Terry Fox Laboratory, BC Cancer Agency, Vancouver, British Columbia, Canada.
Clinic for Special Children, Strasburg, Pa.
J Allergy Clin Immunol. 2017 Oct;140(4):1120-1129.e1. doi: 10.1016/j.jaci.2016.11.051. Epub 2017 Jan 23.
Mutations in the long noncoding RNA RNase component of the mitochondrial RNA processing endoribonuclease (RMRP) give rise to the autosomal recessive condition cartilage-hair hypoplasia (CHH). The CHH disease phenotype has some overlap with dyskeratosis congenita, a well-known "telomere disorder." RMRP binds the telomerase reverse transcriptase (catalytic subunit) in some cell lines, raising the possibility that RMRP might play a role in telomere biology.
We sought to determine whether a telomere phenotype is present in immune cells from patients with CHH and explore mechanisms underlying these observations.
We assessed proliferative capacity and telomere length using flow-fluorescence in situ hybridization (in situ hybridization and flow cytometry) of primary lymphocytes from patients with CHH, carrier relatives, and control subjects. The role of telomerase holoenzyme components in gene expression and activity were assessed by using quantitative PCR and the telomere repeat amplification protocol from PBMCs and enriched lymphocyte cultures.
Lymphocyte cultures from patients with CHH display growth defects in vitro, which is consistent with an immune deficiency cellular phenotype. Here we show that telomere length and telomerase activity are impaired in primary lymphocyte subsets from patients with CHH. Notably, telomerase activity is affected in a gene dose-dependent manner when comparing heterozygote RMRP carriers with patients with CHH. Telomerase deficiency in patients with CHH is not mediated by abnormal telomerase gene transcript levels relative to those of endogenous genes.
These findings suggest that telomere deficiency is implicated in the CHH disease phenotype through an as yet unidentified mechanism.
线粒体 RNA 加工内切核糖核酸酶（RMRP）的长非编码 RNA RNase 成分中的突变导致常染色体隐性遗传疾病软骨毛发发育不全（CHH）。CHH 疾病表型与先天性角化不良症（一种已知的“端粒疾病”）有一些重叠。在某些细胞系中，RMRP 与端粒酶逆转录酶（催化亚基）结合，这使得 RMRP 可能在端粒生物学中发挥作用成为可能。
我们试图确定 CHH 患者的免疫细胞中是否存在端粒表型，并探讨这些观察结果的潜在机制。
我们通过对 CHH 患者、携带者亲属和对照受试者的原代淋巴细胞进行流式荧光原位杂交（原位杂交和流式细胞术）来评估增殖能力和端粒长度。通过使用定量 PCR 和 PBMC 和富集的淋巴细胞培养物中的端粒重复扩增方案，评估端粒酶全酶成分在基因表达和活性中的作用。
CHH 患者的淋巴细胞培养物在体外显示出生长缺陷，这与免疫缺陷细胞表型一致。在这里，我们表明 CHH 患者的原代淋巴细胞亚群的端粒长度和端粒酶活性受损。值得注意的是，当比较杂合 RMRP 携带者与 CHH 患者时，端粒酶活性以基因剂量依赖性方式受到影响。与内源性基因相比，CHH 患者的端粒酶缺乏并不是由异常的端粒酶基因转录水平介导的。
这些发现表明，端粒缺陷通过尚未确定的机制参与 CHH 疾病表型。
