PDF(Pubmed)
Abstract：
Autosomal recessive polycystic kidney disease (ARPKD; MIM#263200) is a severe, hereditary, hepato-renal fibrocystic disorder that leads to early childhood morbidity and mortality. Typical forms of ARPKD are caused by pathogenic variants in the PKHD1 gene, which encodes the fibrocystin/polyductin (FPC) protein. MYC overexpression has been proposed as a driver of renal cystogenesis, but little is known about MYC expression in recessive PKD. In the current study, we provide the first evidence that MYC is overexpressed in kidneys from ARPKD patients and confirm that MYC is upregulated in cystic kidneys from cpk mutant mice. In contrast, renal MYC expression levels were not altered in several Pkhd1 mutant mice that lack a significant cystic kidney phenotype. We leveraged previous observations that the carboxy-terminus of mouse FPC (FPC-CTD) is proteolytically cleaved through Notch-like processing, translocates to the nucleus, and binds to double stranded DNA, to examine whether the FPC-CTD plays a role in regulating MYC/Myc transcription. Using immunofluorescence, reporter gene assays, and ChIP, we demonstrate that both human and mouse FPC-CTD can localize to the nucleus, bind to the MYC/Myc P1 promoter, and activate MYC/Myc expression. Interestingly, we observed species-specific differences in FPC-CTD intracellular trafficking. Furthermore, our informatic analyses revealed limited sequence identity of FPC-CTD across vertebrate phyla and database queries identified temporal differences in PKHD1/Pkhd1 and CYS1/Cys1 expression patterns in mouse and human kidneys. Given that cystin, the Cys1 gene product, is a negative regulator of Myc transcription, these temporal differences in gene expression could contribute to the relative renoprotection from cystogenesis in Pkhd1-deficient mice. Taken together, our findings provide new mechanistic insights into differential mFPC-CTD and hFPC-CTD regulation of MYC expression in renal epithelial cells, which may illuminate the basis for the phenotypic disparities between human patients with PKHD1 pathogenic variants and Pkhd1-mutant mice.
摘要：
常染色体隐性遗传性多囊肾病(ARPKD;MIM#263200)是一种严重的,世袭,肝肾纤维囊性疾病，导致儿童早期发病和死亡。ARPKD的典型形式是由PKHD1基因的致病变体引起的，其编码纤维囊素/多凝集素(FPC)蛋白。MYC过度表达已被认为是肾囊肿形成的驱动因素，但对MYC在隐性PKD中的表达知之甚少。在目前的研究中,我们首次提供了ARPKD患者肾脏中MYC过表达的证据,并证实了cpk突变小鼠的囊性肾脏中MYC上调.相比之下,在几只缺乏显著囊性肾表型的Pkhd1突变小鼠中,肾脏MYC表达水平没有改变.我们利用以前的观察结果，即小鼠FPC（FPC-CTD）的羧基末端通过Notch样加工被蛋白水解切割，转移到细胞核，并与双链DNA结合，检查FPC-CTD是否在调节MYC/Myc转录中起作用。使用免疫荧光，报告基因测定，ChIP,我们证明了人和小鼠FPC-CTD都可以定位到细胞核，结合到MYC/MycP1启动子，并激活MYC/Myc表达。有趣的是,我们观察到FPC-CTD细胞内运输的物种特异性差异。此外，我们的信息学分析揭示了整个脊椎动物门之间FPC-CTD的序列同一性有限,数据库查询确定了小鼠和人肾脏中PKHD1/Pkhd1和CYS1/Cys1表达模式的时间差异.鉴于那个cystin,Cys1基因产物，是Myc转录的负调节因子,基因表达的这些时间差异可能有助于Pkhd1缺陷小鼠的相对肾脏保护免受膀胱形成。一起来看,我们的研究结果为mFPC-CTD和hFPC-CTD调节肾上皮细胞MYC表达的差异提供了新的机制见解，这可能阐明了PKHD1致病变体人类患者与Pkhd1突变小鼠之间表型差异的基础。
