Identification of four murine cDNAs encoding putative protein kinases from primitive embryonic stem cells differentiated in vitro.

Abstract

Protein kinases transduce signals from extracellular ligands in the hematopoietic and other systems through direct phosphorylation of tyrosine, serine, or threonine residues. Little is known about the ligands and receptors that are important in the earliest stages of development-i.e., stem cell self-renewal and lineage commitment. We have made use of the lineage differentiation potential of the murine embryonic stem cell system to clone partial cDNAs encoding four putative protein kinases. Three of the four genes contain the highly conserved residues Asp-Phe-Gly in domain VII of the protein kinase family. These genes are candidates for receptors or downstream effectors of cytokines that regulate self-renewal and lineage commitment in embryogenesis.Much effort has been directed toward isolation and study of primitive stem cells in several tissues, both to understand the biology of these cells and to use them clinically in transplantation and gene therapy (1). Despite real progress on understanding the regulation of the differentiation of mature lineage-specific cells (1, 2), little is known about the process of primitive stem cell self-renewal and function. For example, in the hematopoietic system, while much is known about cytokine regulators of precursor and progenitor cell differentiation, the molecules that regulate hematopoietic stem cell (HSC) self-renewal and lineage commitment are unknown (3).The embryonic stem cell (ESC) in vitro differentiation system provides an opportunity for the study of early developmental events in mammals (4). This system models the transition from pluripotent embryonic cells (blastocyst inner cell mass) to embryonic lineages, including hematopoietic cells (yolk sac blood islands), cardiac myocytes, neurons, and others. In addition, it has been demonstrated that a soluble factor (or factors) present in human umbilical cord serum (HUCS) can alter this developmental cascade, suggesting that ligand-receptor interactions are involved in this process.The information for the coordinated differentiation, cell replication, migration, and cell death required for normal differentiation is transmitted within and between cells by a number of mechanisms. Ligand-receptor pairs are a major component of intercellular communication in the developing and mature animal (5). Several of these ligands mediate their function through receptors that belong to the protein kinase family (6). Protein kinases are enzymes that catalyze the transfer of phosphate from ATP to tyrosine, serine, or threonine residues on the receptor or proteins that are downstream in a signaling cascade. The receptor protein kinases catalyze this reaction when a ligand is bound to the extracellular domain, triggering a cascade ofevents leading to an alteration in cell function such as proliferation or migra-The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.tion. The ...

Differentiating Embryonal Stem Cells Are a Rich Source of Haemopoietic Gene Products and Suggest Erythroid Preconditioning of Primitive Haemopoietic Stem Cells

“…For this reason we have turned our attention to the ES cell system as an in vitro model of developmental hemopoiesis. Other studies have also capitalized on the usefulness of this in vitro differentiation system to identify novel protein kinase cDNAs (56,57) and to characterize a number of hemopoietic and developmental genes (58). We now report that precise definition of the time frame of emergence of primitive hemopoietic stem cells in the EBs (19) has allowed us to use this in vitro differentiation system to generate subtracted FIG.…”

TAM Receptor Tyrosine Kinases: Biologic Functions, Signaling, and Potential Therapeutic Targeting in Human Cancer

“…In addition to the earlier mentioned PCR fragment isolated from rat (Lai and Lemke, 1991), fragments of murine Tyro-3, called Etk-2 (Biesecker et al, 1993), and human Tyro-3 (Polvi et al, 1993) were cloned from mouse embryonic stem cells and human teratocarcinoma cell, bone marrow, and melanocyte cDNA libraries, respectively. In 1994, the murine and human genes were cloned by multiple labs.…”

“…Tyro-3 Brt (m), Dtk (m), Rse, Sky, Tif, Etk-2 (m), Rek (ch) Biesecker et al (1993), Biscardi et al (1996), Crosier et al (1994), Dai et al (1994), Fujimoto and Yamamoto (1994), Lai and Lemke (1991), Lai et al (1994), Mark et al (1994), Ohashi et al (1994), Polvi et al (1993) Axl Ark (m), Ufo, Tyro-7 (r) Janssen et al (1991), Lai and Lemke (1991), Liu et al (1988), O'Bryan et al (1991), Rescigno et al (1991) Mer Eyk (ch), MerTK, Nyk, Tyro-12 (r) Graham et al (1994), Graham et al (1995), Jia et al (1992), Jia and Hanafusa (1994), Lai and Lemke (1991), Ling and Kung (1995) ch, chicken; m, mouse; r, rat.…”

Dietary cholesterol stimulates CYP7A1 in rats because farnesoid X receptor is not activated

“…Total RNA was isolated from frozen rat liver tissues using the single-step RNA isolation method with TRIzol reagent (Invitrogen Life Technologies, Carlsbad, CA), as described by Chomozynski and Sacchi (5). Poly(A) ϩ RNA was isolated from 2 mg total RNA by oligo(dT) cellulose using the FastTrack 2.0 mRNA isolation kit (Invitrogen Life Technologies) described by Biesecker et al (2).…”