Developmental regulation of hemoglobin synthesis in the green anole lizard Anolis carolinensis

Abstract

SUMMARYTetrapod vertebrates possess multiple -and -like globin genes that are ontogenetically regulated, such that functionally distinct hemoglobin (Hb) isoforms are synthesized during different stages of development. The -and -like globin genes of amphibians, birds and mammals are differentially expressed during embryonic development and postnatal life, but little is known about the developmental regulation of globin gene expression in non-avian reptiles. Here we report an investigation into the developmental regulation of Hb synthesis in the green anole lizard Anolis carolinensis. We tested two hypotheses derived from comparative genomic studies of the globin gene clusters in tetrapod vertebrates. First, we tested whether the product of the Anolis  D -globin gene is incorporated into embryonic Hb, thereby performing the role that would normally be performed by the embyronic  E -globin gene (which has been deleted from the green anole genome). Second, we tested whether two 'lizard-specific' -globin paralogs have independently evolved a division of labor between an early-expressed embryonic gene and a later-expressed adult gene. Results of a proteomic analysis revealed that -and -like globin genes of the anole are differentially expressed during embryonic development. However, the same repertoire of -and -chain Hb isoforms was expressed during all stages of development and postnatal life, and the ontogenetic shifts in isoform composition were relatively subtle. In contrast to the pattern that has been documented in other tetrapod vertebrates, it appears that the developmental regulation of Hb synthesis in the green anole lizard does not involve discrete, stage-specific switches in gene activation and gene silencing.

Gene Duplication and the Evolution of Hemoglobin Isoform Differentiation in Birds

“…For each individual specimen, Hb isoform composition was characterized by means of alkaline PAGE and/or thin layer isoelectric focusing (PhastSystem, GE Healthcare Biosciences). Depending on the species, the HbA and HbD isoforms were separated by fast protein liquid chromatography (FPLC), DEAE anion-exchange chromatography, CM-Sepharose cation-exchange chromatography, and/or preparative electrofocusing, as described previously (11,36,43,44). The separate isoHbs were further stripped of organic phosphate and other ions by passing the samples through a mixed bed resin column (MB-1 AG501-X8; Bio-Rad) using FPLC.…”

Hemoglobin–oxygen affinity in high-altitude vertebrates: is there evidence for an adaptive trend?

“…In principle, reversible changes can also be produced by cellular changes in Hb isoform composition. All vertebrates possess multiple α-and β-type globin genes, and therefore express multiple, structurally distinct Hb isoforms during different stages of prenatal development and postnatal life (Hoffmann et al, 2010(Hoffmann et al, , 2012Storz et al, 2011aStorz et al, , 2013Storz, 2016b). In this Review, I focus on postnatally expressed Hb isoforms and blood O 2 transport during adulthood [see Brittain (2002) for a discussion of prenatally expressed Hbs and their functional properties].…”

Gene duplication, genome duplication, and the functional diversification of vertebrate globins

“…Multiple rounds of duplication and divergence have produced diverse repertoires of α- and β-like globin genes that are ontogenetically regulated such that functionally distinct Hb isoforms are expressed during different stages of prenatal development and postnatal life (Alev et al 2009; Brittain 2002; Hardison 2001; Hoffmann et al 2008a,b; Opazo et al 2008a,b, 2009; Storz et al 2011b). Surprisingly, however, phylogenetic analyses of the α- and β-globin gene families have revealed that genes with similar stage-specific expression patterns in different species do not necessarily represent 1:1 orthologs that were inherited from a common ancestor (Czelusniak et al 1982; Hoffmann et al 2010b; Opazo et al 2008a; Storz et al 2011a; Opazo et al 2012).…”