Department of Biochemistry and Molecular Biology, Nippon Medical School, Tokyo, Japan.
Department of Hematology, Nippon Medical School, Tokyo, Japan.
Int J Lab Hematol. 2020 Jun;42(3):316-321. doi: 10.1111/ijlh.13176. Epub 2020 Mar 9.
A cryptic form of dyskeratosis congenita (cDKC) has a gradual onset without the characteristic physical findings of DKC. cDKC is distinguished from other forms of bone marrow failure (BMF) through analysis of telomere shortening and gene mutations. Mutations in the telomerase reverse transcriptase (TERT) and telomere RNA component (TERC) genes have been detected in most Japanese cDKC patients. Therefore, we investigated the impact of each TERT and TERC mutation on telomerase activity.
TERT and TERC mutants observed in DKC or cDKC patients were transfected into Saos-2 or VA13+TERT (TERT-expressing VA13 cells) cells to measure telomerase activity.
Telomerase activity in cells expressing a mutant detected in cDKC patients was significantly lower (P < .0001) than in cells expressing the wild-type genes. In addition, some TERT mutations seen in cDKC (p.P632R, p.T726M) caused weaker (P = .0013) suppression of telomerase activity than others (p.G106W and p.G682D). In contrast, telomerase activity in cells expressing a TERT or TERC mutant detected in DKC patients did not significantly differ from cells expressing the wild-type genes.
These findings suggest that TERT and TERC mutations detected in cDKC patients could potentially contribute to the pathogenesis of cDKC by blocking telomerase activity. However, TERT and TERC mutations detected in DKC patients did not affect telomerase activities, which means studying the telomerase activity of mutants are not always useful for the diagnosis of DKC.
先天性角化不良（cDKC）的一种隐匿形式发病较缓，没有 DKC 的典型临床表现。通过端粒缩短和基因突变分析，cDKC 与其他骨髓衰竭（BMF）形式相区别。在大多数日本 cDKC 患者中，已经检测到端粒酶逆转录酶（TERT）和端粒 RNA 成分（TERC）基因突变。因此，我们研究了每个 TERT 和 TERC 突变对端粒酶活性的影响。
在 DKC 或 cDKC 患者中观察到的 TERT 和 TERC 突变体被转染到 Saos-2 或 VA13+TERT（表达 TERT 的 VA13 细胞）细胞中，以测量端粒酶活性。
cDKC 患者中表达的突变体的细胞中的端粒酶活性明显较低（P<0.0001），而野生型基因表达的细胞中的端粒酶活性较高。此外，cDKC 中观察到的一些 TERT 突变（p.P632R、p.T726M）导致的端粒酶活性抑制作用比其他突变（p.G106W 和 p.G682D）弱（P=0.0013）。相比之下，在 DKC 患者中表达的 TERT 或 TERC 突变体的细胞中的端粒酶活性与表达野生型基因的细胞中的端粒酶活性没有显著差异。
这些发现表明，cDKC 患者中检测到的 TERT 和 TERC 突变可能通过阻断端粒酶活性导致 cDKC 的发病机制。然而，在 DKC 患者中检测到的 TERT 和 TERC 突变并没有影响端粒酶活性，这意味着研究突变体的端粒酶活性对于 DKC 的诊断并不总是有用。
