Isl1 and Ldb Co-regulators of transcription are essential early determinants of mouse limb development

Background: The developing limb has served as an excellent model for studying pattern formation and signal transduction in mammalians. Many of the crucial genes that regulate growth and patterning of the limb following limb bud formation are now well known. However, details regarding the control of limb initiation and early stages of outgrowth remain to be defined. This report is focused on genetic events that pave the way for the establishment of a hindlimb bud. Results: Fgf10 and Tbx are crucial for early phases of limb bud initiation. Here we show that in the absence of Isl1 or of Ldb1/2, there is no hindlimb bud development. Fgf10 expression in the bud mesenchyme is dependent on Isl1 and its Ldb co-regulators. Conclusions: Thus, Isl1 and the Ldb co-regulators of transcription are essential early determinants of mouse limb development. Isl1/Ldb complexes regulate Fgf10 to orchestrate the earliest stages of hindlimb formation.