Isl1 is required for two processes during hindlimb development: initiation of the processes directing hindlimb development in the lateral plate mesoderm and configuring posterior hindlimb field in the nascent hindlimb buds. During these processes, Isl1 expression is restricted to the posterior mesenchyme of hindlimb buds. How this dynamic change in Isl1 expression is regulated remains unknown. We found that two evolutionarily conserved sequences, located 3’ to the Isl1 gene, regulate LacZ transgene expression in the hindlimb-forming region in mouse embryos. Both sequences contain GATA binding motifs, and expression pattern analysis identified that Gata6 is expressed in the flank and the anterior portion of nascent hindlimb buds. Recent studies have shown that conditional inactivation of Gata6 in mice causes hindlimb-specific pre-axial polydactyly, indicating a role of Gata6 in anterior-posterior patterning of hindlimbs. We studied whether Gata6 restricts Isl1 in the nascent hindlimb bud through the cis-regulatory modules. In vitro experiments demonstrate that GATA6 binds to the conserved GATA motifs in the cis-regulatory modules. GATA6 repressed expression of a luciferase reporter that contains the cis-regulatory modules by synergizing with Zfpm2. Analyses of Gata6 mutant embryos showed that ISL1 levels are higher in the anterior of nascent hindlimb buds than in wild type. Moreover, we detected a greater number of Isl1-transcribing cells in the anterior of nascent hindlimb buds in Gata6 mutants. Our results support a model in which Gata6 contributes to repression of Isl1 expression in the anterior of nascent hindlimb buds.
Bibliographical noteFunding Information:
We are grateful to Shinichi Hayashi, Junji Itou, Sho Kawakami, Jennifer Kim, Jenna Matson, Avery Swearer and Samantha Young for their excellent technical assistance and advices, and to Malina Yamashita Peterson for editorial assistance. We also thank Dr. Yi Zhong and Dr. Christine Iacobuzio-Donahue for human GATA6 expression constructs, Dr. Naoko Koyano-Nakagawa for the Zfpm2 expression construct, Dr. Stephanie Ware for the TK-minimum promoter luciferase vector, Dr. Takaaki Matsui for the oligo DNA pulldown assay protocol, and Dr. Naoyuki Wada for critical reading of the manuscript. This study was supported by grants from the National Institute of Arthritis, Musculoskeletal and Skin Diseases to YK ( R01AR064195 , R21AR063782 ) and the National Heart, Lung, and Blood Institute to DJG ( R01HL122576 ). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. The authors have no conflicts to disclose.
- Hindlimb buds
- Transcriptional regulation