Age-related effects on sex chromosome aberrations in equine spermatozoa

Abstract

Many chromosomal anomalies resulting from meiotic disorders lead to the formation of gametes that are incapable of reproductive function and are spontaneously eliminated. However, formation of a zygote with structurally or numerically abnormal genome most often produces a lethal effect early in fetal life. If an animal with a chromosome aberration is born, it often has various developmental defects, including those that reduce fertility or cause infertility. Evaluation of sex cells or embryos is greatly enhanced by the use of fluorescence in situ hybridization (FISH) in the analyses. In most studies, the assessment of sperm maturity is based on fluorescent staining, which may be inadequate for diagnosing aneuploidy. FISH, which has most often been used to study human oocytes and embryos, makes it possible to determine the type of chromosomal aberration (Martini E et.al., et. al. Hum Reprod 12, 20111-2018, 1997) and provides answers to the origin of aneuploidy. Fluorescence in situ hybrydization is rarely used in the assessment of horse germ cells (Bugno M et al. Reprod Domest Anim. 45, 1015– 1019, 2010; Bugno-Poniewierska M et al. Reprod Domest Anim. 46 (5): 787-792, 2011). The aim of this study was a cytogenetic analysis of stallion semen to find sex chromosome aberrations and to determine if there was an association with stallion age. Samples were collected from 31 stallions 3-23 years old. FISH was performed using molecular painting probes for the sex chromosomes, obtained by microdissection and a BAC probe with epidermal growth factor receptor (EGFR) gene (a gene-specific probe for a pair of autosomes). Among the analyzed sperm cells, there were 51.0836 % with X, 47.983% with Y and 1.031% with aberrant chromosomes: nullisomy (1.22%), XY aneuploidy (0.367%), XX disomy (0.173%), YY disomy (0.034%), diploidy (0.029%)