Alternative titles; symbolsPAIRED-LIKE HOMEOBOX GENE 2; PRX2HGNC Approved Gene Symbol: PRRX2Cytogenetic location: 9q34.11 Genomic coordinates (GRCh38): 9:129...
Alternative titles; symbols
HGNC Approved Gene Symbol: PRRX2
Cytogenetic location: 9q34.11 Genomic coordinates (GRCh38): 9:129,665,646-129,722,673 (from NCBI)
▼ Cloning and Expression
By use of semiquantitative RT-PCR with degenerate primers to identify homeobox-related genes (see HOXB13, 604607) in second-trimester fetal fibroblasts, followed by 5-prime and 3-prime RACE, Stelnicki et al. (1998) identified a partial cDNA, which they designated PRX2, that is differentially expressed during fetal versus adult wound healing. The composite 813-nucleotide cDNA encodes a putative 164-amino acid protein with 74% overall identity to mouse Prx2, showing high conservation in the homeodomain and extreme 3-prime region. Northern blot analysis revealed that PRX2 is expressed as a single 1.3-kb transcript. RNAse protection analysis showed that PRX2 is more strongly expressed in normal fetal than in adult skin, much more strongly expressed in both fetal and adult proliferating fibroblasts, and not expressed in keratinocytes. In situ hybridization analysis revealed weak expression in fetal skin, concentrated within the dermal papilla of the developing hair shaft.
Norris et al. (2000) characterized the expression pattern of PRRX2 and PRRX1 (167420) in human tissues by RT-PCR. Although the expression of these human genes were similar to their mouse orthologs, there were notable differences in expression. PRRX2 was detected in human kidney and lung, whereas in mice and chickens neither of these tissues had been reported to express Prrx2.
Norris et al. (2000) mapped the PRRX2 gene to 9q34.1 and the PRRX1 gene to 1q23 by fluorescence in situ hybridization.
▼ Molecular Genetics
Norris et al. (2000) noted similarities of the observed phenotypes of gene-targeted Prrx1, Prrx2, and double mutant mice to those of Nager acrofacial dysostosis (154400), which maps to 9q, and the phenotypically similar Miller postaxial acrofacial dysostosis (263750). Nager syndrome patients have preaxial limb deformities and frequent postaxial hypoplasia, whereas Miller syndrome patients have primarily postaxial (ulnar and fibular) defects. Both types of abnormalities are observed in the Prrx1, Prrx2, double mutant mice. In DNA samples from 8 patients with Nager syndrome and 2 patients with Miller syndrome, Norris et al. (2000) found no mutations in either of the PRRX genes.
▼ Animal Model
Ten Berge et al. (1998) found that, in contrast to Prx1-null mice, Prx2-null mice showed no skeletal defects. They developed double-mutant mice and found that inactivation of both Prx1 and Prx2 resulted in many novel abnormalities in addition to an aggravation of the skeletal abnormalities seen in Prx1-null mice. There were defects in external, middle, and inner ear, reduction or loss of skull bones, a reduced and sometimes cleft mandible, and limb abnormalities that included postaxial polydactyly and bent zeugopods. A single incisor or no incisor was present in the lower jaw, and ectopic expression of Fgf8 (600483) and Pax9 (167416) was found medially in the mandibular arch. Ten Berge et al. (1998) concluded that the Prx genes are involved in epitheliomesenchymal interactions in inner ear and lower jaw and in interactions between perichondrium and chondrocytes in the bones of the zeugopods.