Expression and phylogeny of multidrug resistance protein 2 and 4 in African white backed vulture (Gyps africanus).

Bono Nethathe,Aron Abera,Vinny Naidoo

doi:10.7717/peerj.10422

Abstract

Diclofenac toxicity in old world vultures is well described in the literature by both the severity of the toxicity induced and the speed of death. While the mechanism of toxicity remains unknown at present, the necropsy signs of gout suggests primary renal involvement at the level of the uric acid excretory pathways. From information in the chicken and man, uric acid excretion is known to be a complex process that involves a combination of glomerular filtration and active tubular excretion. For the proximal convoluted tubules excretion occurs as a two-step process with the basolateral cell membrane using the organic anion transporters and the apical membrane using the multidrug resistant protein to transport uric acid from the blood into the tubular fluid. With uric acid excretion seemingly inhibited by diclofenac, it becomes important to characterize these transporter mechanism at the species level. With no information being available on the molecular characterization/expression of MRPs of Gyps africanus, for this study we used next generation sequencing, and Sanger sequencing on the renal tissue of African white backed vulture (AWB), as the first step to establish if the MRPs gene are expressed in AWB. In silico analysis was conducted using different software to ascertain the function of the latter genes. The sequencing results revealed that the MRP2 and MRP4 are expressed in AWB vultures. Phylogeny of avian MRPs genes confirms that vultures and eagles are closely related, which could be attributed to having the same ancestral genes and foraging behavior. In silico analysis confirmed the transcribed proteins would transports anionic compounds and glucose.

Highlights

In India, birds belonging to the Gyps genus (Oriental white-backed vulture, Gyps bengalensis; long-billed vulture, G. indicus and slender-billed vulture, G.tenuirostris) were in grave danger of extinction in the 1990s following their inadvertent exposure to veterinary diclofenac that found its way into their food chain (Oaks et al, 2004)
The assembled transcriptomes was compared to the golden eagle MRP2 (XM_030031380.1) and MRP4 (XM_030036470.1) sequences
The predicted African white backed vulture (AWB) MRP2 (MN691108) and MRP4 (MN691109) genes were submitted to NCBI and consisted of 5212 and 4061bp respectively

Summary

Introduction

In India, birds belonging to the Gyps genus (Oriental white-backed vulture, Gyps bengalensis; long-billed vulture, G. indicus and slender-billed vulture, G.tenuirostris) were in grave danger of extinction in the 1990s following their inadvertent exposure to veterinary diclofenac that found its way into their food chain (Oaks et al, 2004). Following their single exposure to quantities of drug that equated to a dose in the region of 0.8 mg/kg, birds were found dead within 48 h of said exposure with signs of severe visceral gout and associated. One of the theories put forward, suggests that toxicity is due to the inhibition of the uric acid transporter channels in the renal tubular epithelial cells (Naidoo et al, 2007), which would be consistent with diclofenac inhibition of uric acid transport in mammals (Khamdang et al, 2002; Nozaki et al, 2007; Burckhardt, 2012)

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Conclusion