Abstract
Aspartic proteinases (AP) form a multigenic group widely distributed in various organisms and includes pepsins (pep), cathepsins D and E, pregnancy associated glycoproteins (PAGs) as well as plant, fungal, and retroviral proteinases. This study describes the transcript identification and expression localization of the AP within the discoid placenta of the Castor fiber. We identified 1257 bp of the AP cDNA sequence, encoding 391 amino acids (aa) of the polypeptide precursor composed of 16 aa signal peptide, 46 aa pro-piece, and 329 aa of the mature protein. Within the AP precursor, one site of potential N-glycosylation (NPS119–121) and two Asp residues (D) specific for the catalytic cleft of AP were identified (VLFDTGSSNLWV91–102 and GIVDTGTSLLTV277–288). The highest homology of the identified placental AP nucleotide and aa sequence was to mouse pepsinogen C (75.8% and 70.1%, respectively). Identified AP also shared high homology with other superfamily members: PAGs, cathepsins, and napsins. The AP identified in this study was named as pepsinogen/PAG-Like (pep/PAG-L). Diversified pep/PAG-L protein profiles with a dominant 58 kDa isoform were identified. Immune reactive signals of the pep/PAG-L were localized within the trophectodermal cells of the beaver placenta. This is the first report describing the placental AP (pep/PAG-L) in the C. fiber.
Highlights
Within the Rodentia, Castoridae is represented by the only two still-extant species, Castor canadensis (Cc), native in North America and Castor fiber (Cf) in Eurasia
The reconstructed contigs were analyzed for their similarity to aspartic proteinases, which allowed the identification of a 1257 bp complementary DNA (cDNA) sequence of the placental Aspartic proteinases (AP) transcript
Five pairs of homological primers used for PCR amplification were used to obtain the entire AP cDNA sequence
Summary
Within the Rodentia, Castoridae is represented by the only two still-extant species, Castor canadensis (Cc), native in North America and Castor fiber (Cf) in Eurasia. Both species are characterized by their large body size and can be distinguished by karyological analyses indicating 40 or 48 chromosomes in Cc and Cf, respectively [1,2]. Previous multi-gene studies have suggested that the Geomyoidea superfamily—including the pocket gopher species (Geomyidae) and the kangaroo rats and mice (Heteromyidae)—is the closest to both beavers [3,4]. A recent study [6] confirmed the relationship between beavers (Castoridae) and kangaroo rat-related species (Geomyoidea) within a significantly supported mouse-related clade (including Myodonta, Anomaluromorpha, and Castorimorpha). Ongoing conservation has prevented the beaver population from declining again and, as a result, the Cf has been classified by the International Union for Conservation of Nature as the Least Concern category [7]
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