Familial Infertility (Azoospermia and Cryptozoospermia) in Two Brothers-Carriers of t(1;7) Complex Chromosomal Rearrangement (CCR): Molecular Cytogenetic Analysis.

Marta Olszewska,Maciej Kurpisz,Danuta Zastavna,Nijole Pollock,Nataliya Huleyuk,Andrew Georgiadis,Alexander N Yatsenko,Tomasz Stokowy,Svetlana Yatsenko

doi:10.3390/ijms21124559

Abstract

Structural aberrations involving more than two breakpoints on two or more chromosomes are known as complex chromosomal rearrangements (CCRs). They can reduce fertility through gametogenesis arrest developed due to disrupted chromosomal pairing in the pachytene stage. We present a familial case of two infertile brothers (with azoospermia and cryptozoospermia) and their mother, carriers of an exceptional type of CCR involving chromosomes 1 and 7 and three breakpoints. The aim was to identify whether meiotic disruption was caused by CCR and/or genomic mutations. Additionally, we performed a literature survey for male CCR carriers with reproductive failures. The characterization of the CCR chromosomes and potential genomic aberrations was performed using: G-banding using trypsin and Giemsa staining (GTG banding), fluorescent in situ hybridization (FISH) (including multicolor FISH (mFISH) and bacterial artificial chromosome (BAC)-FISH), and genome-wide array comparative genomic hybridization (aCGH). The CCR description was established as: der(1)(1qter->1q42.3::1p21->1q42.3::7p14.3->7pter), der(7)(1pter->1p2 1::7p14.3->7qter). aCGH revealed three rare genes variants: ASMT, GARNL3, and SESTD1, which were ruled out due to unlikely biological functions. The aCGH analysis of three breakpoint CCR regions did not reveal copy number variations (CNVs) with biologically plausible genes. Synaptonemal complex evaluation (brother-1; spermatocytes II/oligobiopsy; the silver staining technique) showed incomplete conjugation of the chromosomes. Associations between CCR and the sex chromosomes (by FISH) were not found. A meiotic segregation pattern (brother-2; ejaculated spermatozoa; FISH) revealed 29.21% genetically normal/balanced spermatozoa. The aCGH analysis could not detect smaller intergenic CNVs of few kb or smaller (indels of single exons or few nucleotides). Since chromosomal aberrations frequently do not affect the phenotype of the carrier, in contrast to the negative influence on spermatogenesis, there is an obvious need for genomic sequencing to investigate the point mutations that may be responsible for the differences between the azoospermic and cryptozoospermic phenotypes observed in a family. Progeny from the same parents provide a unique opportunity to discover a novel genomic background of male infertility.

Highlights

Infertility affects approximately 10–18% of couples of reproductive age [1,2,3]
There are multiple reasons for male infertility, including genetic factors, which determine approximately 10–15% of revealed diminished fertility cases; and approximately 25% of infertile males are diagnosed as idiopathic [1,5,6]
Detailed cytogenetic analysis showed that chromosome 1 had two breakpoints: (i) at the short arm 1p, the suggested breakpoint region was 1p21, and (ii) at the long arm 1q in a band 1q42.3

Summary

Introduction

Infertility affects approximately 10–18% of couples of reproductive age [1,2,3]. It is estimated that approximately 7% of men and 12% of women worldwide are affected and approximately 40–60% of all infertility cases originate from the male side [4,5]. There are multiple reasons for male infertility, including genetic factors, which determine approximately 10–15% of revealed diminished fertility cases; and approximately 25% of infertile males are diagnosed as idiopathic (unexplained etiology) [1,5,6]. The frequency of all chromosomal aberrations detected in the lymphocytes of fertile males is about 0.7%, while in infertile men this increases five-fold [9]. In a population of infertile males, the probability of chromosome aberrations is several times higher when compared to the whole population (i.e., for RCT: 1% of infertile males are carriers, while in oligozoospermia, RCTs are approximately 16% of all identified aberrations; in azoospermia cases, this value is about 4%) [3]. The frequency of chromosomal aberrations in males with azoospermia rises to 20% [2]

Objectives

Methods

Results