PIHbox 9

Function

PlHbox 9 is a sea urchin homeobox gene (Bellomonte et al., 1998).

Protein

PlHbox 9 is a homeobox protein, highly related (95% identity) to the human HB9, a slightly divergent homeobox, that is expressed in cells of the lymphoid lineage and in several tissues of the gastrointestinal tract (Harrison et al., 1994). High sequence conservation can only be found in the homeodomain and seven downstream aminoacids (Bellomonte et al., 1998).

Subcellular location

Expression Pattern

Temporal expression of PIHbox9 determined by RNase protection, showed no expression from fertilization until the beginning of gastrulation. At late gastrula stage (22-24 h post fertilisation) a very faint RNase protected RNA band was detected after prolonged exposure of the flurograph. The abundance of the transcripts increased abruptly by the prism stage (30 h post-fertilisation)/early pluteus (39 h post-fertilisation) stages and declined slightly in the pluteus larva (53 h post-fertilisation).
Spatial expression of PIHbox9 throughout embryogenesis was determined by whole mount in situ hybridisation. Gastrula embryos at 22 h of development were unstained, thus confirming the very low level of expression of PIHbox9 gene at this embryonic stage. Transcripts in 30 h prism stage embryos were instead detected at the ectoderm-endoderm boundary. This hybridisation pattern was confirmed at later stages of development. In most of the 39 h prism/early pluteus embryos, expression of the PIHbox9 gene was confined to a few cells placed at the end of the hind gut and around the anus (Bellomonte et al., 1998).

mRNA level

Temporal accumulation
Method: RNase protection assay
Reference: Bellomonte et al., 1998

Stage 3 h 8 h 10 h 23 h (late gastrula) 30 h (prism) 39 h (early pluteus) 53 h (pluteus larva)

Level - - - + - + + + + +

Spatial localization
Method: Whole mount in situ hybridization
Reference: Bellomonte et al., 1998

Stage 22 h (gastrula) 30 h (prism) 39 h (prism/early pluteus)

Tissue - Ectoderm-endoderm boundary Few cells placed at the end of the hind gut and around the anus

Sequences

GenBank

Regulatory Regions

Regions

Regulatory Connections

Upstream Genes

PIHbox 9

Downstream Genes

Evolutionary Homologues

HB9 H. sapiens

Links

Urchin Web

Bibliography

UrchiNet

Search the GeNet

Stage	3 h	8 h	10 h	23 h (late gastrula)	30 h (prism)	39 h (early pluteus)	53 h (pluteus larva)
Level	-	-	-	+ -	+ +	+ +	+

Stage	22 h (gastrula)	30 h (prism)	39 h (prism/early pluteus)
Tissue	-	Ectoderm-endoderm boundary	Few cells placed at the end of the hind gut and around the anus