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Over the past 50 years, many advances in our understanding of the general principles controlling gene expression during hematopoiesis have come from studying the synthesis of hemoglobin. Discovering how the alpha- and beta-globin genes are normally regulated and documenting the effects of inherited mutations that cause thalassemia have played a major role in establishing our current understanding of how genes are switched on or off in hematopoietic cells. Previously, nearly all mutations causing thalassemia have been found in or around the globin loci, but rare inherited and acquired trans-acting mutations are being found more often. Such mutations have demonstrated new mechanisms underlying human genetic disease. Furthermore, they are revealing new pathways in the regulation of globin gene expression that, in turn, may open up new avenues for improving the management of patients with common types of thalassemia.

Summary: Benign familial infantile seizures (BFIS) is a clinical entity characterized by focal seizures with or without secondary generalization, occurring mostly in clusters, and usually first seen between 4 and 8 months of life. Psychomotor development is normal, and seizures usually resolve within the first year of life. BFIS is a genetically heterogenous condition with loci mapped to chromosomes 19 and 16. Mutations in the voltage-gated sodium channel α2 subunit (SCN2A) gene on chromosome 2 were recently identified in families affected by neonatal and infantile seizures (benign familial neonatal–infantile seizures, BFNIS) with typical onset before 4 months of life. The identification of SCN2A mutations in families with only infantile seizures indicated that BFNIS and BFIS show overlapping clinical features. We report a pedigree showing three affected individuals over three generations. All subjects experienced clusters of focal seizures with or without secondary generalization and onset between 4 and 12 months of life. Response to antiepileptic drugs and the outcome were good. No subjects had other forms of epilepsy later in the life. Neonatal or febrile seizures did not occur in the family. Genetic study in this family revealed a novel heterozygous mutation c.3003 T>A in the SCN2A gene. Comparative analysis of different sodium channel α subunits indicates that the mutated residue is highly conserved throughout the evolution, suggesting an important functional role for this domain. Additional families with the infantile form of benign familial seizures should be investigated to corroborate that BFIS and BFNIS may share the same genetic abnormality.

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.