title: Toll-like receptor 4 restricts retinal progenitor cell proliferation.
abstract: Retinal neurogenesis ceases by the early postnatal period, although retinal progenitor cells (RPCs) persist throughout life. In this study, we show that in the mammalian eye, the function of Toll-like receptor 4 (TLR4) extends beyond regulation of the innate immune response; it restricts RPC proliferation. In TLR4-deficient mice, enhanced proliferation of cells reminiscent of RPCs is evident during the early postnatal period. In vitro experiments demonstrate that TLR4 acts as an intrinsic regulator of RPC fate decision. Increased TLR4 expression in the eye correlates with the postnatal cessation of cell proliferation. However, deficient TLR4 expression is not sufficient to extend the proliferative period but rather contributes to resumption of proliferation in combination with growth factors. Proliferation in vivo is inhibited by both MyD88-dependent and -independent pathways, similar to the mechanisms activated by TLR4 in immune cells. Thus, our study attributes a novel role to TLR4 as a negative regulator of RPC proliferation.
authors.affiliation: Department of Neurobiology, Weizmann Institute of Science, 76100 Rehovot, Israel.
authors.forename: Ravid
authors.initials: R
authors.lastname: Shechter
authors.forename: Ayal
authors.initials: A
authors.lastname: Ronen
authors.forename: Asya
authors.initials: A
authors.lastname: Rolls
authors.forename: Anat
authors.initials: A
authors.lastname: London
authors.forename: Sharon
authors.initials: S
authors.lastname: Bakalash
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Young
authors.forename: Michal
authors.initials: M
authors.lastname: Schwartz
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D002455:Cell Division / Q000502:physiology*; D006706:Homeostasis; D051379:Mice; D018345:Mice, Knockout; D009474:Neurons / Q000166:cytology; D010786:Photoreceptor Cells / Q000166:cytology / Q000502:physiology; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000502:physiology; D016133:Polymerase Chain Reaction; D012160:Retina / Q000166:cytology*; D013234:Stem Cells / Q000166:cytology*; D051197:Toll-Like Receptor 4 / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
chemical_list: C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4