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We attempted to demonstrate a relation between a loss of replication control, centromere dysfunction, and predisposition to non-disjunction. Couples with a Down syndrome offspring were the high-risk probands. One-color FISH (fluorescent in-situ hybridization) was applied to interphase nuclei (lymphocytes). Replication pattern of two pairs of alleles, RB-1 and 21q22, were studied, and the rate of aneuploidy was estimated using two alpha-satellite probes of chromosomes 8 and 18. Our results suggest the existence of an association between replication timing and the rate of non-disjunction. A higher rate of allele asynchrony and aneuploidy was found in older women and in mothers of a Down syndrome offspring. These findings may reflect a predisposition for meiotic non-disjunction in these women.

A 31 years old women underwent amniocentesis because of increased risk for Down syndrome on biochemical screen. Her previous pregnancy ended in a spontaneous abortion. The Karyotype was 46, XY/47, XY, +21, inv(9) with a mosaicism rate of 45%. The husband, which was known to have oligo-terato-asteno-spermia on semen analysis, had a karyotype 46, XY, inv(9)(q11; 13)9qh+. Mono and dual color FISH was applied to his sperm as well as to sperm of normal controls, using centromer probes for 8, 9, 18, 21, X and Y. In this man with inv9 and 9qh+ the rate of disomy was significantly higher then in normal controls for all probes tested (p

The relatively high activity of arylsulphatase C (ASC) in the placenta is a potential risk for the misdiagnosis of arylsulphatase A (ASA) or arylsulphatase B (ASB) deficiency in chorionic villus sampling when assayed by synthetic substrates. A clear distinction between these enzymes can be achieved in either the direct villi or the cultured villi cells. Interestingly, the activity of ASC differed significantly in cultured villi cells when prepared by two different methods, namely, minced villi versus treatment with trypsin and collagenase, while ASA and ASB were not affected by these treatments. Whether ASC was directly affected by one of these treatments or whether a selection of cells with different ASC levels was achieved is not yet clear, but this phenomenon clearly indicates the importance of precise definition of CVS preparations to correlate with the enzyme activity data.