Analyses of genetic abnormalities in type I CD36 deficiency in Japan: identification and cell biological characterization of two novel mutations that cause CD36 deficiency in man

Abstract.

To elucidate genetic abnormalities in type I CD36 deficiency, we analyzed 28 Japanese subjects whose platelets and monocytes/macrophages lacked CD36 on their surface. We identified two novel mutations in the CD36 gene. One was a complex deletion/insertion mutation, in which 3 bp, GAG, were deleted at nucleotide (nt) 839–841, and 5 bp, AAAAC, were inserted at the same position (839–841del→insAAAAC). Mutation 839–841del→insAAAAC led to a frameshift and appearance of a premature stop codon; it was also accompanied with a marked reduction in the amount of CD36 mRNA. The other was a 12-bp deletion at nt 1438–1449 (1438–1449del) accompanied with or without skipping of exon 9 (nt 959–1028). Mutation 1438–1449del led to an inframe 4-amino-acid deletion, whereas exon 9 skipping led to a frameshift and the appearance of a premature stop codon. Expression assay revealed that both 1438–1449del and exon 9 skipping directly caused impairment of the surface expression of CD36. A survey of the five known mutations including 839–841del→insAAAAC and 1438–1449del in type I CD36-deficient subjects demonstrated that the five mutations covered more than 90% of genetic defects among them and that the substitution of T for C at nt 478 (478C→T) was the most common mutation with more than 50% frequency. However, none of the four subjects that possessed isoantibodies against CD36 had 478C→T, suggesting that 478C→T prevents the production of isoantibodies against CD36.