Sertori Robert, Truong Billy, Singh Manoj K, Shinton Susan, Price Rachael, Sharo Andrew, Shultes Paulameena, Sunderam Uma, Rana Sadhna, Srinivasan Rajgopal, Datta Sutapa, Font-Burgada Joan, Brenner Steven E, Puck Jennifer M, Wiest David L
Nuclear Dynamics and Cancer Program, Fox Chase Cancer Center, Philadelphia, PA, United States.
Center for Computational Biology, University of California, Berkeley, Berkeley, CA, United States.
Front Immunol. 2025 Feb 14;16:1539848. doi: 10.3389/fimmu.2025.1539848. eCollection 2025.
Newborn screening for immunodeficiency has led to the identification of numerous cases for which the causal etiology is unknown.
Here we report the diagnosis of T lymphopenia of unknown etiology in a male proband. Whole exome sequencing (WES) was employed to nominate candidate variants, which were then analyzed functionally in zebrafish and in mice bearing orthologous mutations.
WES revealed missense mutations in that were inherited in an autosomal recessive manner. CTF18, encoded by the gene, is a component of a secondary clamp loader, which is primarily thought to function by promoting DNA replication. We determined that the patient's variants in (CTF18 R751W and E851Q) were damaging to function and severely attenuated the capacity of CTF18 to support hematopoiesis and lymphoid development, strongly suggesting that they were responsible for his T lymphopenia; however, the function of CTF18 appeared to be unrelated to its role as a clamp loader. DNA-damage, expected when replication is impaired, was not evident by expression profiling in murine mutant hematopoietic stem and progenitor cells (HSPC), nor was development of Ctf18-deficient progenitors rescued by p53 loss. Instead, we observed an expression signature suggesting disruption of HSPC positioning and migration. Indeed, the positioning of HSPC in morphant zebrafish embryos was perturbed, suggesting that HSPC function was impaired through disrupted positioning in hematopoietic organs.
Accordingly, we propose that T lymphopenia in our patient resulted from disturbed cell-cell contacts and migration of HSPC, caused by a non-canonical function of CHTF18 in regulating gene expression.
新生儿免疫缺陷筛查已发现众多病因不明的病例。
在此，我们报告一名男性先证者病因不明的T淋巴细胞减少症的诊断。采用全外显子组测序（WES）来确定候选变异，然后在斑马鱼和携带直系同源突变的小鼠中对其进行功能分析。
WES揭示了以常染色体隐性方式遗传的错义突变。由该基因编码的CTF18是二级钳式装载器的一个组成部分，主要被认为通过促进DNA复制发挥作用。我们确定患者该基因的变异（CTF18 R751W和E851Q）对功能具有损害性，并严重削弱了CTF18支持造血和淋巴细胞发育的能力，强烈表明它们是导致其T淋巴细胞减少的原因；然而，CTF18的功能似乎与其作为钳式装载器的作用无关。当复制受损时预期会出现的DNA损伤，在小鼠突变造血干细胞和祖细胞（HSPC）的表达谱中并不明显，p53缺失也无法挽救Ctf18缺陷祖细胞的发育。相反，我们观察到一种表达特征，提示HSPC定位和迁移受到破坏。事实上，HSPC在吗啡处理的斑马鱼胚胎中的定位受到干扰，表明HSPC功能因造血器官中定位被破坏而受损。
因此，我们提出我们患者的T淋巴细胞减少是由CHTF18在调节基因表达中的非经典功能导致的HSPC细胞间接触和迁移紊乱所致。
