Expression of chick Fgf19 and mouse Fgf15 orthologs is regulated in the developing brain by Fgf8 and Shh.

Fibroblast growth factors (Fgfs) constitute a family of signaling molecules that play essential roles in development. We have studied the expression pattern of mouse Fgf15 in the developing brain. Fgf19 is another member of the FGF family that has been suggested as the chick and human ortholog of mouse and rat Fgf15. Here, we compare the expression pattern during neural development of chick Fgf19 with mouse Fgf15. Unlike Fgf15, Fgf19 presents an expression in the isthmic alar plate, diencephalic and mesencephalic parabasal plates, hindbrain basal plate, as well as in the zona limitans intrathalamica (zli). Moreover, we explored the regulation between Fgf19 and the signaling molecules of the isthmic and zli organizers: Fgf8 and Shh, respectively. Considering the possibility that Fgf19 plays a similar role in humans and chicks, this finding could explain the significant diencephalic phenotypic differences between humans and mice in models and diseases where the Shh pathway is affected.     

Expression of receptors for neuregulins, ErbB2, ErbB3 and ErbB4, in developing mouse cerebellum

We have examined the expression of ErbB2, ErbB3 and ErbB4 in developing mouse cerebellum. ErbB2, ErbB3 and ErbB4 were all expressed in granule cells during cerebellar development. However, the expression pattern for each ErbB receptor changed with the developmental stage. Variations of signal transduction pathway through combinations of these ErbB receptors might have important roles in controlling cerebellar postnatal development.     

整合素α2、α3在小鼠肾发育过程中的表达

目的:观察细胞外基质(ECM)受体一整合素α2、α3在小鼠肾发育过程中的时空性表达,探讨其与肾发育的关系.方法:应用免疫组织化学、图像分析、体视学及免疫印迹技术对不同胚龄及生后日龄小鼠肾组织中整合素α2、α3表达进行定位观察、定性分析和定量检测.结果:胚龄12 d整合素α2、α3即开始表达,整合素α2在肾小体表达微弱,在肾小管和集合管表达较强;整合素α3在发育各个时期肾小体都有较强表达,在肾小管偶见微弱表达.图像分析、体视学及免疫印迹检测结果显示它们的含量都随着肾的发育逐渐增加.结论:整合素α2、α3在小鼠肾发育中起一定作用,α2主要与肾小管和集合管发育相关,α3主要与肾小体发育相关.     

Differential requirements for Fgf3 and Fgf8 during mouse forebrain development

Multiple Fgfs are expressed during formation and patterning of the telencephalon in vertebrates. Fgf8 has been shown to control the size of the telencephalon and the development of signaling centers in zebrafish and mouse. Next to Fgf8, Fgf3 also influences telencephalic gene expression in the zebrafish. Moreover, Fgf3 and Fgf8 have been shown to have combinatorial functions during forebrain development in this species. Here, we have examined telencephalic development in Fgf3 null mouse mutants and embryos that lack both Fgf3 and Fgf8 in their forebrain. In contrast to zebrafish, Fgf3 mutants show normal forebrain development and expression of telencephalic marker genes. Although double mutants for Fgf3 and Fgf8 show a further reduction of forebrain size no additional changes of telencephalic gene expression are observed compared with Fgf8 mutants. Therefore unlike in zebrafish, Fgf3 is not required for mouse forebrain development whereas Fgf8 has a central role during this process. Developmental Dynamics 237:3417–3423, 2008. © 2008 Wiley‐Liss, Inc.     

Dynamic expression of Wnt signaling-related Dickkopf1, -2, and -3 mRNAs in the developing mouse tooth.

Wnt signaling is essential for tooth formation. Members of the Dickkopf (Dkk) family modulate the Wnt signaling pathway by binding to the Wnt receptor complex. Comparison of Dkk1, -2, and -3 mRNA expression during mouse tooth formation revealed that all three genes showed distinct spatiotemporally regulated expression patterns. Dkk1 was prominently expressed in the distal, incisor-bearing mesenchyme area of the mandibular process during the initial stages of tooth formation. During molar morphogenesis Dkk1 was detected in the dental mesenchyme, including the preodontoblasts. Dkk2 was seen in the dental papilla, whereas Dkk3 was specifically expressed in the putative epithelial signaling centers, the primary and secondary enamel knots. Postnatally, Dkk1 was prominently expressed in the preodonto- and odontoblasts, while Dkk3 mRNAs were transiently seen in the preameloblasts before the onset of enamel matrix secretion. These results suggest that modulation of Wnt-signaling by Dkks may serve important functions in patterning of dentition as well as in crown morphogenesis and dental hard-tissue formation.     

No evidence for ventrally migrating neural tube cells from the mid- and hindbrain.

