Analysis of AMEL-Y Null Allele Caused by Deletion Fragments within the Yp11.2 Region in a Chinese Population.

Background: The application of amelogenin typing as a sex marker incorporated into short tandem repeat (STR) multiplexes is a common practice in sex determination. The null allele of amelogenin Y (AMEL-Y) caused by mutations in the Y chromosome can lead to erroneous interpretations and potentially significant errors in forensic sex determination.

Methods: In this study, the amelogenin gene of 7,359 unrelated male individuals from the Chinese Han population was genotyped using a PowerPlex® 21 kit. Individuals with the AMEL-Y null allele whose sex typing results were discordant were subjected to Y-STR haplotyping and Y chromosome microdeletion detection.

Result: The frequency of the AMEL-Y null allele in our study cohort from Fujian province was 0.027%. Two unrelated male individuals with the AMEL-Y null allele were identified. One individual showed allele dropout at DYS576, DYS570, DYS458, DYS456, and AMEL-Y loci; this deletion was at least 3.59 Mb in length. The other individual and his son presented the same pattern of deletion of DYS522, DYS570, DYS576, and AMEL-Y. However, no loss of sequence-tagged site (STS) loci was found in the three samples after Y chromosome microdeletions were detected. The results of azoospermia factor (AZF) and sex-determining region Y (SRY) gene analyses were positive, and the male sex of the individuals was ultimately confirmed.

Conclusion: AMEL-Y null allele can lead to misjudgment in sex determination. In practical situations, analysis of other Y chromosome genetic markers that are also located in the Yp11.2 region can be valuable for verifying locus deletion and determining the deletion range. Furthermore, the use of combined multimarker detection represents a trend for gender determination in individual identification, particularly in cases where the AMEL-Y null allele is present.