FISH and array CGH characterization of de novo derivative Y chromosome (Yq duplication and partial Yp deletion) in an azoospermic male

Abstract

This study presents a 28-year-old infertile male who was referred to the cytogenetic laboratory for chromosomal analysis after 4 years of regular unprotected intercourse in whom non-obstructive azoospermia was revealed. Standard cytogenetic G-banding was performed on metaphase spreads and a de-novo karyotype 46,X,der(Y)(q11.22;p11.3) was identified. This analysis was followed by flourescence in-situ hybridization(FISH) and array comparative genomic hybridization (aCGH). Finally, the patient's karyotype was identified as 46,X,der(Y)(qter→q11.221::p11.31→qter).ish der(Y) (qter+,pter-,SHOX+,SRY+,Ycen+,DYZ3+;DYZ1+,qter+).arrYq11.221q12(14,448,863-59,288,511) x2, Yp11.32p11.31(104,062-266,388) x0. It is proposed that de-novo derivative monocentric Y chromosome with duplicated region Y qter→q11.221::p11.31→qter with partial deletion of Yp PAR1 region most probably can perturb the conjugation of sex chromosomes during first meiotic division of spermatogenic arrested differentiation (development).

Keywords: FISH; aCGH; azoospermia; der(Y); intrachromosomal duplication and translocation; pseudoisomonocentric.

Figure 1

Cross-section of seminiferous tubules obtained from the testis biopsy of the azoospermic carrier of der(Y)(q11.221;p11.31). (A) Inhibited spermatogenesis at spermatocyte level and tubular hyalinization of lamina propria is visible. (B) In some tubules singular spermatozoa may appear (arrow). Scale bar = 20 μm (staining according to PAS method).

Figure 2

(A) G-bands on normal Y chromosome from control, fertile man. (B) G-bands on der(Y) chromosome of the azoospermic patient identified the duplication of the region q12-q11.2 and inverted translocation of this duplicated region to Ypter. (C) Scheme of normal Y chromosome. The arrows indicate the break points. (D) Scheme of der(Y)(q11.221;p11.31) showing the duplication of the region qter→q11.222∷p11.31→qter and inverted translocation to p11.31 with deletion of PAR1 region. (E) The DAPI image of der(Y) using Yq12 (DYZ3; green) and SHOX (gene specific; red) probes. Two green signals of Yq12 probe and one regularly red signal of SHOX probe showed the duplication of Yq12 region without the deletion of SHOX gene on Yp. (F) The DAPI image of der(Y) using Yq12 (DYZ3; green) and SRY (gene specific; red) probes. Two green signals of Yq12 probe and one regularly red signal of SRY probe showed the duplication of Yq12 region without the deletion of SRY gene on Yp. (G) The DAPI image of der(Y) using Y centromere (DYZ1; red) and Yq (subtelomere; green) probes. The der(Y) contains one regularly red centromere signal and there are visible two green signals because Y qter sequence was duplicated and translocated to Yp arm. (H) mBAND FISH signals (false colours) showed isomonocentric structure of der(Y). Multicolour-labelled profiles were obtained using XCyte Y mBAND probe kit (MetaSystems). DAPI = 4(,6-diamidino-2-phenylindole); FISH = fluorescence in-situ hybridization.

Figure 3

Graphical display of structural rearrangement detected by aCGH on Y chromosome in presented case of der(Y)) (q11.221;p11.31) azoospermic carrier. Probes with negative log ratio coloured as red (deleted 104,062–266,388, size = 162,327bp; 44 probes) and with positive log ratio coloured as navy blue (duplicated 14,448,863–59,288,511, size = 44,839,649bp; 1,045 probes) are encircled. The grey area presents the region which was duplicated and translocated to Yp11.31. aCGH = array comparative genomic hybridization.

Figure 4

The model of an incorrect reparation of the breaks in homologous chromatids of chromosome Y that led to the creation of the two rearranged chromatids which segregated to two different spermatids after second meiotic division in the presented case of der(Y)(q11.221;p11.31) azoospermic carrier.