A show of Hands: Novel and conserved expression patterns of teleost hand paralogs during craniofacial, heart, fin, peripheral nervous system and gut development

Dev Dyn. 2021 Dec;250(12):1796-1809. doi: 10.1002/dvdy.380. Epub 2021 Jun 16.

Abstract

Background: Hand genes are required for the development of the vertebrate jaw, heart, peripheral nervous system, limb, gut, placenta, and decidua. Two Hand paralogues, Hand1 and Hand2, are present in most vertebrates, where they mediate different functions yet overlap in expression. In ray-finned fishes, Hand gene expression and function is only known for the zebrafish, which represents the rare condition of having a single Hand gene, hand2. Here we describe the developmental expression of hand1 and hand2 in the cichlid Copadichromis azureus.

Results: hand1 and hand2 are expressed in the cichlid heart, paired fins, pharyngeal arches, peripheral nervous system, gut, and lateral plate mesoderm with different degrees of overlap.

Conclusions: Hand gene expression in the gut, peripheral nervous system, and pharyngeal arches may have already been fixed in the lobe- and ray-finned fish common ancestor. In other embryonic regions, such as paired appendages, hand2 expression was fixed, while hand1 expression diverged in lobe- and ray-finned fish lineages. In the lateral plate mesoderm and arch associated catecholaminergic cells, hand1 and hand2 swapped expression between divergent lineages. Distinct expression of cichlid hand1 and hand2 in the epicardium and myocardium of the developing heart may represent the ancestral pattern for bony fishes.

Keywords: cichlid; epicardium; fin; gut; hand1; hand2; heart; myocardium; oral teeth; pharyngeal arches; sympathetic.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animal Fins / embryology
  • Animal Fins / metabolism
  • Animals
  • Basic Helix-Loop-Helix Transcription Factors / genetics*
  • Basic Helix-Loop-Helix Transcription Factors / metabolism
  • Branchial Region / embryology
  • Branchial Region / metabolism
  • Cichlids / embryology*
  • Cichlids / genetics
  • Cichlids / metabolism
  • Embryo, Nonmammalian
  • Embryonic Development / genetics*
  • Gene Expression Regulation, Developmental
  • Heart / embryology
  • Intestines / embryology
  • Intestines / metabolism
  • Mesoderm / embryology
  • Mesoderm / metabolism
  • Myocardium / metabolism
  • Peripheral Nervous System / embryology
  • Peripheral Nervous System / metabolism
  • Sequence Homology
  • Skull / embryology
  • Skull / metabolism
  • Tooth / embryology
  • Tooth / metabolism
  • Zebrafish / embryology
  • Zebrafish / genetics
  • Zebrafish / metabolism
  • Zebrafish Proteins / genetics
  • Zebrafish Proteins / metabolism

Substances

  • Basic Helix-Loop-Helix Transcription Factors
  • Zebrafish Proteins
  • hand2 protein, zebrafish
  • helix-loop-helix protein, eHAND