OBJECTIVETo investigate the characteristics of null allele for 17 Y-chromosomal short tandem repeats (Y-STR) loci in a group of infertile males.

METHODSTwo hundred thirty six infertile males featuring non-obstructive azoospermia and severe oligozoospermia were analyzed with an AmpFISTR ((R)) Yfiler (TM) kit. Deletions of azoospermia factor (AZF) fragments were confirmed with Y chromosome sequence-tagged sites (STSs) analysis using modified multiplex PCR.

RESULTSThe overall prevalence of AZF microdeletions was 16.95% (40/236). In the non-obstructive azoospermia group, 13 cases had AZFc deletion, 6 cases had AZFb+c deletion, 2 cases had AZFa deletion, 1 case had AZFb deletion. In the severe oligozoospermia group, 17 cases had AZFc deletion and 1 had AZFb deletion. No AZFa+b+c deletion was detected. Forty cases showed null alleles by scanning of the 17 STR loci. Deletions of DYS438, DYS439, DYS437, DYS389I and DYS389II were found in the 2 cases with AZFa deletion. In patients with AZFb deletion, DYS392 and DYS385a/b were found deleted. Deletions of DYS448 were detected in all of the 30 cases with AZFc deletion. Deletions of DYS392, DYS385a/b, and DYS448 were found in 6 cases with AZFb+c deletion.

CONCLUSIONDeletions of the Y chromosome AZF regions are associated with azoospermia and severe oligozoospermia. Null allele due to complete absence of AZFa, AZFb and AZFc regions may lead to misinterpretation in the sexual assault cases. Revealing the locus heterogeneity in male infertility population can enrich the Y-STR database and facilitate interpretation STR data in forensic DNA testing.