Gene transcripts encoding hypoxia-inducible factor (HIF) exhibit tissue- and muscle fiber type-dependent responses to hypoxia and hypercapnic hypoxia in the Atlantic blue crab, Callinectes sapidus

Hypoxia inducible factor (HIF) is a transcription factor that under low environmental oxygen regulates the expression of suites of genes involved in metabolism, angiogenesis, erythropoiesis, immune function, and growth. Here, we isolated and sequenced partial cDNAs encoding hif-alpha and arnt/hif-beta from the Atlantic blue crab. Callinectes sapidus, an estuarine species that frequently encounters concurrent hypoxia (low O-2) and hypercapnia (elevated CO2). We then examined the effects of acute exposure (1 h) to hypoxia (H) and hypercapnic hypoxia (HH) on relative transcript abundance for hif-alpha and arnt/hif-beta in different tissues (glycolytic muscle, oxidative muscle, hepatopancreas, gill, and gonads) using quantitative real-time RT-PCR. Our results indicate that hif-alpha and arnt/hif-beta mRNAs were constitutively present under well-aerated normoxia (N) conditions in all tissues examined. Further, H and HH exposure resulted in both tissue-specific and muscle fiber type-specific effects on relative hif-alpha transcript abundance. In the gill and glycolytic muscle, relative hif-alpha mRNA levels were significantly lower under H and HH, compared to N, while no change (or a slight increase) was detected in oxidative muscle, hepatopancreas and gonadal tissues. H and HH did not affect relative transcript abundance for arnt/hif-beta in any tissue or muscle fiber type. Thus, in crustaceans the HIF response to H and HH appears to involve changes in hif transcript abundance, with variation in hif-alpha and arnt/hif-beta transcriptional dynamics occurring in both a tissue- and muscle fiber type-dependent manner. (C) 2012 Elsevier Inc. All rights reserved.