Quantitative analysis of constitutive heterochromatin in couples with fetal wastage.

PROBLEM

Heteromorphism of constitutive heterochromatin is a stable evolutionary feature that is thought to cause no phenotypic alterations. Nevertheless, the role of constitutive heterochromatin is still unknown. The instability of constitutive heterochromatin was generally restricted to T-lymphocytes and was associated with variable immunodeficiency. The heterochromatin regions of chromosomes 1, 9, 16, and Y have been postulated to play a role in the immune response and during early embryo development.

METHOD OF STUDY

To investigate a possible influence of constitutive heterochromatin in human reproductive ability, quantitative analysis of constitutive heterochromatin in human chromosomes 1, 9, 16 and Y was done. Thirty couples were divided into two groups, owing to the clinical heterogeneity of their reproductive disorders. The first group included couples with two or more spontaneous abortions as the only pregnancy outcomes, and the second group included couples with a stillborn child with or without malformations. In the control group were couples with one or more healthy children without a history of fetal wastage. All of the persons in this study had normal karyotypes. The amount of constitutive heterochromatin was expressed by relative value using the simple transformation [q/(p + q)]. This value, obtained on GTG-banded metaphase chromosomes, represented an indirect measure of heterochromatin content. The Y/F index was used to express the relative amount of heterochromatin in chromosome Y.

RESULTS

There was a significant increase in the heterochromatin content of the chromosomes 16 homologue pair in males and females with a stillborn or a stillborn malformed child (P < 0.01) and an increase in total heterochromatin cell content compared to controls (P = 0.005). The same couples had significantly increased mean maximal heterochromatin content in the potential zygotes (P < 0.02). The couples who experienced spontaneous abortions only had a minimal total heterochromatin content in the potential zygotes (P < 0.05). The Y/F index was significantly lower in the males in both groups compared to controls (P1 < 0.02; P2 < 0.02).

CONCLUSION

The quantitative analysis of constitutive heterochromatin could be valuable in predicting pregnancy outcome.