The sequence of a mouse Hox 2.9 cDNA clone is presented. The predicted homeodomain is similar to that of the Drosophila gene labial showing 80% identity. The equivalent gene in the Hox 1 cluster is Hox 1.6 which shows extensive similarity to Hox 2.9 both within and outside the homeodomain. Hox 2.9 and Hox 1.6 are the only two mouse members of the labial-like family of homeobox-containing genes as yet identified. Hox 2.9 has previously been shown to be expressed in a single segmental unit of the developing hindbrain (rhombomere) and has been predicted to be involved in conferring rhombomere identity. To analyse further the function of Hox 2.9 during development and to determine if the other mouse labial-like gene Hox 1.6, displays similar properties, we have investigated the expression patterns of these two genes and an additional rhombomere-specific gene, Krox 20, on consecutive embryonic sections at closely staged intervals. This detailed analysis has enabled us to draw the following conclusions: (1) There are extensive similarities in the temporal and spatial expression of Hox 2.9 and Hox 1.6, throughout the period that both genes are expressed in the embryo (7 1/2 to 10 days). At 8 days the genes occupy identical domains in the neuroectoderm and mesoderm with the same sharp anterior boundary in the presumptive hindbrain. These similarities indicate a functional relationship between the genes and further suggest that the labial-like genes are responding to similar signals in the embryo. (2) By 9 days the neuroectoderm expression of both genes retreats posteriorly along the anteroposterior (AP) axis. The difference at this stage between the expression patterns is the persistence of Hox 2.9 in a specific region of the hindbrain, illustrating the capacity of Hox 2.9 to respond to additional positional regulatory signals and indicating a unique function for this gene in the hindbrain. (3) The restriction of Hox 2.9 expression in the hindbrain occurs at 8 1/2 days, approximately the same time as Krox 20 is first detected in the posterior adjoining domain. The mutually exclusive expression of Hox 2.9 and Krox 20 demarcated by sharp expression boundaries suggest that compartmentalisation of cells within the hindbrain has occurred up to 6 h before rhombomeres (morphological segments) are clearly visible. (4) Hox 2.9 expression is confined to the region of rhombomere 4 that shows cell lineage restriction and, unlike Krox 20, is expressed throughout the period that rhombomeres are visible (to 11 1/2 days).(ABSTRACT TRUNCATED AT 400 WORDS)
Expression of the mouse labial-like homeobox-containing genes, Hox 2.9 and Hox 1.6, during segmentation of the hindbrain
P. Murphy, R.E. Hill; Expression of the mouse labial-like homeobox-containing genes, Hox 2.9 and Hox 1.6, during segmentation of the hindbrain. Development 1 January 1991; 111 (1): 61–74. doi: https://doi.org/10.1242/dev.111.1.61
Download citation file:
Advertisement
Cited by
Pathway to Independence programme

We’re excited to announce our new Pathway to Independence programme, aimed at supporting postdocs as they go on the job market. Find out more about the scheme in our Editorial.
Call for papers: Metabolic and Nutritional Control of Development and Regeneration

We are welcoming submissions for our next special issue, which will focus on metabolic and nutritional control of development and regeneration. Submission deadline: 15 May 2023.
Webinar: Increasing the visibility and impact of your research
-HUBSwebinar.jpg?versionId=4486)
Would you like to increase the visibility and impact of your research and raise your profile internationally? If so, register for the very practical webinar we are running in association with HUBS on 23 February 2023.
Transitions in development: Daniel Grimes

Daniel Grimes’s lab studies the consequences of ciliary mutations, including left-right patterning defects and scoliosis. We interviewed Daniel to find out more about his career path, his experience of becoming a group leader and the influence of Jurassic Park.
Preprints in Development
(update)-InPreprints.png?versionId=4486)
As part of our efforts to support the use of preprints and help curate the preprint literature, we are delighted to launch a new article type: ‘In preprints’. These pieces will discuss one or more recent preprints and place them in a broader context.