Comparative genomic studies on the TGF-β superfamily in blue whale

TGF-β supergene family has a wide range of physiological functions including cell adhesion, motility, proliferation, apoptosis, and differentiation. We systematically analyzed and characterized the TGF-β gene superfamily from the whole blue whale (Balaenoptera musculus) genome, using comparative genomic and evolutionary analysis. We identified 30 TGF-β genes and were split into two subgroups, BMP-like and TGF-like. All TGF-β proteins demonstrating a basic nature, with the exception of BMP1, BMP2, BMP10, GDF2, MSTN, and NODAL modulator, had acidic characteristics. All the blue whale (B. musculus) TGF-β proteins, excluding BMP1, are thermostable based on aliphatic index. The instability index showed all proteins except the NODAL modulator was unstable. TGF-β proteins showed a hydrophilic character, with the exception of GDF1 and INHBC. Moreover, all the detected TGF-β genes showed evolutionary conserved nature. A segmental duplication was indicated by TGF-β gene family, and the Ka/Ks ratio showed that the duplicated gene pairs were subjected to selection pressure, indicating both purifying and positive selection pressure. Two possible recombination breakpoints were also predicted. This study provides insights into the genetic characterization and evolutionary aspects of the TGF-β superfamily in blue whales (B. musculus).