The homeoboxB9 (HOXB9) gene is necessary for specification of the anterior-posterior body axis during embryonic development and expressed in various types of cancer.

Here we show that the Wilms tumor transcription factor WT1 regulates the HOXB9 gene in a bidirectional manner. Silencing of WT1 activates HOXB9 in Wt1 expressing renal cell adenocarcinoma-derived 786-0 cells, mesonephric M15 cells and ex vivo cultured murine embryonic kidneys. In contrast, HOXB9 expression in U2OS osteosarcoma and human embryonic kidney (HEK) 293 cells, which lack endogenous WT1, is enhanced by overexpression of WT1. Consistently, Hoxb9 promoter activity is stimulated by WT1 in transiently transfected U2OS and HEK293 cells, but inhibited in M15 cells with CRISPR/Cas9-mediated Wt1 deletion. Electrophoretic mobility shift assay and chromatin immunoprecipitation demonstrate binding of WT1 to the HOXB9 promoter in WT1-overexpressing U2OS cells and M15 cells. BASP1, a transcriptional co-repressor of WT1, is associated with the HOXB9 promoter in the chromatin of these cell lines. Co-transfection of U2OS and HEK293 cells with BASP1 plus WT1 prevents the stimulatory effect of WT1 on the HOXB9 promoter.

Our findings identify HOXB9 as a novel downstream target gene of WT1. Depending on the endogenous expression of WT1, forced changes in WT1 can either stimulate or repress HOXB9, and the inhibitory effect of WT1 on transcription of HOXB9 involves BASP1. Consistent with inhibition of Hoxb9 expression by WT1, both transcripts are distributed in an almost non-overlapping pattern in embryonic mouse kidneys. Regulation of HOXB9 expression by WT1 might become relevant during kidney development and cancer progression.

homeoboxB9 ( HOXB9 ) 基因是胚胎发育过程中前后体轴规范所必需的，并在各种类型的癌症中表达。

在这里，我们显示 Wilms 肿瘤转录因子 WT1以双向方式调节HOXB9基因。WT1的沉默激活HOXB9在Wt1的表达肾细胞腺癌衍生786-0细胞，中肾M15细胞和离体培养的小鼠胚胎肾脏。相比之下，缺乏内源性 WT1 的 U2OS 骨肉瘤和人胚胎肾 (HEK) 293 细胞中的HOXB9表达因 WT1 的过表达而增强。一致地，Hoxb9启动子活性在瞬时转染的 U2OS 和 HEK293 细胞中受到 WT1 的刺激，但在 CRISPR/Cas9 介导的Wt1 的M15 细胞中受到抑制删除。电泳迁移率变化测定和染色质免疫沉淀证明WT1 与过表达 WT1 的 U2OS 细胞和 M15 细胞中的HOXB9启动子结合。BASP1 是 WT1 的转录共阻遏物，与这些细胞系染色质中的HOXB9启动子相关。U2OS 和 HEK293 细胞与 BASP1 加 WT1 的共转染可防止 WT1 对HOXB9启动子的刺激作用。

我们的研究结果将HOXB9鉴定为 WT1 的新型下游靶基因。根据WT1的内源性表达，WT1 的强制变化可以刺激或抑制HOXB9，并且 WT1 对HOXB9转录的抑制作用涉及 BASP1。与WT1对Hoxb9表达的抑制一致，两种转录物在胚胎小鼠肾脏中几乎不重叠。WT1对HOXB9表达的调节可能与肾脏发育和癌症进展有关。