Evolution and Expression of Paxillin Genes in Teleost Fish

Abstract

BackgroundPaxillin family proteins regulate intracellular signaling downstream of extracellular matrix adhesion. Tissue expression patterns and cellular functions of Paxillin proteins during embryo development remain poorly understood. Additionally, the evolution of this gene family has not been thoroughly investigated.ResultsThis report characterizes the evolution and expression of a novel Paxillin gene, called Paxillin-b, in Teleosts. Alignments indicate that Teleost Paxillin-a and Paxillin-b proteins are highly homologous to each other and to human Paxillin. Phylogenetic and synteny analyses suggest that these genes originated from the duplication of an ancestral Paxillin gene that was in a common ancestor of Teleosts and Tetrapods. Analysis of the spatiotemporal expression profiles of Paxillin-a and Paxillin-b using zebrafish revealed both overlapping and distinct domains for Paxillin-a and Paxillin-b during embryo development. Localization of zebrafish Paxillin orthologs expressed in mammalian cells demonstrated that both proteins localize to focal adhesions, similar to mammalian Paxillin. This suggests these proteins regulate adhesion-dependent processes in their endogenous tissues.ConclusionPaxillin-a and Paxillin-b were generated by duplication in Teleosts. These genes likely play similar roles as Paxillin genes in other organisms. This work provides a framework for functional investigation of Paxillin family members during development using the zebrafish as an in vivo model system.

Paxillin genes and actomyosin contractility regulate myotome morphogenesis in zebrafish

“…2I), suggesting this band corresponds to the Pxnb-ins isoform (see Fig. 1A) that has a predicted weight of ~130 kDa (Jacob et al, 2016). These results indicate that MZ double mutants do not produce full-length Pxna or Pxnb proteins and that these recessive mutations are likely null alleles.…”

“…To determine the impact of the pxn mutations on Paxillin protein expression we performed Western blots using an antibody that detects multiple Paxillin family members, including zebrafish pxna and pxnb proteins (Jacob et al, 2016). Using lysates from 4 dpf embryos, a 60 kDa band corresponding to the predicted size of both Pxna and Pxnb was present in single mutant embryos but absent in MZ double mutants (Fig.…”

“…In addition, we recently described a splice isoform of pxnb , which we refer to as pxnb-ins , that has an insertion of three additional coding exons and may encode an ancestral version of the protein (Jacob et al, 2016). Characterization of the spatiotemporal expression patterns of pxna and pxnb during early zebrafish embryo development revealed that these transcripts are maternally supplied and have both unique and overlapping expression profiles (Jacob et al, 2016). For example, pxna mRNA transcription is restricted to the notochord, Kupffer’s vesicle, and developing somites, whereas pxnb mRNA is present more broadly at post-gastrulation stages.…”

“…Interestingly, pxnb mRNA is enriched in the developing heart at 48 hpf, while pxna mRNA was not detected by in situ hybridization in this organ. Conserved expression patterns for Paxillin genes between zebrafish and mammalian embryos in the notochord and somites suggest that these genes may regulate similar processes in vertebrate embryos (Crawford et al, 2003; Hagel et al, 2002; Jacob et al, 2016). The zebrafish also provides a model wherein unique functions of Paxillin gene paralogs between tissues can be explored.…”

“…Loss of both maternal and zygotic expression of Paxillin proteins caused morphogenetic defects in several tissues, including the heart, notochord, and skeletal muscle. Since expression studies have found Paxillin to be enriched at MTJs (Crawford et al, 2003; Jacob et al, 2016), we focused on functions of Paxillin in myotome development. Axial myotomes in vertebrates develop from segmented precursor structures called somites.…”