Biomedical subjects

Yiming Xing

Publications and source records attributed to Yiming Xing.

3 recordsLinked to original sources

PubMed2007

Physical and functional interactions between homeodomain NKX2.1 and winged helix/forkhead FOXA1 in lung epithelial cells.

NKX2.1 is a homeodomain transcription factor that controls development of the brain, lung, and thyroid. In the lung, Nkx2.1 is expressed in a proximo-distal gradient and activates specific genes in phenotypically distinct epithelial cells located along this axis. The mechanisms by which NKX2.1 controls its target genes may involve interactions with other transcription factors. We examined whether NKX2.1 interacts with members of the winged-helix/forkhead family of FOXA transcription factors to regulate two spatially and cell type-specific genes, SpC and Ccsp. The results show that NKX2.1 interacts physically and functionally with FOXA1. The nature of the interaction is inhibitory and occurs through the NKX2.1 homeodomain in a DNA-independent manner. On SpC, which lacks a FOXA1 binding site, FOXA1 attenuates NKX2.1-dependent transcription. Inhibition of FOXA1 by small interfering RNA increased SpC mRNA, demonstrating the in vivo relevance of this finding. In contrast, FOXA1 and NKX2.1 additively activate transcription from Ccsp, which includes both NKX2.1 and FOXA1 binding sites. In electrophoretic mobility shift assays, the GST-FOXA1 fusion protein interferes with the formation of NKX2.1 transcriptional complexes by potentially masking the latter's homeodomain DNA binding function. These findings suggest a novel mode of selective gene regulation by proximo-distal gradient distribution of and functional interactions between forkhead and homeodomain transcription factors.

Amino Acid Motifs↗

PubMed2004

The major podocyte protein nephrin is transcriptionally activated by the Wilms' tumor suppressor WT1.

NPHS1 encodes the structural protein nephrin, which has a crucial role in the filtration barrier of the glomerular podocyte. Mutations or deregulation of NPHS1 are associated with a variety of renal diseases, including the Finnish type congenital nephrotic syndrome. This study analyzed a potential regulation of nephrin by the Wilms' tumor protein, Wt1. Using an inducible U2OS osteosarcoma cell line, it is shown that upon Wt1 induction, endogenous nephrin mRNA becomes highly upregulated. Co-transfection studies demonstrate that Wt1 can activate the nephrin promoter >10-fold. DNase footprinting and mutation analysis identify a Wt1 responsive element in the nephrin promoter, which is required for the binding of Wt1 protein. Mutations or deletion of this Wt1 responsive element completely abolished transactivation of the nephrin promoter by Wt1. Moreover, transgenic analysis demonstrates the requirement of the identified binding site to direct podocyte-specific expression of a reporter gene in transgenic mice, thus confirming the importance of this site for the regulation of nephrin in vivo. Finally, it is shown that nephrin expression is lowest in kidneys of mice that lack specifically the Wt1(-KTS) splice variant, but in comparison with wild-type littermates, it is also reduced in animals with disruption of the Wt1(+KTS) splice variant. Taken together, these data identify nephrin as a direct transcriptional target for Wt1 and underline the importance of Wt1 as a key regulator in podocyte function.

Animals↗

PubMed2002

Early gonadal development: exploring Wt1 and Sox9 function.

Prior to sex determination the gonadal anlage is formed as a bipotential primordium with the capacity to differentiate into either testes or ovaries depending on the presence or absence of the Sry gene. Knockout experiments have implicated five genes in the formation or survival of the gonadal primordium: Wt1, Sf1, Lim1, Lhx9 and Emx2. We are particularly interested in the Wilms tumour suppressor, WT1, which is characterized by complex posttranscriptional modifications. Here we will focus on published in vitro evidence suggesting distinct functions for the various isoforms and present our own results from in vivo experiments. Our data suggest that WT1 is an important regulator of the transcription or stability of the sex-determining gene Sry. One of the first genes expressed after the initial male sex-determining signal is the Sox9 gene. Human SOX9 has been implicated in male-to-female sex reversal. To analyse Sox9 function in mouse development we have performed transgenic experiments and ectopically expressed this gene in XX gonads. Our data indicate that Sox9 is sufficient to induce testis formation in mice. Here we will discuss our new data and present an updated model for Wt1 and Sox9 function in gonad formation and sex determination.

Animals↗