Identification of novel pathogenic gene and genotype phenotype correlation in peroxisome biogenesis disorders

人类过氧化物酶体生物发生障碍（PBD）被细分为12个互补组（CG）。CG 8是其中较常见的一种，与不同的表型相关，从最严重的齐薇格综合征（ZS）到较温和的新生儿肾上腺脑白质营养不良（NALD）和婴儿雷夫苏姆病（IRD）。编码305个氨基酸的膜过氧化物酶的PEX26已被证明缺乏CG8。我们研究了8名CG8患者成纤维细胞中的PEX26基因型，其中4名为ZS表型，2名为NALD，2名为IRD。在所有这些细胞系中，过氧化氢酶主要是胞浆型的，但含有PTS1（SKL过氧化物酶体靶向序列）的蛋白质的输入是正常的。PEX 26的表达在所有八种细胞系中重新建立了过氧化物酶体，证实PEX 26缺陷在CG 8患者中具有致病性。当细胞在30℃下培养时，NALD和IRD表型患者的细胞系中过氧化氢酶输入恢复，但ZS表型患者的程度要小得多，表明温度敏感性与临床表型的严重程度成反比。鉴定了几种类型的突变，包括两名ZS患者的纯合G89R突变。这些PEX26突变在pex26中国仓鼠卵巢细胞中的表达导致与人类细胞系中的细胞表型相似的细胞表型。这些发现证实了PEX26细胞系中的温度敏感性程度可预测PEX26缺陷患者的临床表型。

The human disorders of peroxisome biogenesis (PBDs) are subdivided into 12 complementation groups(CGs). CG8 is one of the more common of these and is associated with varying phenotypes, ranging from the most severe, Zellweger syndrome(ZS), to the milder neonatal adrenoleukodystrophy(NALD) and infantile Refsum disease(IRD). PEX26, encoding the 305-amino-acid membrane peroxin, has been shown to be deficient in CG8. We studied the PEX26 genotype in fibroblasts of eight CG8 patientsfour with the ZS phenotype, two with NALD, and two with IRD. Catalase was mostly cytosolic in all these cell lines, but import of the proteins that contained PTS1, the SKL peroxisome targeting sequence, was normal. Expression of PEX26 reestablished peroxisomes in all eight cell lines, confirming that PEX26 defects are pathogenic in CG8 patients. When cells were cultured at 30℃, catalase import was restored in the cell lines from patients with the NALD and IRD phenotypes, but to a much lesser extent in those with the ZS phenotype, indicating that temperature sensitivity varied inversely with the severity of the clinical phenotype. Several types of mutations were identified, including homozygous G89R mutations in two patients with ZS. Expression of these PEX26 mutations in pex26 Chinese hamster ovary cells resulted in cell phenotypes similar to those in the human cell lines. These findings confirm that the degree of temperature sensitivity in pex26 cell lines is predictive of the clinical phenotype in patients with PEX26 deficiency.