to be around 0.025%, and varies according to ethnic group. Deletions in the AZFc region has a chance of retrieving sperms from testicular biopsy compared to AZFa and b which has very less chances of retrieval. 

The reason of this is that the AZFc region contained DAZ gene, the analogous of which is also contained on chromosome 3 and is known as DAZL which acts as a counter part in the absence of DAZ gene on the y chromosome. The presence of y chromosome microdeletions is tested by extracting DNA from leucocytes and amplifying sequence-tagged sites(STS) on the Y chromosome using the technique called a polymerase chain reaction(PCR). The amplified PCR product was run on agarose gel which is mixed with ethidium bromide, an intercalating dye that binds with double-stranded DNA, to check for the presence or absence of specific regions in the MST region.