Meiotic segregation analysis in male translocation carriers by using fluorescent in situ hybridization

Balanced reciprocal and Robertsonian translocations are the most common structural chromosome abnormalities in humans, with incidences of 0.7 and 1.23 per 1000. These translocations can affect fertility and/or pregnancy outcome because of possibly impaired production of gametes with an unbalanced zygote caused by the parental arrangement. Fertility problems in male translocation carriers are because of various degrees of sperm alterations that are directly related to the disturbance of the meiotic process. Investigation of human sperm chromosomes was performed by karyotyping spermatozoa after penetration of zona-free hamster oocytes, karyotype analysis now being possible to analyse the segregation patterns by using fluorescent in situ hybridization (FISH). Here, we document the results of meiotic segregation analysis for four Robertsonian and four reciprocal translocation carriers by FISH. In the sperm of Robertsonian translocation males, the majority of spermatozoa were normal/balanced. On the other hand, males with reciprocal translocations demonstrated a high rate of unbalanced spermatozoa of about 50% on meiotic segregation, with an unusually high rate (23.5%) of 3 : 1 segregation. This knowledge can be used for genetic counselling of families with these types of translocations.