A novel mutation causing an aberrant splicing in the protein 4.2 gene associated with hereditary spherocytosis (protein 4.2Notame).

We investigated a Japanese patient with protein 4.2 deficiency. SDS-PAGE showed a complete deficiency of protein 4.2, while Western blot analysis revealed a marked decrease in the amount of protein 4.2, and the existence of a doublet of 74 and 72 kDa bands. Direct sequencing and dot-blot hybridization with allele-specific oligonucleotide probes indicated that the proband was compound heterozygous for a missense mutation in codon 142 with Ala-->Thr (GCT-->ACT) and a single nucleotide substitution (G-->A) of the first base of intron 6 (G-->A) of the protein 4.2 gene. The former is the commonest mutation observed in cases of protein 4.2 deficiency, whereas the latter is a novel mutation, located within the consensus sequence of the 5' splicing site (AGGU) (Protein 4.2Notame). RT-PCR analysis using total RNA isolated from reticulocytes of the proband revealed that the intron 6 donor site mutation causes an abnormal splicing; exon 6 is spliced out with intron 6. The abnormal mRNA has a premature termination codon, as the result of a frameshift, and this instability may lead to degradation. Thus, there is a close relation between this mutation and the molecular pathogenesis of protein 4.2 deficiency.