Mutation of the sterol 27-hydroxylase gene (CYP27) results in truncation of mRNA expressed in leucocytes in a Japanese family with cerebrotendinous xanthomatosis.

OBJECTIVES  A Japanese family with cerebrotendinous xanthomatosis (CTX) was investigated for a sequence alteration in the sterol 27-hydroxylase gene (CYP27). The expression of CYP27 has been mostly explored using cultured fibroblasts, prompting the examination of the transcripts from blood leucocytes as a simple and rapid technique.
METHODS  An alteration in CYP27 of the proband was searched for by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis and subsequent sequencing.
Samples of RNA were subjected to reverse transcription PCR (RT-PCR) and the product of the proband was amplified with nested primers and sequenced.
RESULTS  A homozygous G to A transition at the 5 end of intron 7 was detected in the patient.
In RT-PCR analysis, only a truncated transcript was detected in the patient, whereas both normal and truncated transcripts were detected in the siblings.
The sequencing of the patients cDNA fragment disclosed a direct conjuction of exon 6 and exon 8. CONCLUSION  The mutation at splice donor site and the truncation of mRNA were identical with those of a recently reported Italian patient, although different in symptomatology.
The application of blood leucocytes can be a simple technique on analysing a constructive abnormality of CYP27 mRNA.. 
