The fragile X-chromosome: an evaluation of the results in a routine cytogenetic laboratory in the period 1981-1986

Nuclear and chromosomal replication patterns in chorionic villi cells by bromodeoxyuridine labelling and DNA flow cytometry

Cell kinetics of chorionic villi (CV) were studied by BrdUrd-incorporation detected by fluorescence-plus-Giemsa and BrdUrd-antibody techniques, and by DNA flow cytometry. Growth characteristics of long-term cultures of CV resembled fibroblasts with a total cell cycle time of 26 h, final S phase of 9 h, penultimate S phase of 16 h and G2/M phase of 3-4 h. Especially useful for a quick routine diagnostic approach, Ultroser RG, a commercially available serum supplement, significantly increased cell proliferation and stabilized cell cycle lengths to a total cell cycle time of 14 h, final S phase of 7 h, penultimate S phase of 6 h and G2/M phase of 4 h. Moreover, mitotic activity steadily increased in cultured CV, when studying six successive subculturings. This reflects adaptation to the culture conditions rather than an inherent response of cultured CV cells of increasing passage numbers. Native villi exposed to BrdUrd immediately after biopsy show lower rates of uptake than do aliquots after overnight incubation. As shown by BrdUrd-pulse labelling studies, more than 7 h are required to overcome the proposed 'biopsy stress'. This correlates with routine diagnostic techniques, in which many more metaphase cells are observed in short-term cultures than in direct preparations.

Fragile X screening program in a Spanish region

In a Spanish region with a population of one million, we screened 371 mentally retarded males, who had no previous diagnosis for fragile X [fra(X))] syndrome. Fifty-three of the 371 males were fra(X) positive. Of these 44 of 362 or 12.1% were unrelated. Family studies identified a large number of obligate carriers and women at risk for being carriers who were given genetic counseling including prenatal diagnostic information. Considering the age of the carriers and the fertility rate, 23 affected males could be born to these women. The prevention potential of this program suggests that it is highly cost-effective.