Sperm analysis in a subfertile male with a Y;16 translocation, using four-color FISH

Sperm analysis was performed in a male with oligoasthenoteratozoospermia (OAT) and a reciprocal t(Y;16) (q11. 21;q24), using four-color FISH. Intracytoplasmic sperm injection (ICSI) treatment in this patient had resulted in the birth of one chromosomally balanced and two chromosomally normal children. To assess the risk of having a chromosomally unbalanced conception after ICSI, morphologically normal spermatozoa were studied with a set of probes allowing detection of all segregation variants. There were 51% normal or balanced sperm cells. The fraction of sperm products resulting from alternate and adjacent I segregation was 87%, 12% were products of 3:1 disjunction, and the other 1% had other types of aneuploidy. If morphologically abnormal cells were also included in the FISH analysis, nearly 90% of all the spermatozoa were unbalanced. We conclude that although the majority of males with a Y/autosome translocation are infertile due to azoospermia, our patient produces sufficient morphologically and chromosomally normal spermatozoa to have chromosomally normal or balanced offspring after ICSI. Assuming that ICSI with an unbalanced spermatozoon from this patient would result in a nonviable embryo in many cases, the combination of in vitro and subsequent in vivo selection probably results in a risk of unbalanced offspring of much less than 50%. Hence, FISH studies on the sperm of translocation carriers are useful for estimating the risk of having unbalanced offspring after ICSI and in understanding the mechanisms underlying infertility in such carriers.