HUMAN PEROXISOME ASSEMBLY FACTOR-II (PAF-2) - A GENE RESPONSIBLE FOR GROUP-C PEROXISOME BIOGENESIS DISORDER IN HUMANS

Peroxisome-biogenesis disorders (FED) are genetically heterogeneous an d can be classified into at least ten complementation groups. We recen tly isolated the cDNA for rat peroxisome assembly factor-2 (PAF-2) by functional complementation using the peroxisome-deficient Chinese-hams ter-ovary cell mutant, ZP92. To clarify the novel pathogenic gene of P BD, we cloned the full-length human PAF-2 cDNA that morphologically an d biochemically restores peroxisomes of group C Zellweger fibroblasts (the same as group 4 in the Kennedy-Krieger Institute) and identified two pathogenic mutations in the PAF-2 gene in two patients with group C Zellweger syndrome. The 2,940-bp open reading Game of the human PAF- 2 cDNA encodes a 980-amino-acid protein that shows 87.1% identity with rat PAE-2 and also restored the peroxisome assembly after gene transf er to fibroblasts of group C patients. Direct sequencing of the PAF-2 gene revealed a homozygous 1-bp insertion at nucleotide 511 (511 insT) in one patient with group C Zellweger syndrome (ZS), which introduces a premature termination codon in the PAF-2 gene, and, in the second p atient, revealed a splice-site mutation in intron 3 (IVS3+1G-->A), whi ch skipped exon 3, an event that leads to peroxisome deficiency. Chrom osome mapping utilizing FISH indicates that PAF-2 is located on chromo some 6p21.1. These results confirm that human PAF-2 cDNA restores pero xisome of group C cells and that defects in the PAF-2 produce peroxiso me deficiency of group C PBD.