QUANTITATIVE-ANALYSIS OF CONSTITUTIVE HETEROCHROMATIN IN COUPLES WITHFETAL WASTAGE

PROBLEM: Heteromorphism of constitutive heterochromatin is a stable ev olutionary feature that is thought to cause no phenotypic alterations. Nevertheless, the role of constitutive heterochromatin is still unkno wn. The instability of constitutive heterochromatin was generally rest ricted to T-lymphocytes and was associated with variable immunodeficie ncy. The heterochromatin regions of chromosomes 1, 9, 16, and Y have b een postulated to play a role in the immune response and during early embryo development. METHOD OF STUDY: To investigate a possible influen ce of constitutive heterochromatin in human reproductive ability, quan titative 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 abortio ns as the only pregnancy outcomes, and the second group included coupl es with a stillborn child with or without malformations. In the contro l group were couples with one or more healthy children without a histo ry of fetal wastage. All of the persons in this study had normal karyo types. The amount of constitutive her erochromatin was expressed by re lative 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 chro mosome 16 homologue pair in males and females with a stillborn or a st illborn malformed child (P < 0.01) and an increase in total heterochro matin cell content compared to controls (P = 0.005). The same couples had significantly increased mean maximal heterochromatin content in th e potential zygotes (P < 0.02). The couples who experienced spontaneou s abortions only had a minimal total heterochromatin content in the po tential zygotes (P < 0.05). The Y/F index was significantly lower in t he males in both groups compared to controls (Pi < 0.02; P2 < 0.02). C ONCLUSION: The quantitative analysis of constitutive heterochromatin c ould be valuable in predicting pregnancy outcome.