Gene expression analysis of the Xenopus laevis early limb bud proximodistal axis. Issue 11 (20th July 2022)

• Record Type: Journal Article
• Authors: Hudson, Daniel T.; Bromell, Jessica S.; Day, Robert C.; McInnes, Tyler; Ward, Joanna M.; Beck, Caroline W.
• Is Part Of: Developmental dynamics. Volume 251:Issue 11(2022)
• Page Start: 1880
• Page End: 1896
• Publication Date: 2022-07-20
• Subjects: apical ectodermal ridge -- development -- distal -- limb bud -- patterning -- proximal -- retinoic acid -- Xenopus; Morphogenesis -- Periodicals; Anatomy -- Periodicals; Anatomie -- Périodiques; Biologie du développement -- Périodiques; 571.833
• DOI: 10.1002/dvdy.517
• Languages: English
• ISSNs: 1058-8388

Abstract

Abstract: Background: Limb buds develop as bilateral outgrowths of the lateral plate mesoderm and are patterned along three axes. Current models of proximal to distal patterning of early amniote limb buds suggest that two signals, a distal organizing signal from the apical epithelial ridge (AER, Fgfs) and an opposing proximal (retinoic acid [RA]) act early on pattern this axis. Results: Transcriptional analysis of stage 51 Xenopus laevis hindlimb buds sectioned along the proximal‐distal axis showed that the distal region is distinct from the rest of the limb. Expression of capn8.3, a novel calpain, was located in cells immediately flanking the AER. The Wnt antagonist Dkk1 was AER‐specific in Xenopus limbs. Two transcription factors, sall1 and zic5, were expressed in distal mesenchyme. Zic5 has no described association with limb development. We also describe expression of two proximal genes, gata5 and tnn, not previously associated with limb development. Differentially expressed genes were associated with Fgf, Wnt, and RA signaling as well as differential cell adhesion and proliferation. Conclusions: We identify new candidate genes for early proximodistal limb patterning. Our analysis of RA‐regulated genes supports a role for transient RA gradients in early limb bud in proximal‐to‐distal patterning in this anamniote model organism. Key Findings: Transcriptome analysis revealed seven patterns of differential expression across stage 51 Xenopus hindlimb buds, with the distal region most transcriptionally distinct. Two distal (capn8.3, zic5) and two proximal (gata5 and tnn) genes with no previously described role in limb development were identified. Genes linked to Wnt, Fgf and retinoic acid (RA) signaling, cell adhesion and proliferation are differentially expressed across the proximodistal axis. All genes associated with RA signaling are proximal, and genes previously shown to be down‐regulated by RA are distal. Our findings support the presence of patterning gradients of RA across the early limb proximodistal axis in Xenopus.