hox genes + segmental specification

molecular biology

the new methods of RNA in situ hybridisation detects RNA within tissue allowing the spatial mapping of gene expression

results confirm segmentally regulated patterns of expression of hox genes

colinearity

hox gene expression along chromosome mirrors order of expression along body plan

seen clearly in embryo and maintained throughout adult life

transcriptional regulation

transcriptional activation from combinations of segmentation gene products determine the main areas of hox gene expression during early gene development

chromatin based regulation

later on when most segmentation gene products have decayed, hox gene expression is maintained by an epigenetic code, which relies on chromatin proteins

RNA based regulation

recently, RNA processing and microRNA regulation have been shown to control hox gene expression at different developmental stages

homeodomain

a protein molecule involved in DNA binding and gene regulation

all hox genes use it to encode transcriptional factors

evolutionary features of hox genes

• also control AP patterning in mammals

• display a similar genomic structure and expression pattern in most animal groups