, 2001) These results, along with subsequent work by Truchet et

, 2001). These results, along with subsequent work by Truchet et al. (2004) showing induction of

IFN-γ target genes (irf-1 and socs-1) in 2-cell embryos after stimulation with exogenous IFN-γ, indicate there is a functional IFN-γ signaling pathway in mouse early embryos. Our results showing that Atlantic cod ifngr1 transcript is highly expressed in unfertilized eggs click here and 2-cell embryos supports the hypothesis that IFN-γ signaling in the very early embryo is conserved between mammals and teleost fish. IFRD1 (synonyms TIS7 and PC4) proteins are highly conserved transcriptional co-repressors (Vietor and Huber, 2007). Atlantic cod IFRD1 (i.e. the deduced translation of the nucleotide sequence with GenBank accession number ES775268) is over 80% identical to IFRD1 sequences from other teleost fish species such as the zebrafish, torafugu, Nile tilapia, and Atlantic salmon, and over 70% identical to IFRD1 sequences from mammals including the human, rat, and mouse (Supplemental Table 14, and data not shown). Mouse ifrd1 transcript is ubiquitously selleck expressed, with notably high expression

in fertilized eggs ( Su et al., 2002 and Vietor and Huber, 2007). In mammals, ifrd1 is involved in the regulation of cell proliferation and differentiation. For example, in early rat embryos, high ifrd1 transcript expression along the neural tube suggests that this gene is involved in embryonic neuroblast differentiation (reviewed by Vietor and Huber, 2007). In the embryonic mouse, ifrd1 transcript is expressed in several tissues including developing kidney, lung, and the central nervous system ( Buanne et al., 1998). While ifrd1 knockout mice are fertile, they have decreased adult body weight (possibly due to muscle atrophy), altered

muscle regeneration and function, and down-regulated muscle-specific genes ( Vadivelu et al., 2004; reviewed by Vietor and Huber, 2007). It is thought that IFRD1 may down-regulate β-catenin/Tcf-4 transcriptional activity in a histone clonidine deacetylase (HDAC)-dependent manner, and thereby inhibit β-catenin target genes (reviewed by Vietor and Huber, 2007). We demonstrate for the first time that ifrd1 is a highly expressed maternal transcript in a fish species. Apart from our results, and those of Su et al. (2002) showing high ifrd1 transcript expression in fertilized mouse eggs (reviewed in Vietor and Huber, 2007), information is lacking on the expression and potential function of IFRD1 in vertebrate eggs and very early embryos.

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