Identification of genes expressed in the migrating primitive myeloid lineage of Xenopus laevis. Issue 1 (20th November 2015) - Agricola, Zachary N.
Abstract : Background: During primitive hematopoiesis in Xenopus, cebpa and spib expressing myeloid cells emerge from the anterior ventral blood island. Primitive myeloid cells migrate throughout the embryo and are critical for immunity, healing, and development. Although definitive hematopoiesis has been studied extensively, molecular mechanisms leading to the migration of primitive myelocytes remain poorly understood. We hypothesized these cells have specific extracellular matrix modifying and cell motility gene expression.Results: In situ hybridization screens of transcripts expressed in Xenopus foregut mesendoderm at stage 23 identified seven genes with restricted expression in primitive myeloid cells: destrin; coronin actin binding protein, 1a; formin‐like 1; ADAM metallopeptidase domain 28; cathepsin S; tissue inhibitor of metalloproteinase‐1; and protein tyrosine phosphatase nonreceptor 6. A detailed in situ hybridization analysis revealed these genes are initially expressed in the aVBI but become dispersed throughout the embryo as the primitive myeloid cells become migratory, similar to known myeloid markers. Morpholino‐mediated loss‐of‐function and mRNA‐mediated gain‐of‐function studies revealed the identified genes are downstream of Spib.a and Cebpa, key transcriptional regulators of the myeloid lineage.Conclusions: We have identified genes specifically expressed in migratory primitive myeloid progenitors, providing tools to study how different gene networks operate in these primitive myelocytes during development and immunity. Developmental Dynamics 245:47–55, 2016 . © 2015 Wiley Periodicals, Inc. Key Findings: We have identified seven genes specific to differentiating primitive myeloid cells. These genes fall under cytoskeletal and extracellular matrix modifying functions and have precedence for function in white blood cells of higher vertebrates. These genes are downstream of key primitive myeloid transcription factors in Xenopus, spiba and cebpa. These genes provide tools for future studies of functional gene networks in the differentiating primitive myeloid cell in Xenopus.