Analysis of the Expression Pattern of Cajal-Retzius Cell Markers in the Xenopus laevis Forebrain

Cajal-Retzius cells are essential for cortical development in mammals, and their involvement in the evolution of this structure has been widely postulated, but very little is known about their progenitor domains in non-mammalian vertebrates. Using in situhybridization and immunofluorescence techniques we analyzed the expression of some of the main Cajal-Retzius cell markers such as Dbx1, Ebf3, ER81, Lhx1, Lhx5, p73, Reelin, Wnt3a, Zic1, and Zic2 in the forebrain of the anuran Xenopus laevis, because amphibians are the only class of anamniote tetrapods and show a tetrapartite evaginated pallium, but no layered or nuclear organization. Our results suggested that the Cajal-Retzius cell progenitor domains were comparable to those previously described in amniotes. Thus, at dorsomedial telencephalic portions a region comparable to the cortical hem was defined in Xenopus based on the expression of Wnt3a, p73, Reelin, Zic1, and Zic2. In the septum, two different domains were observed: a periventricular dorsal septum, at the limit between the pallium and the subpallium, expressing Reelin, Zic1, and Zic2, and a related septal domain, expressing Ebf3, Zic1, and Zic2. In the lateral telencephalon, the ventral pallium next to the pallio-subpallial boundary, the lack of Dbx1 and the unique expression of Reelin during development defined this territory as the most divergent with respect to mammals. Finally, we also analyzed the expression of these markers at the prethalamic eminence region, suggested as Cajal-Retzius progenitor domain in amniotes, observing there Zic1, Zic2, ER81, and Lhx1 expression. Our data show that in anurans there are different subtypes and progenitor domains of Cajal-Retzius cells, which probably contribute to the cortical regional specification and territory-specific properties. This supports the notion that the basic organization of pallial derivatives in vertebrates follows a comparable fundamental arrangement, even in those that do not have a sophisticated stratified cortical structure like the mammalian cerebral cortex.

Overexpression of Long Non-Coding RNA AP001505.9 Inhibits Dedifferentiation in Human Hyaline Chondrocyte

Background: Autologous chondrocyte implantation (ACI) requires a large number ofhuman hyaline chondrocytes. Unfortunately, human hyaline chondrocytes oftenundergo dedifferentiation in vitro. Long non-coding RNAs (lncRNA) play aregulatory role in gene expression in many pathological and physiological processes.However, their role in human hyaline chondrocyte dedifferentiation remains unclear.This study aimed to investigate the expression profiles of lncRNAs in human hyalinechondrocyte dedifferentiation.Methods: Human hyaline chondrocytes were cultured in vitro and screened for theoccurrence of dedifferentiation using real-time quantitative PCR (qPCR),immunofluorescence, and western blotting. The expression profiles of lncRNAs andmRNAs during dedifferentiation were analyzed by microarray analysis and real-timeqPCR. We used pellet culture to redifferentiate chondrocytes and the expression ofrelated lncRNAs were assessed. The function of lncRNA AP001505.9(ENST00000569966) was determined by overexpression, fluorescence in situhybridization, competing endogenous RNA (ceRNA) analysis, and double luciferaselabeling.Results: We probed human hyaline chondrocytes dedifferentiation and identified 334upregulated and 381 downregulated lncRNAs. The expression of downregulatedlncRNA AP001505.9 in dedifferentiation was reversed by pellet culture. Theoverexpression of AP001505.9 inhibited dedifferentiation by promoting theexpression of SRY-Box transcription factor 9 (SOX-9) and inhibiting the expressionof type I collagen (COL1) both in vitro and in vivo.Conclusion: This study reveals for the first time the expression profiles of lncRNAsin human hyaline chondrocyte dedifferentiation, thereby providing a new perspectivefor exploring the potential mechanism of chondrocyte dedifferentiation.