Expression of homeobox-containing genes in the sea urchin (Parancentrotus lividus) embryo

Abstract

Two homeobox-containing genes that belong to different homeodomain classes have been isolated from a sea urchin genomic library. One, PlHbox11, is the sea urchin homologue of the human and mouse Hox B3 gene, the other, PlHbox12, shows about 55% identity with paired class genes. Expression profile analysis of the two sea urchin Hbox genes suggests that they play different roles during embryogenesis. In fact, PlHbox11 transcripts are rare and are detected only in the pluteus larva and in the Aristotle's lantern and intestine of the adult. The PlHbox12 gene is, on the contrary, transiently expressed in the very early embryo already at the four cell stage; it accumulates at the 64 cell stage and disappears at later stages of development. In situ hybridization experiments to 16 and 32 cell stage whole mount embryos showed localization of the PlHbox12 mRNA to part of the mesomere-macromere region of the early cleavage embryo. These observations suggest a possible role of this gene in early events of cell specification.

Gene regulatory networks and developmental plasticity in the early sea urchin embryo: alternative deployment of the skeletogenic gene regulatory network

“…Transcription commences immediately after fertilization and reaches its maximum rate after only four to five cleavage divisions (Davidson, 1986). The first territories of differential gene expression appear by the 16-cell stage (Di Bernardo et al, 1995;Nasir et al, 1995;Oliveri et al, 2002;Wang et al, 1996;Wikrmanayake et al, 2004). Other manifestations of molecular asymmetry are also evident at this stage, including the polarized nuclear accumulation of ␤-catenin and SoxB1 (Angerer et al, 2005;Weitzel et al, 2004).…”

Hbox1 and Hbox7 are involved in pattern formation in sea urchin embryos

“…Several homeobox sequences have been found in different echinoid species (Dolecki et al 1986;DiBernardo et al 1994;Ruddle et al 1994;Dobias et al 1996;Popodi et al 1996). However, the function of these homeodomain proteins is not well understood in sea urchin development.…”

Organization of an echinoderm Hox gene cluster

“…Thus the relations between the developmental domains of expression of given echinoderm Hox genes and their respective genomic positions might illuminate the evolutionary transformations that led to the appearance of their unique morphological features. (iii) Though fragments of many individual Hox genes had been isolated from sea urchins (7)(8)(9)(10)(11) and starfish (12) by PCR and other methods, their specific classification (and hence the interpretation of their patterns of expression) in many cases required knowledge of their relative genomic positions. Furthermore, (iv) Strongylocentrotus purpuratus, the subject of this work, is a maximal indirect developer (13).…”