A novel single-base substitution (c.1124A>G) that activates a 5-base upstream cryptic splice donor site within exon 11 in the human mitochondrial acetoacetyl-CoA thiolase gene

Mol Genet Metab. 2008 Aug;94(4):417-421. doi: 10.1016/j.ymgme.2008.04.014. Epub 2008 Jun 3.

Abstract

Most mutations related to aberrant splicing occur in conserved splice acceptor and donor sites. Some exonic mutations also affect splicing. We identified and characterized a point mutation (c.1124A>G) in an Australian patient (GK43) with mitochondrial acetoacetyl-CoA thiolase (T2) deficiency. GK43 is a homozygote of c.1124A>G, which activates a cryptic splice donor site 5 bases upstream from c.1124A>G within exon 11, causing aberrant splicing in most transcripts. The aberrant splicing results in c.1120-1163 (44-base) deletion, causing a frameshift in T2 mRNA. A mini-gene splicing experiment confirmed that the c.1124A>G substitution was responsible for this aberrant splicing. This cryptic splice site has a Shapiro and Senapathy score (70.0) in a normal sequence but if mutated, the score (84.3) becomes higher than the one in the authentic splice donor site of intron 11 (81.4). This is an example in which a point mutation activates a cryptic splice donor site motif that is used preferentially over a downstream authentic splice site.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetyl-CoA C-Acetyltransferase / genetics*
  • Acetyl-CoA C-Acetyltransferase / metabolism
  • Alternative Splicing*
  • Base Sequence
  • Cells, Cultured
  • Child, Preschool
  • DNA, Complementary / genetics
  • Exons*
  • Female
  • Fibroblasts / enzymology
  • Fibroblasts / physiology
  • Gene Expression
  • Humans
  • Metabolism, Inborn Errors / enzymology
  • Metabolism, Inborn Errors / genetics*
  • Mitochondria / enzymology*
  • Mitochondria / genetics
  • Point Mutation*
  • RNA Splice Sites*

Substances

  • DNA, Complementary
  • RNA Splice Sites
  • ACAT1 protein, human
  • Acetyl-CoA C-Acetyltransferase