Germinal HPRT splice donor site mutation results in multiple RNA splicing products in T-lymphocyte cultures

We have used peripheral blood T-lymphocyte cultures to analyze the hprt mutation in two Lesch-Nylan syndrome males who are cousins and to confirm the carrier status of female members of the family. Both cDNA and genomic DNA sequencing studies show that this patient carries a hitherto undescribed single base deletion in the exon 5 donor splice site sequence (15: +/- 1, Delta G, base number 31635), The largest cDNA product contained all nine hprt exons plus an insertion of 66 bases of intron 5, consistent with the use of a cryptic splice site in intron 5 (aag(67)/gtaagc). This splicing error would result in a chain terminating codon immediately after exon 5 (15:2-4, taa) and predicts a polypeptide of 133 amino acids, This loss of the normal splice donor site also results in multiple hprt mRNA species, combining the use of the cryptic splice site in intron 5 and splicing errors involving exons 2-6. In addition to defining a new Lesch-Nylan mutation (hpTt(Henryville)), these results provide insight into aberrant splicing of hprt mRNA in T-lymphocytes.