Copy number variants in patients with severe oligozoospermia and Sertoli-cell-only syndrome

Abstract

A genetic origin is estimated in 30% of infertile men with the common phenotypes of oligo- or azoospermia, but the pathogenesis of spermatogenic failure remains frequently obscure. To determine the involvement of Copy Number Variants (CNVs) in the origin of male infertility, patients with idiopathic severe oligozoospermia (N = 89), Sertoli-cell-only syndrome (SCOS, N = 37)) and controls with normozoospermia (N = 100) were analysed by array-CGH using the 244A/400K array sets (Agilent Technologies). The mean number of CNVs and the amount of DNA gain/loss were comparable between all groups. Ten recurring CNVs were only found in patients with severe oligozoospermia, three only in SCOS and one CNV in both groups with spermatogenic failure but not in normozoospermic men. Sex-chromosomal, mostly private CNVs were significantly overrepresented in patients with SCOS. CNVs found several times in all groups were analysed in a case-control design and four additional candidate genes and two regions without known genes were associated with SCOS (P<1×10(-3)). In conclusion, by applying array-CGH to study male infertility for the first time, we provide a number of candidate genes possibly causing or being risk factors for the men's spermatogenic failure. The recurring, patient-specific and private, sex-chromosomal CNVs as well as those associated with SCOS are candidates for further, larger case-control and re-sequencing studies.

Figure 1. Workflow with different arrays (244A, 400K), number of subjects and categorisation of CNVs.

Figure 2. Number of CNVs (A), duplications (B) and deletions (C) separated by array (left: 244A, right: 400K) and patient group (Normo = normozoospermia, Oligo = severe oligozoospermia, SCOS = Sertoli-cell-only syndrome).

Around twice as many CNVs (independent of type and fitting the roughly two-fold increased resolution) were detected with the 440K array and in general more duplications than deletions. No significant differences between patient groups were found.

Figure 3. Number of duplications (upwards) and deletions (downwards) per chromosome (normalised per 100 men) detected by 244A (A) and 400K (B) arrays for normozoospermic controls, oligozoospermic and SCOS patients (open, grey and black bars, respectively).

Significantly different frequencies between the groups are marked with an asterisk. P-values calculated by Fisher's exact test. To correct for multiple testing, P-level for significance was adjusted according to the Bonferroni-Holm procedure.

Figure 4. Plots of −log P-values of frequency comparisons for all recurring CNVs found in patients and controls grouped by chromosome.

P-values calculated by Fisher's exact test. The figure does not include the Y chromosome because no recurring variants were found on it.

Figure 5. Significant negative correlation (r = −0.270, P<0.05) of total sperm count with number of deletions in 78 normozoospermic men analysed by 244A array.

P-value calculated on log-transformed total sperm counts.