An EAV-HP insertion in the 5ʹ flanking region of SLCO1B3 is associated with its tissue-expression profile in blue-eggshell Yimeng chickens (Gallus gallus)

Abstract

We previously reported that blue eggshell color in chickens is associated with a partial endogenous retroviral ( EAV-HP ) insertion in the promoter region of the solute carrier organic anion transporter family member 1B3 ( SLCO1B3 ) gene. The EAV-HP sequence includes numerous regulatory elements, which may modulate the expression of adjacent genes. To determine whether this insertion influences the expression of neighboring genes, we screened the expression of solute carrier organic anion transporter family members 1C1, 1B1 ( SLCO1C1 , SLCO1B1 ), and SLCO1B3 in 13 and 10 tissues from female and male Yimeng chickens, respectively. We observed that the insertion only significantly modulated the expression of SLCO1B3 and did not majorly affect that of SLCO1C1 and SLCO1B1 . High expression of SLCO1B3 was detected in the shell gland, magnum, isthmus, and vagina of the oviduct in female blue-eggshell chickens. We also observed ectopic expression of SLCO1B3 in the testes of male chickens. SLCO1B3 is typically highly expressed in the liver; however, the EAV-HP insertion significantly reduces SLCO1B3 expression. As a liver-specific transporter, a reduction in the expression of SLCO1B3 may affect liver metabolism, particularly that of bile acids. We also detected higher ectopic expression of SLCO1B3 in the lungs of birds heterozygous for the EAV-HP insertion than in homozygous genotypes. In conclusion, we confirmed that the EAV-HP insertion modifies SLCO1B3 expression, and showed, for the first time, similar expression profile of this gene in all parts of the oviduct in females and testis in males. We also observed different levels of SLCO1B3 expression in the liver, which were associated with the EAV-HP insertion, and significantly higher expression in the lungs of birds with heterozygous genotype. The effects of these changes in the SLCO1B3 expression pattern on the function of the tissues warrant further investigation.

An EAV-HP insertion in the promoter region of SLCO1B3 has pleiotropic effects on chicken liver metabolism based on the transcriptome and proteome analysis

“…The difference in the expression of SLCO1B3 between IM+ and IM− chickens was also validated by the qPCR analysis (Fig. S1 ), the primers for which have been described in a previous study 25 . The expression levels of the SLCO1B3 and OATP1B3 in IM+ chickens were both approximately 1/twofold compared with those in IM− chickens.…”

“…In humans, SLCO1B3 is mainly expressed in the liver and its encoded protein OATP1B3, plays an important role in endogenous and exogenous transport processes, which has a closely relationship with bile acids and drug metabolism in liver 3 , 20 . Our previous research also showed that chicken SLCO1B3 was mainly expressed in liver, and the SLCO1B3 homolog gene SLCO1B1 had exceptionally low expression levels in the liver 25 . This may indicate that in chickens, SLCO1B3 plays more important role in the endogenous and exogenous transport processes in the liver.…”

“…The chickens used in this study were randomly selected from the same population of Yimeng chickens according to the eggshell color. We previously reported different levels of SLCO1B3 expression in the liver, which were associated with the IM insert mutation in Yimeng chickens 25 . As predicted, RNA-seq analysis revealed that the expression levels of SLCO1B3 were lower in IM+ chickens than in IM− chickens (Fig.…”

“…1 D). In this region, we predicted an inverted hexanucleotide repeat motif (IR-1) like element 25 , which can be stimulated by bile acids. When we mutant the IR-1 like element (Fig.…”

“…A post-gene mapping study conducted genetic investigation of the SLCO1B3 22 – 24 ; however, its function in chickens has not been widely investigated. Recently, an expression profile of SLCO1B3 was outlined in different tissues between the EAV-HP inserted mutation (IM+) and wild type (IM−) hens, and it indicated that chicken SLCO1B3 also mainly specific expressed in the liver and its expression was significantly decreased in the livers of IM+ chickens 25 . This means that IM+ chickens could be used as an animal model to investigate the function of SLCO1B3 in liver.…”