Monosomy 21 in a human spontaneous abortus. Morphogenetic disturbances and phenotype at the cellular level.

Complex investigation of a spontaneous abortus with monosomy 21 was carried out. Phenotypic expression at the organism and tissue level was characterized by the pathology of the external form of the embryo and by abnormalities of the embryonic facial structures, the stomodeum, the anterior part of the primary gut, and neural tube development. The anomalies found in the embryo indicate primary morphogenetic disturbances arising at the initial stage of organogenesis. Investigation of LHC-431 strain cells derived from musculocutaneous embryonic fragments revealed a complex of cytophenotypic alterations similar to the cellular syndrome of trisomic cells and indicating an insufficient biologic maturity of the mutant cells (alterations of cellular form, disturbances in their contact orientation, underdevelopment of fibrillar apparatus and decreased collagen formation, changes in the accumulation of intracellular metabolic products, decreased growth capacity and alterations of mitotic cycle parameters). It was found that the single chromosome 21 takes part in assocations twice as frequently as would theoretically be expected.