HIGH-FREQUENCY OF DE-NOVO MUTATIONS IN ANKYRIN GENE (ANK1) IN CHILDREN WITH HEREDITARY SPHEROCYTOSIS

Objective: To evaluate the frequency of de novo monoallelic expression of the ANKI gene in hereditary spherocytosis individuals appearing as recessive. Study design: We studied 40 unrelated children with sphero cytosis and their normal parents. The genomic distribution of the anky rin (AC), dinucleotide repeats was evaluated in the patients showing c ombined ankyrin and spectrin deficiency. To search for the absence of mRNA derived from one of the two ANKI genes, cDNA from the heterozygou s patients was amplified using polymerase chain reaction. This was ana lyzed for the (AC), dinucleotide repeats. Results: Thirty-three heredi tary spherocytosis subjects had variable degrees of combined ankyrin a nd spectrin reduction; 19 were found to be heterozygous for the AC rep eat lengths and were further studied. In 12, we found a cDNA polymeras e chain reaction product from one ankyrin gene alone. These findings s trongly suggested the nonexpression of one of the two ANKI genes becau se of the de novo mutational events. Conclusion: The de novo loss of a n ankyrin allele expression is a frequent cause of hereditary spherocy tosis in children with normal parents. Therefore the category of genui nely recessive hereditary spherocytosis cases is further reduced compa red with spherocytosis cases because of de novo mutations. The determi nation of the (AC), microsatellite polymorphisms appears as a helpful and reliable tool for. the discrimination between these two categories .