Copy-number analysis of Y-linked loci in young men with non-obstructive azoospermia: Implications for the rarity of early onset mosaic loss of chromosome Y.

Erina Suzuki,Toru Uchiyama,Kikumi Ushijima,Maki Fukami,Momori Katsumi,Mami Miyado,Yoshitomo Kobori,Hiroshi Okada

doi:10.1002/rmb2.12321

Abstract

PurposeMosaic loss of chromosome Y (mLOY) is a common feature in elderly men. If mLOY can also occur in young men, it may lead to spermatogenic failure due to loss of spermatogenic genes. Indeed, previous studies detected the 45,X/46,XY karyotype in a few young men with spermatogenic failure. The present study aimed to clarify the frequency of cryptic mLOY in reproductive‐aged men with spermatogenic failure.MethodsWe studied 198 men at ages 24‐55 years who presented with etiology‐unknown non‐obstructive azoospermia. Prior this study, these patients underwent G‐banding analysis for 20 leukocytes and were found to have 46,XY karyotype. We analyzed copy numbers of chromosome Y in blood cells by using semi‐quantitative multiplex PCR for AMELY/AMELX, array‐based comparative genomic hybridization (CGH) for the AMELY locus, and droplet digital PCR for SRY, USP9Y, and UTY.ResultsMultiplex PCR showed borderline low AMELY/AMELX ratios in three patients. However, for the three patients, CGH excluded deletion of the AMELY locus, and droplet digital PCR suggested preserved copy numbers of all tested loci.ConclusionThis study highlights the rarity of leukocyte mLOY in reproductive‐aged men with spermatogenic failure. In addition, our data imply that standard karyotyping is sufficient to screen early onset mLOY.

Highlights

We performed semi-quantitative multiplex PCR for all samples to screen Mosaic loss of chromosome Y (mLOY)
Yatsenko et al[9] identified the same karyotype in one of 629 samples from men with severe spermatogenic failure. These results provided the first indication that early onset Mosaic loss of chromosome Y (mLOY) in leukocytes is present in a small percentage of young men with spermatogenic failure
Copy numbers of chromosome Y relative to chromosome X were assessed by comparing the area under the curve of PCR products for AMELY at Yp11.2 to that for AMELX at Xp22.2

Summary

Introduction

We performed semi-quantitative multiplex PCR for all samples to screen mLOY. We utilized a previously established method with slight modifications.[10] In brief, copy numbers of chromosome Y relative to chromosome X were assessed by comparing the area under the curve of PCR products for AMELY at Yp11.2 to that for AMELX at Xp22.2. Samples which showed AMELY/AMELX ratios of ≤0.89 in two independent assays were subjected to the second analysis by droplet digital PCR.

Results

Conclusion