Transcription factor Paired-Box 8 regulates Na+/I- Symporter gene expression in small-intestine absorptive enterocytes

MARTIN, M; MASINI-REPISO, AM; GEYSELS, RC; NICOLA, JP; PEYRET, V; BERNAL BARQUERO, CE

Buenos Aires

Congreso; XVII Latin American Thyroid Society Congress; 2019

Latin American Thyroid Society

Dietary I-absorption in the gastrointestinal tract constitutes the first step in I-metabolism, as the diet is the unique source of I- for land-dwellingvertebrates. The Na+/I- symporter (NIS), anintegral plasma membrane glycoprotein located in the apical membrane (brushborder) of absorptive enterocytes, constitutesthe central component of the I-absorption system in the small intestine.To investigate the mechanisms regulating NIS gene expression in small-intestine absorptive enterocytes.Experiments were performed on isolatedvillus-tip enterocytes and small intestine-derived IEC-6 cells. Pax8 expressionwas evaluated by RT-PCR, western blot and immunofluorescence. NIS generegulatory sequence and Pax8 transcriptional activity were evaluated using genereporter assays.Consistently with NIS beingexpressed exclusively on the brush border of small-intestine, we detected Pax8 expression in isolatedvillus-tip enterocytes. In agreement, we evidenced Pax8 nuclear expression and itstranscriptional activity in IEC-6 cells. Short-hairpin RNA-mediated Pax8knock-down in IEC-6 cells reduces NIS expression, and consequently I-accumulation. Moreover, the activity of the NIS promoter mutant missingPax8-binding sites was significantly impaired. Consistently with the role ofPax8 controlling NIS expression in enterocytes, ChIP analysis revealed Pax8binding to the NIS upstream enhancer, i.e. NIS promoter region containing Pax8binding sites.Considering the key role of Pax8 controlling NIS gene expression inthyroid cells, we report thefirst evidence supporting the role of the transcription factor Pax8 regulating NISgene expression in small-intestineabsorptive enterocytes.