Genetics Branch, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, Maryland, USA.
Cancer Biology and Genetics Program, Sloan-Kettering Institute, New York, New York, USA.
FASEB J. 2022 Sep;36(9):e22430. doi: 10.1096/fj.202200061RR.
Minichromosome maintenance proteins (Mcm2-7) form a hexameric complex that unwinds DNA ahead of a replicative fork. The deficiency of Mcm proteins leads to replicative stress and consequent genomic instability. Mice with a germline insertion of a Cre cassette into the 3'UTR of the Mcm2 gene (designated Mcm2 ) have decreased Mcm2 expression and invariably develop precursor T-cell lymphoblastic leukemia/lymphoma (pre-T LBL), due to 100-1000 kb deletions involving important tumor suppressor genes. To determine whether mice that were protected from pre-T LBL would develop non-T-cell malignancies, we used two approaches. Mice engrafted with Mcm2 Lin Sca-1 Kit hematopoietic stem/progenitor cells did not develop hematologic malignancy; however, these mice died of hematopoietic stem cell failure by 6 months of age. Placing the Mcm2 allele onto an athymic nu/nu background completely prevented pre-T LBL and extended survival of these mice three-fold (median 296.5 vs. 80.5 days). Ultimately, most Mcm2 ;nu/nu mice developed B-cell precursor acute lymphoblastic leukemia (BCP-ALL). We identified recurrent deletions of 100-1000 kb that involved genes known or suspected to be involved in BCP-ALL, including Pax5, Nf1, Ikzf3, and Bcor. Moreover, whole-exome sequencing identified recurrent mutations of genes known to be involved in BCP-ALL progression, such as Jak1/Jak3, Ptpn11, and Kras. These findings demonstrate that an Mcm2 hypomorph can induce hematopoietic dysfunction via hematopoietic stem cell failure as well as a "deletor" phenotype affecting known or suspected tumor suppressor genes.
微小染色体维持蛋白（Mcm2-7）形成六聚体复合物，在复制叉前解开 DNA。Mcm 蛋白的缺乏会导致复制应激，进而导致基因组不稳定。在 Mcm2 基因的 3'UTR 中插入 Cre 盒的生殖系小鼠（命名为 Mcm2 ），由于涉及重要肿瘤抑制基因的 100-1000kb 缺失，导致 Mcm2 表达减少，并且总是会发展为前 T 细胞淋巴母细胞白血病/淋巴瘤（pre-T LBL）。为了确定是否有免受 pre-T LBL 影响的小鼠会发展为非 T 细胞恶性肿瘤，我们采用了两种方法。用 Mcm2 Lin Sca-1 Kit 造血干细胞/祖细胞移植的小鼠没有发展为血液恶性肿瘤；然而，这些小鼠在 6 个月大时因造血干细胞衰竭而死亡。将 Mcm2 等位基因置于无胸腺 nu/nu 背景中完全阻止了 pre-T LBL 的发生，并使这些小鼠的存活率延长了三倍（中位数 296.5 与 80.5 天）。最终，大多数 Mcm2 ;nu/nu 小鼠发展为 B 细胞前体急性淋巴细胞白血病（BCP-ALL）。我们发现涉及已知或疑似参与 BCP-ALL 的基因的 100-1000kb 的反复缺失，包括 Pax5、Nf1、Ikzf3 和 Bcor。此外，全外显子组测序鉴定出涉及 BCP-ALL 进展的已知基因突变，如 Jak1/Jak3、Ptpn11 和 Kras。这些发现表明，Mcm2 低功能突变体可以通过造血干细胞衰竭以及影响已知或疑似肿瘤抑制基因的“缺失体”表型引起造血功能障碍。
