We report on the fragile site expression in lymphocytes from 16
Down syndrome (DS) men aged 24 to 52 years. Among rare fragile sites, 16q22 has been reported to be induced or enhanced by
alpha-interferon. Since DS cells have three copies of the receptor for
alpha-interferon, we hypothesized a possible enhancement of 16q22 expression. This fragile site has also been related to a specific rearrangement in M4
acute nonlymphocytic leukemia. In view of the high incidence of acute
leukemia in DS subjects, we studied the expression of 16q22 in lymphocyte cultures treated with
5-bromodeoxyuridine or
alpha-interferon. We also studied whether the repair deficiency of DS cells could affect the expression of
aphidicolin-induced fragile sites. The level of
chromosomal aberrations was compared with that found in
aphidicolin-treated cultures from 12 normal subjects of the same age. We found neither spontaneous or
BrdU-induced fragility at 16q22 nor induction by
alpha-interferon.
Chromosomal breakage rate was increased in
alpha-interferon-treated cultures in comparison with control cultures of the same subjects.
Aphidicolin-induced fragile sites expression in DS patients did not differ significantly from that found in the lymphocyte cultures from control subjects.