Microdeletion of the AZFc locus with high frequency of mosaicism 46,XY/47XYY in cases of non obstructive azoospermia in eastern population of India
The etiopathology of male infertility is highly complex, involving gene - environment interactions to regulate spermatogenesis. Consequently, genetic analysis becomes imperative for cases of non-obstructive azoospermia (NOA) to identify the causative factors. Cases (n = 111) of NOA referred to the cytogenetics and molecular genetics laboratory of the All India Institute of Medical Sciences in -Patna from 2013-2018 were subjected to 1) karyotyping using GTG bandings techniques, 2) fluorescence in situ hybridization (FISH) for the sex determining region (SRY), and 3) PCR based analysis of STS markers based on microdeletion of the Y- chromosome after isolation of genomic DNA from whole blood. A flow cytometer was used for a cell- kinetic and DNA methylation study after incorporation of 5-azacytidine (5-AzaC) (1.0 ug/mL) in lymphocyte culture. PCR products were analyzed on an agarose gel (1.5%) and bands were visualized on Gel Doc after ethidium bromide staining. Chromosomal abnormalities, including structural numerical variations, were observed in 14 of the karyotypes. Eight cases showed a 46,XY/47,XYY i.e. mosaic pattern; two cases 46, XY/45/XO; a single case with 47,XY +16; two cases with 46,X+ ring Y; a single case with 46,XY+dicentric in chromosome-7; and two cases showed a normal 46,XY karyotypic pattern. Cellular proliferation increased after incorporation of 5-azaC (1.0 µg/mL) for 24 h in lymphocyte culture at the S - phase of the cell cycle. Out of 14 cases analyzed with FISH, three cases showed loss of the SRY region, amongst which two cases were SRY negative (-ve) with a normal 46, XY karyotype. Serum follicle stimulating hormone values were higher (21 U/L) in cases of mosaicism as compared to normal individuals. The frequency of microdeletion deletion of the AZFc region varied in different cases; one case of infertility showing deletion of the Sy 267 STS marker (102bp); loss of a 350bp band (Sy 254) was found in all the cases of infertility. These genetic variations are responsible for dysregulation of spermatogenesis leading to infertility in males. Genetic counselling would be relevant in such cases, before beginning assisted reproductive techniques such as in vitro fertilization.