No missense mutation in choroideremia patients analyzed to date.
OBJECTIVE
To elucidate the status of a previously described missense mutation (1442A>T) reported in the Rab Escort Protein 1 gene of a patient with choroideremia.


METHODS
The base substitution previously described by Donnelly et al. (Hum Mol Genet 1994;3:1017) was first confirmed by direct genomic DNA sequencing. The REP-1 cDNA region encompassing exons 10-14 was then specifically amplified from lymphocyte-derived mRNA. The effect on mRNA splicing of the mutation was analyzed by RT-PCR and cDNA sequencing.


RESULTS
The 1442A>T change located at the penultimate nucleotide of exon 11 causes complete skipping of this exon during the processing of REP-1 mRNA. Loss of exon 11 leads to the translation of a premature termination codon within exon 12.


CONCLUSIONS
RT-PCR analyses demonstrated that the 1442A>T transversion previously described as a possible causative missense mutation does act as a splice-site error and gives rise to a truncated REP-1 protein. The virtual absence of any missense mutation found to be responsible for choroideremia makes the RT-PCR-based protein truncation test the most relevant genotypic diagnostic procedure for identifying mutations in the CHM gene.
Institut de Biologie, Laboratoire de Biochimie Génétique, CNRS ERS 155, Montpellier, France.
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D048868:Adaptor Proteins, Signal Transducing; D019883:Alkyl and Aryl Transferases; D000595:Amino Acid Sequence / Q000235:genetics; D001483:Base Sequence / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D015794:Choroideremia / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D005784:Gene Amplification; D006801:Humans; D015151:Immunoblotting; D008214:Lymphocytes / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D010446:Peptide Fragments / Q000235:genetics; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D020691:rab GTP-Binding Proteins
D048868:Adaptor Proteins, Signal Transducing; C081787:CHM protein, human; D002352:Carrier Proteins; D018076:DNA, Complementary; D010446:Peptide Fragments; D012333:RNA, Messenger; D019883:Alkyl and Aryl Transferases; D020691:rab GTP-Binding Proteins