Identification and Evolution of TGF-β Signaling Pathway Members in Twenty-Four Animal Species and Expression in Tilapia

Abstract

Transforming growth factor β (TGF-β) signaling controls diverse cellular processes during embryogenesis as well as in mature tissues of multicellular animals. Here we carried out a comprehensive analysis of TGF-β pathway members in 24 representative animal species. The appearance of the TGF-β pathway was intrinsically linked to the emergence of metazoan. The total number of TGF-β ligands, receptors, and smads changed slightly in all invertebrates and jawless vertebrates analyzed. In contrast, expansion of the pathway members, especially ligands, was observed in jawed vertebrates most likely due to the second round of whole genome duplication (2R) and additional rounds in teleosts. Duplications of TGFB2, TGFBR2, ACVR1, SMAD4 and SMAD6, which were resulted from 2R, were first isolated. Type II receptors may be originated from the ACVR2-like ancestor. Interestingly, AMHR2 was not identified in Chimaeriformes and Cypriniformes even though they had the ligand AMH. Based on transcriptome data, TGF-β ligands exhibited a tissue-specific expression especially in the heart and gonads. However, most receptors and smads were expressed in multiple tissues indicating they were shared by different ligands. Spatial and temporal expression profiles of 8 genes in gonads of different developmental stages provided a fundamental clue for understanding their important roles in sex determination and reproduction. Taken together, our findings provided a global insight into the phylogeny and expression patterns of the TGF-β pathway genes, and hence contribute to the greater understanding of their biological roles in the organism especially in teleosts.

Transcriptomic analysis of female and male gonads in juvenile snakeskin gourami (Trichopodus pectoralis)

“…49 and used to validate and confirm DEGs. Our study validated DEGs between testis and ovary using qRT-PCR for 21 genes that had previously been demonstrated as involved in gonadal development in teleosts and were specifically expressed in germ cells in various animals [50][51][52][53][54][55][56][57][58] . Our findings showed a significantly positive correlation of DEG analysis results between RNA-seq and qRT-PCR, particularly for DEGs that had a high log 2 fold change.…”

Diverse Signaling by TGFβ Isoforms in Response to Focal Injury is Associated with Either Retinal Regeneration or Reactive Gliosis

“…In contrast, expansion of the pathway members, especially ligands, was observed in jawed vertebrates due to the second round of whole-genome duplication (WGD) in teleosts. Thereby most receptors and their downstream targets (smads) were expressed in multiple tissues indicating they were shared by different ligands (Zheng et al 2018 ). Therefore, understanding the biological role of TGFβ signaling during retinal regeneration especially in teleosts (zebrafish) may lead to identify pathways that can be leveraged for regeneration in mammals.…”

Mismatches between the genetic and phenotypic sex in the wild Kou population of Nile tilapia Oreochromis niloticus

“…Because of a shift in the reading frame of amh Δ Y with a premature stop codon it is thought to give a truncated amh protein lacking the transforming growth factor β ( TGF- β) domain (Eshel et al, 2014; Li et al, 2015). The TGF- β domain is known to be necessary for binding amhs to their receptor amhrII (Li et al, 2015; Zheng et al, 2018). Therefore, only amhY might be the ligand of amhrII (Li et al, 2015).…”