Steroidogenic acute regulatory protein (StAR) gene expression construct: Development, nanodelivery and effect on reproduction in air-breathing catfish, Clarias batrachus

Abstract

tSteroidogenic acute regulatory protein (StAR) is responsible for the relocation of cholesterol across mito-chondrial membrane in vertebrates and is, therefore, a key factor in regulating the rate and timing ofsteroidogenesis. In the present study, we developed chitosan nanoparticle (CNP) conjugated StAR geneconstruct (CNP-pcDNA4-StAR) in a eukaryotic expression vector, pcDNA4/HisMax A. CNPs of 135.4 nmdiameter, 26.7 mV zeta potential and 0.381 polydispersity index were used for conjugation. The loadingefficiency (LE) of pcDNA4-StAR construct with CNPs was found to be 86%. After the 24 h of intramuscularinjection, the CNP-pcDNA4-StAR plasmid could be detected from testis, brain, kidney and muscle tissuesof Clarias batrachus. The transcript levels of important reproductive genes viz. cyp11a1, cyp17a1, 3 -hsd,17 -hsd and cyp19a1 in CNP-pcDNA4-StAR treated group were initially low up to 24 h, but significantlyincreased subsequently up to 120 h. In naked pcDNA4-StAR treated group, the mRNA level of 3 -hsd,17 -hsd and cyp19a1 increased initially up to 24 h, while cyp11a1 and cyp17a1 increased up to 48 hand then started declining. Similar results were obtained for 11-Ketotestosterone and 17 -estradiol. Theresults indicate relatively long lasting effects of nano-conjugated construct compared to the constructalone. Furthermore, the histopathology of gonads and liver authenticates its possible role in the gonadaldevelopment in fish without any adverse effect.