Mouse semaphorin H inhibits neurite outgrowth from sensory neurons.

Mouse semaphorin H (M-semaH) was structurally similar to semaphorin III/D, a mammalian homologue of collapsin 1 which was identified as a collapsing factor for sensory nerves. In this study we investigated the expression patterns of M-semaH mRNA and the protein binding sites in the trunk of mouse embryos. M-semaH mRNA was expressed in the mesenchymal tissues surrounding each dorsal root ganglia. These tissues include the caudal sclerotome and perinotochordal mesenchyme, which were thought to express factors repulsive to axons. M-semaH binding was detected on the spinal nerves. We further investigated, using in vitro co-culture assay, whether M-semaH acted as a chemorepulsive molecule on sensory axons. The results suggested that M-semaH was a candidate for a chemorepellent expressed in the mesenchyme surrounding the sensory ganglia, which is involved in the axonal guidance mechanism of sensory nerves in the trunk.     

Expression of the RET proto-oncogene in human Embryos

The patterns of RET proto-oncogene expression in mouse, rat, and chicken and the anomalies observed in targeted RET mutants suggest that RET plays a major role in development of mouse enteric nervous system and in kidney organogenesis. Here, we report on in situ hybridization studies describing the pattern of RET proto-oncogene expression during early development of human embryos between 23 and 42 days. We show that the RET gene is expressed in the developing kidney (nephric duct, mesonephric tubules, and ureteric bud), the presumptive enteric neuroblasts of the developing enteric nervous system, cranial ganglia (VII+VIII, IX, and X) and in the presumptive motor neurons of the spinal cord. Yet, despite the high level of RET gene expression in the kidney and in the motor neurons of the developing central nervous system in human embryos, only rare cases with renal agenesis have been reported in Hirschsprung disease patients, and no clinical evidence of spinal cord involvement has been shown in patients carrying RET germline mutations (i.e., multiple endocrine neoplasia syndromes and Hirschsprung disease). Am. J. Med. Genet. 80:481–486, 1998. © 1998 Wiley-Liss, Inc.     

用RNA-RNA原位杂交技术研究Robo2在早期鸡胚发育中的表达

目的:探讨Robo2(roundabout homolog 2)在早期鸡胚发育中的表达。方法:利用分子生物学手段,构建Robo2/pSPT18重组质粒,并且制备地高辛标记的Robo2 RNA探针,进而通过RNA-RNA原位杂交技术检测Robo2在早期鸡胚发育中的表达。结果:原条发生前Robo2表达较弱,原条发生后主要表达在原条和神经板。体节期Robo2主要表达在脊索、神经管、体节和血岛部位。冰冻切片后观察到Robo2主要表达在外胚层,而在中胚层和内胚层只有部分表达。结论:阐明了Robo2在早期鸡胚发育中的表达,为进一步研究Robo2在正常生理和病理条件下的功能及作用机制奠定基础。     

Expression of ZIC genes in the development of the chick inner ear and nervous system.

ZIC genes, vertebrate homologues of the Drosophila pair-rule gene odd-paired (opa), function in embryonic pattern formation, in the early stages of central nervous system neurogenesis and in cerebellar maturation. Mouse Zic genes are expressed in restricted, and in some cases overlapping, patterns during development, particularly in the central and peripheral nervous systems. We identified chick ZIC2 in a differential display analysis of the auditory system designed to find genes up-regulated after noise trauma. In this study, we examined the expression of chick ZIC1, ZIC2, and ZIC3 by in situ hybridization in normal inner ear development and in the tissues that influence its development, including the hindbrain, the neural crest, and the periotic mesenchyme. Between Hamburger and Hamilton stages 13 and 24, all three ZIC genes were found in the dorsal periotic mesenchyme adjacent to the developing inner ear. ZIC1 mRNA was expressed in the otocyst epithelium between stages 12 and 24, in some sensory tissue, as well as in a striped pattern in the floorplate of the hindbrain that appears to be complementary to that of Chordin, a gene known to regulate ZIC expression in frogs. Chick ZIC genes are also expressed in the neuroectoderm, paraxial mesenchyme, brain, spinal cord, neural crest, and/or the overlying ectoderm as well as the limb buds. In general, ZIC1 and ZIC2 expression patterns overlapped, although ZIC2 expression was less robust; ZIC3 expression was minimal. These observations suggest that ZIC genes, in addition to their known roles in brain development, may play an important role in the development of the chick inner ear.     

Identification of a novel type II classical cadherin: rat cadherin19 is expressed in the cranial ganglia and Schwann cell precursors during development.

To identify a novel type II classical cadherin, we searched the genome database and found rat cadherin19 (cad19) with high similarity to human cadherin19. We also found nucleotide sequences corresponding to rat cad19 in mouse and chicken genomes. In situ hybridization of rat cad19 revealed that rat cad19 mRNA was initially expressed in cephalic neural crest cells, and then in the cranial ganglia, migrating trunk neural crest cells, the nascent dorsal root ganglia, and the sympathetic ganglia. Expression of cad19 overlapped with that of neural crest markers, including Sox10 and AP-2, but cad19 expression was confined to subpopulations of the neural crest-derived cells, those typically observed in the satellite glia at the periphery of the ganglia and Schwann cell precursors along the peripheral nerves. cad19 mRNA was not detected in cells expressing Phox2b, an epibranchial placode-derived neurons, nor in those expressing neuronal markers such as Hu protein. These observations suggest that cad19 is expressed in neural crest-derived, non-neuronal cells. Although the expression of cad19 mRNA persisted in Schwann cell precursors at E14.5, it was no longer detected in maturing Schwann cells at later stages. These results suggest that cad19 is an evolutionarily conserved cadherin and may be involved in the early development of Schwann cells in the peripheral nervous system.     

