Prenatal detection of 46,XY,rec(5),dup q, inv(5)(p13q33) using DNA analysis, flow cytometry, and in situ hybridization to supplement classical cytogenetic analysis

Abstract

Distinguishing between balanced and unbalanced chromosome complements segregating from parental rearrangements may be difficult using only classical cytogenetic techniques if banding morphology is similar under both expectations. In these situations, supplementing cytogenetic analysis with molecular genetic techniques and flow cytometry may provide increased diagnostic accuracy. To illustrate this, we present a case in which similar band pattern morphology would be expected for both the balanced carrier (heterozygote) and the recombinant dup q chromosome complements segregating from a mother with a balanced inversion [46,XX,inv(5)(p13q33)]. The parents came to Northwestern for consultation after receiving conflicting interpretations of their first amniotic fluid cultures. An ultrasound examination was said to be normal. They inquired whether there were ways to increase their confidence that the complement was unbalanced. Their reluctance to terminate the pregnancy was due to a 6-year history of infertility. After extensive counselling, the couple elected repeat amniocentesis. Further cytogenetic analysis of repeat amniotic fluid cultures by G-banding and R-banding, molecular genetic analysis with highly polymorphic DNA probes, and quantitative flow cytometry were performed. Results agreed that an unbalanced fetal complement was present. Southern blot analysis with a 5p marker definitively demonstrated a lack of maternal 5p material in the fetus, and in situ hybridization showed a 5q marker at either end of the recombinant chromosome. Flow cytometry was consistent with this interpretation. Because of the advanced gestational age, the parents elected to terminate based on cytogenic results of the second amniocentesis, rather than to wait another 1-2 weeks for results of other methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial monosomy 5p and partial trisomy 5q due to paternal pericentric inversion 5(p15.1q35.1)

“…Epstein (1986) suggested that the effects of double segmental aneuploidy could be classified into the following three general categories: 1) one in which the phenotype derives completely or almost completely from that of one of the segmental aneuploidies; 2) one characterized by the presence of some of the features of each of the contributing imbalances; 3) those cases in which the phenotype is a reasonable composite of the individual segmental aneuploid phenotype. Since all the patients excluding two cases (Schroeder et al, 1986;Martin et al, 1988), as well as our case, showed clinical features of partial monosomy 5p and partial trisomy 5q, this double segmental aneuploidy can be classified as a third composite phenotype category which was termed by Carlin and Norman (1978) as a "phenotype hybrid." Among the features noted in our case, severe and complex heart abnormalities, and inguinal hernia were occasioned by partial trisomy 5q, whereas the cat-like cry and dermatoglyphics were presumed to caused by partial monosomy 5p (Beemer et al, 1984).…”

“…So far, six cases in four families (Faed et al, 1972;Ebbin et al, 1979;Beemer et al, 1984;Schroeder et al, 1986) and one fetus (Martin et al, 1988) with partial monosomy 5p and trisomy 5q due to parental pericentric inversion of chromosome 5 have been reported (Table l). Epstein (1986) suggested that the effects of double segmental aneuploidy could be classified into the following three general categories: 1) one in which the phenotype derives completely or almost completely from that of one of the segmental aneuploidies; 2) one characterized by the presence of some of the features of each of the contributing imbalances; 3) those cases in which the phenotype is a reasonable composite of the individual segmental aneuploid phenotype.…”

“…Although too few cases are reported for exact estimates, reasons advanced have been that male carriers might be more fertile than female carriers (Faed et al, 1972). Furthermore it was suggested that when the mother is heterozygous this inversion may be associated with infertility (Martin et al, 1988). Although there might be some exceptions, small inversions generally have a much better genetic prognosis than large inversions.…”

Bivariate flow karyotyping of human chromosomes: Evaluation of variation in Hoechst 33258 fluorescence, chromomycin A3 fluorescence, and relative chromosomal DNA content

“…For chromosomes 14,15,18,19,21,22, and the Y chromosome, the contribution of biological variation to the total variation of HO and/or CA fluorescence is more evident (Table 3). Nevertheless, for most chromosomes our results on the total variation in peak positions are in agreement with the variation in peak position and chromosome length, obtained in other flow cytometric and cytogenetic studies (9,11,24,29).…”

Semi‐automated detection of aberrant chromosomes in bivariate flow karyotypes

“…Bivariate flow karyotyping of human chromosomes has proven to be a helpful tool in the cytogenetic study of congenital and other diseases (1, 2, 5, 9, 14,16,17,24). It can be used to detect several types of aberrations: (1) numerical changes, (2) most nonreciprocal translocations, (3) most reciprocal translocations that exchange different length chromosome segments or equal size segments with different quantities of HO and CA bands, and (4) chromosomal deletions or inse tions.…”