Sperm fluorescence in situ hybridization study in nine men carrying a Robertsonian or a reciprocal translocation: relationship between segregation modes and high-magnification sperm morphology examination

Abstract

Objective: To evaluate whether observation of spermatozoa at × 6,100 magnification can distinguish between those with and without a balanced chromosomal content.

Design: Retrospective research study.

Setting: Genetics laboratory of a university hospital and in vitro fertilization center.

Patient(s): Six men carrying a reciprocal translocation and three men with a Robertsonian translocation.

Intervention(s): Sperm fluorescence in situ hybridization (FISH) with a specific set of three probes for each translocation for determining chromosomal content, performed on both unselected spermatozoa and on spermatozoa selected at × 6,100 magnification according to the Cassuto-Barak classification.

Main outcome measure(s): Chromosomal content in unselected and selected spermatozoa.

Result(s): Chromosomal translocations lead to gametes carrying either a balanced or an unbalanced karyotype in offspring and consequently to changes in chromosome position within sperm nucleus and potentially in nuclear morphology. In the unselected spermatozoa, the rate of chromosomally balanced nuclei ranged from 37.1% to 52.6% and from 70% to 88.6% in reciprocal and Robertsonian translocations, respectively, which is in agreement with published data. In selected spermatozoa, there was no statistically significant difference between the rates of segregation modes when compared with their frequencies in unselected sperm cells.

Conclusion(s): The observation of spermatozoa at high-magnification in translocation carriers cannot be used to select sperm cells with a balanced chromosomal content.