Grouper tsh beta Promoter-Driven Transgenic Zebrafish Marks Proximal Kidney Tubule Development

Kidney tubule plays a critical role in recovering or secreting solutes, but the detailed morphogenesis remains unclear. Our previous studies have found that grouper tsh beta (gtsh beta) is also expressed in kidney, however, the distribution significance is still unknown. To understand the gtshb role and kidney tubule morphogenesis, here, we have generated a transgenic zebrafish line Tg(gtsh beta: GFP) with green fluorescent protein driven by the gtshb promoter. Similar to the endogenous tshb in zebrafish or in grouper, the gtsh beta promoter-driven GFP is expressed in pituitary and kidney, and the developing details of proximal kidney tubule are marked in the transgenic zebrafish line. The gfp initially transcribes at 16 hours post fertilization (hpf) above the dorsal mesentery, and partially co-localizes with pronephric tubular markers slc20a1a and cdh17. Significantly, the GFP specifically localizes in proximal pronephric segments during embryogenesis and resides at kidney duct epithelium in adult fish. To test whether the gtsh beta promoter-driven GFP may serve as a readout signal of the tubular development, we have treated the embryos with retinoic acid signaing (RA) reagents, in which exogenous RA addition results in a distal extension of the proximal segments, while RA inhibition induces a weakness and shortness of the proximal segments. Therefore, this transgenic line provides a useful tool for genetic or chemical analysis of kidney tubule