GSE158820
Transcriptional trajectories highlight the transition from anterior-posterior to proximal-distal patterning in the early limb bud [scRNA-seq]
Limb patterning relies in a large part on the function of the Hox family of developmental genes. While the differential expression of Hox genes shifts from the anterior-posterior (A-P) to the proximal-distal (P-D) axis around embryonic day 11 (E11), whether this shift coincides with a more global change of P-D versus A-P patterning program remains unclear. By performing and analyzing the transcriptome of the developing limb bud from E10.5 to E12.5, at single cell resolution, we have uncovered transcriptional trajectories which revealed a general switch from A-P to P-D genetic program between E10.5 and E11.5. Interestingly, the transcriptional trajectories at E10.5 all end with cells expressing either proximal or distal markers suggesting a progressive acquisition of P-D identity. Moreover, we observed that distally expressed Hox genes, namely Hoxa13 and Hoxd13, act as a key determinant for P-D patterning as their transcriptional control results in their distal restricted expression, which in turn restricts Hoxa11 in the proximal limb bud domain, in progenitor cells of the zeugopod. Finally, we identified three categories of genes expressed in the distal limb mesenchyme characterized by distinct temporal expression dynamics. As anticipated from previous results, HOX13 binding was observed within or in the neighborhood of several of these genes consistent with previous evidence suggesting that the transition from the early/proximal to the late/distal transcriptome of the limb mesenchyme largely relies on HOX13 function. Overall design: Single-cell RNA-seq analysis of mouse forelimb bud at E10.5, E11.5 and E12.5