Abstract The neural crest is a migratory population of cells that originates from the dorsal neural tube in vertebrates. Recently, the existence of a group of ventrally emigrating neural tube (VENT) cells has been proposed, based upon cell labelling studies in the hindbrain of avian embryos. Like crest cells, these VENT cells have been reported to give rise to numerous cell types. VENT cell emigration is thought to occur after embryonic day (E) 3, when neural crest cell production has ceased. Migration of cells from the ventral neural tube into the periphery was inferred retrospectively after examining numerous embryos harvested at different stages. We have attempted to label VENT cells in vivo by using a green fluorescent protein (GFP) expression vector, electroporated into the ventral neural tube after crest cell migration and before the putative migration of the ventrally localised cells. Because GFP can be visualised strongly in living tissue a few hours after electroporation, the migration of labelled cells within the same embryo can be followed. Fluorescent cells labelled in the mid-hindbrain region were examined in ovo and in explant culture. No GFP-expressing cells were detected emigrating from the ventral neural tube from E3 to E5. Our findings are, thus, in disagreement with those of previous studies, which have indicated the existence of VENT cells in the cranial region.     

Expression of P2Y(6) receptors in the developing mouse skeletal muscle and after injury and repair

In this study, single and double-labeling immunofluorescence histochemistry, Western blot and real-time polymerase chain reaction were used to study the expression of P2Y(6) receptors in developing mouse skeletal muscle and during injury and repair. The results show that P2Y(6) receptor immunoreactive (ir) cells were first detected in the dermamyotome at embryonic (E) day 9. The number and immunostaining intensity of the P2Y(6) receptor-ir cells increased from E9 to E13, but decreased from E15 to postnatal day 60 in the developing skeletal muscle system. The expression levels of P2Y(6) receptor protein and mRNA increased rapidly from 1 to 5 days after skeletal muscle injury and then decreased almost to the control level from 7 to 10 days, at the beginning of regeneration. P2Y(6) receptor-immunoreactivity was mainly localized to the ends of single myoblasts and myotube processes in the developing and injury-repair skeletal muscle tissues. These data suggest that the P2Y(6) receptor may be involved in the development and regeneration of skeletal muscle, especially in the migration and extension of the myoblast and myotube in developing and regenerating skeletal muscle.     

Expression of apoptosis protein caspase 3 in developing mouse cerebellum

目的:观察C57/BL6小鼠小脑发生发育过程中的凋亡蛋白caspase 3表达变化,探讨小脑发生发育的可能机制.方法:应用免疫组织化学技术、免疫印迹对胚龄(E)12、14、16、18、20 d和生后(P)1、3、7、14、21、28 d的仔鼠及生后2、3、6、15个月的C57/BL6小鼠小脑的形态变化及caspase 3的分布进行系统观察和定量分析.结果:免疫组织化学结果显示,E12 d～P21 d,caspase 3在小鼠小脑中均有阳性表达,主要分布在神经元的细胞质和细胞核中.E12 d～P7d,caspase 3表达逐渐增多,P14 d～P21 d逐渐减少.免疫印迹分析表明,E18 d～3个月,caspase 3蛋白表达先逐渐增加后逐渐减少,P7d达高峰,3个月后维持在较低水平.结论:小鼠小脑的片层化结构主要形成于胚胎期,出生后片层化结构逐渐发育成熟,小脑得以迅速发育长大.此外,在小脑发育中存在着大量的细胞凋亡现象,其可能在小脑的塑形中发挥重要的作用.     

胰岛素增强子结合蛋白1在小鼠胚胎心的时空分布

目的 观察转录因子胰岛素增强子结合蛋白1（ISL1）在小鼠胚胎心的表达与心、第二生心区及前肠内胚层的发育。 方法 胚龄8～13d小鼠胚胎心共18个,连续石蜡切片,用抗心肌肌球蛋白重链（MHC）、抗ISL1、抗增殖细胞核抗原（PCNA）和抗α-平滑肌肌动蛋白(α-SMA)抗体进行免疫组织化学染色、免疫荧光染色和Western blotting检测。 结果 胚龄9d,ISL1阳性心前体细胞进入流出道远端。胚龄10d,ISL1阳性细胞延伸入流出道近端及静脉窦心肌。胚龄11～12d,心内ISL1表达量逐渐增多并达高峰,动脉端ISL1阳性细胞分布于流出道远端壁、心包内主肺动脉壁及主肺动脉隔,静脉端ISL1阳性细胞主要限于窦房结和静脉瓣。动脉端前肠内胚层细胞索增至最长,周围前生心区ISL1阳性细胞密度也达高峰,并且明显多于后生心区。胚龄13d,心内及第二生心区ISL1阳性细胞显著减少,内胚层细胞索趋于消失。 结论 ISL1阳性细胞在小鼠胚胎心的表达主要集中在胚龄9～13d,其表达模式与第二生心区及前肠内胚层的发育密切相关。     

