Post Date December, 03 2023
In 1976, Tiepolo et al. first reported the genome AZFCS related to spermatogenesis located in the euchromatin portion of the long arm (Yqll) of the Y chromosome. Kent First et al. believe that AZF includes four non overlapping functional subregions: AZFa.AZFb, AZFc, and AZFd, with estimated lengths of 1-3Mbp, 1-3Mbp, and 1.5Mbp, respectively. AZFc can be further divided into three subregions: proximal AZFc (i.e., AZFd), central AZFc (i.e., DAZ), and distal AZFc (i.e., the distal region of DAZ).
Up to now, more than 6000 male infertile patients have been tested for AZF at home and abroad, and it has been found that the proportion of AZF microdeletions is 3% to 30%. Generally, large fragment deletions in the AZF region are limited to the deletion of AZFa, and are common in patients with Sertolicell only syndrome or severe oligospermia, accounting for approximately 7%. Microdeletions of AZF6 or AZFc can be seen in patients with both sertoli cell only syndrome and severe oligospermia; However, AZFd deficiency is commonly seen in patients with mild oligospermia or teratospermia.
Multiple PCR is an effective method for detecting Y chromosome microdeletions. In this article, no AZFa and AZFb region deletions were detected, only AZFb region deletions were detected, which is consistent with the experimental results of Simoni et al. Simoni et al. analyzed the DAZ gene in 168 patients with non obstructive, idiopathic azoospermia, and severe oligozoospermia, and found that there were DAZ deletions in 3 azoospermia and 2 severe oligozoospermia, thereby confirming the hypothesis that DAZ is an important candidate gene for AZF. The incidence of DAZ gene deletion varies greatly from 1.9% to 18% in different research reports.
The two AZFc deletion sites sY254 and sY255 detected in this article are located within the DAZ gene, with a deletion rate of 3.6%, which is relatively low. The reason for the large difference in deletion rates may be related to the criteria for screening patients. Reijo et al., Najmabaci et al. used Gu Wan biopsy to select patients, excluding patients with azoospermia or oligozoospermia who detected sperm in biopsy samples but were unable or difficult to find sperm in semen from the scope of examination.
Because these patients belong to obstructive azoospermia. Therefore, the deletion rate detected by this method is relatively high, reaching 13% and 18%, respectively. Although Gaowan biopsy is very useful for molecular genetic research on DAZ and AZF, it is difficult to accept for male infertility patients, so it is generally difficult to adopt this method of screening patients.
The DAZ gene is only expressed in Kuwan tissue, indicating that the DAZ gene is only involved in male specific physiological processes, which also supports the hypothesis that DAZ is an important gene affecting sperm production. The patients with AZFc deficiency detected in this article are all azoospermia, but some reports have found that patients with oligospermia also have AZF deficiency. Stuppit, et al. studied the Yq11 of a father and son with oligospermia and found that the missing fragment in the son was longer than that in the father, and there were deletions at the sY243 and sY269 loci. However, the RBM1, sY254, and sY255 of the father and son were not missing. Agul nik et al. also believe that DAZ may not be an absolutely necessary gene for human spermatogenesis, and may be affected by other factors, such as genetic background, vas deferens microenvironment, etc.
The sY254 locus contains an exon and an intron, and its PCR amplification product is 400bpoPCR-SSCP. The result shows that there is no point mutation in 48 patients with azoospermia or oligozoospermia. Whether the point mutation at this locus may have little relationship with azoospermia or oligozoospermia is inconclusive. Due to the depletion of genomic DNA in the sample, we were unable to perform sY254 point mutation detection in all 84 patients and 50 normal controls. The sample size of 48 cases is not sufficient to detect point mutations, and the relationship between the two needs to be further explored.
