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Development 2005 Jun 01;13212:2861-71. doi: 10.1242/dev.01872.
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Knockdown of the complete Hox paralogous group 1 leads to dramatic hindbrain and neural crest defects.

McNulty CL , Peres JN , Bardine N , van den Akker WM , Durston AJ .

The Hox paralogous group 1 (PG1) genes are the first and initially most anterior Hox genes expressed in the embryo. In Xenopus, the three PG1 genes, Hoxa1, Hoxb1 and Hoxd1, are expressed in a widely overlapping domain, which includes the region of the future hindbrain and its associated neural crest. We used morpholinos to achieve a complete knockdown of PG1 function. When Hoxa1, Hoxb1 and Hoxd1 are knocked down in combination, the hindbrain patterning phenotype is more severe than in the single or double knockdowns, indicating a degree of redundancy for these genes. In the triple PG1 knockdown embryos the hindbrain is reduced and lacks segmentation. The patterning of rhombomeres 2 to 7 is lost, with a concurrent posterior expansion of the rhombomere 1 marker, Gbx2. This effect could be via the downregulation of other Hox genes, as we show that PG1 function is necessary for the hindbrain expression of Hox genes from paralogous groups 2 to 4. Furthermore, in the absence of PG1 function, the cranial neural crest is correctly specified but does not migrate into the pharyngeal arches. Embryos with no active PG1 genes have defects in derivatives of the pharyngeal arches and, most strikingly, the gill cartilages are completely missing. These results show that the complete abrogation of PG1 function in Xenopus has a much wider scope of effect than would be predicted from the single and double PG1 knockouts in other organisms.

PubMed ID: 15930115
Article link: Development

Species referenced: Xenopus laevis
Genes referenced: dll4 dlx2 egr2 en2 gbx2 gbx2.2 hoxa1 hoxa2 hoxa3 hoxa5 hoxb1 hoxb2 hoxb9 hoxc6 hoxc9-like hoxd1 hoxd3 hoxd4 lsamp myod1 nrp1 otx2 snai1 snai2
Antibodies: Lsamp Ab1
Morpholinos: hoxa1 MO1 hoxa1 MO2 hoxb1 MO1 hoxb1 MO2 hoxd1 MO1 hoxd1 MO2

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