Expression of P2X5 receptors in the mouse CNS

P2X receptors are ATP-gated cationic channels composed of seven known subunits (P2X1-7) which are involved in different functions in neural tissue. The present study investigates the P2X5 receptor expression pattern in the mouse CNS using immunohistochemistry and in situ hybridization histochemistry. The specificity of the immunostaining has been verified by pre-absorption, Western blot and in situ hybridization methods. Heavy P2X5 receptor immunostaining was observed in the mitral cells of the olfactory bulb; cerebral cortex; globus pallidum, anterior cortical amygdaloid nucleus, amygdalohippocampal area of subcortical telencephalon; anterior nuclei, anteroventral nucleus, ventrolateral nucleus of thalamus; supraoptic nucleus, ventromedial nucleus, arcuate nucleus of hypothalamus; substantia nigra of midbrain; pontine nuclei, mesencephalic trigeminal nucleus, motor trigeminal nucleus, ambiguous nucleus, inferior olive, hypoglossal nucleus, dorsal motor vagus nucleus, area postrema of hindbrain; Purkinje cells of cerebellum; and spinal cord. The identification of extensive P2X5 receptor immunoreactivity and mRNA distribution within the CNS of the mouse demonstrated here is consistent with a role for extracellular ATP acting as a fast neurotransmitter.     

Retinoic acid specifically downregulates Fgf4 and inhibits posterior cell proliferation in the developing mouse autopod

Retinoic acid, when administered to pregnant mice on d 11·0 of gestation, causes limb skeletal abnormalities consisting of reduced digital number, shortening of the long bones and delayed ossification. We show here that these effects are correlated with a decrease in cell proliferation within 5 h of retinoic acid administration, specifically in the posterior half of the distal limb bud mesenchyme, from which the distal skeletal elements are generated. There is a specific downregulation of Fgf4 , a gene known to be involved in limb bud outgrowth and expressed only in the posterior part of the apical ectodermal ridge; Fgf8 , which is expressed throughout the apical ectodermal ridge, is unaffected. The reduction in Fgf4 expression is not accompanied by downregulation of Shh , nor of its receptor and downstream target gene Ptc , suggesting that the skeletal reduction defects induced by retinoic acid are mediated specifically by FGF4-induced skeletogenic mesenchymal cell proliferation.     

Retinoic acid specifically downregulates Fgf4 and inhibits posterior cell proliferation in the developing mouse autopod

Retinoic acid, when administered to pregnant mice on d 11·0 of gestation, causes limb skeletal abnormalities consisting of reduced digital number, shortening of the long bones and delayed ossification. We show here that these effects are correlated with a decrease in cell proliferation within 5 h of retinoic acid administration, specifically in the posterior half of the distal limb bud mesenchyme, from which the distal skeletal elements are generated. There is a specific downregulation of Fgf4, a gene known to be involved in limb bud outgrowth and expressed only in the posterior part of the apical ectodermal ridge; Fgf8, which is expressed throughout the apical ectodermal ridge, is unaffected. The reduction in Fgf4 expression is not accompanied by downregulation of Shh, nor of its receptor and downstream target gene Ptc, suggesting that the skeletal reduction defects induced by retinoic acid are mediated specifically by FGF4‐induced skeletogenic mesenchymal cell proliferation.     

Expression patterns and cell cycle profiles of PCNA, MCM6, cyclin D1, cyclin A2, cyclin B1, and phosphorylated histone H3 in the developing mouse retina

A challenge in studying organogenesis is the ability to identify progenitor cell populations. To address this problem, we characterized the expression patterns of cell cycle proteins during mouse retinal development and used flow cytometry to determine the expression profiles in the cell cycle. We found that MCM6 and PCNA are expressed in essentially all retinal progenitor cells throughout the proliferative period and these proteins are readily detectable in all cell cycle phases. Furthermore, their expression levels are downregulated as cells exit the cell cycle and differentiate. We also analyzed the expression of Cyclins D1, A2, and B1, and phosphorylated Histone H3 and found unexpected expression patterns and cell cycle profiles. The combined utilization of the markers tested and the use of flow cytometry should further facilitate the study of stem and progenitor cell behavior during development and in adult tissues.     

Dishevelled2和Vangl2蛋白在小鼠腭板发生中的表达及意义

目的 探讨Dishevelled2和Vangl2蛋白与小鼠腭发育的关系。 方法 将24只孕鼠随机分为8组,每组3只,分别于孕13d上午8时(p13d 8h,以下同）、p13d14h、p13d22h、p14d8h、p14d14h、p14d22h、p15d8h和p15d22h 8个时间点剖宫取胚鼠,常规石蜡切片,采用免疫组织化学及图像分析方法,检测小鼠发生各个时期腭板中Dishevelled2和Vangl2蛋白的分布状况和变化规律。 结果 两种蛋白在不同发育阶段的小鼠腭板上皮和间充质中均有不同程度的表达。Dishevelled2在腭板上皮和间充质均呈现先上升（p13d8h～p13d22h）,而后下降（p13d22h～p14d14h）,之后再次上升（p14d14h～p15d22h）的趋势;Vangle2在腭板间充质也呈现先上升（p13d8h～p13d22h）,后下降（p13d22h～p14d22h）,随后再上升（p14d22h～p15d22h）的趋势,其在上皮中的表达无明显规律。两种蛋白在腭板上皮的表达水平均明显高于其同期间充质的表达水平。 结论 Dishevelled2蛋白和Vangl2蛋白可能直接或间接地参与小鼠腭板的形态发生过程的调节,并且在此过程中两种蛋白均发生着规律性的时空变化。