Ncx, a Hox11 related gene, is expressed in a variety of tissues derived from neural crest cells

We have isolated the murine homeobox gene (Ncx) that belong to a Hox11 gene family. Expression of the Ncx gene was analyzed in total RNAs from embryos by reverse transcribed polymerase chain reaction (RT-PCR). The mRNA was detected in embryos after 9.5 days of embryogenesis (E9.5) and was maximal at E12.5. The RT-PCR also detected the message in total RNAs from adrenal glands and intestine in adult mice. The expression was further examined in various tissues from embryos by in situ hybridization. It was detected in dorsal root ganglia, cranial nerve ganglia (V, IX, X), enteric nerve ganglia and adrenal glands from embryos between E9.5 and E13.5. Since its expression is restricted to tissues derived from neural crest cells, Ncx may play a role in differentiation and proliferation of neural crest lineage cells.     

Characterization of a murine homeo box gene, Hox-2.6, related to the Drosophila Deformed gene

The Hox-2 locus on chromosome 11 represents one of the major clusters of homeo-box-containing genes in the mouse. We have identified two new members (Hox-2.6 and Hox-2.7), which form part of this cluster of seven linked genes, and it appears that the Hox-2 locus is related by duplication and divergence to at least one other mouse homeo box cluster, Hox-1. The Hox-2.6 gene encodes a predicted protein of 250 amino acids, which displays extensive similarity in multiple regions to certain mouse, human, Xenopus, and zebra fish homeo domain proteins. The Drosophila Deformed (Dfd) gene also shares these same regions of similarity, and based on this sequence conservation, we suggest that Hox-2.6 forms part of a vertebrate 'Dfd-like' family. Hox-2.6 is expressed in fetal and adult tissues and is modulated during the differentiation of F9 teratocarcinoma stem cells. In situ hybridization analysis of mouse embryos shows that the Hox-2.6 is expressed in ectodermal derivatives: spinal cord, hindbrain, dorsal root ganglia, and the Xth cranial ganglia. In the central nervous system, expression is observed in the most posterior parts of the spinal cord, with the anterior limit residing in a region of the hindbrain and no expression in the mid- or forebrain. In mesodermal structures, Hox-2.6 is expressed in the kidney, the mesenchyme of the stomach and lung, and the longitudinal muscle layer of the gut. Expression has not been observed in derivatives of embryonic endoderm. The patterns of Hox-2.6 expression in both mesoderm and ectoderm are spatially restricted and may reflect a role for the gene in the response to or establishment of positional cues in the embryo.     

PLEXIN-D1, a novel plexin family member, is expressed in vascular endothelium and the central nervous system during mouse embryogenesis.

The genetic defect in M?bius syndrome 2 (MBS2, MIM 601471), a dominantly inherited disorder characterised by paralysis of the facial nerve, is situated at chromosome 3q21-q22. We characterised the cDNA and predicted protein, and examined the expression pattern during mouse embryogenesis of a positional candidate gene, PLEXIN-D1 (PLXND1). The cDNA for PLXND1 is 7095 base pairs in length, coding for a predicted protein of 1925 amino acids. The protein features all known domains of plexin family members, with the exception of the third Met-related sequence. Northern analysis revealed a very low expression of PLXND1 in adult mouse and adult human tissues. To investigate the expression of PlxnD1 during embryogenesis, RNA in situ hybridisation was performed on mouse embryos from various stages. This investigation revealed expression of PlxnD1 in cells from the central nervous system (CNS) and in vascular endothelium. Early expression in the CNS is located in the ganglia, cortical plate of the cortex, and striatum. At later embryologic stages, neural expression was also seen in the external granular layer of the cerebellum and several nerve nuclei. The expression in the vascular system resides solely in the endothelial cells of developing blood vessels. Based on our results, we suggest that this expression of a member of the plexin family in vascular endothelium could point toward a role in embryonic vasculogenesis.     

CNTF基因在大鼠脊髓中的表达及生后发育的变化

目的 观察CNTF基因在大鼠脊髓中的表达以及生后发育过程中的变化。方法 以地高辛标记（dig）－CNTF cDNA为探针，采用原位杂交法，观察CNTF mRNA在大鼠脊髓中的分布；采用TR－PCR法，半定量分析大鼠生后发育过程中，脊髓CNTF mRNA表达水平的变化。结果 CNTF mRNA原位杂交阳性信号存在于正常大鼠脊髓白质的腹索、外侧索周边的部分胶质细胞中；灰质中未能发现阳性杂交信号。RT－PCR结果显示，大鼠生后1d脊髓细胞中即可见CNTF mRNA表达，但表达量较低；出生15d表达量迅速增加；30d时最高；60d时的表达量有下降的趋势。结论 大鼠脊髓白质的部分胶质细胞可表达CNTF mRNA；大鼠出生后1d CNTF mRNA即有表达，之后随脊髓的发育而呈动态变化的趋势。