Multicolor fluorescence in situ hybridization analysis of the spermatozoa of a male heterozygous for a reciprocal translocation t(11;22)(q23;q11).

A reciprocal translocation between chromosomes 11 and 22 is a site-specific translocation that has been seen in many families with no common ancestry. This translocation is of particular interest because balanced carriers have a 0.7-3.7% risk of having children with the supernumerary der(22), resulting from a 3:1 segregation. We have used a three color fluorescence in situ hybridization (FISH) with specific DNA probes to determine the chromosome segregation pattern of a male carrier of a translocation t(11;22)(q23;q11). The probes selected included a centromeric marker for chromosome 11, a marker closely linked to the centromere of chromosome 22, and a third probe distal to the translocation breakpoint of chromosome 22. The results showed that 3:1 segregation is preferential in this patient, with 40.1% of spermatozoa belonging to this segregation type. Alternate segregation followed with 27.4% of analyzed spermatozoa; 17.6% resulted from adjacent 1 and 12.5% resulted from adjacent 2 segregation. We detected 0.5% of presumably diploid spermatozoa. Complementary adjacent 1 products were observed at statistically different frequencies (P = 0.02). Complementary adjacent 2 products without recombination in the interstitial segments were also seen at different frequencies (P = 0.002). In 3:1 segregation, the products containing one chromosome were observed more frequently than those with three chromosomes (P = 0.0001). The 24,+der(22) gamete was seen more frequently than all of the other gametes combined which had 24 chromosomes resulting from 3:1 segregation. The results of this study demonstrate that in this t(11;22) carrier, 3:1 segregation is preferential but not exclusive.

Meiotic products of a Klinefelter 47,XXY male as determined by sperm fluorescence in-situ hybridization analysis.

The meiotic segregation of 24 spermatozoa obtained from a 47,XXY male is described. Three-colour fluorescence in-situ hybridization with probes for chromosomes X, Y and 18 was used. Five spermatozoa carried an X chromosome, seven carried a Y, six had an XY gonosomal complement, five were missing the sex chromosome and one spermatozoon was presumably diploid with an XX/1818 complement. Our results support the hypothesis that XXY cells are able to complete meiosis. In this patient, the percentage of spermatozoa with an abnormal number of sex chromosomes increased from 1/6 (17%) among spermatozoa with normal morphology to 11/18 (61%) in spermatozoa with abnormal morphology.

Meiotic products of two reciprocal translocations studied by multicolor fluorescence in situ hybridization.

The sperm products of two male carriers of reciprocal translocations were studied by fluorescence in situ hybridization (FISH) using a combination of three probes for each translocation. One patient carried a t(2;18)(p21;q11.2), the other a t(8;9)(q24.2;q32). The probes selected included a centromeric marker for each chromosome involved in the translocation plus a third probe distal to the translocation breakpoint of one of the translocation chromosomes. This assay identifies alternate, adjacent 1, adjacent 2, and 3:1 types of meiotic products. It allows the identification of recombination events and also estimation of the frequency of diploidy. For the t(2;18), the frequency of normal and balanced sperm and of adjacent 1, adjacent 2, and 3:1 products was 43.6%, 29. 8%, 10.5%, and 12.8%, respectively. Similar segregation patterns had been reported for this donor by direct sperm karyotyping of sperm cells. For the t(8;9), the frequency of normal and balanced sperm and of adjacent 1, adjacent 2, and 3:1 products was 44.4%, 41%, 3.1%, and 9.4%, respectively. The frequency of complementary adjacent 1 products was statistically different in both the t(2;18) (P < 0. 0001) and the t(8;9) (P < 0.0001) carrier. When the number of adjacent 2 products with one translocation chromosome (regardless of normal or derivative) was compared to the number of adjacent 2 products with the second translocation chromosome (again, regardless of normal or derivative), no statistical difference was noted for either the t(2;18) (P = 0.32) or the t(8;9) (P = 0.69). Recombination events within the interstitial segment of chromosome 2 were statistically higher than those seen in chromosome 18 (P < 0. 0001), whereas in chromosomes 8 and 9, recombination in the interstitial segments was similar (P = 0.64). The rate of diploidy was similar in both the t(2;18) (0.5%) and the t(8;9) (0.6%). Thus, FISH provides chromosome information on the sperm products produced by translocation carriers, although it cannot provide an assessment of the full chromosome complement of the spermatozoon.

The meiotic segregation pattern of a reciprocal translocation t(10;12)(q26.1;p13.3) by fluorescence in situ hybridization sperm analysis.

The meiotic segregation of chromosomes 10 and 12 was analyzed in a male heterozygous for a reciprocal translocation, t(10;12)(q26.1;p13.3), using fluorescence in situ hybridization (FISH). Centromeric specific probes that detect alpha satellite sequences of chromosomes 10 and 12 were used. A total of 10,049 spermatozoa were analyzed. The frequencies of alternate/adjacent 1, adjacent 2, and 3:1 modes of segregation were: 84.25, 10.95%, and 4.42%, respectively. Diploidy was present in 0.23% of spermatozoa. Similar segregation patterns have been reported for this donor by direct karyotyping of sperm cells. FISH is a valuable technique for studying meiotic segregation patterns in that larger samples can be studied in a relatively short time. However, it does not provide information on the full chromosome complement of the spermatozoon.